Repeatability of Absolute vs Relative Cerebral Blood Flow and Arterial Transit Time for Single-Delay and Multi-Delay Arterial Spin Labelling

Motivation: Arterial Spin Labelling (ASL) is non-invasive making it valuable for longitudinal imaging, therefore knowing the repeatability is crucial. Goal(s): Compare repeatability of single-delay ASL (SD-ASL) and multi-delay ASL (MD-ASL) cerebral blood flow (CBF) and arterial transit time (ATT). Approach: SD-ASL and MD-ASL were repeated on 9 healthy volunteers 14 days apart. Within-subject coefficients of variation (CoVs) for absolute and relative CBF and ATT were assessed in gray and white matter. Results: Absolute CBF had 5% lower CoVs for MD-ASL than SD-ASL. Relative CBF was more repeatable with CoVs 3-4 times lower for both scan-types. ATT was more repeatable than CBF for absolute quantificatio n. Impact: Our repeatability study shows relative CBF has much lower CoV than absolute CBF and therefore relative CBF may be more useful for longitudinal studies. MD-ASL acquisition is preferable, giving lower CoVs for CBF and additional ATT with good repeatability.