Acceleration-selective arterial spin labeling.

In this study, a new arterial spin labeling (ASL) method with spatially nonselective labeling is introduced, based on the acceleration of flowing spins, which is able to image brain perfusion with minimal contamination from venous signal. This method is termed acceleration-selective ASL (AccASL) and resembles velocity-selective ASL (VSASL), with the difference that AccASL is able to discriminate between arterial and venous components in a single preparation module due to the higher acceleration on the arterial side of the microvasculature, whereas VSASL cannot make this distinction unless a second labeling module is used. A difference between AccASL and VSASL is that AccASL is mainly cerebral blood volume weighted, whereas VSASL is cerebral blood flow weighted. AccASL exploits the principles of acceleration-encoded magnetic resonance angiography by using motion-sensitizing gradients in a T2 -preparation module. This method is demonstrated in healthy volunteers for a range of cutoff accelerations. Additionally, AccASL is compared with VSASL and pseudo-continuous ASL, and its feasibility in functional MRI is demonstrated. Compared with VSASL with a single labeling module, a strong and significant reduction in venous label is observed. The resulting signal-to-noise ratio is comparable to pseudo-continuous ASL and robust activation of the visual cortex is observed.