Arterial Transit Time‐Based Multidelay Combination Strategy Improves Arterial Spin Labeling Cerebral Blood Flow Measurement Accuracy in Severe Steno‐Occlusive Diseases

Background Although perfusion imaging plays a key role in the management of steno‐occlusive diseases, the clinical usefulness of arterial spin labeling (ASL) is limited by technical issues. Purpose To examine the effect of arterial transit time (ATT) prolongation on cerebral blood flow (CBF) measurement accuracy and identify the best CBF measurement protocol for steno‐occlusive diseases. Study Type Prospective. Population Moyamoya (n = 10) and atherosclerotic diseases (n = 8). Field Strength/Sequence A 3.0T/3DT1‐weighted and ASL. Assessment Hadamard‐encoded multidelay ASL scans with/without vessel suppression (VS) and single‐delay ASL scans with long‐label duration (LD) and long postlabeling delay (PLD), referred to as long‐label long‐delay (LLLD), were acquired. CBF measurement accuracy and its ATT dependency, measured as the correlation between the relative CBF measurement difference (ASL—single‐photon emission computed tomography [SPECT]) and ATT, were compared among 1) Combo (incorporating multidelay and LLLD data based on ATT), 2) standard (LD/PLD = 1333/2333 msec), and 3) LLLD (LD/PLD = 4000/4000 msec) protocols, using whole‐brain voxel‐wise correlation with reference standard SPECT CBF. The effect of VS on CBF measurement accuracy was also assessed. Statistical Tests Pearson's correlation coefficient, repeated‐measures analysis of variance, t‐test. P