Multi-module ASL MRA sequences for improving visualization of distal small brain vessels

Motivation: Clear visualization of the distal small vessels in brain is important. Goal(s): To develop and evaluate multi-module ASL (MMASL) MRA sequences that combine velocity selective (VS) ASL prepulses and spatially selective ASL prepulses for enhanced imaging of distal small brain vessels. Approach: The VS prepulse was made slab-selective (SS) when combined with spatially selective ASL. Simulations and in vivo experiments were performed to compare ASL MRA sequences with prepulses of PCASL, FAIR, VS, SSVS_PCASL, SSVS_FAIR, SSVS_PCASL_FAIR. Results: Both simulation and in vivo experiment indicates that SSVS-FAIR achieves better visibility of vessels, particularly for distal small vessels. Impact: The results indicate that combining SSVS and FAIR can improve imaging of distal small brain vessels, with little compromise for imaging of the proximal vessels, therefore has a great clinical potential.