Yi Wang¹, Steen Moeller², An T. Vu², Kamil Ugurbil², Essa Yacoub², and Danny JJ Wang^1
1Neurology, UCLA, Los Angeles, CA, United States, ²Center of Magnetic Resonance Research, University of Minnesota, MN, United States

Multiband imaging or simultaneous multi-slice excitation has recently been applied for arterial spin labeling perfusion MRI using Blipped-CAIPI based EPI readout. It has been shown that this technique can expedite ASL imaging acquisition, improve image coverage and/or resolution with little penalty or even gain in SNR. Another advantage of MB acquisition for ASL is shortened T1 relaxation of the label, which degrades ASL signal in conventional sequential 2D EPI readout. However, MB EPI still suffers from susceptibility, N/2 ghosting and other distortion artifacts, especially at high and ultrahigh magnetic fields. In this work, we present a MB turbo-FLASH based pseudo-continuous ASL sequence that is able to provide whole-brain distortion-free perfusion images at both 3 and 7T.

Dimo Ivanov^1,2, Benedikt A Poser^1,2, Laurentius Huber³, Josef Pfeuffer⁴, and Kâmil Uludağ^1,2
1Department of Cognitive Neuroscience, Maastricht University, Maastricht, Netherlands, ²Maastricht Brain Imaging Centre, Maastricht, Netherlands, ³Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ⁴Siemens Healthcare, Erlangen, Germany

Despite potential advantages of performing ASL at 7T, its successful implementation poses significant technical challenges related to SAR constraints and B1-inhomogeneities. In this work, we propose a combination of FAIR QUIPSSII labelling scheme, utilizing optimized tr-FOCI inversion pulses, and simultaneous multi-slice, multi-echo EPI readout for high-SNR whole-brain perfusion measurements. This approach offers high temporal resolution simultaneous CBF and BOLD measurements that can find application in both neuroscientific and clinical studies at 7T.

Marta Vidorreta¹, Evelyne Balteau², Ze Wang^3,4, Enrico De Vita^5,6, David L. Thomas⁵, John A. Detre^4,7, and María A. Fernández-Seara^1
1Functional Neuroimaging Laboratory, CIMA, University of Navarra, Pamplona, Navarra, Spain, ²Cyclotron Research Centre, University of Liege, Liege, Belgium,³Department of Phsychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, United States, ⁴Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States, ⁵Academic Neuroradiological Unit, Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom,⁶Lysholm Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, London, United Kingdom, ⁷Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, United States

Recent technical developments have significantly increased the SNR of ASL perfusion MRI. Despite this, typical ASL acquisitions still employ large voxel sizes. Here, we implemented two optimized ASL sequences that allow whole-brain high-SNR high-resolution ASL acquisitions without increasing scanning duration, featuring pseudo-continuous labeling and segmented 3D readouts with background suppression. Two readout schemes were tested, with Cartesian and spiral-based in-plane trajectories. Perfusion maps were acquired in 15 volunteers with resolution 2x2x4mm3, and quality was assessed via SNR and GM-WM contrast. The spiral-based readout yielded higher SNR due to its inherent central k-space oversampling, and shorter effective TE and readout time.

Cheng Ouyang¹, Aiming Lu¹, Xiangzhi Zhou¹, and Mitsue Miyazaki^1
1Toshiba Medical Research Institute USA, Vernon Hills, IL, United States

The single-artery, or vessel-selective, pCASL sequence has demonstrated to provide regional perfusion maps non-invasively. However, similar to the original pCASL labeling, vessel-selective pCASL is also sensitive to off-resonance effects, which introduce phase errors in the labeling RF train and thus compromise in tagging efficiency. In this work, we propose to restore the signal loss due to off-resonance effects by applying a modified multiple phase correction method in the vessel-selective labeling sequence.

Johanna Kramme¹, Johannes Gregori², Volker Diehl^1,3, Vince Istvan Madai^4,5, Federico C von Samson-Himmelstjerna^1,4, Markus Lentschig³, Jan Sobesky^4,5, and Matthias Günther^1,6
1Fraunhofer MEVIS, Bremen, Bremen, Germany, ²Mediri GmbH, Heidelberg, Germany, ³ZEMODI, Bremen, Germany, ⁴Center for Stroke Research Berlin, Charité Universitätsmedizin, Berlin, Germany, ⁵Department of Neurology, Charité Universitätsmedizin, Berlin, Germany, ⁶University of Bremen, Bremen, Germany

SNR loss due to T1 decay at long TIs can be partly compensated by redistributing the acquisition schemes, resulting in improved perfusion quantification especially for patients with prolonged BATs. Varies redistribution schemes are presented where the number of averages is reduced at short TIs and increased at long once. The impact of the redistribution on perfusion estimation in cases of long BAT is studied and compared to the standard acquisition method. Such a correction is of high clinical relevance in cerebrovascular diseases or elderly patients showing prolonged BAT, as demonstrated in patients and in comparison to volunteers.

Marijn van Stralen¹, Hanke Schalkx², Nicky H.G.M. Peters², Wouter Veldhuis², Maarten S Van Leeuwen², Maurice A.A.J. van den Bosch², Josien P.W. Pluim¹, and Esben T. Petersen^2
1Image Sciences Institute, University Medical Center, Utrecht, Netherlands, ²Radiology, University Medical Center, Utrecht, Netherlands

Spin labeling (SL) MRI of the liver has not yet been widely investigated. Previously used single time point readout does not take bolus arrival time differences into account, hampering quantification. Therefore, SL-MRI with Look-Locker (LL) readout was investigated with pulsed and pseudo-continuous labeling strategies in healthy volunteers. We found regional and intersubject differences in bolus arrival time. Hepatic SL-MRI with LL readout could successfully quantify portal venous perfusion, with both labeling strategies, and was comparable to flow-based perfusion.

Zhiqiang Li¹, Michael Schär^1,2, Dinghui Wang¹, Nicholas R Zwart¹, and James G Pipe^1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ, United States, ²Philips Healthcare, Cleveland, OH, United States

Various segmented 3D acquisitions have been developed for Arterial Spin Labeling. Conventional spiral TSE ASL uses a spiral-out readout to collect data on a stack of spiral trajectory. So not only the spin echo is not aligned with the center of k-space, but it also requires the number of slices be equal to (or a multiple of) ETL. Here a 3D spiral TSE sequence is proposed by employing a spiral-in/out readout on a distributed spiral trajectory. The preliminary results demonstrate that the proposed technique can produce comparable or better image quality when compared to 3D GRASE ASL.

Ilaria Boscolo Galazzo¹, Michael A Chappell², David L Thomas³, Xavier Golay³, Paolo Manganotti¹, and Enrico De Vita^3,4
1Department of Neurological and Movement Sciences, University of Verona, Verona, Italy, ²Institute of Biomedical Engineering, University of Oxford, Oxford, United Kingdom, ³Academic Neuroradiological Unit, Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom, ⁴Lysholm Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, London, United Kingdom

3D-GRASE is one of the most efficient readout schemes for Arterial Spin Labeling (ASL) when whole brain coverage is desired. Due to the length of the echo train, single-shot 3D-GRASE images exhibit severe T2 blurring along the partition-encoding direction. We present a procedure to reduce the blurring effect in single inversion-time data, combining a multi-shot 3D-GRASE-ASL sequence with a post-acquisition deblurring algorithm. The application of this algorithm allows a reduction of the number of shots needed for each image. As more averages can be collected for a fixed acquisition time, this method improves the available signal-to-noise ratio and data quality.

