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 SIblood. We used SItissue with normal perfusion measured from obtained clinical images by ASL and compared it with SIblood. 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, SIblood significantly exceeded SItissue. 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.

Hemodynamic ischemia of the anterior choroidal artery and reversal by carotid artery stenting 10 years after ipsilateral superficial temporal artery-middle cerebral artery bypass for symptomatic left middle cerebral artery stenosis.

The pathogenesis of anterior choroidal artery (AChA) territory infarction includes various mechanisms, but hemodynamic causes are rare and difficult to diagnose. 77- year-old man, who had moderate left ICA stenosis and he had treated with STA-MCA bypass surgery for severe symptomatic left MCA stenosis 10 years earlier, was admitted with right hemiparesis and confused state. On admission, magnetic resonance imaging and angiography demonstrated patent bypass, but severe stenosis of left ICA with no opacification of the left AChA and A1 portion of the left ACA. Diffusionweighted imaging demonstrated ischemic lesion in the left corona radiata. Together with clinical findings, hemodynamic ischemia of the AChA region was suspected and left carotid artery stenting resulted in prompt improvement of symptoms. Hemodynamic ischemia of the AChA territory is rare, however, should be considered as a potential target of treatment when the ipsilateral ICA, A1 and M1 show stenoocclusive lesions.