Arterial spin labeling perfusion MRI: Inter-vendor reproducibility and clinical applicability

Arterial spin labeling (ASL) is a perfusion magnetic resonance imaging (MRI) technique that non-invasively measures cerebral blood flow (CBF). The first part of this thesis concerns the inter-vendor reproducibility of ASL. Studies in this thesis show that on a total gray matter (GM) level, long-term physiological perfusion fluctuation dominates technical differences between ASL sequences and scanners. However, CBF data from smaller regions of interest were only comparable when sequences were made as identical as possible on different vendor MRI systems. Major effects include different readout modules, differences in effective post-labeling delay leading to differences in transit time sensitivity, the extent of the point spread function and the efficiency of background suppression. Furthermore, slight differences in sequence parameters can have a larger effect than differences in MRI hardware.
The second part of this thesis investigates several potential clinical applications of ASL. We show that white matter (WM) perfusion signal can be measured in the elderly, but also that the WM region of interest should be carefully eroded to avoid contamination with GM CBF. We demonstrate the statistical benefits of modest vascular crushing in a large population of elderly with hypertension. In the same population, WM lesion volume was correlated with WM lesion CBF but not with normal appearing WM or GM CBF. In children with sickle cell disease, we show correlations between CBF and hematological parameters that are both involved in the pathogenesis of WML and are key targets in the treatment of this disease.