Zhe Zhang, Xiaodong Ma, Erpeng Dai, Hua Guo

Multi-shot EPI can achieve high resolution diffusion imaging but shot-to-shot phase variation correction is indispensable. Previous multi-shot EPI diffusion imaging methods can be categorized into two groups based on different phase navigation strategies: navigator acquired from a second echo and navigator calculated from image-echo itself using parallel imaging technique. These methods may suffer prolonged scan time or limitation from high reduction factor penalty. In this work, we proposed a new strategy for efficient navigating in multi-shot DWI using 1D navigator acquisition with parallel imaging and iterative reconstruction. Results show the proposed methods can effectively correct the motion-induced artifacts in diffusion imaging.

Sevgi Kafali, Tolga Cukur, Emine Saritas

Multiple acquisitions have to be averaged to achieve reasonable signal-to-noise ratio (SNR) in high-resolution diffusion tensor imaging (DTI). However, involuntary global/local motions during diffusion-sensitizing gradients create k-space shifts, and global/local phase differences between different acquisitions, complicating image reconstruction. In this work, we propose a phase-correcting joint non-local means reconstruction that effectively prevents phase cancellations and reduces noise. This technique jointly utilizes the images from different diffusion-encoding directions to preserve the fractional anisotropy (FA) map. Results are demonstrated for in vivo spinal cord DTI and on a simulated DTI dataset. 

Jonathan Sperl, Tim Sprenger, Ek Tan, Marion Menzel, Christopher Hardy, Luca Marinelli

Diffusion Kurtosis Imaging (DKI) suffers from high sensitivity to noise and therefore requires long scanning times (up to 150 diffusion weighted images, DWIs). This work proposes a model-based denoising technique to overcome this limitation: A generalized multi-shell spherical deconvolution model is formulated and DWIs are denoised by a projection into the space spanned the model. We demonstrate noise reduction for DKI metrics yielding improved image quality of kurtosis maps from as few as 30 DWIs. This corresponds to greater than four-fold reduction in scan time as compared to the widely used 140-DWI acquisitions.

Erpeng Dai, Xiaodong Ma, Zhe Zhang, Chun Yuan, Hua Guo

Recently, simultaneous multi-slice (SMS) has been proved to be effective for accelerating single-shot EPI (ssh-EPI) based diffusion weighted imaging (DWI). More importantly, SMS can be combined with multi-shot interleaved EPI (iEPI) DWI to achieve high resolution and high throughput simultaneously. However, signal dropout problems may exist in the final DW images, especially at high SMS acceleration factors. The main reason is the prominent cerebrospinal fluid (CSF) pulsation, which may degrade the reconstruction performance. In this study, the reconstruction algorithm is augmented by using iteration and data rejection. In-vivo experiments have demonstrated that the augmented algorithm can effectively alleviate the signal dropout problems.

Xiaodong Ma, Zhe Zhang, Erpeng Dai, Chun Yuan, Hua Guo

To improve the image quality for navigator-free multi-shot DTI reconstruction, the inter-image correlation constraint is introduced. Group sparsity and anisotropic sparsity are proposed as two specific implementations, using the POCS-ICE algorithm. Results show that both constraints can improve the image quality with increased SNR. In addition, anisotropy sparsity has less blurring and can better maintain the detailed structures.

Qiuting Wen, Brian Dale, Shivraman Giri, Yu-Chien Wu

High-resolution diffusion-weighted MRI often relies on multi-shot acquisitions, which suffer from long acquisition time. Rotating single-shot acquisition (RoSA) was proposed to accelerate high-resolution diffusion MRI by taking advantage of the similarity between diffusion-weighted images.  In RoSA only a strip of k-space (i.e., blade) per diffusion direction is acquired, and high-resolution image was achieved via composite reconstruction. In this work, we implemented RoSA with parallel imaging. We demonstrated that improved data quality and imaging speed was achieved in both simulation and in human data.

Jana Hutter, Paddy Slator, Anthony Price, Ana Gomes, Laura McCabe, Maria Kuklisova, Paul Aljabar, Mary Rutherford, Joseph Hajnal

Conventional diffusion MRI acquisitions acquire all slices per volume with the same diffusion weighting. This can have two drawbacks: Excessive heating of gradient hardware caused by multiple repeats of the same combination of large drive currents, and low signal at high b-values, which impairs motion correction based on image registration. For placental diffusion MRI, where large slice stack are needed for spatial coverage  and anatomical structure can be lost after diffusion, both of these factors can be extreme. We propose intra-volume interleaving of different diffusion weightings, ordered to facilitate image registration for motion correction and minimise gradient heating.

Daniel Olson, Andrew Nencka, Volkan Arpinar, L. Tugan Muftuler

Simultaneous Multi-slice (SMS) techniques excite multiple slices simultaneously to accelerate MRI data acquisition. However, slice separation during image reconstruction is not exact and results in coupling between separated voxels. While this may not be critical for most anatomic imaging methods, small but consistent leakage of information from another slice in a DTI dataset will cause bias in diffusion parameter estimates. Here, we propose a randomized-slice pairing technique to alleviate this problem in diffusion MRI acquisitions.

Óscar Peña-Nogales, Rodrigo de Luis-Garcia, Santiago Aja-Fernández, Yuxin Zhang, James Holmes, Diego Hernando

Diffusion-Weighted MRI (DW-MRI) often suffers from motion-related artifacts in organs that experience physiological motion. Importantly, organ motion during the application of diffusion gradients results in signal losses, which complicate image interpretation and bias quantitative measures. Motion-compensated gradient designs have been proposed, however they typically result in substantially lower b-values or severe concomitant gradient effects. In this work, we develop an approach for design of first- and second-order motion-compensated gradient waveforms based on a b-value maximization formulation including concomitant gradient nulling, and we compare it to existing techniques. The proposed design provides optimized b-values with motion compensation and concomitant gradient nulling.

Xiaoxi Liu, Edward S. Hui, Cui Di, Nan-Kuei Chen, Hing-Chiu Chang

Due to the assumption of 2D phase variations, the feasible maximum slab thickness is relatively thin (e.g. < 25 mm) for 3D multi-shot diffusion-weighted echo-planar imaging. We have thus proposed a new method in another study to correct for 3D inter-shot phase variations, thereby significantly increasing the feasible maximum slab thickness. In this study, we have demonstrated by simulations and experiments that slab thickness can be significantly increased to allow whole brain coverage with a TR that achieves optimal SNR efficiency.

Robert Bergen, Lawrence Ryner

Diffusion-weighted magnetic resonance imaging (DWI) is routinely used in prostate cancer assessment, but suffers from image distortions primarily due to the tissue-air interface at the rectal cavity. Readout-segmented echo planar imaging (RESOLVE) improves image quality through segmented acquisition of k-space, increasing bandwidth in the phase direction. However, distortions of several millimeters may still exist in RESOLVE images. This study quantified distortions in a prostate phantom by varying the number of RESOLVE segments and using field mapping correction techniques. Field mapping correction decreased image distortion by 28% compared to the 7-segment RESOLVE scan.

Grant Yang, Hua Wu, Qiyuan Tian, Adam Kerr, Robert Dougherty, Jennifer McNab

Double diffusion encoding (DDE) sequences can measure microscopic diffusion anisotropy even in complex structures such as cortex or crossing fiber regions in white matter.  However, DDE sequences require long TEs to accommodate the additional diffusion gradients, resulting in lower signal-to-noise ratio (SNR) and reduced slice coverage limiting its clinical feasibility. In this work, we implement a DDE sequence with simultaneous multi-slice (SMS) to improve the SNR efficiency and allow for full-brain DDE scans in a clinically feasible time.     

Filip Szczepankiewicz, Carl-Fredrik Westin, Hans Knutsson

The powder-averaged signal is used in several analysis techniques in diffusion MRI. Assuming uniformly distributed diffusion encoding directions, it is calculated simply as the arithmetic signal average. However, perfectly uniform sampling is generally unattainable.

We demonstrate how non-uniformity can be accounted for by using weighted signal averaging, and we describe how optimal weights can be calculated for existing diffusion encoding schemes to yield improved accuracy of the powder average estimate.

Lars Mueller, Tristan Kuder, Frederik Laun

The possibility to simultaneous compensate for flow, concomitant fields and eddy currents in diffusion weighted MRI were examined by means of numerical simulations. For this purpose, sequences with three to five gradient pulses and one or two refocusing pulses were examined. It is shown that it is possible to effectively minimize all three effects with different sequences. For short to intermediate echo times, it is beneficial to use only one refocusing pulse, while for long echo times two refocusing pulses can yield higher b-values. There is a trade-off between compensation of more effects and the achievable b-value.

Zhangxuan Hu, Chun Yuan, Hua Guo

Multi-shot techniques can help to achieve high spatial resolution in diffusion imaging. Due to the application of diffusion gradients, phase errors are induced by shot-to-shot motions, which need to be corrected during image reconstruction. Some phase correction approaches have been proposed, such as SENSE+CG, POCS-ICE, and PR-SENSE. Compressed sensing (CS) method has been used in image reconstruction and shows great insensitivity to noise, and can be effectively solved by the Alternating Direction Method of Multipliers (ADMM) algorithm. In this work, the ADMM method of CS reconstruction is used in multi-shot diffusion imaging and proved that it can provide higher reconstruction quality.

Koji Sakai, Hiroshi Imai, Hiroyasu Ikeno, Jun Tazoe, Masashi Yasuike, Hitomi Nagano, Himanshu Bhat, Kei Yamada

To find clinically feasible combinations of parameter for simultaneous multi-slice echo planar imaging (SMS-EPI) acquisition diffusion tensor imaging (DTI), we investigated the combinations of SMS factors and the amounts of inter-slice image shift to find which one can provide better signal-to-noise ratio (SNR) by two different head coils (20ch and 32ch), respectively. The SMS factors 2 and 3 with imaging shifts (>1/2) on 32ch judged clinically feasible and can be substituted on conventional DTI. The SMS factor 2 with imaging shifts 0, 1/2, 1/4 on 20ch head coil judged clinically feasible.

Chia-Ling Chang, Jr-Yuan Chiou, Ming-Long Wu, Shang-Yueh Tsai, Stephan Maier, Bruno Madore, Tzu-Cheng Chao

A novel technique, Fast Diffusion Imaging with High Angular Resolution, is proposed to achieve whole-brain HARDI scans for clinical applications with better geometrical fidelity and shorter scan time. The present study compares tractography results and diffusion properties of each analyzed fiber tract among four-fold segmented (multi-shot) HARDI scans with different acceleration rates and a clinically used sequence with two-fold SENSE. A fully sampled four-shot HARDI scan was used as the reference. The results suggest that the novel acceleration strategy permits a four-minute scan with fairly compatible results while the clinically used method takes ten minutes. 

Baxter Rogers, Allen Newton, E Welch, Jeffrey Luci, Heidi Edmonson, Bennett Landman

Accurate and reliable quantitative diffusion MRI depends on correcting for spatially varying errors in applied diffusion gradients due to nonlinearity of the gradient coil fields. We measured the temporal and inter-scanner variability of a phantom-based correction protocol on four different scanners. Estimated errors in diffusion gradient b-value and direction were significant, and differed between scanners. Scanner differences in temporal stability indicated the need for site-specific calibrations.

Óscar Peña-Nogales, Diego Hernando, Santiago Aja-Fernández, Rodrigo de Luis-Garcia

Mapping of the apparent diffusion coefficient (ADC), estimated from a set of diffusion-weighted (DW) images acquired with different b-values, often suffers from low SNR, which can introduce large variance in ADC maps. Unfortunately, there is no consensus on the optimal b-values to maximize the noise performance of ADC map. In this work, we determine the optimal b-values to maximize the noise performance of ADC mapping by using a Cramér-Rao Lower Bound (CRLB) approach under realistic noise assumptions. The strong agreement between the CRLB-based analysis, Monte-Carlo simulations, and ADC phantom experiment, suggests the utility of this approach to optimize DW-MRI acquisitions.

Jiancheng Zhuang

The diffusion weighted images acquired with the multiband sequence or the Lifespan protocols shows a type of slice distortion artifact. We find that this artifact is caused by the eddy currents, which can be induced by the diffusion gradient associated with either current DW image or the previous DW images. The artifact can be corrected by further tuning the compensation circuit in the MR hardware, or by a correction algorithm which includes the diffusion gradients from the current and previous DW images. 

Erpeng Dai, Xiaodong Ma, Zhe Zhang, Chun Yuan, Hua Guo

Interleaved EPI (iEPI) with a 2D navigator is an effective way to acquire high-resolution and less-distorted DWI. The inter-shot phase variations can be corrected with acquired 2D navigator. However, the performance is limited by the geometric distortion mismatch between the navigator-echo and image-echo. Parallel imaging can be used to reduce the navigator distortion, but can cause noise amplification. Previously, the effects of the navigator were studied with in vivo experiments, but the effects of distortion and noise were mixed together. In this study, the effects of navigator distortion and noise are studied individually with both DWI and DTI simulations.

Darryl McClymont, Irvin Teh, Hannah Whittington, Jürgen Schneider

Cardiac DTI is subject to long scan times and low SNR, which invariably leads to a trade-off between the number of averages and diffusion-encoding directions to acquire. However, the exact relationship between the diffusion tensor and these parameters is unclear. In this work we utilise DTI data from five high quality ex-vivo rat hearts, and vary the SNR between 2 and 97 and the number of directions between 7 and 61. Results show that the apparent diffusion coefficient is optimised for scan time when SNR is maximised and directions are minimised, whereas parametric angle measurements are time-optimised with more directions. At typical in-vivo settings, we estimate that fractional anisotropy is being overestimated by up to 20%, while the precision of sheetlet angles may be as poor as ±36 degrees.

Manoj Shrestha, Pavel Hok, Ulrike Nöth, Ralf Deichmann

Diffusion-weighted (DW) MRI with single-refocused spin-echo preparation suffers from eddy-current induced image distortions. In this study, a method for substantial reduction of eddy-current artifacts is proposed. Dummy scans comprising DW gradients prior to the acquisition of each multi-slice data volume yield a steady state of eddy-currents and thus comparable distortions across the volume which subsequently can be corrected via an advanced setting of the eddy-current correction FMRIB software library tool. In comparison to the commonly used twice-refocused spin-echo sequence for eddy-current compensation, the proposed method is less sensitive to radiofrequency inhomogeneities and offers higher signal-to-noise ratio due to shorter echo-time.  

