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Oxygenation and hematocrit dependence of transverse relaxation rates of blood at 3T
Author(s) -
Zhao Jason M.,
Clingman Chekesha S.,
Närväinen M. Johanna,
Kauppinen Risto A.,
van Zijl Peter C.M.
Publication year - 2007
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21342
Subject(s) - oxygenation , hematocrit , blood volume , nuclear magnetic resonance , relaxation (psychology) , blood oxygenation , chemistry , nuclear medicine , cardiology , medicine , physics , radiology , functional magnetic resonance imaging
Knowledge of the transverse relaxation rates R 2 and R 2 *of blood is relevant for quantitative assessment of functional MRI (fMRI) results, including calibration of blood oxygenation and measurement of tissue oxygen extraction fractions (OEFs). In a temperature controlled circulation system, these rates were measured for blood in vitro at 3T under conditions akin to the physiological state. Single spin echo (SE) and gradient echo (GRE) sequences were used to determine R 2 and R 2 * , respectively. Both rates varied quadratically with deoxygenation, and changes in R 2 *were found to be due predominantly to changes in R 2 . These data were used to estimate intravascular blood oxygenation level dependent (BOLD) contributions during visual activation. Due to the large R 2 *in venous blood, intravascular SE BOLD signal changes were larger than GRE effects at echo times above 30 ms. When including extravascular effects to estimate the total BOLD effect, GRE BOLD dominated due to the large tissue volume fraction. Magn Reson Med 58:592–596, 2007. © 2007 Wiley‐Liss, Inc.