Blood longitudinal (T1) and transverse (T2) relaxation time constants at 11.7 Tesla

ObjectThe goal of the study was to determine blood T1 and T2 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 methodsT1 and T2 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 (B0).ResultsT1 was positively correlated with Temp, independent of Y, and negatively correlated with Hct. T2 was negatively correlated with Temp and Hct, but positively correlated with Y, in a non-linear fashion. T1 increased linearly with B0, whereas T2 decreased exponentially with B0.ConclusionThis study reported blood T1 and T2 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.

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