Functional Perfusion Imaging Using Pseudo-Continuous ASL with Low-Flip-Angle Segmented 3D Spiral Readouts

Jon-Fredrik Nielsen¹, Luis Hernandez-Garcia¹

Arterial Spin Labeling (ASL) provides quantitative and reproducible measurements of cerebral blood flow, and is an attractive method for functional MRI. Most existing ASL fMRI protocols are based on 2D multislice or 3D spin-echo, and suffer from low image signal-to-noise ratio (SNR) or through-plane blurring. 3D ASL with multi-shot (segmented) readouts can improve the SNR efficiency relative to 2D multislice, and does not suffer from T2-blurring. We characterize the temporal SNR of a segmented 3D spiral ASL sequence, and investigate the effects of RF phase-cycling scheme and flip angle schedule on the ASL time-course signal. We conclude that RF-spoiled segmented 3D spiral ASL with a cubic flip angle schedule starting at 15o can produce high-quality functional activation maps with only modest through-plane blurring.