Jia Guo¹ and Eric C. Wong^2
1Bioengineering, UC San Diego, La Jolla, California, United States, ²Radiology and Psychiatry, UC San Diego, California, United States

Transit delay (TD) sensitivity remains the main source of error in local CBF quantification using ASL. Compared with PASL and PCASL, Velocity-Selective ASL (VSASL) labels spins on the basis of flow velocity instead of location. In theory, VSASL eliminates the gap between the tagging and imaging regions and the associated long and heterogeneous TDs. However, it has not been verified by direct measurement of TDs in VSASL. This study is the first one to provide direct experimental evidences of VSASL being insensitive to TD, in contrast to PASL and PCASL. The averaged TDs of PCASL, PASL and VSASL were 1.28±0.28s (mean±std), 1.09±0.28s and 0.24±0.07s respectively, via multi-TI experiments.

Weiying Dai¹ and David Alsop^1
1Radiology, Beth Israel Deaconess Medical Center & Harvard Medical School, Boston, MA, United States

Arterial spin labeling (ASL) has proven to be useful tool both in clinical and research applications. Transforming ASL images of multiple subjects to a common space is first critical step for any statistical inference. However, the low SNR of ASL and bright voxels outside the brain complicate accurate and automated normalization. Here, we propose a robust and automated normalization procedure by taking advantage of the recent advancements of T1 based normalization. The normalization method is very robust and accurate and has been tested in all 146 subjects scanned in a representative elderly cohort.

Weiying Dai¹, Ajit Shankaranarayanan², and David Alsop^1
1Radiology, Beth Israel Deaconess Medical Center & Harvard Medical School, Boston, MA, United States, ²Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States

Brain resting state fluctuation networks has been reported contributing to the variability in Arterial Spin Labeling (ASL) measurements. However, a larger, globally correlated fluctuation appears to be the greatest contributor. Here we employ cardiac and respiratory cycle measurements during repeated ASL measurements to assess the systemic physiologic contribution to ASL fluctuations and to separate them from fluctuations with more brain specific origins. Five healthy volunteers were scanned using resting state ASL imaging with physiological monitoring of cardiac and respiratory signals. Global ASL signals was associated with cardiac phase but not with respiratory phase. After removing the cardiac noise, a large globally correlated fluctuation still exists, suggesting the presence of a global brain network independent of other resting state networks.

Benjamin Kandel^1,2, James C. Gee³, Jiongjiong Wang⁴, and Brian B Avants^3
1Bioengineering, University of Pennsylvania, Philadelphia, PA, United States, ²Penn Image Computing and Science Laboratory, Philadelphia, PA, United States, ³Penn Image Computing and Science Laboratory, University of Pennsylvania, PA, United States, ⁴University of California Los Angeles, CA, United States

Cerebral blood flow (CBF) is partially determined by brain structure. Current methods for analyzing CBF imaging techniques, such as arterial spin labeling, only take into account limited anatomical information. We propose a method that uses a dictionary learning approach to provide a more rigorous decomposition of CBF images into a component that can be predicted by structural information and a "purely functional" component that cannot be predicted using brain structure. This technique has shown to predict a greater proportion of CBF than segmentation maps, and can be used for assessing the relative contributions of CBF and structural imaging.

Zahra Shirzadi¹, David E Crane¹, Benjamin I Goldstein^2,3, Sandra E Black^1,4, and Bradley J MacIntosh^1,5
1HSF Canadian Partnership for Stroke Recovery, Sunnybrook Research Institute, Toronto, Ontario, Canada, ²Evaluative Clinical Sciences, Brain Sciences Research Program, Sunnybrook Research Institute, Toronto, Ontario, Canada, ³Departments of Psychiatry and Pharmacology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada, ⁴Division of Neurology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada, ⁵Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Arterial spin labeling (ASL) can be used to provide quantitative cerebral blood flow (CBF) images; however, the intrinsic low signal-to-noise ratio (SNR) limits its clinical applications. We propose a novel analysis approach that works in automated fashion by rejecting portions of the ASL data based on whether head motion during the individual difference image reduced the CBF sensitivity. Compared to conventional ASL analysis, our approach improved SNR by 9% (p-value<0.001) among 67 participants ranging in age from 14 to 88 years old. We also conducted between groups comparison to assess the impact of age and brain disorders on image quality.

Wen-Chau Wu^1,2, Shu-Fen Jiang³, and Shu-Hua Lien^3
1Graduate Institute of Oncology, National Taiwan University, Taipei, Taiwan, ²Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, ³Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan

In pseudocontinuous arterial spin-labeling (PCASL), labeling efficiency () is sensitive to field inhomogeneity. Multiphase PCASL (MP-PCASL) calibrates  by tracking image intensities with varied phase offsets () in the labeling pulses. In the present study, we investigated the feasibility of generating flow maps by combining the MP-PCASL images obtained at a subset of 's. Results show that the measurements of individual 's in MP-PCASL can be combined to provide perfusion mapping with an SNR  0.6-fold of the value provided by single-phase PCASL. The gain of SNR is expected to appear when the background-induced phase exceeds 50⁰.

Marco Battiston¹, Marco Castellaro¹, Carlo Boffano², Maria Grazia Bruzzone², and Alessandra Bertoldo^1
1Department of Information Engineering, University of Padova, Padova, Italy, ²Neuroradiology Department, IRCCS Foundation Neurological Institute "C.Besta", Milano, Italy

Labeling efficiency is a critical parameter in pseudo Continuous Arterial Spin Labeling since it directly scales quantitative estimates of Cerebral Blood Flow, but is subject to several sources of variability, that make difficult its assessment with numerical simulations. Phase Contrast MRI offers a way to estimate labeling efficiency in vivo. In this study a fully automated tool for labeling efficiency estimation is proposed, and tested on a group of healthy subjects. It provides labeling efficiency estimates in agreement with commonly accepted values for pCASL, and improves a previous method allowing reproducible analysis, useful in quantitative comparisons between different studies.

Joost P.A. Kuijer¹, Alexandra De Sitter¹, Maja A.A. Binnewijzend², Frederik Barkhof², and Rudolf M. Verdaasdonk^1
1Physics and Medical Technology, VU University Medical Center, Amsterdam, NH, Netherlands, ²Radiology, Nuclear Medicine and PET Research, VU University Medical Center, Amsterdam, NH, Netherlands

Partial volume correction (PVC) is regularly applied to quantify the cerebral perfusion of grey and/or white matter. PVC methods are usually validated with simulated datasets, however these might not model all aspects of real ASL data. In this study two checks are proposed to evaluate a PVC method: downsampling or spatial low-pass filtering of both perfusion and PVE maps should not alter the perfusion for each tissue type. These checks were applied to ASL data of six healthy volunteers and the linear regression PVC method. While the simulated data suggest a proper PVC, real ASL data fail the proposed check.