Roger Grimm, Adam Froemming, Stephen Riederer

Diffusion images obtained with spin echo – echo planar imaging (SE-EPI) can be acquired quickly and efficiently. In prostate applications areas of susceptibility can cause image distortion. The purpose of this work is to address these distortions with the use of multi-shot EPI techniques. A previously defined term, pseudo-gradient, is shown to be a useful analytical tool to explain and guide in the choice of acquisition parameters. Phantom and in-vivo results show the benefits of multi-shot scans to reduce distortions.

Marco Lawrenz, Jürgen Finsterbusch

Double diffusion encoding (DDE) experiments with two weighting periods applied successively in the same acquisition are a promising tool to investigate microscopic tissue properties, e.g. the cell eccentricity and the related diffusion anisotropy on a microscopic scale. Recent experiments detected the signal pattern typical for microscopic diffusion anisotropy in human cortical gray matter in vivo but were hampered by an additional signal modulation that could be related to field inhomogeneities near the skull. In this study, cross-term-compensated DDE experiments are performed to investigate the effect of field inhomogeneities on the detection of the microscopic diffusion anisotropy.

Marcel Gratz, Harald Quick

A method is presented that extends the concept of calculated DWI for the generation of high tissue contrast from trace-weighted data. Using the whole range of b-values including the physically inaccessible negative b-values, image segmentation, visual hinting and ROI generation can be provided for assistance of the clinical readers. 24 patient data sets involving different pathologies were used to test the feasibility and clinical potentials of the new approach. It was found that the extrapolation to negative b-values helps to extract fluid regions, whereas internal structures of lesions and noise masking may be obtained with high b-values.

Elizabeth Hutchinson, Neda Sadeghi, Okan Irfanoglu, Mary Whitman, Michelle Delisle, Elizabeth Engle, Carlo Pierpaoli

Brain volume registration using diffusion tensor information faithfully matches anatomic features that are not accessible to structural registration algorithms such as white matter tracts.  Thus, inspection of the deformation fields from DT-based registration using TBM (D-TBM) is advantageous for revealing local morphometric differences when compared with conventional TBM.  In this study, D-TBM was used to evaluate morphometric differences and heterogeneity of abnormalities in a mouse model of dysgenesis.

Jingjing Jiang, Wenzhen Zhu

Stretched-exponential diffusion weighted imaging (SEM-DWI) provided a more accurate estimate than conventional DWI in grading gliomas. Moreover, SEM-DWI derived α value could effectively differentiate EGFR negative and positive group and had a significantly negative correlation with EGFR expression . Therefore, it was concluded that SEM-DWI might be applied as an effective imaging biomarker in grading gliomas and predicting of EGFR status and thus in guiding individual treatment and targeted therapy.

Yan Tan, Hui Zhang, Xiaochun Wang, Dandan Zheng

Ultral-High-b-value DWI (UHBV-DWI) was shown to improve the diagnostic performance of DWI in grading gliomas. We compare the value of MRI UHBV-DWI and conventional DWI for grading astrocytomas, and to analyze the correlation of respective parameters with aquaporin (AQP) expression. We found UHBV-ADC (0.810) showed a larger area under the curve (AUC) than that of ADC (0.713) (P < 0.05). The ADC value showed a negative correlation with AQP4 mRNA expression (r = -0.357; P = 0.024). UHBV-ADC value positively correlated with the AQP4 mRNA expression (r = 0.646; P < 0.01). So UHBV-DWI allowed for a more accurate grading of cerebral astrocytoma as compared to DWI. UHBV-ADC may be related with the AQP4 mRNA levels.

Yuxi Pang, Dariya Malyarenko, Michael Schar, Lisa Wilmes, David Newitt, Michael Jacobs, Thomas Chenevert

To eliminate technical variability in quantitative diffusion imaging applications, the systematic bias in diffusion weighting gradients should be corrected. The major source of this bias is the system-specific spatial gradient non-linearity (GNL) that can be rectified using gradient design information independent of the scanned object. This study characterizes the residual sources of nonuniform diffusion weighting introduced by imperfect object-dependent B0 shimming. Using controlled de-shim gradients, we show that an imperfect shim leads to systematic offsets of the otherwise symmetric GNL profile relative to the isocenter. The empiric strategies are proposed to mitigate the shim-induced errors in ADC measurements.

Gergely David, Patrick Freund, Siawoosh Mohammadi

In this manuscript, we investigate how application of established post-processing methods (spatial registration and robust tensor fitting) and of a newly introduced outlier rejection technique referred to as reliability masking influence the statistical power of a clinical spinal cord DTI study. The assessment was performed using a previously published clinical dataset investigating microstructural correlates of spinal degeneration in cervical spondylotic myelopathy (CSM). We found that the established post-processing methods had almost no influence on the statistical power by which the microstructural differences is observed, whereas reliability masking increased the statistical power by more than 13%.

Barbara Wichtmann, Aapo Nummenmaa, Qiuyun Fan, Thomas Witzel, Elizabeth Gerstner, Alexandra Golby, Sandro Santagata, Bruce Rosen, Lothar Schad, Lawrence Wald, Susie Huang

Linear Multi-scale Modeling (LMM) of diffusion MRI data is a recently developed DWI analysis technique for separating orientation distributions of restricted and hindered diffusion water compartments over a range of length scales, thereby allowing more detailed characterization of tissue microstructure. Here, we apply the LMM framework to characterize a low-grade oligodendroglioma prior to resection. We use the distinct microstructural signature of the tumor to delineate tumor extent and use results from pathology and numerical simulations to refine our understanding of the tumor microstructure.

Hong-Hsi Lee, Els Fieremans, Dmitry Novikov

We explore axial diffusivity dependence on both diffusion time and gradient pulse width in major white matter tracts. This allows us to differentiate between two possible arrangements of restrictions (e.g. beads) along fibers: (1) short-range disorder, or (2) “hyperuniform” disorder (arrangement qualitatively closer to periodic). Unexpectedly, model prediction for hyperuniform disorder is more consistent with our data than for short-range disorder. If conformed histologically in human or animal studies, this would mean that restrictions along axons are not “purely” randomly distributed but rather spatially correlated − perhaps, for optimizing physiological constraints.

Min Tang, Wei Di, Xin Zhang, Jie Gao, Kaining Shi, Xiaohong Wu, Xiaoling Zhang

To observe the microstructural longitudinal alterations in neural tissues after ischemic stroke and assess the correlation with clinical outcome and NODDI metrics. 18 subjects were enrolled. Intra-cellular volume fraction(Vic) and orientation dispersion index(OD) exhibited positive correlations with NIHSS scores of patients at day 30. The correlation of the susceptibility with the NODDI metrics and prognosis is higher than the ADC values with it. NODDI may provide a more promising and reliable methods for microstructural reorganization follow-up stroke than other measures previously used in studies of stroke recovery. 

wentao wang, LI Yang, Xixing HU, Robert Grimm, caixia Fu, XU Yan, mengsu zeng, shengxiang rao

Diffusion Kurtosis Imaging (DKI) maps, preoperative radiological features and clinical-pathologic findings were calculated to assess their diagnostic accuracy for microvascular invasion (MVI) of hepatocellular carcinoma (HCC) in patients who were undergoing curative liver resection. Multivariate regression analysis was performed to identify independent predictive factors for MVI. The study shows that Mean Kurtosis (MK), non-smooth margin, peritumoral enhancement and incomplete radiological capsule suggest a high probability of microvessel invasion of HCC. Multivariate analysis confirmed that MK and capsule integrity show statistical significance correlation with MVI. In conclusion, MK and capsule appearance might be the predictors for MVI of primary hepatocellular carcinoma.

Ashley Stokes, Jack Skinner, Laura Bell, Adrienne Dula, Thomas Yankeelov, C. Quarles

The purpose of this study is to investigate the influence of post-processing method on the reproducibility of brain diffusion metrics, including apparent diffusion coefficients (ADCs) and intra-voxel incoherent motion (IVIM) parameters, in healthy controls and to apply these results in a cohort of brain tumor patients undergoing treatment. ADC was highly reproducible for all methods. The IVIM diffusion and perfusion fraction showed the highest reproducibility using constrained fitting, while IVIM pseudo-diffusion showed limited reproducibility. By establishing limits of repeatability for ADC and IVIM metrics, these methods can be applied in neuropathology to determine significant changes related to treatment effects. 

Alexandru Avram, Elizabeth Hutchinson, Peter Basser

We compute the higher-order statistics of the 3D spin displacement probability distributions measured with mean apparent propagator (MAP) MRI and quantify microstructural tissue parameters such as the mean kurtosis (MK), axial kurtosis (K_?), radial kurtosis (K_⊥) and kurtosis fractional anisotropy (FA_K). This extension of the family of MAP tissue parameters provides a direct link between the frameworks of MAP MRI and other advanced diffusion techniques facilitating interpretation of findings in clinical MAP MRI studies in the context of existing literature on advanced diffusion MRI applications.

Tom Dela Haije, Andrea Fuster, Luc Florack

In this work we introduce the barrier orientation distribution function (ODF) as an alternative to the fiber ODF that can be computed with constrained spherical deconvolution. The barrier ODF is computed directly from the data, without the need to e.g. specify a single fiber response function.

Jian Cheng, Peter Basser

In this abstract, inspired by microscopic theoretical treatment of phases in liquid crystals¹, we introduce a novel mathematical framework, called Director Field Analysis (DFA), to study local geometric structural information of white matter. DFA extracts some meaningful scalar indices related with the degree of orientational alignment, dispersion, and orientational distortion, from the Orientation Distribution Function (ODF) field reconstructed by Diffusion Tensor Imaging (DTI) or High Angular Resolution Diffusion Imaging (HARDI).

Maryam Afzali, Hu Cheng, Sharlene Newman

Many denoising techniques have been proposed in an attempt to remedy the low signal-to-noise ratio (SNR) of diffusion weighted images (DWI) [1-3], especially with high b values. It was shown that denoising might benefit DWI data processing such as fiber tracking [4]. However, denoising is not widely accepted as a mandatory step in the preprocessing of DWI data due to little well documented study about the effect of denoising. In this work, we tested if denoising can overcome the low SNR in tensor based diffusion analysis and fiber tracking. 

Amritha Nayak, Neda Sadeghi, M Irfanoglu, Carlo Pierpaoli

During postnatal brain development brain structures undergo large changes in size, shape, composition and microstructural appearance. Diffusion tensor imaging (DTI) is an MRI modality particularly informative on white matter. We perform tensor based morphometry (TBM) using deformation fields constructed using all scalar and directional information provided by diffusion tensor data (DTBM) to measure volumetric changes of brain structures from neonate to adulthood. Our results indicate that DTBM reveals interesting patterns in the developmental trajectories for different structures in the human brain. This information would be important to characterize deviation from normal developmental patterns due to developmental delay or other disorders.

Marina Rakic, Luis Lacerda, Ahmad Beyh, Pedro Luque-Laguna, Rachel Barrett, Francisco De Santiago Requejo, Steven Williams, Gareth Barker, Fernando Zelaya, Flavio Dell'Acqua

A well-known dilemma in DW-MRI acquisitions is to determine the extent to which signal-to-noise ratio (SNR) can be can be sacrificed in favour of higher spatial resolution on one hand, and in favour of shorter acquisition time on the other. In this study we quantify the reproducibility of spherical deconvolution results at 3 spatial resolutions with and without denoising, as it is still unclear how denoising methods6 affect the uncertainty in subsequent diffusion model fitting and whether it introduces or improves bias in modelled fibre direction.

Henrik Jensen, Francois Lauze, Mads Nielsen, Sune Darkner

We present a non-rigid registration method for Diffusion-Weighted MRI which uses a density and scale space approach to estimate image similarity. It allows us to employ smooth intensity-invariant similarity measures, such as Mutual Information (MI), in contrast to the model-driven registrations. Using the inherent microstructure of High Angular Resolution Diffusion Imaging (HARDI) scans, we obtain a less regularized and more flexible registration that can be used on either raw diffusion signals or reconstructions of the fiber orientations. We show some promising results on Human Connectome Project (HCP) subjects and an artificial example.

Yadi Li, Haibo Dong, Feng Li, Gaoyan Wang, Nadan Zhao, Yong Zhang, Wenhua Zhou

No previous in vivo studies have investigated drug-related changes of microstructural integrity of amygdala-hippocampus-nucleus accumbens circuit using diffusion tensor imaging. This study demonstrated reduced microstructural integrity of this circuit in methamphetamine users by applying automated and semi-automated segmentation techniques to acquire regions of interest. The microstructural impairment of hippocampal subiculum and basolateral amygdala might be implicated in the development of anxiety and psychosis. Enhanced anatomical connectivity between left BLA and bilateral NAc may underlie the relapse of MA intake and production of psychosis.

Samira Bouyagoub, Charlotte Clarke, Nicholas Dowell, Tobias Wood, Hui Zhang, Mara Cercignani

NODDI is a popular diffusion MRI technique that estimates indices about tissue microstructure. However it makes a priori assumptions, particularly fixing intrinsic diffusivity (DI) to be the same throughout the brain. We aim to validate this assumption by combining NODDI with mcDESPOT, which enables an independent estimation of the CSF volume fraction. By doing this, we enable NODDI to estimate voxel-wise maps of DI as well as of the perpendicular diffusivity by removing the tortuosity constraint. Our estimated DI maps show that the assumed value is more suitable for white matter than gray matter and resulted in sharper contrast in neurite density maps but noisier orientation dispersion (ODI) maps. Removing the tortuosity assumption restored the ODI but degraded the quality of the neurite density map.

Ben Hipwell, Tom Roberts, Paul Sweeney, Angela D'Esposito, Morium Ali, Eleftheria Panagiotaki, Mark Lythgoe, Daniel Alexander, Rebecca Shipley, Simon Walker-Samuel

We report the development of a novel in-silico modelling framework for probing the in-vivo diffusion MRI signal in tumours, based on high-resolution (5-10µm) optical imaging data from complete tumours. Blood flow in tissue substrates was estimated using fluid dynamical modelling. We then simulated the MRI signal using a Monte Carlo approach, and fitted the VERDICT model. VERDICT has previously been proposed as a method to noninvasively quantify histological features of tissue, including intracellular, extracellular and vascular volume fractions, cell radius and blood flow. We report preliminary findings of a good correspondence between the ground truth and measured values.

