Clinical Investigative Study Assessment of Perfusion Deficits in Ischemic Stroke Using 3D-GRASE Arterial Spin Labeling Magnetic Resonance Imaging with Multiple Inflow Times Marc E. Wolf, MD, Vanessa Layer, MD, Johannes Gregori, PhD, Martin Griebe, MD, Kristina Szabo, MD, Achim Gass, MD, Michael G. Hennerici, MD, PhD, Matthias G ¨ unther, PhD, Rolf Kern, MD From the Department of Neurology, Universit¨ atsmedizin Mannheim, University of Heidelberg, Mannheim, Germany (MEW, VL, MG, KS, AG, MGH, RK); mediri GmbH, Heidelberg, Germany (JG, MG); Fraunhofer MEVIS – Institute for Medical Image Computing, Bremen/Germany (MG); FB 1, Universit¨ at Bremen, Bremen, Germany (MG). Keywords: Acute stroke, cerebral is- chemia, cerebral hemodynamics, MRI, perfusion imaging. Acceptance: Received April 12, 2013, and in revised form July 17, 2013. Ac- cepted for publication August 3, 2013. Correspondence: Address correspon- dence to Dr. Rolf Kern, MD, Depart- ment of Neurology, Universit¨ atsmedizin Mannheim University of Heidelberg, 68135 Mannheim, Germany. Email: kern@neuro.ma.uni-heidelberg.de. The project was funded by the Fed- eral Ministry of Education and Re- search (BMBF), Junior Research Group “Bioimaging”, Project No. 01EV0702. J Neuroimaging 2014;24:453-459. DOI: 10.1111/jon.12064 ABSTRACT BACKGROUND AND PURPOSE Arterial spin labeling (ASL) MRI provides information on tissue perfusion by consecu- tive readout of labeled blood captured in arteries or the microvasculature without using contrast agents. METHODS We used a single-shot 3D acquisition and readout technique for ASL with multiple inflow times (TI) to evaluate hemodynamic compromise and dynamics of arterial blood inflow expressed by the bolus arrival time (BAT). Thirty-six patients with ischemic stroke were examined with a standard multimodal MRI protocol including dynamic susceptibility con- trast (DSC) and multi-TI ASL perfusion imaging. Time-to-peak maps were used to classify hemodynamic impairment as either hypo- or hyperperfusion. RESULTS Overall there was a good agreement of ASL perfusion maps with DSC perfusion imaging on visual analysis. Correlations were found between ASL-BAT/(DSC-)Mean transit time (MTT) (r = .416; P < .01) and ASL-CBF/MTT (r = –.489; P < .01). Using ASL, BAT in ischemic territory was delayed by 55% (P = .001) in patients with hypoperfusion (n = 28); CBF was reduced by 39% (P<.001). All patients with hyperperfusion (n = 6) had higher CBF on ASL. CONCLUSIONS The use of ASL with multiple TI allows the contrast-free assessment of hemodynamic im- pairment in ischemic stroke patients. Quantitative ASL perfusion analysis reliably demon- strates areas of delayed BAT and reduced CBF matching findings of DSC. Background and Purpose In acute ischemic stroke, cerebral perfusion is impaired due to an obstruction of brain-supplying arteries. The severity of per- fusion deficits differs between the ischemic core and the penum- bra where the brain tissue is considered at risk of infarction. 1 Cerebral hypoperfusion with reduction of cerebral blood flow (CBF) and/or cerebral blood volume (CBV) typically occurs after acute embolic occlusion of an intracranial vessel, or may be chronic in long-standing and progressive atherosclerotic ob- struction. In the acute phase, these changes may be dynamic with regard to vessel recanalization and tissue reperfusion. Hy- perperfusion usually reflects increase of CBF and/or CBV af- ter recanalization and vasoparesis or in pathological states of high energy demand. 2–4 In acute stroke, assessment of both hypo- and hyperperfusion over time may have therapeutic im- plications since thrombolysis may be needless or even harm- ful if vessel recanalization had already occurred. Furthermore diffusion-/perfusion-mismatch constellations are important for the option of thrombolysis in patients beyond the 4.5-hour time- window. 5 Several imaging methods are available for the semiquanti- tative or quantitative analysis of impaired CBF and/or CBV, eg, SPECT, PET, Xenon-CT, and dynamic susceptibility con- trast perfusion MRI (DSC-MRI). 6 In acute stroke, DSC-MRI is commonly used to assess cerebral perfusion due to its wide availability and since this approach was shown to be very sensi- tive for the detection of hemodynamic impairment. 7 However, one of the drawbacks of DSC-MRI and the other perfusion imaging techniques is the necessity to inject contrast agents. Gadolinium-based contrast imaging has limitations in patients with chronic renal insufficiency with the risk of nephrogenic systemic fibrosis. 8, 9 Copyright ◦ C 2013 by the American Society of Neuroimaging 453