Joint Annual Meeting ISMRM-ESMRMB 2014 10-16 May 2014 Milan, Italy

PERFUSION (16:00-18:00)
2697-2727 Arterial Spin Labeling
2728-2760 Perfusion & Permeability

Arterial Spin Labeling

Wednesday 14 May 2014
Traditional Poster Hall  16:00 - 18:00

2697.   Whole-brain distortion-free pseudo-continuous arterial spin labeling using multiband turbo-FLASH at 3 and 7T
Yi Wang1, Steen Moeller2, An T. Vu2, Kamil Ugurbil2, Essa Yacoub2, and Danny JJ Wang1
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.

2698.   Whole-brain Perfusion Measurements at 7T using Pulsed Arterial Spin Labelling and Simultaneous Multi-slice Multi-echo Echo Planar Imaging
Dimo Ivanov1,2, Benedikt A Poser1,2, Laurentius Huber3, Josef Pfeuffer4, and Kâmil Uludağ1,2
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.

2699.   Whole-brain High-resolution ASL at 3T
Marta Vidorreta1, Evelyne Balteau2, Ze Wang3,4, Enrico De Vita5,6, David L. Thomas5, John A. Detre4,7, and María A. Fernández-Seara1
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.

2700.   Single-Artery Pseudo-Continuous Arterial Spin Labeling with Off-Resonance Correction
Cheng Ouyang1, Aiming Lu1, Xiangzhi Zhou1, and Mitsue Miyazaki1
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.

2701.   Improving perfusion quantification in Arterial Spin Labeling for delayed arrival times by using optimized acquisition schemes
Johanna Kramme1, Johannes Gregori2, Volker Diehl1,3, Vince Istvan Madai4,5, Federico C von Samson-Himmelstjerna1,4, Markus Lentschig3, Jan Sobesky4,5, and Matthias Günther1,6
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.

2702.   Spin labeling MRI with Look-Locker readout for improved portal venous perfusion quantification
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. Petersen2
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.

2703.   Arterial Spin Labeling Using 3D Spiral TSE with A Distributed Spiral-In/Out Trajectory
Zhiqiang Li1, Michael Schär1,2, Dinghui Wang1, Nicholas R Zwart1, and James G Pipe1
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.

2704.   Reducing blurring artifacts in 3D-GRASE ASL by integrating new acquisition and analysis strategies
Ilaria Boscolo Galazzo1, Michael A Chappell2, David L Thomas3, Xavier Golay3, Paolo Manganotti1, and Enrico De Vita3,4
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.

2705.   Comparison of Transit Delay Sensitivity between Pseudo-Continuous ASL, Pulsed ASL and Velocity-Selective ASL
Jia Guo1 and Eric C. Wong2
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.

2706.   Robust, Accurate and Automated Normalization of 3D Arterial Spin Labeling Brain Images
Weiying Dai1 and David Alsop1
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.

2707.   Globally Correlated Brain Signals Using Resting State Arterial Spin Labeling
Weiying Dai1, Ajit Shankaranarayanan2, and David Alsop1
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.

2708.   Decomposing cerebral blood flow MRI into functional and structural components
Benjamin Kandel1,2, James C. Gee3, Jiongjiong Wang4, and Brian B Avants3
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.

2709.   An automated post processing analysis to increase detectability of cerebral blood flow arterial spin labeling images in the presence of head motion
Zahra Shirzadi1, David E Crane1, Benjamin I Goldstein2,3, Sandra E Black1,4, and Bradley J MacIntosh1,5
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.

2710.   Signal-to-noise ratio of perfusion mapping using multiphase pseudocontinuous arterial spin-labeling MRI
Wen-Chau Wu1,2, Shu-Fen Jiang3, and Shu-Hua Lien3
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 (lower case Greek alpha) is sensitive to field inhomogeneity. Multiphase PCASL (MP-PCASL) calibrates lower case Greek alpha by tracking image intensities with varied phase offsets (lower case Greek phi) 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 lower case Greek phi's. Results show that the measurements of individual lower case Greek phi's in MP-PCASL can be combined to provide perfusion mapping with an SNR greater than or equal to 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.

2711.   ATLES: AuTomatic Labeling efficiency EStimation
Marco Battiston1, Marco Castellaro1, Carlo Boffano2, Maria Grazia Bruzzone2, and Alessandra Bertoldo1
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.

