View Presentation Video

Felix Horger^1,2,3, Raphael Tomi-Tricot^1,2,3,4, Pierluigi Di Cio^1,3, Joseph Hajnal^1,2,3, and Shaihan Malik^1,2,3
1Biomedical Engineering Department, School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom, ²Centre for the Developing Brain, School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom, ³London Collaborative Ultra high field System (LoCUS), London, United Kingdom, ⁴MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom

Keywords: MR Fingerprinting/Synthetic MR, In Silico

The temporal low-rank property of signals produced by MR Fingerprinting can be used to circumvent reconstruction of individual time frames. Instead, temporally compressed components are estimated. Since every acquired sample then contributes to every compressed component, it is unclear which k-space sampling pattern is optimal. This work collects evidence for higher robustness of radial sampling towards measurement errors and its superior ability to resolve rapidly varying temporal signals, compared to a Cartesian pattern, simulated in a realistic scenario and supported by an in vivo observation. The aim is making informed decisions about optimal sampling patterns for MRF.

View Presentation Video

Yupeng Wu¹, Zhichao Wang², Qifan Pang¹, Gaiying Li¹, Mengying Chen¹, Xu Yan³, Caixia Fu⁴, Yang Song³, and Jianqi Li^1
1Shanghai key lab of magnetic resonance, East China Normal University, Shanghai, China, ²Zhejiang Lab, Hangzhou, China, ³MR Scientific Marketing, Siemens Healthineers, Shanghai, China, ⁴MR Application Development, Siemens Shenzhen Magnetic Resonance Ltd, Shenzhen, China

Keywords: Pulse Sequence Design, CEST & MT, GRE FLASH TrueFISP

For clinical implementation, chemical exchange saturation transfer (CEST) imaging must be fast with high signal‐to‐noise ratio (SNR), 3D coverage, and produce robust contrast. In general, CEST imaging with fast low angle shot GRE sequence (FLASH) can achieve fast acquisition, but may yield low SNR efficiency. This study evaluated APT and NOE maps for single saturation 3D CEST imaging with True FISP and FLASH sequences, respectively. We found that True FISP could achieve better SNR of Z-spectrum and obtain more reliable CEST effects contrast. 3D True FISP sequence is expected to become a more promising 3D CEST-GRE sequence for clinical application.

View Presentation Video

Oscar van der Heide^1,2, Mariya Doneva³, Peter Koken³, Jakob Meineke³, Miha Fuderer^1,2, Cornelis A.T. van den Berg^1,2, and Alessandro Sbrizzi^1,2
1Computational Imaging Group for MR Diagnostics and Therapy, Center for Image Sciences, University Medical Center Utrecht, Utrecht, Netherlands, ²Department of Radiology, Division of Imaging and Oncology, University Medical Center Utrecht, Utrecht, Netherlands, ³Philips Research, Hamburg, Germany

Keywords: MR Fingerprinting/Synthetic MR, Quantitative Imaging

MR Fingerprinting (“MRF”) and MR Spin Tomography in Time-domain (“MR-STAT”) are quantitative MRI techniques that allow multiple quantitative tissue parameter maps (e.g. T1, T2 and proton density) to be estimated from a single short scan. In this work, we compare the accuracy and precision of Cartesian MR-STAT and spiral MRF on gel phantoms and in-vivo. On gel phantoms we get excellent agreement with reference measurements. In-vivo we observe differences in reconstructed T1 values. As for the precision, a more in-depth study is required to take into account differences in noise-suppression mechanisms (i.e. k-space apodization and spiral sampling window).

 

View Presentation Video

Riwaj Byanju¹, Gyula Kotek¹, Mika W. Vogel², Juan A Hernandez-Tamames¹, and Dirk H. J. Poot^1
1Erasmus MC, Rotterdam, Netherlands, ²GE Healthcare, Hoevelaken, Netherlands

Keywords: Pulse Sequence Design, Quantitative Imaging

We propose a 3D extension of the novel MP-b-nSSFP sequence, which interleaves RF pulse types for Multiparametric mapping from the transient response. Comparing selective versus non-selective refocusing pulses we observe lower bias with non-selective pulses, despite modelling the spatially varying effect of the pulses in the fitting process. Phantom and in-vivo comparison to QRAPTEST (MAGIC) are performed.