David D Shin¹, Youngkyoo Jung², Ho-Ling Liu³, and Thomas T Liu^1
1Center for Functional MRI, University of California, San Diego, La Jolla, CA, United States, ²Radiology, Wake Forest School of Medicine, Winston-Salem, North Carolina, United States, ³Department of Medical Imaging & Radiological Sciences, Chang Gung University, Taoyuan, Taiwan

MPPCASL is a promising technique for mitigating the adverse effects of off-resonance fields and gradient imperfections on the inversion efficiency in PCASL. In MPPCASL, the blood magnetization is modulated with multiple RF phase offsets, and the resulting signal is then fit to a model function to generate a CBF estimate. In the original MPPCASL approach, a model function assuming a fixed flow velocity was used. Here we investigate a fitting procedure that fits for both flow velocity and CBF. We find that the new fitting approach provides more accurate estimates of CBF over a wide range of velocities and also provides an estimate of the flow velocity.

Yi Dang¹, Jia Guo², Jue Zhang^1,3, and Eric Che Wong^4
1Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China, ²Department of Bioengineering, University of California San Diego, CA, United States,³College of Enigneering, Peking University, Beijing, Beijing, China, ⁴Department of Radiology and Psychiatry, University of California San Diego, CA, United States

Random vessel-encoded arterial spin labeling was proposed to simultaneously measure perfusion territories and detect feeding arteries without prior knowledge of their positions. However, the source location of a territory is often blurred so that it is difficult to be manually identified. In addition, mixed supply in one territory may lead to incorrect vessel detection and decoding of perfusion territories. In the present study, we propose a new data processing pathway for R-VEASL based on region growing and matching pursuit for automatic detection of vascular territories and source vessel locations. This RG-MP method also can resolve mixed supplies.

Marco Castellaro¹, Denis Peruzzo², Carlo Boffano³, Maria Grazia Bruzzone³, and Alessandra Bertoldo^1
1Department of Information Engineering, University of Padova, Padova, Italy, ²Department of Neuroimaging, Research institute IRCCS "E. Medea", Bosisio Parini, Lecco, Italy, ³Neuroradiology Department, IRCCS Foundation Neurological Institute "C.Besta", Milano, Italy

Since ASL technique has been proposed, is necessary to and compute the average of a high number of repetitions to achieve a good SNR. This process can be affected by the presence of outliers in the data that could be caused by several artefacts or physiological tissue signal fluctuation. These outliers can highly impact estimation of perfusion. This work presents a novel method to exclude corrupted volumes and achieve more reliable estimates of perfusion. The method proposed was able to distinguish between corrupted and uncorrupted volumes on both simulated and real data.

David D Shin¹, Michael A Chappell², and Thomas T Liu^1
1Center for Functional MRI, University of California, San Diego, La Jolla, CA, United States, ²Institute of Biomedical Engineering & FMRIB Centre, University of Oxford, Oxford, United Kingdom

Multiphase PCASL is a variant of PCASL that mitigates the tagging efficiency loss resulting from off-resonance fields and gradient imperfections. Instead of acquiring the ASL data at two RF phase offsets, the signals from multiple phase offsets are acquired and then fit to an expected inversion response curve to form an estimate of the perfusion signal. In this work, an alternate Bayesian nonlinear method is presented that incorporates a spatial prior on the model parameters. Using ten healthy subjects, the quantified CBF maps from the two methods are compared within gray matter, white matter, and in regions where the original fitting approach greatly overestimates CBF.

Marco Castellaro¹, Esben Thade Petersen², Xavier Golay³, Alessandra Bertoldo¹, and Michael A Chappell^4
1Department of Information Engineering, University of Padova, Padova, PD, Italy, ²Departments of Radiology and Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands, ³Institute of Neurology, University College London, London, United Kingdom, ⁴Institute of Biomedical Engineering, University of Oxford, Oxford, Oxford, United Kingdom

QUASAR is an established sequence for the study of perfusion that uses arterial spin labelling principles. It exploits the use of a vascular crushing gradient to extract signals from blood both in arteries and in tissue. Model-free and model-based approaches have been proposed to estimate perfusion and other parameters of interest. In this work a more realistic relationship between the crushing gradients and the blood flow is introduced based on the principles of perfusion tensor imaging. It is able to provide quantification of flow speed in arteries exploiting information already present in the data, which might be valuable in pathologies.

Ramesh Paudyal¹, Chun-Xia Li¹, Edward J. Auerbach², and Xiaodong Zhang^1
1Yerkes Imaging Center, Yerkes Regional Primate Research Center, Emory University, Atlanta, GA, United States, ²Center for MR Research, University of Minnesota, MN, United States

Arterial spin labeling (ASL) can be used to study stroke and other cerebrovascular diseases. Biexpoential fit to the signal decay data arising from the vascular and tissue compartments acquired using a modified diffusion weighted (DW) - ASL perfusion technique yields the fast and slow diffusion components and their respective volume fractions. In this study, we demonstrated the differences in the fitted parameter in both the slow and fast diffusing components in the white and gray matter in non-human brain primates using diffusion weighted (DW) - ASL perfusion data.

Steffen N Krieger^1,2, Claudine J Gauthier², Parnesh Raniga^1,3, Dale Tomlinson¹, Paul Finlay⁴, Richard McIntyre^1,4, Robert Turner², and Gary F Egan^1
1Monash Biomedical Imaging, Monash University, Melbourne, Victoria, Australia, ²Max-Plank Institute for Human Cognitive and Brain Sciences, Leipzig, Saxonia, Germany,³The Australian e-Health Research Centre, CSIRO Preventative Health Flagship, CSIRO Computational Informatics, Herston, Queensland, Australia, ⁴Monash Medical Centre, Melbourne, Victoria, Australia

Several inversion recovery MRI sequences have started to use hyperoxic or hypercapnic gas breathing challenges in order to study brain physiology. Increased inhaled concentrations of O₂ and CO₂ can, however, lead to changes in blood T₁ which might influence the accuracy of these techniques. We used an IR Look-Locker EPI MRI sequence to estimate cerebral arterial and venous blood T₁ changes during the inhalation of 7 gas mixtures. Our results indicate that hyperoxic-hypercapnic as well as normoxic-hypercapnic breathing challenges with high CO₂ contents lead to decreased blood T₁ which might be a useful information for eg ASL and calibrated BOLD studies.

Manus Joseph Donahue¹, Carlos Faraco¹, Lindsey Dethrage¹, Swati Rane¹, Megan Strother¹, Jeroen Hendrikse², and Jeroen Siero^2
1Vanderbilt University, Nashville, TN, United States, ²University Medical Center Utrecht, Utrecht, Netherlands

We perform multi-TI ASL measurements to simultaneously quantify CBF and AAT in multiple brain regions in response to different types of common gas stimuli: (i) room air, (ii) 5% CO2 / 95% room air (i.e., CO2/air), and (iii) 5% CO2 / 95% O2 (i.e., carbogen). Relative to room air, in all lobes, CBF was higher with CO2/air (P<0.05; range=14.9-24.5%) and carbogen (range=9.3-21.6%) stimulus, and AAT lower (P<0.05; CO2/air range=-13.4 - -20.6%; carbogen range=-9.2 - -12.1%). Values can be used as an exemplar for understanding how hypercarbia-induced CBF changes are influenced by blood water arrival time.