2712.   Consistency Checks for Partial Volume Correction of ASL perfusion maps
Joost P.A. Kuijer1, Alexandra De Sitter1, Maja A.A. Binnewijzend2, Frederik Barkhof2, and Rudolf M. Verdaasdonk1
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.

2713.   Improved CBF Quantification with Flow-adaptive Model Function for Multiphase PCASL – A Monte Carlo Simulation Study
David D Shin1, Youngkyoo Jung2, Ho-Ling Liu3, and Thomas T Liu1
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.

2714.   New data processing pathway for automatic detection of vascular territories and source vessel locations using random VEASL
Yi Dang1, Jia Guo2, Jue Zhang1,3, and Eric Che Wong4
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.

2715.   A bootstrap approach to detect corrupted volume in ASL data
Marco Castellaro1, Denis Peruzzo2, Carlo Boffano3, Maria Grazia Bruzzone3, and Alessandra Bertoldo1
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.

2716.   Robust and Fast Quantification of CBF measures for Multiphase PCASL using Bayesian Nonlinear Model Fitting
David D Shin1, Michael A Chappell2, and Thomas T Liu1
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.

An improved arterial model for QUASAR ASL that permits estimation of arterial flow speed
Marco Castellaro1, Esben Thade Petersen2, Xavier Golay3, Alessandra Bertoldo1, and Michael A Chappell4
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.

2718.   Assessment of Water Diffusion Compartmentation in the Non-Human Primate Brain
Ramesh Paudyal1, Chun-Xia Li1, Edward J. Auerbach2, and Xiaodong Zhang1
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.

2719.   Quantification of cerebral arterial and venous blood T1 during hyperoxia and hypercapnia
Steffen N Krieger1,2, Claudine J Gauthier2, Parnesh Raniga1,3, Dale Tomlinson1, Paul Finlay4, Richard McIntyre1,4, Robert Turner2, and Gary F Egan1
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.

2720.   Changes in arterial arrival time (AAT) and cerebral blood flow (CBF) with hypercarbia and hypercarbic hyperoxia
Manus Joseph Donahue1, Carlos Faraco1, Lindsey Dethrage1, Swati Rane1, Megan Strother1, Jeroen Hendrikse2, and Jeroen Siero2
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.

2721.   Combined use of arterial spin labeling and MRS to determine the severity of injury in neonates with hypoxic-ischaemic encephalopathy
Magdalena Sokolska1,2, Maia Proisy3, Cristina Uria-Avellanal3, Alan Bainbridge2, Ernest Cady2, David Thomas1, Nicola Robertson3, and Xavier Golay1
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.

2722.   Accuracy and precision of pseudo-continuous arterial spin labeling perfusion during baseline and hypercapnia: a head-to-head comparison with 15O H2O positron emission tomography
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 Nederveen1
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.

2723.   Arterial spin labelling characterization of cerebral perfusion during normal maturation from late childhood into adulthood: normal ‘reference range’ values
Patrick W Hales1, Jamie M Kawadler1, Sarah E Aylett2, Fenella J Kirkham3, and Christopher A Clark1
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.

2724.   A Reproducibility Study of Arterial Spin Labeling based Glomerular Filtration Rate Estimate
BIN CHEN1, Hao Li1, Ya Cao1, Chengyan Wang1, Xiaoying Wang1,2, JUE ZHANG1,3, and Jing Fang1,3
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.

2725.   Repeatability and Variability of Pre-Clinical Hepatic Arterial Spin Labelling
Rajiv Ramasawmy1,2, 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.

2726.   Selective ASL delineates borderzone territories in patients with stenosis of the middle cerebral artery
Andrea Federspiel1, Mirjam Rachel Heldner2, Urs Fischer2, Jan Gralla3, and Roland Wiest3
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.

2727.   Comparison of velocity and acceleration selective arterial spin labeling with 15O H2O positron emission tomography.
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 Osch1
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.


Perfusion & Permeability

Wednesday 14 May 2014
Traditional Poster Hall  16:00 - 18:00

2728.   Slice Accelerated Spin and Gradient Echo (SAGE) Perfusion Imaging
Eric Peterson1, Heiko Schmiedeskamp1, Julian Maclaren1, Nils Forkert1, Samantha Holdsworth1, Rafael O'Halloran1, Eric Aboussouan1, William Grissom2, Salil Soman1, and Roland Bammer1
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.