View Presentation Video

Sara E Sacher¹, Michael Carl², Hollis G Potter¹, and Matthew F Koff^1
1Hospital for Special Surgery, New York, NY, United States, ²GE Healthcare, San Diego, CA, United States

Keywords: Pulse Sequence Design, Quantitative Imaging, Ultrashort echo time

The relative accuracy of an ultrashort echo time (UTE) based T1ρ sequence was compared to a MAPSS based T1ρ sequence in the evaluation of articular cartilage. Scanning with similar parameters between the acquisitions was performed, producing similar T1ρ values in all cartilage sub-compartments except for the femoral trochlea (TrF). TrF MAPSS-T1ρ values were shorter than TrF UTE-T1ρ values (10.91% difference, p = 0.0028). Overall, there was reasonable agreement between the two sequences indicating that UTE-T1ρ may be a promising method to use in place of conventional MAPSS sequences to quantify T1ρ values of articular cartilage. 

View Presentation Video

Nils Marc Joel Plähn¹, Adèle Mackowiak², Berk Açikgöz³, and Jessica Bastiaansen^3
1Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern Universit, Bern, Switzerland, ²Department of Radiology, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland, ³Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland

Keywords: Data Analysis, High-Field MRI, phase-cycled bSSFP, Aceton fraction quantification

A novel Off-Resonant encoded Analytical parameter quantification using Complex Linearized Equations (ORACLE) method using phase-cycled bSSFP profiles was developed. The approach decodes complex asymmetry profiles in multi-compartment systems for simultaneous proton fraction, T₁/T₂  ratio,  T₁ and T₂ quantification. The approach was validated in simulations and in an acetone-water phantom at 3T and 7T. Simulations and experiments validated the proposed method for multi-parameter quantification using phase-cycled bSSFP for two compartment singlet systems with high accuracy and precision. This provides the first step towards proton fraction quantification of more complex multiplet-systems, such as fat or myelin, exploiting complex asymmetry profiles.
 

Mikhail Zubkov¹ and Irina Melchakova^1
1School of Physics and Engineering, ITMO University, Saint Petersburg, Russian Federation

Keywords: Data Acquisition, Pulse Sequence Design

MRI serves as a non-invasive way of assessing the degree of iron overload. This is done via T2*-mapping commonly performed with muti-echo gradient echo sequences. This approach fails in cases with extreme iron overload where the relaxation times drop down to submillisecond range. A method allowing ultra-short T2* mapping is simulated, employing a temporal acquisition offset in a spin-echo pulse sequence. Two acquisitions are suggested: one – before the spin-echo centre, and another – after, resulting in two different T2*-weighted images, acquired with half-line radial encoding. This method allows obtaining T2*-weighted images with weightings starting effectively at zero echo time.

View Presentation Video

Jaejin Cho^1,2, Tae Hyung Kim³, Avery JL Berman⁴, Yohan Jun^1,2, Xiaoqing Wang^1,2, Borjan Gagoski^2,5, and Berkin Bilgic^1,2,6
1Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Computer Engineering, Hongik University, Seoul, Korea, Republic of, ⁴Carleton University, Ottawa, ON, Canada, ⁵Fetal-Neonatal Neuroimaging & Developmental Science Center, Boston Children’s Hospital, Boston, MA, United States, ⁶Harvard/MIT Health Sciences and Technology, Cambridge, MA, United States

Keywords: Data Acquisition, Quantitative Imaging, T2 and T2* mapping

We demonstrate T₂ and T₂^* mapping and joint reconstruction for multi-echo, multi-shot EPI data from a variable flip angle, blip-up and -down undersampling (VUDU) for spin and gradient echo (SAGE) acquisition. VUDU-SAGE employs a blip-up and -down acquisition strategy for correcting B₀ distortion, and FLEET-ordering for motion-robust multi-shot EPI while maximizing signal using variable flip angles. VUDU-SAGE acquires five echoes consisting of two gradient-echo, two mixed, and one spin-echo contrasts. We jointly reconstruct all echoes and estimate T₂ and T₂^* maps using Bloch dictionary matching. In-vivo experiment presents T₂ and T₂^* map at 1x1x4mm³ resolution with a 9-second acquisition.

View Presentation Video

Megan Co¹, Brian Raterman², Arunark Kolipaka^1,2, and Benjamin A Walter^1,3
1Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States, ²Department of Radiology, The Ohio State University, Columbus, OH, United States, ³Spine Research Institute, The Ohio State University, Columbus, OH, United States

Keywords: Data Acquisition, Quantitative Imaging, Spine, Intervertebral Disc

T1ρ and T2 mapping have been developed to quantitively assess intervertebral disc (IVD) degeneration by quantifying proteoglycan and water content, respectively. In addition, magnetic resonance elastography (MRE) has been validated to quantify shear stiffness. This study determines how water content affects MRI relaxation times and MRE-derived mechanical properties. Our results showed that hydration has an influence on T1ρ and T2 relaxation times and MRE-derived shear stiffnesses and that there is a correlation between relaxation times and shear stiffnesses. This highlights MRI as a non-invasive technique to quantify tissue composition and mechanical properties to assess degenerative changes within the IVD.  

