Simultaneous Intracranial Angiography and Susceptibility Imaging (SIAS) by Combining Velocity-Selective ASL and...

Intracranial angiography and susceptibility imaging are two important modalities for assessment of cerebral disorders. This study aims to develop a simultaneous intracranial angiography and susceptibility imaging (SIAS) sequence with high acquisition efficiency and good visibility of distal cerebral vessels.

SIAS embeds multi-echo susceptibility-weighted imaging (SWI) within the velocity-selective arterial spin labeling (VSASL) MRA. Sequence parameters, including lines per shot (LPS) and SWI flip angle (FA), were optimized in healthy volunteers. Mutual influence between VSASL and SWI acquisition was also evaluated. SIAS was then compared with conventional VSASL, TOF, and SWI. Quantitative metrics included arterial length, sharpness and intensity; vein sharpness; and susceptibility values. Artery-vein separation in SIAS-VSASL was performed using a susceptibility-guided strategy.

Lower LPS improved distal vessel depiction but reduced carotid siphon visibility in both conventional VSASL and SIAS-VSASL. A centric-in SWI readout enhanced vein sharpness and yielded better visualization of proximal arteries. Increasing SWI FA also improved vein sharpness but reduced vessel length. SIAS-VSASL visualized distal artery better than TOF, and improved proximal artery sharpness over VSASL. SIAS-SWI yielded sharper vein depiction and reliable susceptibility quantification. The proposed susceptibility-guided post-processing enabled effective artery-vein separation in SIAS-VSASL.

SIAS provides good visualization of small arteries while supporting hemorrhage detection, quantitative susceptibility mapping reconstruction, and venous imaging, which facilitate artery-vein separation in SIAS-VSASL. It demonstrates strong potential for comprehensive assessment of brain disorders.