Magdalena Sokolska^1,2, Maia Proisy³, Cristina Uria-Avellanal³, Alan Bainbridge², Ernest Cady², David Thomas¹, Nicola Robertson³, and Xavier Golay^1
1UCL Institute of Neurology, London, London, United Kingdom, ²UCH Medical Physics and Bioengineering, London, London, United Kingdom, ³UCL Institute for Women's Health, London, United Kingdom

Cerebral blood flow (CBF) reflects cerebral metabolic demand, and can be altered in neonates with brain injury. Proton MR spectroscopy (MRS), in particular thalamic Lac/NAA peak ratio, has been shown to be the best predictor of clinical outcome so far1. Adding estimation of CBF to MR spectroscopy (MRS) has the potential to both increase understanding of the injury cause and progression and to help develop and assess new neuroprotective treatments. CBF can be quantified non-invasively using Arterial Spin Labeling (ASL). The aim of this study was to investigate neurophysiological changes in babies with suspected hypoxic ischaemic brain injury using MRS and ASL.

Dennis F R Heijtel¹, Henri J M M Mutsaerts¹, Esther Bakker², Patrick Schober³, Markus F Stevens⁴, Esben T Petersen⁵, Bart N M van Berckel², Charles B L M Majoie¹, Jan Booij⁶, Matthias J P van Osch⁷, Ed T vanBavel⁸, Ronald Boellaard², Adriaan A Lammertsma², and Aart J Nederveen^1
1Radiology, Academic Medical Center, Amsterdam, Netherlands, ²Radiology and Nuclear Medicine, VU University Medical Center, Amsterdam, Netherlands, ³Anesthesiology, VU University Medical Center, Amsterdam, Netherlands, ⁴Anesthesiology, Academic Medical Center, Amsterdam, Netherlands, ⁵Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ⁶Nuclear Medicine, Academic Medical Center, Amsterdam, Netherlands, ⁷C.J. Gorter Center for High Field MRI, Radiology, Leiden University Medical Center, Leiden, Netherlands, ⁸Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, Netherlands

In this study we assessed the accuracy and precision of quantitative pCASL-based CBF and CVR measurements by performing a head-to-head comparison with ¹⁵O H₂O PET, based on quantitative CBF measurements during baseline and hypercapnia. We demonstrate that pCASL CBF imaging is accurate during both baseline and hypercapnia with a precision comparable to ¹⁵O H₂O PET.

Patrick W Hales¹, Jamie M Kawadler¹, Sarah E Aylett², Fenella J Kirkham³, and Christopher A Clark^1
1Imaging & Biophysics Unit, Institute of Child Health, University College London, London, United Kingdom, ²Great Ormond Street Hospital, London, United Kingdom,³Neurosciences Unit, Institute of Child Health, Univsersity College London, London, United Kingdom

We used arterial spin labelling MRI to measure changes in cerebral haemodynamics during normal development, between 8-32 years of age. We present mean and normal reference ranges for T1, M0 (equilibrium longitudinal magnetization), cerebral blood flow (CBF), bolus arrival time and bolus duration. A negative correlation with age was seen in CBF and T1 throughout cortical grey matter. Increased bolus dispersion with age was observed in the anterior and posterior arterial territories, and gender differences were seen in the evolution of M0. These data will help when optimizing ASL protocols for paediatric imaging, and identifying age-matched perfusion abnormalities in pathologies.

BIN CHEN¹, Hao Li¹, Ya Cao¹, Chengyan Wang¹, Xiaoying Wang^1,2, JUE ZHANG^1,3, and Jing Fang^1,3
1Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, Beijing, China, ²Radiology, Peking University First Hospital, Beijing, Beijing, China, ³College of Engineering, Peking University, Beijing, Beijing, China

Glomerular filtration rate (GFR) measurements have been studied with various kinetic models, however, all these techniques are based on gadolinium contrast agent. Arterial blood spin labeling MR imaging uses the water spins of blood as an endogenous tracer, therefore it is completely noninvasive. In this study, we aimed to investigate the variable-TE based FAIR-ASL technique in measuring GFR in human kidneys. Volunteer experiments show good reproducibility of the established method in renal function estimation.

Rajiv Ramasawmy^1,2, Adrienne E. Campbell-Washburn³, Sean Peter Johnson¹, Jack Anthony Wells¹, Rosamund Barbara Pedley², Mark Francis Lythgoe†¹, and Simon Walker-Samuel†^1
1Centre for Advanced Biomedical Imaging, University College London, London, Greater London, United Kingdom, ²Cancer Institute, University College London, London, Greater London, United Kingdom, ³National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States

Hepatic ASL (hASL) is an emerging area of research interest. We present repeatability and variability analysis of a respiratory-triggered flow-sensitive alternating inversion recovery (FAIR) Look-Locker arterial spin labelling (ASL) technique to measure mouse liver perfusion. To evaluate the liver ASL technique, repeatability and variability statistics were produced for repeat measurements within a single imaging session and between imaging sessions separated by one week. We show that the repeatability of the technique is potentially sufficient to allow longitudinal monitoring of pre-clinical liver perfusion in models of diseases such as cancer and cirrhosis.

Andrea Federspiel¹, Mirjam Rachel Heldner², Urs Fischer², Jan Gralla³, and Roland Wiest^3
1Psychiatric Neurophysiology, University Hospital of Psychiatry, University of Bern, Bern, Bern, Switzerland, ²Department of Neurology and Stroke Center, University of Bern, Bern, Bern, Switzerland, ³Institute of Diagnostic and Interventional Neuroradiology, University of Bern, Bern, Bern, Switzerland

In the present study the relationship between cerebral blood flow (CBF) and CBF velocity was investigated in a cohort of twenty patients with intracranial stenosis. After rigorous treatment physiology-related artefacts of vessel-selective arterial spin labeling (sASL) time series a significant positive linear relationship located within the anterior and posterior watershed areas of the middle cerebral artery (MCA). The findings of the present study suggest that regional CBF measures along watershed territories as measured by sASL are reliable markers of sufficient collateral supply.

Sophie Schmid*¹, Dennis F.R. Heijtel*², Henri J.M.M. Mutsaerts², Ronald Boellaard³, Adriaan A. Lammertsma⁴, Aart J. Nederveen², and Matthias J.P. van Osch^1
1C.J. Gorter Center for High Field MRI, Radiology, Leiden University Medical Center, Leiden, Netherlands, ²Radiology, Academic Medical Center, Amsterdam, Netherlands,³Radiology, VU University Medical Center, Amsterdam, Netherlands, ⁴Department of Nuclear Medicine and PET Research, VU University Medical Center, Amsterdam, Netherlands

The aim of this study was to compare AccASL and VS-ASL with ¹⁵O H₂O PET. Quantitative VS-ASL overestimated GM CBF by 17% compared to PET. A comparable correlation coefficient for Dual VS-ASL and pCASL with PET CBF was found, evaluated voxelwise at the single subject level; AccASL and Single VS-ASL showed lower correlation with PET CBF. The change in the correlation coefficient by including a fraction of PET aCBV was minor for all scans.

