Abstract #2040

Measuring Bi-Exponential Transverse Relaxation of the ASL Signal at 9.4T to Estimate Arterial Oxygen Saturation and the Time of Exchange of Labelled Blood Water Into Cortical Brain Tissue

Jack A. Wells¹, Bernard Siow¹, Mark F. Lythgoe¹, David L. Thomas²

¹UCL Centre for Advanced Biomedical Imaging, UCL Division of Medicine and Institute of Child Health, London, United Kingdom; ²Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London. ML and DT are joint senior authors.

The transverse decay of the FAIR ASL signal at 5 inflow times (TIs) was measured in the rat brain at 9.4T. Bi-exponential behavior was observed that appears to derive from different T2 values associated with the intra-vasculature (IV) and extra-vascular (EV) compartments. A two compartment bi-exponential model was used to assess the relative contribution of the IV and EV compartments to the ASL signal at the 5 TIs, without needing to assume a constant T2 for labeled blood water in the vessels. This novel method was applied to estimate tissue transit time and the oxygen saturation on the arterial side of the vasculature