Chuanzhu Sun, Lijun Bai, Hao Yan, Shan Wang, Xiaocui Wang

More than 75% of traumatic brain injuries (TBI) seeking medical attention are mild, and the outcome of mild TBI (mTBI) is heterogeneous. Currently we are in badly need of the methods of classifying mTBI into more homogeneous subgroups since there is not a sensitive and valid biomarker identified right now. In current study, we aim to investigate whether different subgroups exist in a large cohort patients and to predict neuropsychological outcome in the future.

Yi-Cen Ting , Chou-Ming Cheng, Tzu-Chen Yeh

In this work, primary tumors of the central nervous system, including glioma and meningiomas, were studied with NODDDI.   The parameters derived from NODDI was examined to differentiate peritumoral edema and characterize complex structural abnormalities using diffusion MRI (dMRI) of a clinical MRI scanners. As a result, a better understanding of this perplexity with the aid of modern imaging is clearly necessary to define the blurred tumor margins and confront the recurrences in long-term treatment.

yuanqiang zhu, lin liu, tian dai, ziliang xu, yibin xi, hong yin, wei qin

ract-based spatial statistical analyses was used to investigate whether the individual differences in cognitive instability after SD was related to differences in WM structure. Resistant group exhibited significantly higher FA than vulnerable group, significant negative correlations were found between numbers of psychomotor vigilance task(PVT)lapses and FA in multiple regions. Our results also showed that 63% of individual variability in PVT lapse may be explained by variations in FA within superior longitudinal fasciculus and splenium of the corpus callosum. These findings suggested that cognitive instability after SD is closely associated with individual differences in WM integrity.

Delphine Estournet, Justine Beaujoin, Fabrice Poupon, Achille Teillac, Jean-François Mangin, Cyril Poupon

In this work, we demonstrate that Monte-Carlo simulations combined with fingerprint approaches can be used to develop decoding tools of the micro-structure using a dictionary learning approach. The validation has been done on a test object mimicking the mid-sagittal plane of a corpus callosum with axon diameters varying according to histological studies. The robustness of the decoding obviously depends on the richness of the dictionary, but, contrary to analytical approaches with highly non linear equations hard to fit practically, such MC approach do not have this kind of limitation, thus opening the way to decode more complex tissue cellular configurations.

Darya Morozov, Debbie Anaby, Inbar Seroussi, Nir Sochen, Yoram Cohen

Various diffusion MRI approaches were suggested to study the complex water diffusion in neuronal tissues and gleaning microstructural information thereof. Nevertheless, to date, only few attempts were done to correlate between the microstructural features obtained from single diffusion encoding (SDE) and double diffusion encoding (DDE) MRI experiments. The main objective of the present study is to compare between the microstructural information obtained from both diffusion MRI methodologies, under similar experimental conditions, when performed on a fixed porcine spinal cord.

Siawoosh Mohammadi, Isabel Ellerbrock, Luke Edwards

Different MRI biomarkers for fiber and myelin density have been proposed for MR g-ratio mapping, leaving open the question which biomarker is optimal. Here, we compare four different MRI biomarkers for fiber density using standard Stejeskal-Tanner diffusion encoding to the microscopic diffusion anisotropy (MA) measured by double-diffusion encoding. Thereby, we hypothesize that a better measure of the microscopic environment shows higher (and more significant) correlations to the MA metric. Our preliminary results showed that the marker by Kaden et al. (2016) shows higher correlation to MA than NODDI, suggesting it to be a better biomarker for fiber density.

Santiago Coelho, Leandro Beltrachini, Jose Pozo, Alejandro Frangi

Biophysical tissue models are a solid tool for obtaining specific biomarkers with diffusion MRI. However, the assumptions they rely on are sometimes inaccurate and may lead to erroneous results. Some limitations of the Neurite Orientation Dispersion and Density Imaging (NODDI) model are tackled by NODDIDA (NODDI with Diffusivities Added), at the cost of an extended acquisition protocol. Here we adapt NODDIDA to a Double Diffusion Encoding scheme to improve the parameter estimation for reduced acquisition protocols. We demonstrate through in silico experiments that under similar experimental conditions, this novel approach increases both the accuracy and precision of the parameter estimates.

Dan Wu, Hanbing Lu, Yihong Yang, Jiangyang Zhang

Synopsis: Diffusion functional MRI (DfMRI) has been proposed to detect neuronal activations more directly than BOLD-fMRI, but its sensitivity to cell swelling associated with neuronal activities remains less known. Numerical simulations suggest that oscillating gradient spin echo (OGSE) diffusion MRI is more sensitive to changes in cell size than conventional pulsed gradient spin echo (PGSE) diffusion MRI. In adult rat brain DfMRI experiments with forepaw stimulation, ADC measured by OGSE showed significant reductions during stimulation, and the reductions were significantly larger than those measured by PGSE, suggesting OGSE may be more sensitive to cell swelling associated with neuronal activation than PGSE.

Marco Lawrenz, Jürgen Finsterbusch

Double diffusion encoding experiments with two weighting periods applied successively offer access to microscopic tissue properties and can provide information complementary to diffusion tensor imaging. The MA index derived from such measurements with long mixing times, depends on the cell eccentricities, i.e. the microscopic diffusion anisotropy, and can be determined in the human brain. However, its derivation is based on ideal timing parameters, infinitely short gradient pulses and long diffusion and mixing times that cannot be gained in practice. In this study, the effect of realistic timing parameters on the MA of restricted diffusion is investigated with Monte Carlo simulations.

Gaetan Duchene, Frank Peeters, Jorge Abarca-Quinones, Thierry Duprez

Recently, Double Diffusion Encoding (DDE) has been proposed for quantification of pore size distributions in a voxel or a Region Of Interest. Although the technique has been validated on animals with experimental MR systems, its translation to human scanners is challenging, mainly because of the limited gradient strength available on clinical systems. In this work, we present a validation of DDE on a clinical scanner on a biological phantom (asparagus). Furthermore, we restricted the acquisition time to 16 minutes which remains acceptable in clinical conditions.   

Muhamed Barakovic, David Romascano, Gabriel Girard, Maxime Descoteaux, Jean-Philippe Thiran, Alessandro Daducci

Over the last decade microstructure imaging has become commonly endorsed to estimate quantitative features of neuronal tissue. However, those techniques estimate the microstructure only locally. Microstructure informed tractography was recently proposed to bolster microstructure estimates by accounting for the structure of the white matter bundles. The purpose of this study was to extend this novel technique for evaluating bundle-specific axon diameter distributions and investigate bundle-specific properties in the human brain. The experiment was performed on the MGH adult HCP dataset. The findings suggest potential application in the estimation of the axon diameter distribution along white matter bundles in whole-brain tractograms.

Kerstin Demberg, Frederik Laun, Peter Bachert, Dieter Höpfel, Tristan Kuder

Diffusion pore imaging enables the detection of the average shape of arbitrary closed pores in an imaging volume element. Until now, an experimentally challenging phase measurement, either by measuring with a long-narrow gradient profile or by employing double diffusion encodings, was a prerequisite to obtain the full information on the Fourier transform of the pore image. In this study, we present a first experiment, where the phase information is recovered alone from the magnitude information acquired by q-space imaging. To solve this phase problem, we adopted a phase retrieval algorithm that is widely applied to X-ray diffraction data.

Kevin GINSBURGER, Jean-François MANGIN, Cyril POUPON

In this work, we used the extended Multiple Correlation Function (MCF) method to derive analytical expressions of the NMR signal in multilayered cylinder geometries for an arbitrary direction of the magnetic field gradient. Each layer of the cylinder is characterized by a diffusion coefficient and a relaxation time and each boundary between adjacent layers is characterized by a value of permeability in order to allow the modeling of the multilayered structure of axons surrounded by its myelin sheat.

Luis Lacerda, Gareth Barker, Flavio Dell'Acqua

Despite the abundance of models to describe the diffusion propagator, its usefulness has not yet been explored in a clinical/clinical research setting. In this study, we have compared global diffusion propagator imaging metrics to recently described measures of anisotropy and probability profiles at different displacement scales to characterise microstructure. Moreover, we have shown that these metrics offer complementary information to the ones currently established. Finally we have also acquired a "Reference Dataset" with several different diffusion weightings and demonstrated that by choosing the right combination, accurate reconstruction of both types of metrics is possible for clinically acceptable scan times. 

Ting Gong, Mu Lin, Hongjian He, Qiuping Ding, Jianhui Zhong

Diffusional kurtosis imaging (DKI) is a significant extension of diffusion tensor imaging, providing sensitive biomarkers to diseases at the cost of lengthy acquisition and post-processing time. Fast DKI method operating with kurtosis tensor and based on axially symmetric approximation was then proposed to overcome the disadvantage. To explore the clinical utility of fast DKI, a Monte Calo simulation was conducted on a tissue model to validate the sensitivity of fast kurtosis measurements to four microstructural changes. The results suggest that fast DKI method is reliable with reduced scan time but considerable sensitivity to microstructural Changes frequently occurred in neurological diseases.

Giorgia Grisot, Joseph Mandeville, Anastasia Yendiki

The time constraints of in vivo diffusion MRI require a compromise to be made between spatial and angular resolution. Given the lack of ground truth on the configuration of human brain connections, determining the optimal operating point along this trade-off is still an open problem. We use high-SNR ex vivo human data at microscopic resolution to study the effect of spatial and angular resolution on dMRI tractography accuracy. Our findings show that voxel size has a much more dramatic effect on tractography reconstruction of challenging white matter configurations than the number of gradient directions.

Takuya Aoike, Noriyuki Fujima, Masami Yoneyama, Suzuko Aoike, Hiroyuki Sugimori, Kinya Ishizaka, Kohsuke Kudo

The purpose of this study was to assess the variation of T2 values by T2 map with the pre-pulse of diffusion gradient (=DW-T2 map). T2 value of GM was gradually decreased as b-value increased. From this result, water diffusivity based selective removal of tissue component such as perfusion fraction or extracellular extravascular space can be obtained using DW-T2 map technique. This technique can reveal the more detain in the human brain tissue characteristics.

Thomas Roberts, Harpreet Hyare, Ben Hipwell, Andrada Ianus, James Breen-Norris, Eleftheria Panagiotaki, David Atkinson, Shonit Punwani, Jeremy Rees, Sebastian Brandner, Daniel Alexander, Simon Walker-Samuel

VERDICT (Vascular, Extracellular, and Restricted Diffusion for Cytometry in Tumours) MRI is a diffusion imaging technique which has shown promise in revealing information about tumour microstructure beyond ADC measures and structural imaging. We report the first application of VERDICT to human brain tumours. In this feasibility study, we characterise a mixed group of brain tumours using VERDICT, which includes a range of both low and high-grade gliomas; compare the VERDICT parameter maps with ADC maps, post-contrast T1w images and histological grading; and examine the repeatability of the technique.

Nicolas Kunz, Stéphane Sizonenko, Rolf Gruetter, Petra Hüppi, Yohan van de Looij

Diffusion tensor imaging (DTI) has been widely used to study rodent brain development. Nevertheless, the parameters derived from DTI are sensitive to, but non-specific to, the tissue’s microstructure. Recently, NODDI (neurite orientation dispersion and density imaging) has been proposed. We aimed to estimate the real input of NODDI derived parameters in rodent brain development. ODI appears more accurate and specific to reflect GM (increase with dendritic arborization) and WM (decrease with myelination) development than FA and could be a very important parameter in the assessment of perinatal brain injuries. Conclusion about the other NODDI estimates requires further experiments.

Samira Bouyagoub, Nicholas Dowell, Charlotte Clarke, Tobias Wood, Hui Zhang, Mara Cercignani

There is an increasing demand for specific tissue microstructure markers that can be related to demyelination and axonal loss. Quantitative MRI techniques are sensitive to microscopic changes but tend to be non-specific. We propose to combine NODDI, a popular MRI diffusion technique, with mcDESPOT, a multi-component relaxation analysis technique, to obtain separate estimates of the volumes of myelin, extra-cellular and intra-cellular spaces. This multimodal MR approach opens the possibility to disentangle changes to myelination and axonal density with the exciting prospect of achieving in vivo histology.

Gabriel Varela-Mattatall, Alexandra Tobisch, Rüdiger Stirnberg, Steren Chabert, Tony Stöcker, Cristian Tejos, Pablo Irarrazaval

Measuring non-Gaussianity in the diffusion signal has revealed new possibilities for discovering new biomarkers for clinical applications. Therefore, it results desirable to incorporate and quantify the non-Gaussian trait of the diffusion propagator in Diffusion Spectrum Imaging. Unfortunately, the established index known as Kurtosis is sensitive to noise, making it unfeasible to obtain from the noisier, but higher resolution propagator. In this work, we propose an alternative index known as Negentropy. We demonstrate from noisy simulations and in-vivo DSI data the robustness of the Negentropy index against Kurtosis.

Susie Huang, Thomas Witzel, Qiuyun Fan, Barbara Wichtmann, Aapo Nummenmaa, Lawrence Wald, Eric Klawiter

In this work, we apply the TractCaliber approach to a group of healthy subjects and show that distinct tract-specific estimates of axon diameter may be obtained in different white matter tracts in the normal human brain. Larger diameter axons are consistently estimated in the corticospinal tracts and are shown to be distinct from those in the cingulum, an adjacent and orthogonal white matter tract. The development of robust tract-specific axon diameter-weighted maps may be useful for refining existing tractography algorithms.

Francesco Grussu, Marco Battiston, Ferran Prados, Torben Schneider, Enrico Kaden, Sébastien Ourselin, Rebecca Samson, Daniel Alexander, Claudia Gandini Wheeler-Kingshott

Multimodal imaging is very promising for characterising brain microstructure in vivo, but it is usually performed employing a variety of signal readouts, which disrupts the spatial correspondence of the multimodal features. Here we demonstrate a multimodal imaging protocol for detailed characterisation of brain microstructure with unified single-shot EPI readout. Our aim is to provide macromolecular volume via inversion recovery spin echo, neurite morphology via diffusion imaging in close spatial alignment and thus to combine those for estimating myelin g-ratio. We show that our protocol enables the evaluation of parametric maps with high reproducibility that capture biological differences among healthy subjects. 

Shin Tai Chong, Hung-Wen Kao, Chien-Yuan Lin, Chiao-Chi Chen, Ching-Po Lin, Chen Chang

We hypothesized that the model-based diffusion model, Neurite Orientation Dispersion and Density Imaging (NODDI), could help probing microstructures of brain tumos in different types and gradings. The model perfomed better than a conventional diffusion model in differetiating meningiomas and gliomas in different grades while the two models showed significant differences of the diffusion indices between meningiomas and gliomas. In the NODDI analysis, both VF_ic and VF_ec show great potential to probe the cellularity of brain tumors.

