Oxygenation and hematocrit dependence of transverse relaxation rates of blood at 3T

Authors

  • Jason M. Zhao,

    1. Department of Radiology, Division of MRI Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
    2. F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
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    • Jason M. Zhao and Chekesha S. Clingman contributed equally to this project

  • Chekesha S. Clingman,

    1. Department of Radiology, Division of MRI Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
    2. F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
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    • Jason M. Zhao and Chekesha S. Clingman contributed equally to this project

  • M. Johanna Närväinen,

    1. A.I. Virtanen Institute, University of Kuopio, Kuopio, Finland
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  • Risto A. Kauppinen,

    1. School of Sport and Exercise Sciences, University of Birmingham, Birmingham, United Kingdom
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  • Peter C.M. van Zijl

    Corresponding author
    1. Department of Radiology, Division of MRI Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
    2. F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
    • Johns Hopkins University School of Medicine, Dept. of Radiology, 217 Traylor Bldg., 720 Rutland Ave., Baltimore, MD 21205
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Abstract

Knowledge of the transverse relaxation rates R2 and Rmath image 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 R2 and Rmath image, respectively. Both rates varied quadratically with deoxygenation, and changes in Rmath image were found to be due predominantly to changes in R2. These data were used to estimate intravascular blood oxygenation level dependent (BOLD) contributions during visual activation. Due to the large Rmath image 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.

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