Accuracy of parenchymal cerebral blood flow measurements using pseudo-continuous arterial spin labeling in healthy volunteers

Background and Purpose: Arterial spin-labeling method for CBF assessment is widely available but its accuracy is not fully established. We investigated the accuracy of a whole brain arterial spin-labeling technique for assessment of the mean parenchymal CBF (pCBF) and the effect of ageing in healthy volunteers. Phase-contrast MRI was used as the reference method.
Materials and Methods: Ninety-two healthy volunteers were included: 49 young (age range 20-30y) and 43 elderly (65-80y). Arterial spin-labeling pCBF values were averaged over the whole brain to quantify mean pCBFASL.
Total CBF was assessed with phase-contrast MRI as the sum of flow in the internal carotids and vertebral arteries, and subsequent division by brain volume returned the pCBFPCMRI. Accuracy was considered as good if there was less than 5 mL/min/100g in systematic difference against the reference method and if the 95% limits of agreement interval are equal or better than ±10 mL/min/100g
Results: pCBFASL was correlated with pCBFPCMRI (r=0.73, P<0.001).
Significant differences were observed between pCBFASL and pCBFPCMRI in young (P=0.001) as well as in elderly (P<0.001), and the systematic differences were -4±14 mL/min/100g (mean ± 2SD) in young and +6±12 mL/min/100g in elderly. Young subjects showed higher pCBF than elderly for both pCBFPCMRI (Young:57±8, Elderly:54±7 mL/min/100g, P=0.05) and pCBFASL (Young:60±10, Elderly:48±10 mL/min/100g, P<0.001).
Conclusion: Regarding accuracy of the arterial spin-labeling, limits of agreements were too wide while the systematic overestimation in young and underestimation in elderly was close to acceptable. Age-related decrease in pCBF was augmented in arterial spin-labeling compared to phase contrast MRI.