Eric Peterson¹, Heiko Schmiedeskamp¹, Julian Maclaren¹, Nils Forkert¹, Samantha Holdsworth¹, Rafael O'Halloran¹, Eric Aboussouan¹, William Grissom², Salil Soman¹, and Roland Bammer^1
1Radiology, Stanford University, Stanford, CA, United States, ²Biomedical Engineering, Vanderbilt, Nashville, TN, United States

Spin and Gradient Echo (SAGE) imaging has been recently developed in order to more robustly generate perfusion parameters, as well as incorporate the ability to determine tissue leakage in vivo. These properties make it a very potent imaging sequence, however by acquiring both spin and gradient echo images, the repetition time is significantly increased. This necessitates acquiring fewer slices with a longer repetition time than would be necessary for either spin or gradient echo imaging alone. This work presents increased slice coverage and acceleration of SAGE using simultaneous multi-slice imaging.

Cornelius Eichner^1,2, Kourosh Jafari-Khouzani¹, Stephen Cauley¹, Himanshu Bhat³, Pavlina Polaskova¹, Ovidiu C Andronesi¹, Otto Rapalino¹, Robert Turner², Lawrence L Wald¹, Steven Stufflebeam¹, and Kawin Setsompop^1
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, ²Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, ³Siemens Healthcare Sector, Boston, MA, United States

Gadolinium contrast based dynamic susceptibility contrast (DSC) MRI of combined gradient and spin echo (GESE) is an important clinical method to quantify perfusion in healthy and tumorous brain tissue. High temporal sampling is necessary to sufficiently resolve bolus passage, however limits slice-coverage. This work proposes a blipped CAIPI simultaneous-multiple-slice (SMS) method to improve slice range. DSC data with and without SMS were acquired on three tumor patients. SMS DSC with two-fold slice acceleration achieves similar SNR and perfusion metrics as standard acquisitions, whilst allowing doubled slice coverage. The results also point to improved temporal sampling rate with constant slice-coverage.

Thomas Christen¹, Deqiang Qiu¹, Wendy Wei Ni¹, Heiko Schmiedeskamp¹, Michael E Moseley¹, and Greg Zaharchuk^1
1Department of Radiology, Stanford University, Stanford, California, United States

It has been recently suggested that following a bolus of contrast agent (CA) with a combined spin- and gradient-echo sequence can bring valuable information about vessel architecture and oxygenation. While promising, the approach might however suffer from low signal to noise ratio as well as contrast agent leakage if a gadolinium based CA is used. As an alternative, we propose to follow an injection of ferumoxytol, an FDA-approved ultra-small paramagnetic iron oxide (USPIO) compound. We scanned 10 volunteers to study the feasibility of approach and combined the results with bolus perfusion and quantitative BOLD analyses.

Benjamin Lemasson¹, Nicolas Pannetier², Thomas Christen³, Greg Zaharchuk³, Norbert Schuff², and Emmanuel Barbier^1
1U836, Iserm, Grenoble, France, ²Va medical center, Centre for neurodegenerative des eases, San Francisco, CA, United States, ³Stanford University, Department of Radiology, Stanford, CA, United States

Cerebral blood volume fraction (BVf) and vessel size index (VSI) can be mapped with a steady-state approach. To optimize the protocol in the brain, we evaluated the impact of three different doses of contrast agent and three different MRI sequences on the results obtained in healthy rats (n=5). When mapping BVf and VSI at 4.7T, the use of an echo time beyond 60ms decreases the CNR. Regarding the CA dose, no significant changes has been observed on BVf map whereas the use of 200µmol of Fe/kg yields the best CNR at the Spin-echo time but two-third of the dose appears almost equivalent in term of CNR.

Amit Mehndiratta¹, Fernando Calamante², Bradley J MacIntosh³, David E Crane³, Stephen J Payne¹, and Michael A Chappell^1
1Institute of Biomedical Engineering, University of Oxford, Oxford, Oxfordshire, United Kingdom, ²Florey Institute of Neuroscience and Mental Health, Heidelberg, Victoria, Australia, ³Medical Biophysics, Sunnybrook Research Institute, University of Toronto, Toronto, ON, Canada

Bolus dispersion can be a significant source of error in estimation of both perfusion and tissue residue function in DSC-MRI. In this study the recently proposed non-parametric CPI method was extended with dispersion-kernel (DK) to address dispersion effects. Three DKs were evaluated to identify the appropriate model for dispersion in-vivo. The performance of the proposed approach was assessed using simulations. In-vivo data from a patient with arteriosclerotic disease was also analysed. Addition of a DK in perfusion analysis was found to be useful both in simulations and in-vivo, but with no consistent benefit of one DK over other was observed.

Steven P. Sourbron^1
1University of Leeds, Leeds, United Kingdom

Conventional tracer-kinetic analysis of DSC- and DCE-MRI assumes that all voxels are isolated systems supplied by the same arterial concentration. Here a more general tracer-kinetic field theory is developed that models voxels as interconnected systems that only exchange indicator with their immediate neighbours. Explicit field models are derived for total blood flow, microvascular blood flow, endothelial permeability and interstitial diffusion. With these models, the spatial structure of the measured concentration can be exploited to characterize perfusion anisotropy, and to eliminate systematic errors due to bolus dispersion and large-vessel contamination.

Steven P. Sourbron^1
1University of Leeds, Leeds, United Kingdom

Tracer-kinetic field theory models indicator transport as an exchange between voxels and thus eliminates bolus-dispersion errors caused by the assumption of a global AIF. Here a numerical approach is proposed to reconstruct the parameter fields from the measured concentrations. Initial simulations are performed to investigate practicality and stability with respect to noise and temporal undersampling. The results suggest that the reconstruction is feasible on standard PC’s and provides accurate results at realistic levels of noise and temporal resolution. A practical advantage is that the boundary concentrations can be reconstructed, eliminating the need for a separate AIF measurement.

Moran Artzi^1,2, Guy Nadav^1,3, Gilad Liberman¹, Orna Aizenstein¹, and Dafna Ben Bashat^1,4
1Functional Brain Center, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel, ²Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel, ³Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel, ⁴Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel

Cerebral blood volume (CBV) obtained using DSC is an important parameter for brain tumor assessment. DCE can also be used to extract blood plasma volume (Vp). This study investigated the relationship between DSC-CBV and DCE-Vp. A high correlation between cerebral DCE-Vp and DSC-CBV was detected in 22 healthy subjects. In three patients with brain tumors, similar maps were obtained with values above the threshold of 1.75, indicating malignant tumors. These results suggest DCE as preferable to DSC for blood volume assessment; this method has high spatial resolution, is less sensitive to susceptibility artifacts and provides additional information regarding tissue permeability.

Andre Hallack¹, Michael A. Chappell¹, E. Mark Anderson², Fergus V. Gleeson², Mark J. Gooding³, and Julia A. Schnabel^1
1Institute of Biomedical Engineering, Oxford University, Oxford, United Kingdom, ²Department of Radiation Oncology and Biology, Oxford University, Oxford, United Kingdom, ³Mirada Medical, Oxford, United Kingdom

This work presents a study on relaxation time (T₁₀) estimation on variable flip angle SPGR sequences for pharmacokinetic analysis of tumours on DCE-MRI using the Tofts model. Its aim is to assess the amount of patient motion found during these acquisitions and its effects on T₁₀, K_trans and k_ep estimation. 21 rectal tumour SPGR sequences were registered to estimate motion. Moreover, while using synthetic data, T₁₀ e, K_trans and K_ep estimation error was evaluated for various degrees of deformation. Overall, an average motion of 0.42mm was found, which translates into 10% T₁₀, 16% K_trans and 5% k_ep mean error.

