ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore

Scientific Session: Arterial Spin Labeling

Thursday, May 12, 2016
Room 324-326
16:00 - 18:00
Moderators: Maria Fernandez-Seara, Henk Mutsaerts

Automatic adaption of ASL labeling parameters: Walsh-sorted time-encoded pCASL with a dynamic feedback algorithm
Nora-Josefin Breutigam1, Federico von Samson-Himmelstjerna1, and Matthias Günther1
1MR Physics, Fraunhofer MEVIS, Bremen, Germany
A dynamic feedback algorithm to find the optimal free-lunch (FL) bolus-length in a multi-TI Hadamard-encoding scheme is presented. An estimated FL bolus-length is often not ideal for the examined subject. In arterial spin labeling (ASL) this frequently results in unwanted arterial transit-delay (ATD) artefacts. The proposed method allows approaching the optimal FL bolus-length individually by analyzing intermediate decoded perfusion-weighted images during a running MRI scan. The aim is to reduce the FL bolus-length as much as necessary, but to keep it as long as possible to yield maximal signal.

Combined Angiography and Perfusion using Radial Imaging and Arterial Spin Labeling
Thomas W. Okell1
1FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
A new golden angle radial arterial spin labeling acquisition method is proposed in which labeled blood water is continuously imaged as it passes through the large arteries and into the tissue.  Both angiographic and perfusion images can then be reconstructed from the same raw data set at any retrospectively chosen time points and temporal resolution.  This makes efficient use of the post-labeling delay dead time to provide a more complete assessment of blood flow into the brain, which may be of use in a variety of cerebrovascular diseases.

Comparison of perfusion signal acquired by ASL prepared IVIM and conventional IVIM to unravel the origin of the IVIM-signal
Xingxing Zhang1, Carson Ingo1, and Matthias J.P. van Osch1,2
1C. J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, 2Leiden Institute for Brain and Cognition, Leiden, Netherlands
ASL-prepared IVIM is proposed to study the arterial IVIM signal as a function of post-labeling-delay. The D*-value as calculated from ASL-IVIM decreases as a function of PLD, reaching a plateau for PLDs>2000ms. Signal from conventional IVIM shows an intermediate D*-value corresponding to the ASL-IVIM-signal for a PLD of ~1750ms indicating the IVIM signal does not only originate from the microvasculature, but also includes vascular signal. The alternative explanation of extravasation of labeled spins into the extravascular compartment seems unlikely, since the observed D* at these PLDs are still a factor 3~4 higher than the diffusion coefficient of the slow compartment.

Flow territory instability may provide a new measure of hemodynamic reserve capacity in patients with intracranial stenosis
Daniel Arteaga1, Megan Strother1, Taylor Davis1, Carlos Faraco1, Lori Jordan2, Allison Scott1, and Manus Donahue1
1Radiology, Vanderbilt University, Nashville, TN, United States, 2Neurology, Vanderbilt University, Nashville, TN, United States
Non-invasive, hemodynamic markers are needed to better characterize stroke risk in patients with symptomatic intracranial (IC) stenosis. We developed and applied a planning-free vessel-encoded pseudo-continuous arterial spin labeling sequence in IC stenosis patients during room air and hypercapnia to examine the extent of geometrical changes in cerebral blood flow territories. IC stenosis patients demonstrated increased shifting relative to healthy controls; among IC stenosis patients, shifting was higher in those who experienced non-cardioembolic stroke within two-years. Shifting of cerebral blood flow territories may provide a novel marker of hemodynamic impairment and stroke risk.

Comparing Single-Delay, Sequential Multi-delay, and Hadamard Multi-delay ASL for Measuring CBF and Arterial Transit Delay in Normal Subjects and Patients with Cerebrovascular Disease - Permission Withheld
Samantha Holdsworth1, Audrey Fan1, Marc Lebel2, Zungho Zun3, Ajit Shankaranarayanan4, and Greg Zaharchuk1
1Department of Radiology, Stanford University, Stanford, CA, United States, 2GE Healthcare, Calgary, Canada, 3George Washington University, Washington, DC, United States, 4GE Healthcare, Menlo Park, CA, United States
One promising approach to multi-delay ASL is to perform the labeling using a Hadamard-encoded method, which promises to improve the SNR efficiency compared with sequential multi-delay ASL.  In this study, we compared single-delay ASL, sequential multi-delay ASL, and Hadamard-encoded multi-delay ASL in normal subjects and in patients with cerebrovascular disease.  Consistent with theory, Hadamard-encoding had better SNR than sequential multi-delay ASL for measuring CBF and arterial transit delay.