View Presentation Video

Peng Li¹, Yinghao Zhang¹, Xin Lu², and Yue Hu^1
1Harbin Institute of Technology, Harbin, China, ²De Montfort University, Leicester, United Kingdom

Keywords: Pulse Sequence Design, MR Fingerprinting

The optimal design of the Magnetic resonance fingerprinting (MRF) sequence is still challenging due to the optimization of high-degrees-of-freedom acquisition parameters. In this paper, we propose a novel unsupervised learning-based pulse sequence design framework for efficient MRF sequence optimization. Specifically, we propose a novel pulse sequence generation network (PSG-Net) that fully exploits the sequence correlation to generate the optimal pulse sequence from a zero-initialized input. To achieve improved precision of parameter estimation, we use a predefined pulse sequence performance evaluation function that can directly represent tissue quantification separability as the loss function to update the parameters of the PSG-Net.

View Presentation Video

Merijn Berendsen¹, Maša Bozic-Iven^1,2, Joao Tourais¹, Chiara Coletti¹, Ingo Hermann^1,2, and Sebastian Weingärtner^1
1Delft University of Technology (TU Delft), Delft, Netherlands, ²Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany

Keywords: Pulse Sequence Design, Pulse Sequence Design

Phased-based techniques have shown promise for scan time efficient quantification of T₂ relaxation times. However, previously proposed methods use an unbalanced Gradient Echo approach, which shows residual sensitivity to B₁⁺ and T₁ changes. In this work, a dual phase-cycled balanced SSFP approach is proposed. Simulations and phantom measurements show its resilience against field inhomogeneities. Excellent agreement between phase values was obtained in phantom and simulations. Initial phantom acquisitions at 3T yield T₂ maps with visually high map quality and close agreement to a spin-echo reference. Future evaluation of in vivo robustness and inter- and intra-subject repeatability is warranted.

View Presentation Video

Yao Sui^1,2, Onur Afacan^1,2, Camilo Jaimes^1,2, Ali Gholipour^1,2, and Simon K Warfield^1,2
1Harvard Medical School, Boston, MA, United States, ²Boston Children's Hospital, Boston, MA, United States

Keywords: Image Reconstruction, Quantitative Imaging

Any MRI practices prefer high resolution, high signal-to-noise ratio, short scan time, and high contrast. Unfortunately, fast scan leads to low resolution while high-resolution scan results in a reduced signal-to-noise ratio. In particular, it is challenging for radiologists and technologists, who perform MRI scans, to find optimal sequence parameters for each patient, leading to sub-optimal contrast. We developed a new methodology that enables fast and high-resolution brain MRI with improved signal-to-noise ratio and optimal contrast between white-matter and gray-matter for each individual patient, based on quantitative imaging and reconstruction techniques. Experiments on clinical data demonstrated the advantages of our approach.

View Presentation Video

Chu-Yu Lee¹, Olivia Lullmann², Emily J Steinbach², Daniel R Thedens¹, Lyndsay A Harshman², and Vincent A Magnotta^1
1Department of Radiology, The University of Iowa, Iowa City, IA, United States, ²Department of Pediatrics, The University of Iowa, Iowa City, IA, United States

Keywords: Data Processing, Relaxometry, R2*; Macroscopic field; Correction

Macroscopic field variations result in an overestimate of R₂*. One common approach to correct the bias is to utilize a three-parameter fit; however, the fitting is subject to overfitting. This study presents a new two-stage fitting of the three-parameter model by assuming that the macroscopic field variation is slowly varying in space. Using a numerical simulation and in vivo mice data, we demonstrate that the proposed method allows for a more accurate R₂* measurement, and is less sensitive to noise.

Simin Li¹, Taishan Kang², Jian Wu¹, Weikun Chen¹, Zhigang Wu³, Jiazheng Wang³, Congbo Cai¹, and Shuhui Cai^1
1Department of Electronic Science, Xiamen University, Xiamen, China, ²Department of Radiology, Zhongshan Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China, ³MSC Clinical & Technical Solutions, Philips Healthcare, Beijing, China

Keywords: Image Reconstruction, Quantitative Imaging

Most quantitative magnetic resonance imaging (qMRI) methods are time-consuming. Multiple overlapping-echo detachment (MOLED) imaging can achieve quantitative parametric mapping for a single slice within hundred milliseconds. To further accelerate MOLED, we combine MOLED with multiband SENSE (MB-SENSE) technology to achieve simultaneous multi-slice T₂ mapping. To solve the problem of reconstructed image quality degraded caused by a high multiband factor MB, a plug-and-play (PnP) approach with prior denoisers was applied for image restoration to realize denoising at a high MB. The proposed multiband multiple overlapping-echo detachment (MB-MOLED) imaging can achieve sub-second T₂ mapping of the whole brain with a high MB.

