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