Thomas Perret^1,2, Clément Debacker^1,2, Nicolas Pannetier^3,4, and Emmanuel L Barbier^1,2
1U836, INSERM, Grenoble, France, ²Grenoble Institut des Neurosciences, Université Joseph Fourier, Grenoble, France, ³Radiology, University of California San Francisco, San Francisco, California, United States, ⁴Center for Imaging of Neurodegenerative diseases, Veterans Affairs Medical Centre, San Francisco, California, United States

Using numerical simulation of DCE-MRI experiments, we investigated the interstitial space fraction (porosity) effect on MR signal. The strategy proposed estimates both permeability and porosity using multiple echo times. Simulations demonstrate that porosity has a strong impact on MR signal therefore on permeability estimates. Results show the feasibility of a method to obtain improved estimates of permeability and of tissue porosity.

Ben R Dickie¹, Anita Banerji^2,3, Catharine M West⁴, and Chris J Rose^2,3
1Christie Medical Physics and Engineering, Christie Hospital, Manchester, Greater Manchester, United Kingdom, ²Centre for Imaging Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom, ³Biomedical Imaging Institute, University of Manchester, Manchester, United Kingdom, ⁴Institute of Cancer Sciences, University of Manchester, Manchester, United Kingdom

A novel method for estimating DCE-MRI parameters is presented. Precontrast T1, M0, and model parameters are estimated jointly, differing from current practice where precontrast T1 and M0 are estimated prior to the model parameters (sequentially). The precision of the two methods were compared using a software phantom capable of simulating realistic abdominal anatomy, contrast enhancement (as modelled with the two-compartment exchange model) and non-linear local motion. Joint estimation led to significant improvements in the precision for all model parameters. In data with motion corruption, significant improvements in precision were observed for estimates of plasma perfusion and relative interstitial volume only.

Cristina Lavini^1
1Department of Radiology, Academic Medical Center, Amsterdam, Netherlands

Simulations are presented that aim at assessing the relative effect of input parameters (i.e. parameters describing the Arterial Input Function or the parameters needed to calculate the tissue contrast agent concentration) on the calculated pharmacokinetic parameters in Tofts’ modelling of DCE-MRI. It highlights the fact that for accurate measurement of the pharmacokinetic parameters, the accuracy of the parameters describing the initial part of the AIF is significantly more important than that of the slow decay, and that an accurate T1 measurement and a correct scaling of the AIF with respect to the tissue concentration is essential for accurate Ktrans measurement.

Frank G Zoellner¹, Philip Schmidt¹, and Lothar R Schad^1
1Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Baden-Wuerttemberg, Germany

Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) in conjunction with pharmacokinetic modelling can be used to assess physiological parameters like perfusion and permeability. The aim of this study was to investigate the effect of weighted fits applied to DCE-MRI data, using both simulated and measured samples, and the overall goal was to quantify if weighting leads to a better fit performance.It could be shown that in most of the studied tissues the errors of the fit parameters decreased when linear weights were applied. Initial results of the in vivo data of the rat shown made clear that weighting has a small but positive effect on the fit performance in living tissue

Tammo Rukat^1,2 and Stefan A Reinsberg^1
1Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada, ²Institut für Physik, Humboldt Universität zu Berlin, Berlin, Germany

The benefits from mixed model inference in pharmacokinetic models of DCE-MRI by means of Akaike and the Bayesian information criterion is investigated. Data is simulated based on published mouse and human AIFs and the MMID4, that approximates true tissue physiology. K^trans estimates are shown to benefit in accuracy and precision for a variety of investigated tissues.

Ben R Dickie¹, Catharine M West², and Chris J Rose^3,4
1Christie Medical Physics and Engineering, Christie Hospital, Manchester, Greater Manchester, United Kingdom, ²Institute of Cancer Sciences, University of Manchester, Manchester, United Kingdom, ³Centre for Imaging Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom,⁴Biomedical Imaging Institute, University of Manchester, Manchester, United Kingdom

The two-compartment exchange model can be fitted to DCE-MRI signal-time curves yielding estimates of plasma flow (Fp), plasma-interstitial exchange flow (FE) and relative plasma volume (vp) and relative interstitial volume (ve). The precision of these estimates is not likely to be uniform for all tissue types and this variation has not been studied in the literature. We present an evaluation of such errors for data with SNR of 5 and temporal resolution of 2.5s and show that as the plasma flow of the tissue of interest decreases below 0.1 ml/ml/min, relative errors in Fp and FE begin to rapidly increase.

Tingting Wu¹, Jinnan Wang², Yan Song³, Xiaotao Deng³, Xihai Zhao¹, Rui Li¹, Anqi Li³, Shuo Chen¹, Chun Yuan^1,4, and Huijun Chen^1
1Center for Biomedical Imaging Research, Tsinghua University, Beijing, Beijing, China, ²Philips Research North America, Briarcliff Manor, New York, United States, ³Beijing Hospital, Beijing, China, ⁴Dept. of Radiology, University of Washington, Seattle, Washington, United States

We evaluated the reproducibility of pharmacokinetic measurement by using contrast concentration conversion with pre-T1 mapping in DCE-MRI of experimental thin vessel wall (thickness < 1mm). We found that concentration conversion with pre-T1 mapping has poorest reproducibility, compared with normalized intensity curves and contrast concentration conversion with fixed pre-T1. Thus, adding pre-T1 mapping for concentration conversion in the analysis of DCE-MRI is not worthwhile on thin vessel wall imaging. Both concentration conversion with assumed pre-T1 or directly using the normalized signal curves are more preferable.

Martin Lowry¹, Lawrence Kenning², and Lindsay W Turnbull^1
1Centre for MR Investigations, Hull York Medical School at University of Hull, Hull, East Yorkshire, United Kingdom, ²Centre for MR Investigations, University of Hull, Hull, East Yorkshire, United Kingdom

Volumetric quantification of pharmacokinetic parameters for from DCE-MRI data is hampered by low SNR and computational time. An algorithm using principal component analysis and k-means clustering was developed which simultaneously alleviates both these factors to rapidly produce parameter maps with increased precision. The method reduced processing times by 60-fold with no change in mean parameter values. Maps of vb appeared more homogeneous with far fewer non fitting voxels. The proposed algorithm could remove the need for off-line processing thus making quantitative DCE-MRI more clinically acceptable

Melanie Freed¹ and Sungheon Kim^1
1Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, NY, United States

In this study, we quantitatively evaluate temporal blurring of DCE-MRI data sets generated using a k-space weighted image contrast image sharing technique with golden-angle view ordering (GA-KWIC) by examining the effect on estimated pharmacokinetic model parameters in simulation. Estimated Ktrans values have a larger bias for smaller lesions and higher true Ktrans values, resulting in errors in estimated diagnostic accuracy for discrimination of benign and malignant lesions. However, the errors incurred are small compared to other sources of error in clinical studies. Therefore, GA-KWIC can be used to improve temporal resolution of DCE-MRI data without negatively impacting diagnostic accuracy estimation.

