Arterial spin labeling measurement of cerebral perfusion in children with sickle cell disease

Abstract

To evaluate the applicability of arterial spin labeling (ASL) cerebral blood flow (CBF) measurements in children with sickle cell disease (SCD). We included 12 patients and five controls. Conventional magnetic resonance imaging (MRI) (T2, fluid attenuated inversion recovery [FLAIR], and MR angiography) was performed to diagnose silent infarcts, vasculopathy, or leukoencephalopathy. Pseudo-continuous ASL was performed to measure CBF using two postlabeling delays to identify transit-time effects. Perfusion estimates were corrected for hematocrit and blood velocity in the labeling plane and compared to phase-contrast MR. CBF asymmetries between the flow maps of the left and right internal carotid arteries were tested for significance using paired t-tests. Significant asymmetries were expressed in terms of an asymmetry ratio (AR = absolute difference/mean). An AR >10% was considered clinically relevant. Mean CBF was higher in patients than in controls. Agreement between CBF and flow improved after applying hematocrit and velocity corrections. At a 2100 msec postlabeling delay one patient had a clinically relevant asymmetry. No association was observed between CBF asymmetries and silent infarcts. Care must be taken in the interpretation of ASL-CBF measurements in SCD patients. A long postlabeling delay with blood velocity correction anticipates overestimation of CBF asymmetries.