View Presentation Video

Teresa Nolte¹, Masami Yoneyama², Chiara Morsch¹, Alexandra Barabasch¹, Maximilian Schulze-Hagen¹, Johannes M. Peeters³, Christiane Kuhl⁴, and Shuo Zhang^5
1Diagnostic and Interventional Radiology, Uniklinik RWTH Aachen University, Aachen, Germany, ²Philips Japan, Tokyo, Japan, ³Philips Healthcare, Best, Netherlands, ⁴Diagnostic and Interventional Radiology, University Hospital RWTH Aachen, Aachen, Germany, ⁵Philips GmbH Market DACH, Hamburg, Germany

Keywords: Image Reconstruction, Diffusion/other diffusion imaging techniques, Noise

Further acceleration of diffusion MRI in clinical examinations is desired but challenging mainly due to low signal and associated potential bias in the quantitative apparent diffusion coefficient (ADC) values. Artificial intelligence-based denoising and image reconstruction may provide a solution to address this challenge. We investigate and compare different image reconstruction methods, including conventional parallel imaging, compressed sensing, and a deep learning-based technique, in ADC accuracy and precision using a diffusion phantom with illustration of the principle in numeric simulation. 

Zebo Huang¹, Weiqiang Dou², and Wenwei Tang^1
1Nanjing Maternity and Child Health Care Hospital, Nanjing, China, ²GE Healthcare, MR Research China, Beijing, P.R. China, Beijing, China

Keywords: MR Fingerprinting/Synthetic MR, Uterus, LVSI

This study aimed to investigate whether synthetic-MRI derived quantitative maps can predict lymphovascular interstitial infiltration (LVSI) status in cervical cancer. 49 patients with cervical cancer were recruited with the status of LVSI confirmed by pathology. Synthetic MRI derived T1, T2 and PD mapping were obtained for each patient. Statistical differences were shown in T1 and PD values between LVSI-positive and LVSI-negative patients. An optimal diagnostic efficacy was further shown for T1+PD with high AUC of 0.777. With these findings, it can be concluded that relaxation maps derived from synthetic MRI may be helpful for predicting LVSI status in cervical cancer.

Ling Sang¹, Weiyin Vivian Liu², Hu Chen³, and Wen Chen^1
1Department of Radiology, Taihe Hospital, Wuhan, China, ²GE Healthcare, Beijing, China, ³Department of Radiology,Taihe Hospital, Wuhan, China

Keywords: Data Acquisition, Relaxometry

Brain MAGiC imaging became widely applied in multi-center cooperation and in an individual longitudinal follow-up; however, acquisition with a backup coil at an emergency situation (i.e., a sudden coil breakdown) or a coil with different numbers of channels has not been explored on a 1.5T scanner yet. In contrast to small variation of PD values in the whole brain, T2 values varies relatively dramatically especially in cerebellum and showed statistically different between scans using different coils. It is worth noting that existence of inter-coil relaxometry difference should be careful for diagnosis.  

View Presentation Video

Chinmay Rao¹, Jakob Meineke², Nicola Pezzotti³, Marius Staring¹, Matthias van Osch¹, and Mariya Doneva^2
1Leiden University Medical Center, Leiden, Netherlands, ²Philips Research, Hamburg, Germany, ³Philips Research, Eindhoven, Netherlands

Keywords: MR Fingerprinting/Synthetic MR, MR Fingerprinting

Traditional MR fingerprinting involves matching the acquired signal evolutions against a dictionary of expected tissue fingerprints to obtain the corresponding tissue parameters. Since this dictionary is essentially a discrete representation of a physical model and the matching process amounts to brute-force search in a discretized parameter space, there arises a tradeoff between discretization error and parameter estimation time. In this work, we investigate this tradeoff and show via numerical simulation how a neural net-based approach solves it. We additionally conduct a phantom study using 1.5T and 3T data to demonstrate the consistency of neural net-based estimation with dictionary matching.

View Presentation Video

Noriyuki Tawara¹ and Daiki Tamada^2
1Department of Radiological Sciences, Faculty of Health Sciences, Japan Healthcare University, Sapporo, Japan, ²Department of Radiology, Yamanashi University, Yamanashi, Japan

Keywords: Visualization, Visualization

The objective of this study was to reproduce the generation process of Steady-State and FLASH Band in MRI phenomena that cannot be reproduced by the actual equipment because of the restrictions imposed by venders, in order to directly confirm their relationship with pulse sequences. MRI simulation can reproduce Bloch equation faithfully, and thus it is possible to reproduce the relation between pulse sequences and the phenomena related to MRI as numerical data.