Dylan Henssen, Jeroen Mollink, Erkan Kurt, Jules Janssen Daalen, Robert van Dongen, Ronald Bartels, Tamas Kozicz, Anne-Marie van Cappellen van Walsum

To optimize neuromodulation therapy of orofacial pain, a more profound insight in the trigeminal pathways in the human brainstem is of crucial importance. Using ex-vivo, 11.7T magnetic resonance imaging, polarized light microscopy and myelin staining methods, both the ventral and dorsal trigeminothalamic tracts can be visualized in humans. The combination of these visualization techniques strengthens the validity of these findings although the number of specimens forms a limitation. Future research must show whether these results are reproducible in more human brains and whether the described tracts could lead to new neuromodulation targets for the treatment of orofacial pain.

David Romascano, Muhamed Barakovic, Anna Auría, Tim Dyrby, Jean-Philippe Thiran, Alessandro Daducci

Axon diameter distributions (ADDs) change during brain development and are altered in several brain pathologies. Mapping ADDs non-invasively using dMRI could provide a useful biomarker, but existing methods are either parametric, orientation-dependent, summarize the whole ADD as a single measure or use non-standard protocols. We propose to estimate the ADD from an orientation-invariant PGSE protocol optimized for axon diameter sensitivity, using a discrete linear model with smoothness and sparsity regularization. To our knowledge, we are the first to show that PGSE sequences can be used to extract orientationally invariant and non-parametric ADD estimates.

Joao Periquito, Katharina Paul, Till Huelnhagen, Yiyi Ji, Min-Chi Ku, Kathleen Cantow, Erdmann Seeliger, Bert Flemming, Dirk Grosenick, Andreas Pohlmann, Thoralf Niendorf

T₂^* mapping does not fully represent renal tissue oxygenation. Diffusion-weighted imaging (DWI) can provide information about confounding factors, which can be used to correct T₂^*. The most widely used DWI technique SE-EPI is sensitive to magnetic field inhomogeneities and hence prone to geometric distortions. In this work we propose a diffusion-weighted Rapid Acquisition Refocusing Enhancement (RARE) variant for DWI of the rat kidney free of geometric distortions. Phantom experiments validated the diffusion weighting implementation in the common RARE sequence. Ex-vivo and in-vivo experiments using diffusion-weighted RARE showed no geometric distortions at 9.4 Tesla.

Fang Dong, Shi Cheng

Cardiac diffusion tensor imaging is an effective way to depict the fiber structure of the myocardium. A navigator(NAV)-based stimulated-echo (STEAM) method was proposed by Nielles-Vallespin to obtain cDTI in vivo. However, its use of a biofeedback process where the subjects had to adapt their breathing pattern in real-time can hinder its clinical implementation. In this abstract, we optimized the NAV accept/reject algorithm, using which the scanning efficiency and the image SNR were both largely improved. Therefore, our work laid a great foundation for the clinical use of free breathing cDTI in the future.

Jie Zhu, Ying Li, Jie Luo, Dan Zheng, Min Chen

Identification of subtypes and pathological grades of renal cell carcinoma (RCC) prior to treatment has clinical significance in determining a treatment strategy and evaluating prognosis. In our research, we detected microstructural differences of RCC by using diffusion kurtosis imaging (DKI). The results showed that DKI had good inter- and intra-observer reproducibility of RCC as a new reliable noninvasive biomarker. Kurtosis metrics showed statistical differences between RCC and contralateral renal parenchyma, among the subtypes of RCC, and between low- and high- grade clear cell RCCs. Thus, DKI has the potential application in depicting the microstructural characteristics of RCC.

Dattesh Shanbhag, Tetsuya Wakayama, Reem Bedair, Andrew Patterson, Fiona Gilbert, Rakesh Mullick, Martin Graves

IVIM-DWI data can be potentially corrupted by eddy currents, susceptibility artifacts, motion and image reconstruction methods.  We hypothesized that artifacts in IVIM imaging could be separated from true diffusion decay using an independent component analysis (ICA) methodology. In this work , we demonstrate that with ICA based filtering of raw IVIM data, transients in IVIM data are removed, with consequent improvement in IVIM model fit quality and reduction in saturated values in pseudo-diffusion D*maps. This should therefore improve confidence in interpreting IVIM parametric maps in clinical practice.

Bart Philips, Katharina Paul, Thoralf Niendorf, Tom Scheenen

Diffusion weighted imaging is an important modality in assessing and detecting prostate cancer, but often suffers from distortion artifact introduced by the EPI readout. We propose a TSE-BLADE split-echo sequence that has the potential for obtaining non-distorted diffusion weighted imaging of the prostate, while obtaining accurate ADC estimations. It is shown to be robust to motion and phase induced artifacts that pester multi-shot diffusion weighted imaging, in phantom measurements and initial patient results.

Qingsong Yang, Ze-Zhong Ye, Joshua Lin, Peng Sun, Chunyu Song, Yasheng Zhu, Jianping Lu, Sheng-Kwei Song

Due to the overlapping apparent diffusion coefficient of prostate cancer (PCa), inflammation, and benign prostatic hyperplasia (BPH), mpMRI commonly results in false-positive PCa diagnosis. Based on the histology of whole mount section from prostatectomy, heterogeneous pathologies was clearly seen in the mpMRI-defined cancer region. Our recently-developed diffusion MRI histology (D-Histo) approach successfully differentiated and quantified PCa, inflammation and BPH. We report mpMRI and D-Histo results on 178 PCa-suspicious patients to demonstrate the causes of mpMRI false-positive PCa diagnosis.

Alan Penn, Barry Reich, Etta Pisano, Vandana Dialani, Elodia Cole, David Brousseau, Milica Medved, Gregory Karczmar, Guimin Gao, Hiroyuki Abe

We describe a new methodology for discriminating benign from malignant breast lesions on DWI for women with dense breasts and show that the new methodology results in statistically significant improvement over standard ADC methods.   The methodology uses computer models that can be constructed independently from the three directional DWI signals or from the trace signal.  Preliminary results show improved discrimination is obtained using the multi-directional models when compared to using the trace.  The methodology can be adapted for computer-aided-detection by tiling the image, independently marking each tile with areas of suspicion, and constructing a mosaic from the marked tiles.

Xiangde Min, Zhaoyan Feng, Liang Wang, Zhongping Zhang

We performed multi-b value diffusion-weighted imaging (DWI) to compare four phenomenological models (mono-exponential, bi-exponential, stretched exponential, and diffusion kurtosis imaging) with in vivo prostate cancer DWI data. A secondary aim is to compare results for different b-value ranges. The result showed that ADC derived from conventional mono-exponential model high b value (about 3200s/mm2) is an optional parameter for peripheral zone prostate cancer detection.

mi Yang, xiaodong Ji, Zhizheng Zhuo, shuang Xia

The diffusion weighted imaging has been widely used in clinical disease diagnosis, and the ADC value plays a key role in this progress. At present, the ADC values of normal organs and tissues have been reported, but few studies have been done on ADC values of normal bone marrow within different anatomical parts. In this study, the ADC values within different anatomical parts of bone marrow were measured and analyzed by using WB-DWI (whole body diffusion weighted imaging). And we furtherly evaluated the relationship of these ADC values with age and gender.

Jin Yamamura, Tony Schmidt, Axel Heinemann, Roland Fischer, Gerhard Adam, Sarah Keller

In this original study and the first of its kind, the characteristic postmortem time course of liver ADC values were assessed over 24h after death. This results could be important as potential marker for tissue quality in liver transplantation. With the knowledge of the ex vivo data, DWI may be added to the MRI methods for a virtual autopsy. 

Wengjing Chen, Juan Zhang, Dan Long, Zhenchang Wang, Jianming Zhu

The purpose was to use intra-voxel incoherent motion (IVIM) measurement in DWI to distinguish benign from malignant breast tissues. IVIM-derived parameter maps D, f, and D* were computed using segmented fitting method with proper threshold b-value. The region of interests were avoided the area of calcification. With pathological diagnosis as the gold standard, receiver operating characteristic (ROC) curves for three parameters and f × D* reflect that the area under the curve (AUC) of D and f × D* are 0.862 and 0.726, respectively. It suggested that these two parameters have high significance for the diagnosis of breast cancer lesions. 

Ferdinand Seith, Jana Taron, Christina Pfannenberg, Konstantin Nikolaou, Christina Schraml, Petros Martirosian

Simultaneous multislice diffusion weighted imaging (SMS-DWI) is a promising technique to shorten scan time in MRI. Aim of our study was to compare the diagnostic performance of SMS-DWI to conventional DWI for multiparametric whole-body examinations of oncologic patients in PET/MRI. We performed an evaluation in three steps: First in a phantom study, second in a volunteer study and third in a patient study with 20 oncologic patients. We found that SMS-DWI led to a significant reduction of scan time and, although suffering from slightly impaired image quality, provided reliable ADC values and lesion conspicuity of PET positive lesions.

Qungang Shan, Jingbiao Chen, Ronghua Yan, Yao Zhang, Hao Yang, Xin Li, Zhongping Zhang, Yunhong Shu, Churong Lin, Tianhui Zhang, Bingjun He, Zhuang Kang, Xi Long, Jin Wang

HCC is the second cause of cancer-related deaths and most HCC patients are accompanied with hepatitis B virus-related cirrhosis in China. Ki67 is a protein reflecting the proliferative activity of HCC and could be used as a predictor of prognosis. We assessed the value of the texture parameters in evaluating the expression of Ki67of HBV-related HCCs by whole tumor analysis. Our results showed that Dclusterprominence showed best diagnostic performance among all texture parameters. ADC and IVIM derived texture parameters might be used as useful and noninvasive biomarkers for evaluating the expression of Ki67 of HBV-related HCCs.

Roshan Karunamuni, Joshua Kuperman, Tyler Seibert, Natalie Schenker, Rebecca Rakow-Penner, Jose Teruel Antolin, Pal Erik Goa, David Karow, Anders Dale, Nathan White

This study explored the relationship between restriction spectrum imaging (RSI) and diffusion kurtosis imaging. Regions of interest for suspicious lesions and background tissue were identified in four patients with PIRADS 5 lesions. Kurtosis was estimated using either the signal fractions obtained from the RSI fit or the cumulant expansion for the NMR diffusion signal. A strong relationship was observed between RSI-derived restricted signal fraction and RSI-derived kurtosis. The performance of these two metrics was comparable in discriminating between suspicious lesions and background prostate tissue, and both outperformed the cumulant expansion approximation to kurtosis. 

Hiroshi Kusahara, Yuki Takai, Yoshimori Kassai

In this study is to adapt the short-TE cDWI (sTE-cDWI) technique, including the “Zero-TE”, validated previously in the brain⁴ to the abdominal region. The algorithm under evaluation allows computing diffusion images for arbitrary combinations of TE and b-value based on three acquisitions (3-points method). With this method we demonstrate it is possible to suppress T2 shine-through effects and as well as improve the signal-to-noise and contrast-to-noise ratios of tissues with short T2 and low ADC. The clinical benefits of the method and the preliminary results on volunteers are discussed.

Jakob Weiss, Petros Martirosian, Jana Taron, Ahmed Othman, Thomas Kuestner, Michael Erb, Jens Bedke, Fabian Bamberg, Konstantin Nikolaou, Mike Notohamiprodjo

Diffusion-weighted (DW) MRI of the prostate has increased the diagnostic accuracy for the detection of prostate cancer. However, acquisition time of DWI is still relatively long. Therefore, we evaluated the feasibility of simultaneous multi-slice (SMS) DWI for accelerated MRI of the prostate. Qualitative and quantitative image analyses in phantom, volunteer and patient measurements revealed similar image quality for DWI_SMS as compared to standard DWI sequences. Thus, DWI_SMS seems feasible for clinical routine in order to optimize patient throughput and economic efficiency, which is desirable, due to the recent implementation of prostate MRI into clinical guidelines and the expected increase in patient numbers.

Kaining Shi, Fengmao Chiu, Yunlong Yue, Lee Jiang, Lili Zuo, Yanfang Jin

To improve the stability of the nonlinear curve fitting of IVIM, the Fussy clustering technique (FCM) and data driven Bayesian approach are combined with IVIM in the imaging of thyroid tumors. Both FCM and Bayesian approach can improve the homogeneity of IVIM parameters. With limited sample size, FCM has similar diagnosis efficiency with conventional method using less calculation time, while Bayesian approach doesn’t increase the diagnosis efficiency.

Yanfen Cui, Xiaotang Yang , Yong Zhang

This retrospective study was to determine the diagnostic accuracy of apparent diffusion coefficient (ADC) values to assess the response to CRT in patient with local advanced rectal cancer by using histogram analysis derived from single-section (SS) and whole-tumor volume (WTV) regions of interest (ROIs). and found that  Post-CRT ADC histogram metrics yield greater accuracy in discrimination between good and poor responders, especially in improving the specificity, compared with the mean ADC values.   

Yoshihiko Fukukura, Yuichi Kumagae, Masanoari Nakajo, Kiyohisa Kamimura, Aya Umanodan, Takashi Iwanaga, Tomoyuki Okuaki, Takashi Yoshiura

This study focused on the feasibility of DKI for differentiating benign from malignant uterine lesions. The ADC and D of malignant tumor (MT) were significantly lower than those of endometrial hyperplasia (EH) (p=0.005 and 0.004), uterine fibroid (UF) (both, p<0.001), normal endometrium (NE) (both, p<0.001), and normal myometrium (NM) (both, p<0.001), which indicative of the increased cellularity within uterine malignant tumor that resulted in restricted water diffusion. K was significantly higher in MT than in EH (p=0.003), UF (p<0.001), NE (p<0.001), and NM (p<0.001), possibly representing complexity of tissue microstructure in MT compared to benign lesions. DKI enables differentiate benign from malignant uterine lesions.

Hiroki Hori, Toshio Yamaguchi, Hisashi Yoshihara, Youko Murakami, Yoshiyuki Konishi, Yoshihiro Muragaki, Jinichi Sasanuma, Kazuo Watanabe

The objective of this retrospective study is to evaluate the differences of the accuracy in endometrial adenocarcinoma using FOCUS DWI compared to that using conventional SS-EPI DWI. We calculated the accuracy by the interpretation of magnetic resonance (MR) imaging and the pathology. The accuracy in the FOCUS DWI was significantly better than that in the SS-EPI DWI. This may be due to the decrease of distortion in DWI, which induced the artifacts. There was improvement of the accuracy using the FOCUS DWI in the patient who had suspected endometrial adenocarcinoma.  

