Perioperative cerebral blood flow measured by arterial spin labeling with different postlabeling delay in patients...

Arterial spin labeling (ASL) is a non-invasive technique for measuring cerebral perfusion. Its accuracy is affected by the arterial transit time. This study aimed to (1) evaluate the accuracy of ASL in measuring the cerebral perfusion of patients who underwent carotid endarterectomy (CEA) and (2) determine a better postlabeling delay (PLD) for pre- and postoperative perfusion imaging between 1.5 and 2.0 s.

A total of 24 patients scheduled for CEA due to severe carotid stenosis were included in this study. All patients underwent ASL with two PLDs (1.5 and 2.0 s) and computed tomography perfusion (CTP) before and after surgery. Cerebral blood flow (CBF) values were measured on the registered CBF images of ASL and CTP. The correlation in measuring perioperative relative CBF (rCBF) and difference ratio of CBF (DR_CBF) between ASL with PLD of 1.5 s (ASL_1.5) or 2.0 s (ASL_2.0) and CTP were also determined.

There were no significant statistical differences in preoperative rCBF measurements between ASL_1.5 and CTP (p = 0.17) and between ASL_2.0 and CTP (p = 0.42). Similarly, no significant differences were found in rCBF between ASL_1.5 and CTP (p = 0.59) and between ASL_2.0 and CTP (p = 0.93) after CEA. The DR_CBF measured by CTP was found to be marginally lower than that measured by ASL_{2.0_1.5} (p = 0.06) and significantly lower than that measured by ASL_{1.5_1.5} (p = 0.01), ASL_{2.0_2.0} (p = 0.03), and ASL1_{.5_2.0} (p = 0.007). There was a strong correlation in measuring perioperative rCBF and DR_CBF between ASL and CTP (r = 0.67-0.85, p < 0.001). Using CTP as the reference standard, smaller bias can be achieved in measuring rCBF by ASL_2.0 (-0.02) than ASL_1.5 (-0.07) before CEA. In addition, the same bias (0.03) was obtained by ASL_2.0 and ASL_1.5 after CEA. The bias of ASL_{2.0_2.0} (0.31) and ASL_{2.0_1.5} (0.32) on DR_CBF measurement was similar, and both were smaller than that of ASL_{1.5_1.5} (0.60) and ASL_{1.5_2.0} (0.60).

Strong correlation can be found in assessing perioperative cerebral perfusion between ASL and CTP. During perioperative ASL imaging, the PLD of 2.0 s is better than 1.5 s for preoperative scan, and both 1.5 and 2.0 s are suitable for postoperative scan.