TRADITIONAL POSTER - ismrm

Poster Sessions
1766. Combined Assessment of Vascular Territories and Haemodynamic Parameter Maps
Rebecca Susan Dewey 1,2 , Dorothee P. Auer 1 , Susan T. Francis 2
1 Division of Academic Radiology, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom; 2 Sir Peter Mansfield
Magnetic Resonance Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom
Watershed areas are brain regions supplied by the most distal branches of the cerebral arteries and are most susceptible to haemodynamic ischaemia. We
assess the use of territorial ASL to define Left and Right Internal Carotid, Anterior Cerebral, and Basilar Artery territories to distinguish the watershed area,
and assess its correspondence with haemodynamic parameters (perfusion rate, arterial blood volume and arterial and tissue transit times) from multiphase
ASL. Specified anatomical regions are assessed for vascular supply and haemodynamic parameters. Combining these techniques, an atlas of parameters can
be formed for region-specific perfusion and position and functional effects of watershed areas.
1767. Simultaneous Measurements of Arterial Transit Times and Water Exchange Rates by Diffusion-
Weighted ASL
Keith S. St. Lawrence 1,2 , Jodi Miller 1 , Jiongjiong Wang 3
1 Imaging, Lawson Health Research Institute, London, ON, Canada; 2 Medical Biophysics, University of Western Ontario, London,
ON, Canada; 3 Radiology, University of Pennsylvania, Philadelphia, PA, United States
The arterial transit time (τa) and the exchange rate of water (kw) across the blood-brain barrier were determined using diffusion-weighted arterial spin
labelling (ASL) with multiple post-labelling delay times. τa was determined using bipolar gradients to suppress the arterial signal (i.e., the FEAST method)
and kw was determined using bipolar gradients strong enough to suppress all vascular signals and a kinetic model to characterize water exchange across the
BBB. Averaged over four volunteers, kw was 119 min-1 in grey matter and τa was 1.26 s. From repeat measurements, the intra-subject coefficient of
variation of kw was 12%.
1768. Flow-Weighted Arterial Transit Time Mapping of the Human Brain
Toralf Mildner 1 , Stefan Hetzer 1 , Wolfgang Driesel 1 , Karsten Müller 1 , Harald E. Möller 1
1 NMR unit, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany
Mapping of Arterial Transit times by Intravascular Signal SElection (MATISSE) was performed with and without a mild flow-weighting (FW). The arterial
transit times, δa , of the flow-weighted data were increased on average by about 700 ms and the signal amplitudes roughly were halved. Flow-through signals,
i. e. signals of arterial vessels permeating the voxel, are removed almost completely, although the MATISSE signal still is expected to be of vascular origin.
The fact that δa with mild FW was found to be easily larger than 2 s might be important for the quantification of CBF in standard dual-coil CASL
experiments.
1769. Arterial Transit Delay Measurement Using Pseudo-Continuous ASL with Variable TR and Interleaved
Post-Labeling Delays
Kun Lu 1 , Thomas T. Liu 1 , Youngkyoo Jung 1
1 Center for Functional MRI, UCSD, La Jolla, CA, United States
Conventional arterial transit delay measurements consist of a series of separate ASL experiments acquired at several different post-labeling delays. Such
measurements are usually time-consuming and can be formidable overheads for ASL studies. The time requirement also makes the measurements highly
sensitive to motion. This study presents a simple yet effective modification of the conventional method for measuring transit delay with shorter scan time
and less motion sensitivity. Such a method could be beneficial to all ASL studies.
1770. Eliminating the Partition Coefficient from ASL Perfusion Quantification with a Homogeneous
Contrast Reference Image
Weiying Dai 1 , Philip M. Robson 1 , Ajit Shankaranarayanan 2 , David C. Alsop 1
1 Radiology, Beth Israel Deaconess Medical Center,Harvard Medical School, Boston, MA, United States; 2 Global Applied Science
Laboratory, GE Healthcare, Menlo Park, CA, United States
Conventional ASL perfusion quantification requires division by a proton density reference image and assumes a uniform brain-blood partition coefficient.
The brain-blood partition coefficient is not constant, however, and may especially differ in areas of pathology. In cortical regions where CSF, white matter
and gray matter may all be mixed within a voxel, division by the proton density image can also add nonlinear systematic errors. Here we propose using an
optimized inversion preparation to generate an image whose intensity is essentially independent of tissue type. This highly homogeneous image can replace
the proton density image and makes the assumption of a brain-blood partition coefficient unnecessary. In-vivo results demonstrate that such homogeneous
contrast is achievable and can be used to improve the pixel-by-pixel perfusion measurement.
1771. Potential Tracking of Oxygen Consumption Using Arterial Spin Labeling Susceptibility Imaging
Johannes Gregori 1,2 , Norbert Schuff 3,4 , Matthias Günther 1,5
1 Institute for Medical Image Computing, Fraunhofer MEVIS, Bremen, Germany; 2 Neurology, Universitätsmedizin Mannheim,
Heidelberg University, Mannheim, Germany; 3 Radiology & Biomedical Imaging, University of San Francisco, San Francisco, CA,
United States; 4 Center for Imaging of Neurodegenerate Diseases (CIND), VA Medical Center, San Francisco, CA, United States;
5 mediri GmbH, Heidelberg, Germany
We present ASL time series measurements with spin/gradient double echo spiral 3D-GRASE readout to quantify R2' of the ASL difference signal. R2' can
give information about blood oxygenation and blood volume, while ASL time series are used to investigate perfusion dynamics. Using the combination of
both techniques, we can measure the changes of R2' over different inflow times and discuss the physiological underlyings.