Zhaoyan Feng, Xu Yan, Xiangde Min, Liang Wang

We performed multi-b value and multi-TE diffusion imaging with two repetition on healthy human prostate to evaluate the influence of TE on reproducibility and quantification of IVIM diffusion model. The result showed that the Dstar and f parameters of IVIM model had high CVs and particularly high variability, while conventional ADC and D showed high reproducibility and a moderate TE-dependency in the peripheral zone and mild TE-dependency in the central zone. This work suggests that using diffusion parameters as quantitative biomarkers should consider the reproducibility and TE-dependency in clinical studies.

Jin Shang, Hui Zhang, Miaoling Li, Jian Yang, Rong Wang*

DWI has been proven to improve prostate cancer detection, and it reflects and measures the diffusion of water molecules within biological tissues due to thermal Brownian motion. However, to improve the significance of DWI, it is necessary to evaluate separately the two components of diffusion: the puremolecular diffusion and the perfusion-related diffusion originating from capillary microcirculation. IVIM-DWI, applying a bi-exponential fitting function, allows the extraction of pure molecular diffusion parameters (D) and perfusion-related diffusion parameters (D* and f). Therefore, the aim of this study is to further characterize and compare the biexponential nature of the diffusion related signal decay with multiple b-factors for PZ PCa and healthy PZ areas.

Xu Yan, Zan Ke, Minxiong Zhou, Caixia Fu, Xiangde Min, Liang Wang

This study compared a fast SE-EPI-based T2 mapping method with a conventional CPMG-based method. The SE-EPI method is based on multi-TE data and can be integrated into a diffusion sequence with very fast acquisition speed (around 30 s). The voxel-by-voxel and region of interest (ROI)-based comparisons were performed using two methods, which showed that their T2 maps have a strong correlation. In addition, the clinical validation showed that the T2 maps of the two methods have similar statistical significance and can be used to differentiate between prostate cancer (PCa) and benign prostatic hyperplasia (BPH). This work suggests that the SE-EPI-based method is a quick quantification method, and could be used or combined with diffusion and other quantification methods for multi-parametric analysis. In addition, it may also have potential applications in body regions which are susceptible to motion artifacts.

Sophie van Baalen, Bart Vroling, Martijn Froeling, Bennie ten Haken

To visualize the anisotropy of diffusion and pseudodiffusion, we have performed a two-tensor fit (D and D*) on IVIM data in healthy volunteers. We have performed tractography on both tensors and compared the results with tractography perfomed using a conventional DTI tensor fit. Tracking was possible using both D and the D* derived tensors and resulted in patterns similar to conventional tractography. We conclude that diffusion and pseudodiffusion both have an anisotropic component that can be visualized using tractography, which indicates that they both likely  contribute to the coherent diffusion anisotropy that is detected in conventional monoexponential DTI.

David Berry, Shangting You, John Warner, Lawrence Frank, Shaochen Chen, Samuel Ward

Diffusion tensor imaging has been proposed as a tool to non-invasively assess skeletal muscle microstructure, which would be of significant clinical value. However, its application to the assessment of changes in muscle microstructure associated with injury, pathology, or age remain poorly defined because it is difficult to precisely control muscle microstructural features in vivo. Recent advances in bottom up fabrication technologies allow precision-engineered diffusion phantoms with histology informed skeletal muscle geometry to be manufactured. Therefore, the goal of this study was to develop skeletal muscle phantoms at relevant size scales in order to relate microstructural features to MRI-based diffusion measurements.

Paul Baron, Dirk Poot, Piotr Wielopolski, Edwin Oei, Juan Hernandez-Tamames

Diffusion weighted STEAM with UTE readout is a promising acquisition method to measure diffusion in tissues with short T2 and T2*, such as tendons, ligaments and menisci. However, the accuracy of the ADC obtained with this method has not been studied before. Using experiments and Bloch simulations we show that the ADC can be biased, especially when a short TR is used, and that this bias depends on T1 and T2. Randomization of the diffusion gradient direction reduces the bias, providing clear suggestions to improve acquisition and/or post processing that reduces the ADC bias.

Damien McHugh, Fenglei Zhou, Penny Hubbard Cristinacce, Josephine Naish, Geoffrey Parker

This work investigates the stability of a water-based biomimetic tumour tissue phantom, and evaluates its potential as a tool for validating diffusion-weighted (DW) MRI measurements. As with biological tissue, and unlike most previous phantoms for tumour DW-MRI, the phantom’s apparent diffusion coefficient depends on diffusion time, with values stable over six months. DW-MRI-based estimates of microstructural parameters exhibited bias, possibly indicating limitations in the analysis model or acquisition scheme. It is envisaged that such phantoms will aid investigation of DW-MRI tumour microstructural models, and more generally will act as realistic test objects for comparing DW-MRI-derived biomarkers obtained from different scanners/sites.

Sudhir Pathak, Catherine Fissell, David Okonkwo, Walter Schneider

A novel Textile Anisotropic Brain Imaging Phantom incorporating textile hollow fibers (taxons with inner/outer diameter 12/34 micron) is used to validate diffusion MRI imaging (dMRI).  The taxon intra and extra spaces can be filled with water or deuterium.  A taxon crossing pattern and a packing density pattern is manufactured to test orientation and the amount of taxons. NODDI based Intra-cellular volume fraction is correlated with the amount of taxons (r2=0.96) as compared to FA which is poor predictor with r2=0.11. Fiber crossings are estimated using Constrained Spherical Deconvolution techniques and can be resolved for angles greater then 45 degrees.

Arush Honnedevasthana Arun, Shivaprasad Chikop, Nithin Vajuvalli, Rashmi Rao, Sairam Geethanath

Diffusion weighted MRI is used to measure diffusion properties in the brain. In this paper, the method for the creation of an anatomically and mechanically realistic brain phantom from polyvinyl alcohol cryogel (PVA-C) and a 3D printable brain phantom using Poly Lactic Acid (PLA) PLA is proposed. PVA-C is material widely used in medical imaging phantoms because of its mechanical similarities to soft tissues. This brain phantom will allow testing and optimization of diffusion based MR methods.

Vincent Lee, Ashok Panigrahy, Vincent Schmithorst, Thomas Chenevert, Borjan Gagoski, Deqiang Qiu, Peter LaViolette, Jeffrey Berman, Timothy Verstynen, Fang-Cheng Yeh

In this study we explore whether scanner-related-variabilities contribute to an individual’s distinct fingerprint – and whether the fingerprint specificity would be robust as a biomarker by scanning the same subject across multiple vendors and multiple scanner in four institutions. Both Diffusion Tensor Imaging and Multi-shell Multi-band diffusion imaging (MSMBDI) was tested, and differences within acquisition type (using fractional anisotropy and normalized quantitative anisotropy) and between acquisition types comparisons (using q-space diffeomorphic reconstruction) analysis were examined.  We found that scanner may contribute partly to the fingerprint patter, but the fingerprint was robust at maintaining pattern, especially in MSMBDI to warrant further studies.

Joshua Yung, Yao Ding, Ken-Pin Hwang, Carlos Cardenas, Hua Ai, Michael Boss, Thomas Chenevert, Clifton Fuller, R Stafford

The purpose of this study was to determine the quantitative variability of apparent diffusion coefficient values across a large fleet of MR systems. Using a NIST traceable magnetic resonance imaging diffusion phantom, imaging was reproducible and the measurements were quantitatively compared to known values. Significant differences in identical phantoms were not observed, but uncertainty in the measurements was seen at low apparent diffusion coefficient values. The same trend was observed when the diffusion phantoms were imaged in 20 different MR systems. The characterization of ADC variability for these systems provides an improved quality control for quantitative diffusion weighted imaging. 

Xiaopeng Zhou, Ken Sakaie, Josef Debbins, Robert Fox, Mark Lowe

SPRINT-MS is a large-scale longitudinal phase II trial including 27 3T MRI scanners to evaluate the treatment of progressive multiple sclerosis with Ibudilast.  DTI measures showed high reproducibility in a longitudinal multicenter study, making it appropriate for use as a biomarker. The longitudinal design of the SPRINT-MS trial is expected to mitigate the systematic influence of SNR on DTI, but the observed trend may be useful as a correction factor in cross-sectional studies.

Shir Levy, Darya Morozov, Inbar Seroussi, Leah Bar, Nir Sochen, Yoram Cohen

Numerous different models provide detailed microstructure information from diffusion MRI data. In order to challenge them, there is a need for complex phantoms with known structural characteristics. For this purpose, we present a novel phantom, consists of spherical fixed yeast cells and cylindrical microcapillaries. Despite of its complexity, arising from the different size, geometry and size distribution of the restricted compartments, there is a good correlation between the known ground truth and the features that were extracted from fitting single diffusion encoding (SDE) MRI experimental data, assuming continued or discrete weight of size distribution.  

Gideon Oluniran, Marcelo Lemos, Jeorg Ederle, Jozef Jarosz, Gareth Barker, Jonathan Ashmore

Although advanced tractography techniques exists and are well documented, many validation methods are not applicable to brain tumour cases and do not examine the possibility of proposing standard probabilistic thresholds. Using a novel approach, we investigate certain thresholds (‘safe’ thresholds) which can be applied to probabilistic tractography to reduce false representation of tracts, aid maximal tumour resection, and limit neurofunctional deficit from surgical treatments. We also examine optimal region of interest (ROI) location.  ‘Safe’ thresholds can be determined, and with a wider confidence when tractography is defined with inclusion regions.

Miguel Molina-Romero, Pedro Gómez, Jonathan Sperl, Andrew Stewart, Derek Jones, Marion Menzel, Bjoern Menze

Here we present blind source separation (BSS) as a new tool to analyse multi-echo diffusion data. This technique is designed to separate mixed signals and is widely used in audio and image processing. Interestingly, when it is applied to diffusion MRI, we obtain the diffusion signal from each water compartment, what makes BSS optimal for partial volume effects correction. Besides, tissue characteristic parameters are also estimated. Here, we first state the theoretical framework; second, we optimise the acquisition protocol; third, we validate the method with a two compartments phantom; and finally, show an in-vivo application of partial volume correction.

Lipeng Ning, Tanguy Duval, Julien Cohen-Adad, Yogesh Rathi

We propose to validate the PICASO (Precise Inference and Characterization of Structural Organization)¹ biophysical model of tissue microstructure using a full-slice histology of cat spinal cord. The PICASO model was fit to high resolution diffusion MRI (dMRI) of a cat spinal cord to estimate microstructural measures of diffusion disturbance, which is directly related to axonal packing and density. We found that the structural disturbance coefficient (SDC) in the direction orthogonal to the fiber orientation from the PICASO model was strongly correlated with the axonal density obtained from histology^2, with a correlation coefficient of r=0.67. Thus, the SDC could provide very precise information about the microscopic arrangement of axons or cells in biological tissue.

Ryusuke Irie, Koji Kamagata, Aurelien Kerever, Suguru Yokosawa, Yosuke Otake, Hisaaki Ochi, Kazuhiko Tagawa, Hitoshi Okazawa, Ryo Ueda, Kohske Takahashi, Kanako Sato, Masaaki Hori, Eri Hirasawa, Shigeki Aoki

Diffusional kurtosis imaging (DKI) is a sensitive technique to analyze brain microstructure but that has little histological foundation. In this study, we evaluated a relationship between DKI parameters with neurite density measured by a confocal microscopy of the cleared mouse brain. There was a strongly positive correlation between neurite density and DKI parameters in the caudate nucleus and putamen, whereas the correlation between neurite density and fractional anisotropy was moderate. DKI reflect neurite density in an area with crossing fibers, so that can evaluate more complex microstructures than diffusion tensor imaging.

Koji Sakai, Toshiaki Nakagawa, Ryusuke Nakai, Hiroyasu Ikeno, Seiji Yamaguchi, Hiroaki Takadama, Kei Yamada

Multi-site study gives large statistical power for the results. Some intrinsic differences among scanners are recognizing as an inevitable property. Isotropic diffusion has already been discussing. In contrast, anisotropic diffusion has been evading the endeavor because of the absence of an easily available anisotropic diffusion phantom. We compared DTI measures among five different MR scanners at three different sites using commercially and easily available astriction cotton. The averaged coefficient of variation for longitudinal repeated acquisitions of DTI on five different MR scanners were stable. The scan-rescan properties of five different MR scanners can be comparable by anisotropic diffusion phantom.

Joshua Yung, Hua Ai, Ho-Ling Liu, R Stafford

The purpose of this study was to characterize ADC values when varying imaging parameters in a diffusion-weighted (DW) FSE sequence with Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) k-space trajectory. The QIBA diffusion phantom was used to quantitatively evaluate the different pulse sequences. The DW PROPELLER sequence showed good agreement with the QIBA SE EPI sequence with the ETL=20 and b-value of 0 and 2000 s/mm² sequence having with a r²=0.9034. The DW PROPELLER sequence is promising for quantitative evaluation of ADC values and this study may help improve clinical protocols using diffusion weighted imaging.

Ezequiel Farrher, Johannes Lindemeyer, Farida Grinberg, Ana-Maria Oros-Peusquens, N. Jon Shah

Studies performing diffusion-weighted MRI on anisotropic fibre phantoms suffer from microscopic background field gradients induced by differences in the magnetic susceptibility of the employed materials. We present a particularly promising approach that makes use of a matched magnesium chloride solution to eliminate these effects. The method is thoroughly studied and successfully validated on a crossing-fibre phantom containing two perpendicularly crossing fibre populations. The obtained results are no longer subject to any orientation-dependence with respect to B₀.

Yu-Chun Lin, Gigin Lin, Chun-Chieh Wang

To investigate the biological meaning of apparent diffusion coefficient (ADC) in tumors following radiotherapy. Five mice bearing TRAMP-C1 tumor were half-irradiated. Diffusion-weighted images were acquired using multiple b-values of up 0 to 3000 s/mm². The pixelwise ADC positively correlated with extracellular space and nuclear size, and negatively correlated with nuclear count, cytoplasmic space and nuclear space. Optimal ADC was achieved at b-value of 800 s/mm² in determining the treatment response. Pixelwise ADC values correlate with histology metrics might be a means of in vivo radiomics biomarkers for evaluating tumor heterogeneity and responses to radiotherapy.