2729.   Slice Accelerated Gradient-Echo Spin-Echo Dynamic Susceptibility Contrast Imaging with blipped CAIPI for Increased Slice Coverage
Cornelius Eichner1,2, Kourosh Jafari-Khouzani1, Stephen Cauley1, Himanshu Bhat3, Pavlina Polaskova1, Ovidiu C Andronesi1, Otto Rapalino1, Robert Turner2, Lawrence L Wald1, Steven Stufflebeam1, and Kawin Setsompop1
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.

Advanced Analysis of USPIO Injection in Normal Volunteers
Thomas Christen1, Deqiang Qiu1, Wendy Wei Ni1, Heiko Schmiedeskamp1, Michael E Moseley1, and Greg Zaharchuk1
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.

2731.   Mapping blood volume fraction and vessel size index at steady-state: Impact of contrast agent dose and spin-echo time
Benjamin Lemasson1, Nicolas Pannetier2, Thomas Christen3, Greg Zaharchuk3, Norbert Schuff2, and Emmanuel Barbier1
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.

2732.   Correction of Bolus Dispersion in the quantification of perfusion and haemodynamics using DSC-MRI
Amit Mehndiratta1, Fernando Calamante2, Bradley J MacIntosh3, David E Crane3, Stephen J Payne1, and Michael A Chappell1
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.

2733.   Tracer-kinetic field analysis in DCE-MRI and DSC-MRI: theory and examples
Steven P. Sourbron1
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.

2734.   Tracer-kinetic field analysis in DCE-MRI and DSC-MRI: the reconstruction problem
Steven P. Sourbron1
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.

2735.   Brain blood volume assessment using DCE in comparison to DSC methods
Moran Artzi1,2, Guy Nadav1,3, Gilad Liberman1, Orna Aizenstein1, and Dafna Ben Bashat1,4
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.

2736.   Sources of errors in pharmacokinetic analysis of DCE-MRI
Andre Hallack1, Michael A. Chappell1, E. Mark Anderson2, Fergus V. Gleeson2, Mark J. Gooding3, and Julia A. Schnabel1
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, Ktrans and kep estimation. 21 rectal tumour SPGR sequences were registered to estimate motion. Moreover, while using synthetic data, T10 e, Ktrans and Kep estimation error was evaluated for various degrees of deformation. Overall, an average motion of 0.42mm was found, which translates into 10% T10, 16% Ktrans and 5% kep mean error.

2737.   Impact of tissue porosity in DCE-MRI: a numerical simulation study
Thomas Perret1,2, Clément Debacker1,2, Nicolas Pannetier3,4, and Emmanuel L Barbier1,2
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.

2738.   Joint estimation of precontrast T1 and DCE-MRI perfusion and permeability parameters significantly improves precision of parameter estimates
Ben R Dickie1, Anita Banerji2,3, Catharine M West4, and Chris J Rose2,3
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.

2739.   Comparing the relative effect of input parameter errors on the accuracy of the pharmacokinetic parameters in Tofts’ model.
Cristina Lavini1
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.

2740.   Investigation of Weighted Fits applied to Compartment Models of Dynamic Contrast Enhanced Magnetic Resonance Imaging
Frank G Zoellner1, Philip Schmidt1, and Lothar R Schad1
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

2741.   Information Criteria weighted Parameter Estimates in DCE-MRI
Tammo Rukat1,2 and Stefan A Reinsberg1
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. Ktrans estimates are shown to benefit in accuracy and precision for a variety of investigated tissues.

2742.   Precision of two-compartment exchange model parameter estimates: dependence on tissue physiology
Ben R Dickie1, Catharine M West2, and Chris J Rose3,4
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.

2743.   Comparison of contrast concentration conversion methods for pharmacokinetic analysis of Dynamic Contrast Enhanced (DCE) MRI in the thin vessel wall: T1 mapping is not worthwhile by introducing more variance
Tingting Wu1, Jinnan Wang2, Yan Song3, Xiaotao Deng3, Xihai Zhao1, Rui Li1, Anqi Li3, Shuo Chen1, Chun Yuan1,4, and Huijun Chen1
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.

2744.   Rapid DCE-MRI parameter generation using principal component analysis and clustering
Martin Lowry1, Lawrence Kenning2, and Lindsay W Turnbull1
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

Effect of k-Space Weighted Image Contrast with golden-angle view ordering on diagnostic accuracy for lesion discrimination
Melanie Freed1 and Sungheon Kim1
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.

2746.   Assessment of Scan-Rescan Variability in DCE-MRI Parameters Using Multiple Models
Edward Ashton1, Jean Tessier2, and Oliver Krieter3
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.

