Off-resonance effects on infant pCASL

Motivation: The image quality of ASL in infants is variable. Goal(s): To investigate the labeling efficiency in infant pCASL. Approach: Labeling efficiency was simulated using the Bloch equation. Prospective scans were performed on 11 subjects, with pCASL at 60mm and 90mm below the AC-PC line, MRA, and B0 map. Results: Blood flow velocity has negligible effects on the labeling efficiency at the on-resonance frequency. The combined effects of off-resonance and the high blood flow velocity are the primary cause of the variable image quality. pCASL images at 60mm showed improved SNR in 8 /11 infants, compared to that of 90mm. Impact: This study examined the factors contributing to variable ASL images in infant and provided a preliminary solution by selecting the labeling plane.