Akiko Imaizumi, Takayuki Obata, Yasuhiko Tachibana, Masayuki Inubushi, Mitsuru Koizumi, Kyosan Yoshikawa, Ming-Rong Zhang, Katsuyuki Tanimoto, Rintaro Harada, Takashi Uno, Tsuneo Saga

To investigate the usefulness of diffusion-weighted imaging (DWI) for visualizing hypoxia of head and neck carcinoma, the correlation between DWI parameter estimates and ¹⁸F-fluoroazomycin arabinoside (FAZA) positron emission tomography (PET) activity was evaluated. The diffusion coefficients and fractions of the fast and slow compartments according to the 2-compartment model (D_fast, D_slow and F_fast, F_slow) were estimated. The diffusional kurtosis (K) and the corrected diffusion coefficient (D) were also obtained according to the diffusional kurtosis imaging (DKI) method. Amongst the DWI estimates, D_slow and K were significantly correlated with FAZA-PET activity, which suggests they might be useful as indicators of hypoxia.

Tina Jeon, Emil Vutescu, Eric Aronowitz, Henning Voss, Jonathan Dyke, Darryl Sneag

High-resolution DTI is a promising tool to evaluate peripheral nerve regeneration following surgical repair of nerve injury. The spatial resolution achieved with 7.0 T allowed us to more confidently interrogate the nerve for measuring fractional anisotropy (FA) and diffusivity and to perform fiber tracking as compared to 3.0 T. Among DTI metrics, FA correlated the greatest with axonal density and diameter. These findings support that DTI has the potential to measure axonal regeneration in the peripheral nerves at preclinical and clinical field strengths.

Mariaulpa Sahalan, Aritrick Chatterjee, Nyoman Kurniawan, Gary Cowin, Laurence Gluch, Carl Power, Geoffrey Watson, Kevin Tay, Julie Fletcher, David Taylor, Roger Bourne

Improvement of sensitivity and specificity in DWI-based assessment of nodal diseases is dependent on a better understanding of how nodal microstructures affect the water diffusivity in tissue. In this abstract we report the first diffusion microimaging investigation of formalin fixed node tissue with the aim of assessing any correlation between mean diffusivity and cellularity. Mean diffusivity was calculated in ROI corresponding to distinct node sub-structures. Nuclei were segmented semi-automatically to measure the cellularity metrics: nuclear count and nuclear area. The results showed there is no significant correlation between mean diffusivity with cellularity metrics in the nodal tissues.

Cara Foley, Enrico Kaden, Kiran Seunarine, Matt Hall, David Carmichael, Jonathan Clayden, Chris Clark

Diffusion Tensor Imaging (DTI) is a widely used neuroimaging technique, but it lacks specificity. Advanced diffusion models aim to yield greater biophysical information than DTI. This information is redundant if the parameters cannot be accurately reproduced across time-points. Multi-shell diffusion images were acquired on a single 3T scanner at two time-points for ten healthy adults. Mean parameter values from SMT-based microscopic diffusion anisotropy imaging and DTI were obtained in white matter, cortex and thalami. The advanced model performed similarly well to DTI in white matter, but was less consistent in the cortex and thalami, potentially due to its increased complexity. 

Tanguy Duval, Victoria Smith, Eric Klawiter, Nikola Stikov, Julien Cohen-Adad

Translating quantitative MRI to clinical research raises many challenges in term of acquisition strategy, modeling of the MRI signal, artifact corrections (sensitivity to motion and distortion) and metric extraction (template registration and partial volume effects). In this work, we wanted to validate the repeatability of this entire framework, from the acquisition to the extraction of the metrics using a template-based approach. We took advantage of the 300 mT/m gradients from the connectome scanner for estimating robustly AxCaliber metrics, MTV, and g-ratio in the spinal cord of eight healthy subjects, scanned and rescanned in two different sessions. Our results show good scan-rescan repeatability (r>0.7, small deviations <5%), and demonstrate the capability of these metrics to detect inter-subjects (through ICC) and inter-fiber-pathways differences (through ANOVA analysis).

Neil Jerome, Matthew Orton, James d'Arcy, David Collins, Martin Leach, Dow-Mu Koh

Respiratory motion represents a serious confounding factor for abdominal imaging; for more complex diffusion models such as IVIM, acquisition of diffusion-weighted images in successive breath-holds offers control of motion for sharper images. In this patient study, DWI was performed in free-breathing and consecutive breath-holds, without registration, on successive days without intervention to determine repeatability. Derived tumour ROI parameters from ADC and IVIM models were not significantly affected between breathing regimes, but observed coefficients of variation for free-breathing were smaller for all pseudo-diffusion related parameters. Breath-holding is time inefficient, and free-breathing allows more data collection for development of robust DWI markers.

Muhamed Barakovic, David Romascano, Gabriel Girard, Maxime Descoteaux, Jean-Philippe Thiran, Alessandro Daducci

Volumetric analysis of bundles derived from tractography is a popular statistical measure used in neurological disorder studies. Recent research performed by Gauvin shows that different bundles saturate with different tractography parameters, however, to achieve that saturation millions of streamlines need to be computed. In this investigation, the aim was to use microstructure informed tractography, a novel technique that combine tractography and microstructure models, to study the saturation of the bundles. This study has found that generally microstructure informed tractography makes the volume estimation less sensitive to tracking parameters. The findings may have profound implications in volumetric analysis in group studies.

Kwok-shing Chan, David G. Norris, José P. Marques

Structure tensor informed fibre tractography (STIFT) based on diffusion images at 3T and gradient-echo images at 7T has shown improvement in the accuracy of white matter bundles tracking in the presence of kissing and crossing fibres. In this study, we implemented STIFT using both DWI and GRE images at 3T. We further demonstrated white matter contrast presence in T₂* mapping and quantitative susceptibility mapping derived from GRE data can be used to compute structure tensor. The benefits of STIFT are shown in two tractography applications.

Stephan Meesters, Pauly Ossenblok, Louis Wagner, Olaf Schijns, Paul Boon, Luc Florack, Anna Vilanova, Remco Duits

An accurate delineation of the optic radiation (OR) is useful in reducing the risk of a visual field deficit after temporal lobe resective surgery. However, tractography, especially of the probabilistic kind, is prone to generate spurious (false-positive) streamlines that are poorly aligned with the surrounding bundle. Fiber-to-bundle coherence measures are applied to identify and remove spurious fibers, which together with test-retest parameter estimation can provide a reconstruction of the OR that is robust to the stochastic realization of probabilistic tractography. Pre- and post-operative comparison of the OR is performed for epilepsy patients to quantify the accuracy of damage prediction.

Zhanlong Yang, Geng Chen, Dinggang Shen, Pew-Thian Yap

Construction of brain atlases is generally carried out using a two-step procedure involving registering a population of images to a common space and then fusing the aligned images to form an atlas. In practice, image registration is not perfect and simple averaging of the images will blur structures and cause artifacts. In diffusion MRI, the problem is even more challenging, since the alignment of gross anatomical structures does not necessarily guarantee the alignment of the microstructural information captured in each voxel. In this situation, it is unclear for example how signals characterizing fiber bundles of varying orientations, which can occur naturally across subjects, should be fused to form the atlas. Moreover, the commonly used simple averaging method is sensitive to outliers.
 

Iain Bruce, Christopher Petty, Hing-Chiu Chang, Nan-Kuei Chen, Allen Song

In this diffusion MRI study, we investigated the impact of high angular resolution (high-Q) and high spatial resolution (high-K) on complex fiber structures. It was found that while high-Q was able to resolve crossing fibers within a given region, high-K provided additional spatial details of these crossing fibers in the same location. In addition, diffusion data from high-K improved characterization of high-curvature fibers, which cannot be adequately resolved with high-Q. It is thus concluded that high-K is preferred when both crossing and high-curvature fibers need to be resolved, as in human connectome analysis.

STAVROS DIMITRIADIS, MARK DRAKESMITH, SONYA BELLS, GREG PARKER, DAVID LINDEN, DEREK JONES

Sinopsis:To evaluate the reliability of well-known network metrics over alternative weighting strategies using diffusion MRI. Methods: Using ten different network weighting strategies to construct structural networks from repeat dMRI scans, we estimated the reliability of network metrics estimated over the networks. Additionally, the recognition accuracy was estimated for each of the ten strategies. Results: We demonstrated excellent ICC for six network metrics for the seven out of network weighting strategies. Recogniton accuracy was 100% accurate for the number and percentage of streamlines and tract volume. Conclusions: Our results highlight the importance of reliable network metrics from structural brain networks.

Nicole Wake, Steven Baete, Ying-Chia Lin, Fernando Boada, Daniel Sodickson

The objective of this study was to create a workflow to view 3D fiber tracts derived from diffusion spectrum imaging (DSI) in augmented reality (AR) and to test the application of visualizing tractography models in AR.   Visualizing tractography in AR may allow for enhanced comprehension of the connectivity in the brain which could impact patient care and management.

Lia Talozzi, Claudia Testa, Stefano Zanigni, Stefania Evangelisti, Laura Gramegna, Claudio Bianchini, Paola Fantazzini, Caterina Tonon, David Manners, Raffaele Lodi

We studied the arcuate fasciculus in both cerebral hemispheres in 29 healthy subjects, by evaluating GM projections and along-tract diffusion properties and tract curvature, obtained with three tractography methods: probabilistic ball-and-sticks model, deterministic and probabilistic spherical deconvolution. In all subjects we detected the arcuate in both hemispheres. For all the tractography methods we measured a bigger tract volume on the left, but detected more tracts branching towards GM terminations on the left only with the probabilistic methods, that influenced both the tract curvature and its diffusion parameters. The probabilistic tractography methods better described arcuate connectivity, which is more complex in the left hemisphere.   

Weining Wu, Hesham Hamoda, Lipeng Ning, Borjan Gagoski, Kiera Sarill, P. Ellen Grant, Martha E. Shenton, Deborah Waber, Nikos Makris, Gloria McAnulty, Yogesh Rathi

Structural abnormalities in frontal lobe connections have been observed in adults/children with ADHD in earlier studies using diffusion tensor imaging (DTI)³. This abstract investigates microstructural differences in frontal-lobe white matter connectivity using advanced diffusion imaging methods. 47 white matter fiber bundles connecting frontal areas as parcellated by Freesurfer were extracted using a novel whole-brain tractography algorithm^4,1, which allowed estimation of specific diffusion properties such as cellular volume and cellular density from advanced diffusion MRI (dMRI) data. After correcting for multiple comparisons, 6 significant white matter pathways were found to have lower cellular volume and density in ADHD compared to controls.

Jack Rutland , Rebecca Feldman, Lara Marcuse , Madeline Fields , Bradley Delman , Priti Balchandani, Rafael O'Halloran

The present study aims to identify the connectivity of the seizure onset zone (SOZ) in patients with MRI-negative epilepsy. Motivated by recent findings of aberrant white matter structure in epilepsy we hypothesized differences in structural connectivity. To test this we compared structural connectivity in a group of 8 epilepsy subjects and 8 healthy controls. We also investigated differences in connectivity in SOZ and non-SOZ areas in the epilepsy group. Hyper-connectivity was found in epilepsy subjects compared to controls. Additionally, hyper-connectivity was found in SOZ compared to non-SOZ related regions. These findings may have implications for diagnosis and surgical intervention in MRI-negative epilepsy. 

John Nouls, Alexandra Badea, Robert Anderson, Gary Cofer, G. Johnson

The complex neural architecture and brain connectivity of mouse models of human disease can be studied ex vivo by diffusion tensor imaging; however, acquisition times are long and make cohort studies prohibitively time-consuming. Throughput can be increased by the simultaneous use of multiple coils placed in proximity to the magnet isocenter. We quantify the impact of the multiple-coil configuration on throughput, on diffusion metrics used in tractography, and on mouse brain connectivity matrices. We show that fractional anisotropy is underestimated off-isocenter, while the main eigenvector direction is minimally affected. The effect on brain connectivity networks is currently being quantified.

Yuan Tian, Lin Ma, Zhenyu Liu, Zhenchao Tang, Xin Lou, Jie Tian, Mingge Li

To explore if a DTI protocol could provide a model to predict the degree of vision recovery in NMOSDs patients. 37 patients were employed in the study, including 20 patients of well vision recovery and 17 patients of poor vision recovery. With the diffusion measure of multiple white and grey matters as features, a Lasso-Logistic regression model and a Support Vector Machine (SVM)-based classification model were constructed. The results show area under curve (AUC) of 0.7618 (P=0.008) and accuracy (ACC) of 0.7297 (0.006). The method shows promising prediction performance, and it has the potential to improve the clinical treatment design. 

Hunter Moss, George Glenn, Emilie McKinnon, Jens Jensen

An investigation into the minimum b-value necessary to characterize the fiber orientation density function (fODF) with fiber ball imaging (FBI) for white matter fiber tractography (WMFT) is presented. Using high angular resolution diffusion imaging (HARDI) data, we assessed the angular difference between principal directions across b-values using a high b-value benchmark, as well as the number of fiber crossings based on fODF peak detection. WMFT was performed using the reconstructed fODFs and was viewed qualitatively. Overall, the results indicated convergence near b = 4000 s/mm² suggesting this to be the minimum b-value needed for FBI-WMFT.

Guillaume Theaud, Bixente Dilharreguy, Gwénaëlle Catheline, Maxime Descoteaux

A common way to seed tractography is thresholding the Fractional Anisotropy (FA). This technique is problematic for aging diffusion MRI studies because the FA decreases dramatically in regions of White Matter Hyperintensities (WMH) and thus, the tractography can erroneously start or stop in these WMH regions. We show the importance for tractography pipelines to correct for WMH in their tracking masks. We show that the non-correction can lead to approximately 15% erroneous streamlines, which are false connections that can pollute the structural connectome and lead to misinterpretations.

Martin Cousineau, Maxime Descoteaux, Hiromasa Takemura

Two common approaches to tractography seeding are using the whole-brain white matter mask, or the gray and white matter interface. Using a dataset with two acquisitions per subject and a state of the art processing pipeline, we compared the test-retest reproducibility of the shape and tract profiles of major white matter bundles for both seeding strategies. We found that both seeding strategies have regions in the brain where they are more reproducible. We propose an ensemble method combining both strategies as a possible way to make tractometry from white matter bundles more robust.

