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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