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Abstract #1130

Relaxation of Blood at High Field: Another Exchange Regime

Ksenija Grgac1,2, Qin Qin1,3, Michael McMahon1,3, Jason Zhao1, Peter C.M. van Zijl1,3

1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States; 2Department of Chemistry, Johns Hopkins University, Baltimore, MD, United States; 3F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States

To study the intravascular BOLD mechanism, we used a physiologically controlled blood perfusion system at 9.4T under oxygenated conditions for a series of hematocrits. Previous studies have shown that, at such high fields, the two-site (eryhtrocyte-plasma) fast exchange model can not describe oxygenation-based relaxation changes properly in that it gives incorrect lifetimes for water in erythrocytes (1-3ms). We show that, for the physiological range of hematocrits, a general two-site exchange model (including slow, fast and intermediate regimes) can appropriately describe blood relaxation in oxygenated blood and provides an erythrocyte lifetime of 12.23.7ms, in agreement with literature values