Qiqi Tong, Ting Gong, Jing Jin, Xiujue Zheng, Lude Cheng, Hongjian He, Jianhui Zhong

Reliable tractography of specific abnormal brain nerves such as the facial nerve displaced by vestibular schwannoma is necessary for estimating risk before the surgery. Single-shot diffusion EPI sequence has been used previously to reconstruct tractography of facial nerve but suffered severe distortion in the basicranial region. Here we performed high resolution anatomical and diffusion scans in patients with vestibular schwannoma, in order to track the facial nerve and provide reliable result for the surgeons to evaluate the surgical risk.

Ivy Uszynski, Hervé Mathieu, Jean-Christophe Deloulme, Emmanuel Barbier, Cyril Poupon

Diffusion MRI is a powerful tool to investigate the structural connectivity of the brain and to characterize its microstructure. In this study, we propose to adapt the white matter bundles clustering approach - previously achieved on humans - to the mouse in order to establish the foundations of a novel atlas of the structural connectivity. To this aim, 3D High Angular Resolution Diffusion Imaging (HARDI) was performed ex vivo on C57Bl6 mice brains (100µm isotropic) at 9.4T and clusters of fibers were computed using an automated procedure across the entire brain.

Hsien-Te Su, Pin-Yu Chen, Yu-Jen Chen, Yung-Chin Hsu, Wei-Chi Li, Tzu-Yi Hong, Li-Fen Chen, Jen-Chuen Hsieh, Wen-Yih Tseng

To investigate plasticity of white matter tracts in expert dancers and pianists, we used diffusion spectrum imaging to measure generalized fractional anisotropy (GFA) of 76 major white matter tracts. A novel metric called tract covariance was defined as the correlation between each pair of tracts in variations of the mean GFA values across subjects. As compared with control subjects, expert dancers showed overall enhancement of the tract covariance, whereas expert pianists showed enhancement specific to sensory-motor processing. The findings underline the different effects on white matter tract plasticity following different types of long-term training. 

Moo Chung, Jamie Hanson, Nagesh Adluru, Andrew Alexander, Richard Davidson, Seth Pollak

We present evidence that the structural brain network follows the exponential decay law; these data are inconsistent with the view the brain follows the more complicated truncated exponential power law. Our model is then used in application, to show that children exposed to high levels of early life stress have more sparsely connected hub nodes. These data are consistent with rodent models of the effects of stress on synaptogenesis.

Merry Mani, Mathews Jacob, Baolian Yang, Vincent Magnotta

Echo planar imaging data are often corrupted by Nyquist ghost artifacts resulting from the eddy current induced shifts between the odd & even phase encodes. Current EPI methods often rely on calibration scans that are collected prior to the data acquisition to correct for Nyquist ghosts. Unfortunately, this approach is often insufficient for the recovery of diffusion-weighted (DW) data, since the ghosting artifacts also depend on the segmentation of the EPI read-outs and diffusion weighting. We introduce a comprehensive algorithm to simultaneously correct for the eddy-current errors as well as the motion-induced artifacts in DW images that does not require any calibration scans.

Sophie Sébille, Anne-Sophie Rolland, Romain Valabregue, Carine Karachi, Marie-Laure Welter, Stéphane Lehéricy, Eric Bardinet, Mathieu Santin

The goal of this work was to compare diffusion and microstructure parameters estimation when the sample is soaked or not in gadolinium before imaging (Gd-staining). We found that Gd-staining is suitable for diffusion imaging experiment, leading to higher SNR and higher useful b-values. Meanwhile, care must be taken for several microstructure parameters estimation as T1 may vary during experiment.

Lingceng Ma, Congbo Cai, Zhong Chen, Shuhui Cai, Hongyi Yang, Kai Zhong

A new diffusion imaging method, single-scan diffusion mapping through overlapping-echo detachment planar (DM-OLED) imaging sequence with corresponding separation algorithm, was proposed. The method can get reliable diffusion mapping by a single-scan in about 120ms.The diffusion mapping gained by DM-OLED has immunity to motion and higher time resolution compared with conventional multi-scan diffusion methods. Experimental results of mouse brains verified the accuracy and the motion-tolerance of DM-OLED. As a reliable fast diffusion measurement tool, DM-OLED can be boded well for further uses in clinical real-time measurements.

Jeffrey Paulsen, Iris Zhou, Phillip Sun

Kurtosis imaging enables valuable diagnostics of stroke and other tissue pathologies.  It can arise directly from restricted diffusion, but also from sub-voxel heterogeneity in the ADC.  Utilizing double diffusion contrast, we are able to remove these heterogeneity contributions.  We show this targeted ‘microscopic’ kurtosis contrast yields unique contrast in-vivo in a live rat brain: highlighting white/gray matter boundaries.

Nathan Skinner, Shekar Kurpad, Brian Schmit, L. Tugan Muftuler, Matthew Budde

To improve image quality for investigation of spinal cord injury, a reduced field of view excitation scheme was implemented on a Bruker 9.4T imaging system. This was combined with an optimized orthogonal filter-probe diffusion weighted imaging sequence to improve specificity for axonal injury with a short acquisition time. Application in a rat spinal cord injury model showed sensitive detection of diffusivity changes 48 hours post-injury with improved image quality compared to a standard full field of view acquisition. These advances provide support for this technique as a potential biomarker of injury severity with the ability for translation into clinical systems.

Filip Szczepankiewicz, Jens Sjölund, Freddy Ståhlberg, Jimmy Lätt, Markus Nilsson

Diffusion weighting along more than one direction at a time (tensor-valued encoding) can be used to probe features of the microstructure that are not accessible by conventional encoding. For example, it enables diffusional variance decomposition (DIVIDE) which can separate the effects of microscopic anisotropy, orientation dispersion, and heterogeneous isotropic diffusivity. Tensor-valued encoding is usually demanding with respect to gradient performance, limiting its applicability to high-performance MRI systems. However, a recent method for optimized encoding significantly reduced the demand on gradient performance, which warrants an investigation of the applicability of such encoding on a wider range of MRI hardware configurations. In this study, we demonstrate whole-brain diffusional variance decomposition (DIVIDE) in less than 8 minutes at a wide range of clinical MRI systems with different hardware configurations.

Alexandra Tobisch, Rüdiger Stirnberg, Robbert Harms, Thomas Schultz, Alard Roebroeck, Monique Breteler, Tony Stöcker

This study investigates the applicability of two advanced diffusion MRI protocols in population imaging: 3-shell High Angular Resolution Diffusion Imaging (HARDI) and Diffusion Spectrum Imaging accelerated through Compressed Sensing theory (CS-DSI). Group analysis of 20 subjects indicates that CS-DSI performs comparable to 3-shell HARDI in the estimation of microstructure parameters and adds the advantage of high b-value acquisitions, further complimentary biomarkers from the diffusion propagator and a high potential to deliver data well-suited for future developments.

Harri Merisaari, Christian Federau

Intravoxel incoherent motion (IVIM) perfusion imaging has been shown to be applicable in clinical brain examinations, but those images are known to be noisy. To better quantify the necessary conditions to produce homogenous IVIM perfusion images in the brain, we studied the properties of signal noise as function of b-value and of localization in the brain. We compared the image quality of the perfusion maps as function of number of average to the maximal quality IVIM perfusion maps obtained during a 1 hour acquisition time.

Yuhui Xiong, Xiaodong Ma, Zhe Zhang, Yishi Wang, Hua Guo

Single-shot echo planar imaging (EPI) DTI (SS-DTI) has been commonly used in clinical cervical spine (C-spine) MR scans to get functional and pathologic information as it’s fast and straightforward, but high resolution SS-DTI image suffers from severe geometric distortion. Field mapping method is a classical and simple distortion correction technique, but its performance in C-spine SS-DTI is limited. We used echo planar spectroscopic imaging (EPSI) sequence to acquire the field-map, and modified the conventional field-map post-processing method to promote the correction efficacy. The results show that the proposed method is effective and fast in C-spine SS-DTI distortion correction.

Weiguo Li, Jin Gao, Andrew Gordon, Kejia Cai, Andrew Larson, Richard Magin

Brown adipose tissue (BAT) is increasingly considered a target organ for the treatment of metabolic disease. Persuasive evidence has shown that enhance­ment of the function of brown and beige adipocytes in humans could be very effective for treating type 2 diabetes and obesity. However, clinical studies have been limited by the lack of non-invasive tools for characterizing this tissue in humans.  In this study, we explored the feasibility of using high b-value diffusion-weighted MRI for detecting the distribution of interscapular brown adipose tissue. 

Ezequiel Farrher, Farida Grinberg, Zaheer Abbas, N. Jon Shah

Free-water elimination allows one to reduce the bias in DTI metrics induced by partial-volume effects. In this work, we propose a versatile approach for the optimisation of the diffusion weighting settings, given a limited acquisition time, based on a parameterised Cramér-Rao lower-bound. The optimisation shows robust convergence.

Casey Vieni, Benjamin Ades-Aron, Bettina Conti, Timothy Shepherd, Yvonne Lui, Dmitry Novikov, Els Fieremans

We investigated the effect of intravoxel incoherent motion (IVIM) on the brain diffusion MRI signal in a cohort of 143 control patients. We compared the diffusivities derived from a mono-exponential fit at b =0 and 1ms/μm² versus at b = 0.25 and 1 ms/μm². This allowed for a quantitative assessment of the IVIM signal fraction f* in specific brain matter types. Our results show a significant difference in the mean diffusivity of about 3% in white matter and up to 7% in grey matter, with corresponding f* estimated to be about 2% and 6% in white and grey matter respectively.

Wenchuan Wu, Peter Koopmans, Karla Miller

For joint k-q reconstruction, it’s beneficial to incoherently under-sampling k-space for different q-space points to utilize the complimentary k-space information. As nearby q-space points in general share more similarities than distant points, it is hypothesized that locally-incoherent k-space sampling can further improve the joint k-q reconstruction. In this work, we propose a method to design locally-incoherent k-space sampling patterns based on a graph colouring algorithm. Results show the proposed method achieves better reconstruction than existing sampling schemes.

Zijing Dong, Erpeng Dai, Fuyixue Wang, Yuantao Gu, Chun Yuan, Hua Guo

Multi-shot interleaved EPI is an effective method to acquire high-resolution and less distorted diffusion weighted images, but with relatively low acquisition efficiency, especially for diffusion tensor imaging. Here, a novel model-based reconstruction is proposed for accelerated multi-shot diffusion imaging with simultaneous multi-slice (SMS) and partially parallel imaging (PPI). The method can directly estimate diffusion tensors from the undersampled k-space data, by integrating information of all shots and diffusion encoding directions. Simulation and in-vivo experiment demonstrated that the proposed method can achieve higher acceleration efficiency and improved accuracy in tensor estimation compared with conventional 2D GRAPPA.

Zijing Dong, Fuyixue Wang, Zhe Zhang, Erpeng Dai, Xiaodong Ma, Yuantao Gu, Hua Guo

Single-shot EPI is the most widely used sequence in diffusion tensor imaging. However, severe distortion in single-shot EPI limits its application for higher resolution images. Multi-shot EPI DTI can reduce distortion but results in longer acquisition time especially when a large number of diffusion-encoding directions are used. Here, we propose a model-based reconstruction framework for EPI DTI to estimate diffusion tensors from undersampled EPI sequences, in order to achieve high resolution diffusion imaging in a shorter scan time. The effectiveness of the proposed model-based method to get precise tensor estimation is validated by DTI simulation and in-vivo experiments.

Joseph Holtrop, Bradley Sutton

The ability to use multiple shots in diffusion weighted imaging has enabled acquisitions with higher resolutions and higher SNRs. The methods currently being used to achieve higher resolutions rely on navigator information to correct for mismatches in coherent motion during the diffusion encoding between shots. The resolution of the navigator is a critical factor, too low and the corrections are incomplete, too high and there is a significant time or echo time penalty. This work presents an analysis for determining the resolution requirements for navigation. This work found that using a navigator resolution of 6 mm produces reliable results and allows shorter acquisitions to be used.

Eric Gibbons, Patrick LeRoux, Shreyas Vasanawala, John Pauly, Adam Kerr

This abstract presents a novel reconstruction for the nCPMG SS-FSE sequence.  A theoretical justification for this approach is given.  This reconstruction and sequence is demonstrated in phantom and in vivo and is shown to be quantitatively and qualitatively robust.  

Steen Moeller, Essa Yacoub , Sudhir Ramanna, Emily Kittelson, Kamil Ugurbil, Christophe Lenglet

The use of locally low-rank matrix approximation methods for noise variance reduction provides a powerful tool for diffusion MRI to increase the quality of very high b-value acquisitions. Using a clinical system, we demonstrate the feasibility of multi-shell high angular resolution diffusion imaging with b-value up to 10,000s/mm².

Ha-Kyu Jeong

IRIS has been proposed for diffusion-weighted (DW) image reconstruction with 2D-navigated motion correction from highly aliased DW-MRI data using multishot and regularly subsampled SENSE implementations simultaneously. In this work, it is demonstrated that IRIS framework can be extended for multiband DW image reconstruction for reconstructing motion-free multiband multishot DW images.

Li Guo, Zhongbiao Xu, Yingjie Mei, Wenxing Fang, Chenguang Zhao, Wufan Chen, Yanqiu Feng, Feng Huang

IRIS corrects the motion-induced inter-shot phase errors for multi-shot diffusion-weighted imaging by extracting the phase information from an additional navigator data, which may cause the distortion mismatch between the image and navigator data. To solve the distortion mismatch issue in IRIS without using B0 field map, we propose to extract the coil sensitivities and phase information from navigator data by using an eigen-analysis scheme. The performance of the proposed method is demonstrated in both phantom and in vivo data sets.

Chaoyi Zhang, Dan Wu, Jiangyang Zhang, Dong Liang, Jingyuan Lyu, Ukash Nakarmi, Rong-Rong Chen, Leslie Ying

This abstract presents a novel method for diffusion tensor image (DTI) directly from highly under-sampled data acquired at multiple diffusion gradients. This method formulates the diffusion tensor estimation as a problem of parametric manifold recovery. We solve the recovery problem by alternatively shrinking the diffusion weighted images, estimating diffusion tensor, and enforcing data consistency constraint. The experimental results demonstrate that the proposed method is able to reconstruct the diffusion tensors accurately at high acceleration factors with low computational complexity.

