Usefulness of Post-labeling Delay for the Assessment of Bright Vessel Appearance by Arterial Spin Labeling

OBJECTIVE: This study was performed to clarify the differences in blood flow strength, blood vessel diameter, and post-labeling delay (PLD) by physical experiments, and to examine whether bright vessel appearance (BVA) can be observed by arterial spin labeling (ASL). METHODS: We introduced simulated blood flow (25 cm/sec, 12.5 cm/sec) using a specially made phantom of fixed tubes in a plastic container. At each speed, we scanned at several points of PLD using ASL imaging. We measured the signal in the tube to obtain a signal intensity (SI). We revised the T1 level from the SI and obtained SI(blood). We used SI(tissue) with normal perfusion measured from obtained clinical images by ASL and compared it with SI(blood). RESULTS: In tubes with a narrow inner diameter, the signal slightly decreased. SI also decreased under slow flow compared with fast flow. At each flow rate, SI(blood) significantly exceeded SI(tissue). CONCLUSION: PLD distinguishes spin in brain tissue from 1525 msec to 2525 msec, and it can be observed. As spin signal decreases when the flow rate is slow, attention is necessary for observation. Assessment at PLD1525–2525 msec where normal perfusion was obtained suggested that BVA can be observed.