Hypoglycemia-induced changes in global and regional cerebral blood flow; impact of type 1 diabetes and impaired awareness of hypoglycemia
Evita Wiegers1, Kirsten Becker1, Hanne Rooijackers2, Cees Tack2, Arend Heerschap1, Bastiaan de Galan2, and Marinette van der Graaf1,3
1Radiology and Nuclear Medicine, Radboud umc, Nijmegen, Netherlands, 2Internal Medicine, Radboud umc, Nijmegen, Netherlands, 3Pediatrics, Radboud umc, Nijmegen, Netherlands
Hypoglycemia-induced changes in global and regional cerebral blood flow (CBF) were investigated in patients with type 1 diabetes (T1DM) and impaired (IAH) or normal awareness of hypoglycemia (NAH) and in healthy subjects. CBF-weighted images were acquired using pseudo-continuous arterial spin labeling MRI. Global CBF increased in response to hypoglycemia in T1DM IAH subjects, but not in T1DM NAH or in healthy controls. Hypoglycemia induced regional relative increases in CBF in the thalamus of both T1DM NAH and healthy controls, and in the frontal lobes of T1DM NAH, while no such increases were found in the T1DM IAH group.

Fast measurement of blood T1 in the internal carotid artery at 3T
Wenbo Li1,2, Peiying Liu1, Hanzhang Lu1, John J. Strouse3, Peter C.M. van Zijl1,2, and Qin Qin1,2
1Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 2F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States,3Division of Pediatric Hematology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
The knowledge of arterial blood T1 is important to quantify cerebral blood flow with ASL or the inversion time for VASO experiments.  We used a fast blood T1 protocol to measure the arterial T1 values in the internal carotid artery in vivo. Ex-vivo experiments were conducted to validate our method. Excellent correlation and agreement was found between in vivo and ex vivo results. The group-averaged arterial blood T1 value over 9 healthy volunteers was 1864+/-92ms (Hct=0.41+/-0.04), which is 200 ms longer than the widely adopted number obtained from bovine blood experiments. The arterial T1 value per subject was found to have significant correlation with the individual Hct values.

Non-contrast Pulmonary Perfusion at 3T using FAIR with inflow saturation and background suppression
Joshua S. Greer1,2, Yue Zhang2, Christopher Maroules2, Orhan K. Oz2, Ivan Pedrosa2,3, and Ananth J. Madhuranthakam2,3
1Bioengineering, University of Texas at Dallas, Richardson, TX, United States, 2Radiology, UT Southwestern Medical Center, Dallas, TX, United States, 3Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States
Flow Alternating Inversion Recovery (FAIR) has been studied extensively for pulmonary perfusion imaging at 1.5T, but suffers from low SNR, and is often corrupted by bright signal in the major vasculature and image misregistration artifacts due to respiratory motion. The purpose of this study was to evaluate FAIR at 3T for increased SNR and compare against SPECT perfusion, to combine FAIR with inflow saturation to reduce signal in the major pulmonary vessels, and to combine FAIR with background suppression strategies to minimize artifacts due to image misregistration.

Velocity Selective Adiabatic Pulses for Arterial Spin Labeling
Luis Hernandez-Garcia1, Jon-Fredrik Nielssen2, and Douglas Noll1
1FMRI Laboratory, University of Michigan, Ann Arbor, MI, United States, 2Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
We introduce a class of adiabatic RF pulses that can invert the magnetization of spins moving at specific velocity bands, regardless of their position within the coil.  Velocity selective adiabatic pulses (VSAI) are more robust to B1 inhomogeneity than their non-adiabatic counterparts. We discuss the theory and design considerations and demonstrate their utility in an ASL experiment on a human brain at 3T.

Incorporation of labeling efficiency measurement into a normal pCASL perfusion scan without SNR-penalty
Zhensen Chen1, Xihai Zhao1, Wouter Teeuwisse2, Bida Zhang3, Peter Koken4, Jouke Smink5, and Matthias J.P. van Osch2
1Certer for Biomedical Imaging Research, School of Medicine, Tsinghua University, Beijing, China, People's Republic of, 2C. J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, 3Philips Research China, Beijing, China, People's Republic of, 4Innovative Technologies, Research Laboratories, Philips Technologie GmbH, Hamburg, Germany, 5Philips Healthcare, MR Clinical Science, Best, Netherlands
The pCASL perfusion sequence was modified to incorporate a labeling efficiency measurement during the post-labeling delay. Our in vivo data showed that the incorporated labeling efficiency measurement had no influence on SNR of the perfusion measurements, with almost no additional time penalty. The additional labeling efficiency measurement was demonstrated its ability to identify severe underestimation of CBF caused by sub-optimal labeling, proofing its clinical potential. Moreover, the measured labeling efficiency is artery-specific, which is important because arteries may have different labeling efficiency due to differences in flow velocity and/or off-resonance effects.

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