2747.   Prostate cancer localization by magnetic resonance dispersion imaging
Massimo Mischi1, Simona Turco1, Cristina Lavini2, Marcel Breeuwer3, Jean de la Rosette4, Mark Engelbrecht2, and Hessel Wijkstra1,4
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.

2748.   Evaluation of Vascular Transfer Constants using Dynamic T1-Mapping during Contrast Agent Administration
Uwe Klose1, Sotirios Bisdas1, Herbert Köstler2, and Johannes Tran-Gia2
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 Cp(t). Ktransvalues could be estimated as slopes of fitted straight lines in the Patlak plot. Remarkably low residuals between data points and fitted lines were found.

2749.   Quantification of subtle blood-brain barrier permeability in white matter using DCE-MRI
Anna K Heye1, Michael J Thrippleton1, Maria del C Valdés Hernández1, Paul A Armitage2, and Joanna M Wardlaw1
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.

2750.   Clinical implementation of the Linear Reference Region Model for Dynamic Contrast-Enhanced MRI
Adam Bernstein1, Phillip H Kuo2, Mark D. Pagel3, and Julio Cardenas-Rodriguez3
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.

2751.   DCE-MRI and T2* Measurement in Women with Heavy Menstrual Bleeding Treated with Dexamathasone
Lucy E Kershaw1, Gillian MacNaught2, Mayank Serge Madhra3, Hilary O Critchley3, and Scott IK Semple2
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.

2752.   The relationship between the quantitative pharmacokinetic parameters of DCE-MRI and the types of uterine fibroids based on T2WIs
Chenxia Li1,2, Hao Fu1, Rong Wang1, Jiayin Tong1, Supin Wang2, and Jian Yang1,2
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.

2753.   Influence of respiration-induced signal variations on the quantification of pulmonary perfusion parameters in free-breathing MRI
Olaf Dietrich1, Michael Ingrisch1, Felix Schwab1, Daniel Maxien2, Konstantin Nikolaou2, and Maximilian F. Reiser1,2
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.

2754.   Blind Multichannel Deconvolution for Estimation of a Parametric AIF in DCE-MRI of Mice
Radovan Jirik1, Karel Soucek2,3, Eva Drazanova1, Lucie Grossová1,4, 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.

2755.   Dynamic Contrast-enhanced MRI Perfusion in a Unilateral Ureteral Obstruction (UUO) Mouse Model
Wei Zha1, David J. Niles1, Shannon Reese2, Arjang Djamali2, and Sean B. Fain1
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.

Evaluation of flow and permeability weighting in the volume transfer constant obtained by DCE-MRI using contrast media with different molecular sizes
Cheng-He Li1, Fang-Hsin Chen1, Yu-Shi Lin2, Ji-Hong Hong1,3, and Ho-Ling Liu1
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 (Ktrans) 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 (Fp) were obtained. This study found that Ktrans was more correlated with PS (r2=0.72) than Fp (r2=0.09) when using Gadomer, and more correlated with Fp (r2=0.64) than PS (r2=0.47) when using Gd-DTPA.

2757.   Acute changes in cellular-interstitial water exchange rate in DB-1 Melanoma xenografts after lonidamine administration as a marker of tumor energetics and ion transport
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 Glickson1
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.

2758.   Application of a biodegradable, macrocyclic, polydisulfide-based contrast agent for monitoring tumor angiogenesis using dynamic contrast enhanced MRI
Anthony S. Malamas1, Erlei Jin1, John Haaga2, and Zheng-Rong Lu1
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.

2759.   Combined evaluation of 18F-FDG PET Metabolic Parameters and MRI Perfusion Parameters for the Prediction of Neoadjuvant Chemotherapy Response in Osteosarcoma
In ok Ko1, Byung Hyun Byun2, Ji-ae Park1, Kyeong Min Kim1, and Sang Moo Lim2
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 SUVmax from the 18F-FDG PET after neoadjuvant chemotherapy and < 0.03 min-1, 58%, 83%, and 71%, respectively, for Ktrans from the DCE-MRI after neoadjuvant chemotherapy. By using the combined criterion of SUVmax < 5 and Ktrans < 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.

2760.   Absolute quantification of CBF on rodent brain with D2O as tracer of 1H MRI
Chin-Tien Lu1, Zi-Min Lei1, Sheng-Min Huang1, Shin-Lei Peng1, Kung-Chu Ho2, Chi-Shiun Chiang1, Chu-Fang Wang1, and Fu-Nien Wang1
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.