ISMRM 21st Annual Meeting & Exhibition 20-26 April 2013 Salt Lake City, Utah, USA

Arterial Spin Labeling
Monday 22 April 2013
Room 355 EF  14:15 - 16:15 Moderators: Luis Hernandez-Garcia, Esben T. Petersen

14:15 0101.   
Fast Cerebral Flow Territory Mapping Using Vessel Selective Dynamic Arterial Spin Labeling
Xingxing Zhang1, Eidrees Ghariq1, Sophie Schmid1, Wouter M. Teeuwisse1, Andrew G. Webb1, and Matthias J.P. van Osch1
1C.J.Gorter center for high field MRI, Radiology, Leiden university medical center, Leiden, Zuid-Holland, Netherlands

Vessel selective dynamic ASL (VS-DASL) was proposed to do a fast cerebral flow territory mapping. The results were in good agreement with traditional vessel selective ASL. The percentage of correctly classified voxels in the flow territory map proved that VS-DASL has potential to map the flow territories in a short scan time (~30-60s), enabling the use in patients with acute stroke.

14:27 0102.   
The Use of k-Means Clustering and Bayesian Inference Framework for the Processing of Vessel-Encoded P-CASL Images as Compared with Super-Selective P-CASL MRI
Nolan S. Hartkamp1, Michael Helle2, Michael A. Chappell3,4, Thomas W. Okell4, Reinoud P H Bokkers1, Jeroen Hendrikse1, and Matthias J.P. van Osch5
1Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2Philips Research Laboratories, Hamburg, Germany, 3Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford, United Kingdom, 4FMRIB Centre, University of Oxford, Oxford, United Kingdom, 5C.J. Gorter Center, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands

We show that the territorial perfusion maps produced by VE p-CASL agree reasonably well with the perfusion maps acquired with super-selective p-CASL. Special consideration should be taken when using k-means clustering since it tends to fail in regions with high mixed perfusion, such as the deep gray matter. VE p-CASL with k-means clustering appears suitable as a general purpose T-ASL strategy, but the Bayesian framework is preferable since it can determine mixed perfusion. This is however only reliable where the VE p-CASL images contain sufficient vessel selectivity. To accurately determine the perfusion territories of a vessel, super-selective p-CASL is still recommended.

14:39 0103.   VENTI: Venous Territory Imaging Using Remote Sensing
Eric Wong1 and Jia Guo2
1Radiology/Psychiatry, UC San Diego, La Jolla, CA, United States, 2Bioengineering, University of California San Diego, La Jolla, CA, United States

In recent years, several methods have been introduced for mapping of arterial perfusion territories using arterial spin labeling. In this work, we adapt these remote sensing principles for mapping of vascular territories on the venous side, using spatial encoding of tissue water, and phase contrast based acquisition of signal from draining veins. Possible applications include venous thrombosis, multiple sclerosis, and mapping of oxygenation extraction.

14:51 0104.   
High Temporal Resolution Sampling of Tracer Kinetic Curves Using Time Encoded PCASL with Look-Locker Readout.
Wouter M. Teeuwisse1, Sophie Schmid1, Andrew G. Webb1, and Matthias J.P. van Osch1
1Radiology, C.J.Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, ZH, Netherlands

Time encoded pseudo continuous arterial spin labeling (te-pCASL, a.k.a. Hadamard encoded pCASL) combined with a Look-Locker (LL) read out was applied to sample the tracer kinetics curve with high temporal resolution (50 ms). To improve LL performance a flip angle sweep and a temporal shift of LL images in subsequent acquisitions were implemented. Perfusion signal curves in arteries and tissue were fitted and variants of perfusion modeling were evaluated. Measurement of tissue perfusion in the visual cortex demonstrated decreased arterial cerebral blood volume (aCBV) and arterial transit time (ATT) upon visual stimulation while cerebral blood flow (CBF) increased.

15:03 0105.   
Time Efficient Determination of Spin Compartments by Time Encoded Arterial Spin Labeling
Sophie Schmid1, Wouter M. Teeuwisse1, Eidrees Ghariq1, Andrew Webb1, Hanzhang Lu2, and Matthias J.P. van Osch1
1C.J.Gorter Center for High Field Magnetic Resonance, Radiology, Leiden University Medical Center, Leiden, Zuid-Holland, Netherlands, 2UT Southwestern Medical Center, Dallas, Texas, United States

The aim of this study is to employ a method to measure the transverse relaxation time as a function of the inflow time and to distinguish spin compartments based on their T2 in a highly time-efficient and voxelwise manner. By the use of Time encoded (also known as Hadamar encoded) pseudo Continuous Arterial Spin Labeling (te-pCASL) in combination with T2-Relaxation-Under-Spin-Tagging (TRUST) it is feasible to be more specific due to the short bolus duration and reduce the measurement time, while still keeping an equal SNR compared to separate multi-timepoint pCASL scans.