Edward Ashton¹, Jean Tessier², and Oliver Krieter^3
1Imaging Science, VirtualScopics, Inc., Rochester, NY, United States, ²F. Hoffman-La Roche Ltd., Basel, Switzerland, ³Roche Diagnostics GmbH, Penzberg, Germany

This study examines the scan-rescan variability of five parameters obtainable from DCE-MRI scans. The analysis models examined are the Standard Tofts, Extended Tofts, and Distributed Parameter. Two model-free parameters are also reviewed. Data were acquired from six GBM patients, each scanned twice within a single week. Coefficients of variability were calculated for each of six parameters: KTrans (Standard Tofts), KTrans (Extended Tofts), PS (Distributed Parameter), as well as IAUC90 and AUCBN90, which do not require an analysis model. Results show KTrans (Standard) and AUCBN90 to be the least variable assessments, while PS shows the highest variability of the parameters studied.

Massimo Mischi¹, Simona Turco¹, Cristina Lavini², Marcel Breeuwer³, Jean de la Rosette⁴, Mark Engelbrecht², and Hessel Wijkstra^1,4
1Electrical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, ²Radiology, Academic Medical Center University of Amsterdam, Netherlands, ³Philips Healthcare, Netherlands, ⁴Urology, Academic Medical Center University of Amsterdam, Netherlands

MR dispersion imaging (MRDI) is proposed as a new method for characterization of the microvascular architecture by assessment of contrast intravascular dispersion in DCE MRI. Dispersion is estimated by fitting a new model that integrates the Tofts’ model for extravascular leakage together with a solution of the convective-dispersion equation. Based on the established link between angiogenesis and cancer growth, this method is evaluated for localization of prostate cancer by comparison with histology results following radical prostatectomy. Without need for an arterial input function, MRDI enables accurate localization of prostate cancer, as confirmed by our initial validation with 90 MRI slices in 15 patients.

Uwe Klose¹, Sotirios Bisdas¹, Herbert Köstler², and Johannes Tran-Gia^2
1Department of Diagnostic and Interventional Neuroradiology, University Hospital of Tübingen, Tübingen, Germany, ²Institute of Radiology, University of Würzburg, Würzburg, Germany

A new fast T1 mapping method, based on the acquisition of 1000 single radial trajectories within a time of 6 s, allows the direct observation of T1 changes during DCE measurements. A single slice of a patient with a primary brain lymphoma was examined. In four regions, the dynamic T1 values were evaluated and Patlak plots were calculated, using the signal in the superior sagittal sinus to estimate the plasma concentration C_p(t). K^transvalues could be estimated as slopes of fitted straight lines in the Patlak plot. Remarkably low residuals between data points and fitted lines were found.

Anna K Heye¹, Michael J Thrippleton¹, Maria del C Valdés Hernández¹, Paul A Armitage², and Joanna M Wardlaw^1
1Brain Research Imaging Centre, Division of Neuroimaging Sciences, University of Edinburgh, Edinburgh, Scotland, United Kingdom, ²Academic Unit of Radiology, Department of Cardiovascular Science, Medical School, University of Sheffield, Sheffield, England, United Kingdom

This study uses T1-weighted DCE-MRI to quantify subtle blood-brain barrier permeability in normal-appearing white matter and white matter lesions of patients with mild stroke. We calculated Patlak’s pharmacokinetic parameters and two model-free measurements, all of which suggest that permeability is enhanced in white matter lesions when compared to normal-appearing white matter. Moreover, we investigated the relationship between model-free and pharmacokinetic parameters, showing moderate to strong correlations.

Adam Bernstein¹, Phillip H Kuo², Mark D. Pagel³, and Julio Cardenas-Rodriguez^3
1Department of Biomedical Engineering, University of Arizona, Tucson, AZ, United States, ²Department of Medical Imaging, University of Arizona, Tucson, AZ, United States, ³Department of Biomedical Engineering and Arizona Cancer Center, University of Arizona, Tucson, AZ, United States

In this work we analyzed retrospectively DCE MRI data of 17 patients. A comparison between the Linear Reference Region Model (LRRM) and the standard non-linear Reference Region Model (NLRRM) was performed. Clinical DCE MRI can be processed 90-400 times faster with the LRRM than with the NLRRM. The fitting RMSE was systematically 6-7 times higher for the NLRRM compared to the LRRM. Our results suggest that the LRRM is more reliable than the NLRRM when DCE MRI data with low SNR and temporal resolution is available.

Lucy E Kershaw¹, Gillian MacNaught², Mayank Serge Madhra³, Hilary O Critchley³, and Scott IK Semple^2
1Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, Gtr Manchester, United Kingdom, ²CRIC, University of Edinburgh, Edinburgh, United Kingdom, ³MRC Centre for Reproductive Health, University of Edinburgh, Edinburgh, United Kingdom

The aim of this study was to develop a DCE-MRI and T2* measurement protocol for monitoring dexamethasone therapy in women with heavy menstrual bleeding. A high spatial resolution protocol was developed that differentiated between inner and outer myometrium. Uptake curves could be markedly different in shape between patients, but T2* and DCE-MRI parameters were found to be similar to those described in previous work. No significant differences were found pre and post therapy but quantitative blood loss is not yet available for correlation with the measured parameters.

Chenxia Li^1,2, Hao Fu¹, Rong Wang¹, Jiayin Tong¹, Supin Wang², and Jian Yang^1,2
1Department of Radiology, The First Affiliated Hospital of Xi' an Jiaotong University, Xi'an, Shan Xi Province, China, ²Department of Biomedical Engineering, School of Life Science and Technology of Xi' an Jiaotong University, Xi'an, Shan Xi Province, China

The aim of this study is to investigate the relationship between the quantitative pharmacokinetic parameters of DCE-MRI and 3 fibroid types based on T2WIs. 23 fibroids (11 cases of type 1, 7 cases of type 2, 5 cases of type 3) in 23 females underwent T1WIs, T2WIs and DCE-MRI. It demonstrated that the Ktrans were no significant difference among the 3 types, suggesting the similar capillary permeability among them. Kep of type 3 was higher than type 1 and 2,which indicated that the wash-out of type 3 is faster and more heat energy may be taken away during ablation. Therefore, the quantitative pharmacokinetic parameters of DCE-MRI provide sensitive method in the patients selection for MRg HIFU.

Olaf Dietrich¹, Michael Ingrisch¹, Felix Schwab¹, Daniel Maxien², Konstantin Nikolaou², and Maximilian F. Reiser^1,2
1Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, LMU Ludwig Maximilian University of Munich, Munich, Germany, ²Institute for Clinical Radiology, LMU Ludwig Maximilian University of Munich, Munich, Germany

Recently, the feasibility of free-breathing dynamic contrast-enhanced (DCE) MRI for quantification of lung perfusion has been demonstrated. The purpose of our study was to analyze the influence of breathing-induced signal variations on the accuracy and precision of calculated perfusion parameters. Lung DCE-MRI data of 5 healthy volunteers were analyzed to determine typical data properties; signal curves in lung tissue were simulated and evaluated using a 1-compartment model. If analyzed without noise, the statistical variations of determined flow and volume parameters show clearly the influence of respiration-induced signal variations; at realistic noise levels, however, the influence of respiration is relatively low.

