Blood longitudinal (T 1) and transverse (T 2) relaxation time constants at 11.7 Tesla
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The goal of the study was to determine blood T 1 and T 2 values as functions of oxygen saturation (Y), temperature (Temp) and hematocrit (Hct) at an ultrahigh MR field (11.7 T) and explore their impacts on physiological measurements, including cerebral blood flow (CBF), blood volume (CBV) and oxygenation determination.
Materials and methods
T 1 and T 2 were simultaneously measured. Temperature was adjusted from 25 to 40°C to determine Temp dependence; Hct of 0.17–0.51 to evaluate Hct dependence at 25 and 37°C; and Y of 40–100% to evaluate Y dependence at 25 and 37°C. Comparisons were made with published data obtained at different magnetic field strengths (B 0).
T 1 was positively correlated with Temp, independent of Y, and negatively correlated with Hct. T 2 was negatively correlated with Temp and Hct, but positively correlated with Y, in a non-linear fashion. T 1 increased linearly with B 0, whereas T 2 decreased exponentially with B0.
This study reported blood T 1 and T 2 measurements at 11.7 T for the first time. These blood relaxation data could have implications in numerous functional and physiological MRI studies at 11.7 T.
KeywordsBOLD fMRI High fields ASL VASO TRUST
We thank Hsiao-Ying Wey of the Research Imaging Institute and Saaussan Madi of Bruker Biospin for technical support. This work was supported by in part by the NIH (R01EY014211, R01EY018855) and VA MERIT. We are also grateful for the resources and support from NIH/NCRR (S10 RR023038), from the Defense Advanced Research Projects Agency (Comprehensive Facility for Animal Imaging Research (CFAIR), HR0011-07-C-0027), and the Texas Emerging Technology Fund from the Office of the Governor of Texas.
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