15:15 0106.   
Assessing Intracranial Vascular Compliance Using Dynamic Arterial Spin Labeling
Lirong Yan1, Robert Smith1, Collin Liu2, Emily Kilroy1, Yufen Chen3, and Danny J.J. Wang1
1Neurology, UCLA, Los Angeles, CA, United States, 2Neurology, USC, Los Angeles, CA, United States, 3Radiology, Northwestern University, Chicago, IL, United States

Vascular compliance (VC) is an important risk factor for cardiovascular disorders and stroke. In this study, we propose a novel MRI technique for assessing intracranial VC by synchronizing dynamic arterial spin labeling (ASL) scans with systolic and diastolic cardiac phases respectively. VC is estimated as the ratio between changes in arterial blood volume (BV) and changes in blood pressure (BP) between systolic and diastolic phases (i.e., VC=¦¤BV/¦¤BP). Our results showed that intracranial VC mainly occurs in big arteries, gradually decreases in small arteries and arterioles, and finally disappears in capillaries and tissue. Initial data also showeda decreased VC with aging.

15:27 0107.   
Simultaneous Acquisition of Cerebral Blood Volume, Blood Flow and Blood Oxygenation Weighted MRI Signals at 7T
Steffen N. Krieger1,2, Laurentius Huber1, Gary F. Egan2, and Robert Turner1
1Neurophysics, Max-Plank Institute for Human Cognitive and Brain Sciences, Leipzig, Saxonia, Germany, 2Monash Biomedical Imaging, Monash University, Melbourne, Victoria, Australia

Beside the classical blood oxygenation level dependent (BOLD) contrast methods, cerebral blood volume (CBV) and cerebral blood flow (CBF) based functional MRI (fMRI) measurements have recently become frequently used tools in neuroscience. However, the quantitative relationships between each of these parameters is not yet fully understood. We present an fMRI technique that simultaneously measures CBV, CBF and BOLD signals. This method benefits from the high static magnetic field strength of 7T as well as the implementation of slab-selective VASO and a multiple EPI-readout in order to correct for BOLD contamination effects in the CBV- and CBF weighted MRI signals.

15:39 0108.   Multi-Bolus Pulsed ASL for Improved Renal Perfusion Quantification
Xiang He1, Serter Gumus1, Ayaz Aghayev1, and Kyongtae Ty Bae1
1Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States

High pulsatile blood flow/velocity in the descending aorta renders the labeling bolus of a standard pulse ASL (PASL) experiment to be limited within a single cardiac RR interval. In this study, we took advantage of such temporally uneven blood flow to generate multiple labeling boluses across consecutive RR intervals. We demonstrated that the proposed multi-bolus PASL scheme improved the sensitivity of renal PASL perfusion signal by ~30 to 50%.

15:51 0109.   Simultaneous Arterial Spin Labelling MRI and H2O15 Position Emission Tomography
Ke Zhang1, Hans Herzog1, Christian Filss1, Thomas Fischer2, Walter Sturm3, Burkhard Brocke2, and Nadim Jon Shah1,4
1Institute of Neuroscience and Medicine 4, Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany, 2Neurobiology of Personality and Neurogenetics, Department of Psychology, Dresden Universi Laboratory, Dresden, Germany, 3Clinical Neurology, University Hospital Aachen, Aachen, Germany,4Department of Neurology, JARA, RWTH Aachen University, Aachen, Germany

A number of studies have compared ASL-MRI and 15O-water PET for the evaluation of ASL reliability and reproducibility. But none of these studies had the possibility to perform both techniques simultaneously to minimize the physiological variations. In this work, a simultaneous ASL-MRI and 15O-water PET approach has been implemented on a hybrid MR-PET for a truly quantitative comparison between the two methods in absolutely the same physiological and functional status.

16:03 0110.   Investigating White Matter Perfusion Using Optimal Sampling Strategy Arterial Spin Labeling (OSS-ASL) at 7T
Alexander Graeme Gardener1 and Peter Jezzard1
1FMRIB Centre, Nuffield Department of Clinical Neurosciences, Oxford, United Kingdom

The measurement of White Matter perfusion (WM-CBF) using Arterial Spin Labeling techniques has proven difficult due to the low Contrast-to-Noise ratio and long labeled blood transit times found in this tissue. An Optimal Sampling Strategy approach was used to weight TI acquisition times to later blood arrival. This was combined with an ultra-high field 7T scanner to improve CNR and benefit from longer T1 relaxation time in labeled blood. It is shown that reasonable WM-CBF quantification can be achieved consistently in healthy human subjects. Fitted CBF and bolus arrival times were comparable to literature values.