Radovan Jirik¹, Karel Soucek^2,3, Eva Drazanova¹, Lucie Grossová^1,4, Michal Standara⁵, Jirí Kratochvíla⁴, Ondrej Macícek⁴, Aneta Malá¹, Torfinn Taxt⁶, and Zenon Starcuk, Jr.^1
1Institute of Scientific Instruments of the ASCR, Brno, Czech Republic, ²Department of Cytokinetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czech Republic, ³Center of Biomolecular and Cellular Engineering, International Clinical Research Center, Brno, Czech Republic, ⁴Dept. of Biomedical Engineering, Brno Univ. of Technology, Brno, Czech Republic, ⁵Dept. of Radiology, Masaryk Memorial Cancer Institute, Brno, Czech Republic, ⁶Dept. of Biomedicine, Univ. of Bergen, Bergen, Norway

The contribution presents a new method for estimation of the arterial input function in dynamic contrast-enhanced MRI. A new parametric AIF model is introduced and a new blind multichannel deconvolution scheme is proposed. The esimated AIF is then used to provide perfusion-parameter maps. The method is evaluated on synthetic and real mouse data.

Wei Zha¹, David J. Niles¹, Shannon Reese², Arjang Djamali², and Sean B. Fain^1
1Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ²Medicine, University of Wisconsin-Madison, WI, United States

Quantitative renal perfusion is promising for the diagnosis and prognosis of kidney function. This study used DCE-MRI to monitor renal perfusion changes during obstructive nephropathy in a 7-day unilateral ureteral obstruction mouse model. A 3-compartmental model was used to quantify the tissue perfusion with gamma-variate curve fitting. Decreased cortical perfusion was found in the obstructed kidney in both NADPH oxidase isoform2 (NOX2) knock out (KO) and wild-type (WT) mice on Day 7. Results suggest the alteration in renal perfusion may be an early, sensitive indicator of the progression of renal fibrosis.

Cheng-He Li¹, Fang-Hsin Chen¹, Yu-Shi Lin², Ji-Hong Hong^1,3, and Ho-Ling Liu^1
1Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan, ²Diagnostic Radiology, Chang Gung Memorial Hospital, Keelung, Taiwan, ³Radiation Oncology, Chang Gung Memorial Hospital - Linkou, Taoyuan, Taiwan

This study aimed to evaluate the different flow versus permeability weighting in volume transfer constant (K^trans) when using contrast media with different molecular sizes and the extended Tofts model (ETM). Fourteen mice bred with tumors underwent DCE-MRI with either Gd-DTPA or Gadomer. The data were analyzed by using both ETM and the adiabatic approximation to the tissue homogeneity (AATH) model from which permeability-surface-area-product (PS) and plasma flow (F_p) were obtained. This study found that K^trans was more correlated with PS (r²=0.72) than F_p (r²=0.09) when using Gadomer, and more correlated with F_p (r²=0.64) than PS (r²=0.47) when using Gd-DTPA.

Kavindra Nath¹, Ramesh Paudyal², David S Nelson¹, Stephen Pickup¹, Rong Zhou¹, Dennis B Leeper³, Daniel F Heitjan¹, Charles S Springer⁴, Harish Poptani¹, and Jerry D Glickson^1
1University of Pennsylvania, Philadelphia, Pennsylvania, United States, ²Emory University, Atlanta, Georgia, United States, ³Thomas Jefferson University, Philadelphia, Pennsylvania, United States, ⁴Advanced Imaging Research Center, Oregon Health & Science University, Portland, Oregon, United States

The aim of the current study was to evaluate whether the changes in ATP levels after lonidamine (LND) administration in DB-1 melanoma xenografts correlated with changes in tumor i, a measure of mean lifetime of intracellular water protons using the Shutter Speed Model (SSM) in addition to Ktrans and ve. LND is a small molecule that inhibits the monocarboxylate transporter-1 (MCT-1) that reduces tumor pH and bioenergetics. We observed a significant decrease in Ktrans but increase in i following LND administration, which is associated with a change in cell size and membrane permeability or ion transport. Changes in Ktrans and i might serve as surrogate biomarkers, indicating that DCE-MRI not only measures tissue vascular hemodynamics, but also the transport activity and transmembrane water exchange or cycling.

Anthony S. Malamas¹, Erlei Jin¹, John Haaga², and Zheng-Rong Lu^1
1Case Western Reserve University, Cleveland, OH, United States, ²University Hospital Case Medical Center, Cleveland, OH, United States

A novel biodegradable polydisulfide-based macrocyclic contrast agent was developed for dynamic contrast enhanced (DCE) MRI. The new macromolecular agent selectively extravasates from leaky tumor vessels, while minimizing potentially toxic side effects due to cleavage of disulfide bonds incorporated into its backbone. This agent was utilized to study anti-angiogenic effects of Bumetanide, an inhibitor of NKCC cotransporters that has recently exhibited anti-tumoral capabilities, in colon cancer xenografts. DCE-MRI revealed that the polydisulfide contrast agent is able to detect significant reductions in the permeability and plasma volume fraction parameters, which were then verified by a decrease in CD31 expression upon IHC analysis.

In ok Ko¹, Byung Hyun Byun², Ji-ae Park¹, Kyeong Min Kim¹, and Sang Moo Lim^2
1Korea Institute of Radiological & Medical Science, seoul, nowon-gu, Korea, Democratic People's Republic of, ²Department of Nuclear Medicine, Korea Institute of Radiological & Medical Science, seoul, nowon-gu, Korea, Democratic People's Republic of

We evaluated the potentials of 18F-FDG PET metabolic parameters and dynamic contrast-enhanced (DCE) MRI perfusion parameters to predict the histologic response after neoadjuvant chemotherapy before surgery in patients with osteoscarcoma, using sequential PET/CT and MR imaging system. The cutoff values, sensitivity, specificity, and accuracy for predicting good histologic response were < 5, 92%, 58%, and 75%, respectively, for SUV_max from the 18F-FDG PET after neoadjuvant chemotherapy and < 0.03 min-1, 58%, 83%, and 71%, respectively, for K^trans from the DCE-MRI after neoadjuvant chemotherapy. By using the combined criterion of SUV_max < 5 and K^trans < 0.03 min^-1, sensitivity, specificity, and accuracy were 67%, 100% and 84%, respectively. Our results suggest that combining 18F-FDG PET metabolic parameters and DCE-MRI perfusion parameters should be an effective method to predict the histologic response to NAC in osteosarcoma.

Chin-Tien Lu¹, Zi-Min Lei¹, Sheng-Min Huang¹, Shin-Lei Peng¹, Kung-Chu Ho², Chi-Shiun Chiang¹, Chu-Fang Wang¹, and Fu-Nien Wang^1
1Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan, ²Department of Nuclear Medicine, Chang Gung Memorial Hospital, Linkou Medical Center, Linkou, Taiwan

Due to the characteristic of free diffusion, the local volume of distribution of D₂O can be assumed as the whole voxel space, and hence make it as a suitable tracer for measuring the CBF. In this study, we aimed to investigate the feasibility of absolute quantification of CBF on rat brain via indirect detection of deuterium by 1H MRI. CBF maps by Single exponential fitting on the washout curve and SVD deconvolution of AIF was showed.