Hernan Jara, Osamu Sakai, Stephan Anderson, Jorge Soto

Purpose: To test the high spatial resolution limits of the white matter fibrography (WMF) technique within the scan time constrains of clinical MRI of about ten minutes total scan time and to optimize the image processing algorithms for rendering the white matter (WM) connectome at the highest level of anatomic detail. Methods: Healthy volunteer was scanned with the quadra-FSE pulse at high spatial resolution in 10min. Results: WMF connectome was constructed using ultra-high b-value (34,000s/mm2) synthetic MRI. Conclusion: High spatial resolution direct rendering of the human brain connectome can be accomplished with a 10min scan.

Qiuting Wen, Mark Graham, Sourajit Mustafi, Ivana Drobnjak, Hui Zhang, Yu-Chien Wu

In this study, we investigate two denoising methods for diffusion MRI: the local PCA approach and Marchenko-Pastur (MP) PCA approach.  Ground-truth diffusion-weighted images of the human brain are developed and used for noise simulation.  Two diffusion-weighting b-values and two noise levels are generated as input data for both denoisers.  Metrics of diffusion tenor imaging (DTI) and neurite orientation distribution and density (NODDI) are computed after denoising and compared between denoise methods.  

Mark Graham, Ivana Drobnjak, Hui Zhang

It is necessary to correct for susceptibility artefacts in DW-MR, but there are a number of available strategies to choose from. In this work we apply a simulation framework, previously used to assess motion and eddy current correction strategies, to quantitatively evaluate methods for susceptibility correction.  Our results indicate that methods that use reversed phase-encoding data perform the best. Furthermore they show that non-linear registration of diffusion data to a structural target in insufficient to fully correct for the susceptibility artefact. 

Maximilian Pietsch, David Raffelt, Thijs Dhollander, J-Donald Tournier

Spatial normalisation of high angular resolution diffusion images (HARDI) is an important prerequisite for group-level analysis of tissue microstructure. In this study, we extend a technique for non-linear registration of orientation density functions by including other non-WM tissue types into the metric driving the registration, and investigate the benefits this provides in terms of overall alignment. Our results show that including additional non-WM tissue types in the registration metric improves the performance of the registration, as assessed by visual inspection (sharper features), and in simulations (slight reduction in residuals)

Christopher Kelly, Max Pietsch, Serena Counsell, J-Donald Tournier

The first step in a diffusion MRI pre-processing pipeline typically involves the manual removal of heavily motion-corrupted volumes. However, this process is both time consuming and potentially subjective. We propose to automate this process by training multiple deep convolutional neural networks (CNNs) and decision trees to achieve near human-level accuracy for rejection of outliers.

Daisuke Yoshimaru, Toshiaki Miyati, Yuichi Suzuki, Yuhki Hamada, Nozomi Mogi, Ayumu Funaki, Ayumi Tabata, Maki Tobari, Takayoshi Nishino

We evaluated hepatocellular degeneration using DKI analysis with the breath hold technique compared with the pathological appearance about chronic hepatic diseases and hepatic fibrosis. Using this DKI method in the liver the stage of hepatic fibrosis can be classified into normal hepatic fibrosis and early hepatic fibrosis, and into early hepatic fibrosis and advanced hepatic fibrosis. Thus, we consider that DKI analysis can reflect pathological classification accurately. We considere that this DKI method will be required to evaluate the degree of hepatic fibrosis and to monitor the progress of hepatic fibrosis as an additional sequence in a clinical routine.

Esha Baidya Kayal, Devasenathipathy K, Kedar Khare, Raju Sharma, Sameer Bakhshi, Amit Mehndiratta

Histological necrosis is the current gold standard for response evaluation in Osteosarcoma treated with neoadjuvant chemotherapy (NAC). However it is applicable only after tumour resection on completion of NAC. Thus, a non-invasive early marker of NAC response is desirable. We performed NAC response evaluation using Intra-voxel Incoherent Motion (IVIM) Diffusion weighted MRI using tumour volume change and histogram analysis. Tumour volume change and histogram analysis revealed similar and clinically useful information in chemotherapy response to Osteosarcoma.

Dongyun Li, Chunxue Liu, Xiu Xu, Ed Wu, Zhongwei Qiao

Autism spectrum disorder (ASD) is classified as a neuro-developmental disease with a dramatically increasing prevalence from 4 in 10000 to recently 1 in 68 children. SHANK-3 proteins are multidomain scaffold proteins of the postsynaptic density and also play a role in synapse formation and dendritic spine maturation. Recent human genetic studies suggest the potential association between molecular defects of SHANK-3 and ASD. DTI  imaging and TBSS analysis was applied to study how SHANK-3 gene mutation results in severe microstructure of white matter. Results showed significant damage in SHANK-3 group but no positive findings between  ASD and typical development controls. These results calls for attention to re-examine the previous neuroimaging studies of ASD or other neuro-developmental diseases where the positive correlations could be contaminated with unexplored genetic mutation influence.

Eo-Jin Hwang, Joon-Yong Jung, Jin Kyoung Oh, Mun Young Paek

Intravoxel incoherent motion (IVIM) based analysis of diffusion weighted imaging (DWI) has been suggested as a non-invasive tool to characterize tumor hypoxia, but no study has been performed to directly measure its parameters within the hypoxic tumor regions. In this study, we qualitatively and quantitatively compared IVIM parameters with ¹⁸F- misonidazole PET imaging and tested the feasibility of using non-invasive imaging strategy to define tumor hypoxia. Our preliminary result successfully related perfusion fraction values to standardized uptake values (SUVs) from PET and showed a potential of DWI as a tool to evaluate tumor oxygenation. 

Qiyuan Tian, Grant Yang, Christoph Leuze, Ariel Rokem, Brian Edlow, Jennifer McNab

We propose a practical, model-free, Fourier reconstruction framework for obtaining the diffusion propagator and the diffusion orientation distribution function (ODF) from multi-b-shell diffusion data. Signals on each b-shell are scaled to account for non-uniform sampling density in q-space. Diffusion propagators and ODFs are obtained using a Discrete Fourier Transform and an analytic ODF solution. The method is demonstrated on data from the Human Connectome Project and shown to be both effective and broadly applicable to multi-b-shell data.

Robbert Harms, Rainer Goebel, Alard Roebroeck

Using high resolution HCP WU-Minn data and GPU accelerated software (MDT; https://github.com/cbclab), the aims of this study were to evaluate dMRI microstructure indices over white matter tracts, evaluate the effect sizes between tracts as an upper limit for effect size of diffusion microstructure indices between subjects and finally the influence of possible confounds on those other aims. We report sizeable effects between tracts within subjects for several indices. Also, two clear confounds for diffusion microstructure studies where identified, first, partial volume effects in small and large cross-section tracts, second, model selection on the number of intra-axonal model compartments.

ANNE-CHARLOTTE PHILIPPE, LAVAULT SOPHIE, FICK RUTGER, WASSERMANN DEMIAN, VALABREGUE ROMAIN, DERICHE RACHID, LEVY RICHARD, ARNULF ISABELLE, LEHERICY STEPHANE

Kleine-Levin syndrome (KLS) is a rare neurological disorder characterized by episodes of severe hypersomnia, apathy, cognitive impairment, derealization and behavioral disturbances. Between episodes, patients have normal sleep, mood and behavior. Apathy is a prominent clinical feature of KLS but its pathophysiology is not known. Here we used mean apparent propagator to investigate white matter changes in KLS and correlated diffusion changes with apathy scores. Results showed that the corpus callosum was involved in KLS during episodes and mean RTAP measures in the corpus callosum correlated with apathy scores. Results were in accordance with known motivation-based circuits involving the orbitomedial frontal cortex.

Farida Grinberg, Ezequiel Farrher, Kerstin Konrad, Irene Neuner, N. Jon Shah

Frequently used methods in between-group comparisons of diffusion tensor and diffusion kurtosis imaging metrics, such as region-of-interest analysis or atlas-based analysis, are subject to errors due to partial volume effects. In this work we demonstrate that the application of a simple diffusion-kurtosis-informed template significantly reduces partial volume effects and, in turn, improves the between-group atlas-based analysis. In particular, a better differentiation of diffusion metrics was achieved in the study of a group of children versus a group of adults.

Zhenchao Tang, Zhenyu Liu, Xinwei Cui, Enqing Dong, Jie Tian

In the current study, we employed multivariate pattern analysis method together with Diffusion Tensor Imaging measures to make prediction on the cognitive performance of Type 2 diabetes mellitus (T2DM) patients, and explore the white matter tracts associated with cognitive changes in T2DM. The prediction model obtained relatively satisfying performance in the Montreal Cognitive Assessment (MoCA) scores estimation among T2DM patients, suggesting the effectiveness of the multivariable analysis method. The white matter identified in the current study mainly concerned the tracts closely related with cognitive function and memory performance, which were consistent with the finding of previous T2DM cognitive studies.

Samuel St-Jean, Max Viergever, Alexander Leemans

Diffusion MRI suffers from relatively long scan times and low signal to noise ratio (SNR), which limits the acquired spatial resolution. In this work, we propose a unified framework for denoising and upsampling diffusion datasets based on a sparse representation of the diffusion signal. Our proposed method shows less blurring and increased anatomical details in the pons region when compared to denoising and subsequent spline interpolation. At the junction of the corpus callosum, the corticospinal tract and the cingulum, finer structures are also preserved as evidenced by a high resolution invivo acquisition.

Hamed Mesri, Martijn Froeling, Max Viergever, Anneriet Heemskerk, Alexander Leemans

Nonuniformities of gradient magnetic fields in diffusion-weighted MRI can introduce systematic errors in estimates of diffusion measures. While there are correction methods that can compensate for these errors, as presented in the Human Connectome Project, such non-linear effects are assumed to be negligible for typical applications and, hence, gradient nonuniformities are mostly left uncorrected. In this work, we evaluated the effect of ignoring such diffusion gradient nonuniformities on measures derived from diffusion tensor imaging. In particular, we simulated deviations from the ground-truth in terms of b-value and diffusion gradient orientation and investigated the resulting bias in fractional anisotropy and orientation of the first eigenvector. Our results demonstrate that not including a correction strategy to mitigate diffusion gradient imperfections especially for high quality data may lead to a significant bias for diffusion measure estimates.

Greg Parker, Derek Jones

Diffusion weighted imaging is prone to artefacts. Sources including hardware instability, bulk motion and cardiac pulsation can all induce spurious signal intensities (i.e. corruption) which negatively affect derived measurements. To combat this an additional processing step may be added to detect (and subsequently reject) such corrupted data points; however, with the increasing use of multi-shell acquisitions a number of existing approaches (constrained to a single b-value shell and/or unsuitable diffusion tensor models) are no longer applicable, limiting available choices. With this abstract we propose a new multi-shell detection algorithm and provide preliminary experimental results.

Jordan Chad, Ofer Pasternak, David Salat, J. Chen

A Free Water Elimination (FWE) technique is applied to investigate changes in DTI parameters in the human white matter during healthy aging. Our results suggest that age-related changes in DTI metrics often reflect increased extracellular free water with age. DTI with FWE unmasks the effects of free water, revealing authentic tissue microstructure.

Rachel Steiner, Sarah Short, Rebecca Santelli, Audrey Verde, Aditya Gupta, François Budin, Katherine Gilmore, Nagesh Adluru, Guido Gerig, John Gilmore, Martin Styner

Given the increasing popularity and wealth of DWI data in the field of neuroimaging, there is a critical need for the development of publically available resources that enable widespread application of a set of template fibers for atlas based along-tract analysis supporting an adequate and reliable analysis of DTI in newborns in both practice and in clinical research settings. To address this gap, we developed a Neonate DTI atlas that represents a typically developing human brain during the first few weeks of life. To the best of our knowledge, we are the first to develop a population atlas with this magnitude of quality and sample size, as well as with a comprehensive set of template fibers for semi-automatic tract based analysis. The DTI atlas and the tracts will be made available through NITRC.

Steven Baete, Ying-Chia Lin, Fernando Boada

High quality diffusion acquisitions are routinely used to study white matter architecture and brain connectivity in vivo. A key step for successful tractography of neuronal tracts is correct identification of the tract directions in each voxel. Here we propose a fingerprinting-based methodology for identifying these fiber directions in Orientation Distribution Functions. This ODF-fingerprinting approach improves the detection of fiber pairs with small crossing angles whilst maintaining fiber direction precision. This improvement will aid fiber tracking algorithms in accurately displaying neuronal tracts and calculating brain connectivity.

Geng Chen, Dinggang Shen, Pew-Thian Yap

Many existing algorithms for estimation of the fiber orientation distribution function (ODF) inherently assume Gaussian noise distribution. Against this assumption, the non-central chi noise distribution of diffusion signals causes bias in fiber ODF estimation. In this work, we introduce a means of transforming the diffusion-weighted signals to have a Gaussian noise distribution with the help of the recently introduced x-q space non-local means (XQ-NLM) algorithm. We show that this signal mapping improves estimation of fiber ODFs.

Mustafa Irfanoglu, Amritha Nayak, Jeffrey Jenkins, Carlo Pierpaoli

Here we present a series of improvements and new features of the TORTOISE diffusion MRI data processing software (www.tortoisedt.org). TORTOISEv3 has been programmed in C++ and it is now significantly faster, can be batched and it fully benefits from modern multi-core CPU architectures. The DIFFPREP module brings a multitude of new and state-of-art features including DWI denoising, Gibbs ringing removal, and the ability to perform motion and eddy currents distortion correction for very high b-value data. The new DIFFCALC module can perform MAP-MRI propagator estimation and the output can be easily imported in other software packages for statistical analysis and atlas creation.

David Raffelt, Thijs Dhollander, J-Donald Tournier, Rami Tabbara, Robert Smith, Eric Pierre, Alan Connelly

Apparent Fibre Density (AFD) is a measure derived from un-normalised fibre orientation distributions. To make AFD quantitative across subjects, images need to be intensity normalised and bias field corrected. Here we present a fast and robust approach to simultaneous bias field correction and intensity normalisation by exploiting tissue compartment maps derived from multi-tissue constrained spherical deconvolution. We performed simulations to show that the method can accurately recover a ground truth bias field, while also demonstrating qualitative results on in vivo data.

Alberto De Luca, Filippo Arrigoni, Alessandra Bertoldo, Martijn Froeling

Pseudo continuous description of the diffusion MRI (dMRI) signal through multi-compartment deconvolution is a promising technique to disentangle different water pools in the brain. In this work we verified whether a deconvolution based approach with L₂ regularized priors could improve the repeatability of DTI metrics computed on the brain data of 3 volunteers acquired twice. Signal fractions of free water and perfusion could reliably be quantified and removed from the diffusion signal, improving the repeatability of MD estimation both in gray and white matter.