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PURPOSE To evaluate different T2 -oxygenation calibrations for estimating venous oxygenation in people with sickle cell anemia (SCA). METHODS Blood T2 values were measured at 3 T in the internal jugular veins of 12 healthy volunteers and 11 SCA participants with no history of stroke, recent transfusion, or renal impairment. T2 -oxygenation relationships of both sickled and normal blood samples were calibrated individually and compared with values generated from published models. After converting venous T2 values to venous oxygenation, whole-brain oxygen extraction fraction and cerebral metabolic rate of oxygen were calculated. RESULTS Sickle blood samples' oxygenation values calculated from our individual calibrations agreed well with measurements using a blood analyzer, whereas previous T2 calibrations based on normal blood samples showed 13%-19% underestimation. Meanwhile, oxygenation values calculated from previous grouped T2 calibration for sickle blood agreed well with experimental measurement on averaged values, but showed up to 20% variation for several individual samples. Using individual T2 calibrations, the whole-brain oxygen extraction fraction and cerebral metabolic rate of oxygen of SCA participants were 0.38 ± 0.08 and 172 ± 42 µmol/min/100 g, respectively, which were comparable to those values measured on healthy volunteers. CONCLUSION Our results confirm that sickle blood T2 values not only depend on the hematocrit and oxygenation values, but also on other hematological factors. The individual T2 calibrations minimized the effect of heterogeneity of sickle blood between different SCA populations and improved the accuracy of T2 -based oximetry. The measured oxygen extraction fraction and cerebral metabolic rate of oxygen of this group of SCA participants were found to not differ significantly from those of healthy individuals.

PURPOSE: To evaluate different T(2)-oxygenation calibrations for estimating venous oxygenation in people with sickle cell anemia (SCA). METHODS: Blood T(2) values were measured at 3T in the internal jugular veins of 12 healthy volunteers and 11 SCA participants with no history of stroke, recent transfusion, or renal impairment. T(2)-oxygenation relationships of both sickled and normal blood samples were calibrated individually and compared with values generated from published models. After converting venous T(2) values to venous oxygenation, whole-brain oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO(2)) were calculated. RESULTS: Sickle blood samples’ oxygenation values (Y) calculated from our individual calibrations agreed well with measurements using a blood analyzer, while previous T(2) calibrations based on normal blood samples showed 13–19% underestimation. Meanwhile, Y values calculated from previous grouped T(2) calibration for sickle blood agreed well with experimental measurement on averaged values, but showed up to 20% variation for several individual samples. Using individual T(2) calibrations, the whole-brain OEF and CMRO(2) of SCA participants were 0.38+/−0.08 and 172+/−42μmol/min/100g, respectively, which were comparable to those values measured on normal volunteers. CONCLUSION: Our results confirm that sickle blood T(2) values not only depend on Hct and Y, but also on other hematological factors. The individual T(2) calibrations minimized the effect of heterogeneity of sickle blood between different SCA populations and improved the accuracy of T(2)-based oximetry. The measured OEF and CMRO(2) of this group of SCA participants were found to not differ significantly from those of healthy people.

Purpose To develop a fast protocol for measuring T1 values in the internal carotid artery (ICA), to validate this technique with in vitro measurements, and to evaluate its reproducibility. Methods A modified Look–Locker sequence was optimized to enable rapid determination of T1 in the ICA at 3T. T1 values from the ICA were compared with in vitro measurements on individually sampled venous blood oxygenated to arterial levels. A test–retest reproducibility study was also conducted. Results The group-averaged arterial blood T1 value was 1908 ± 77 ms for six women (hematocrit = 0.39 ± 0.03) and 1785 ± 55 ms for seven men (hematocrit = 0.45 ± 0.02), which is 100–200 ms longer than the widely adopted value obtained from bovine blood experiments. The arterial T1 value per subject correlated significantly with individual hematocrit values. The intrasession and intersession coefficients of variation were 1.1% and 2.1%, respectively, indicating good precision and reproducibility of our method. Reasonable agreement was observed between the in vivo and in vitro results with a correlation coefficient of 0.78. Conclusion The proposed method can provide fast arterial T1 measurement on individual subjects. When not performing such a subject-specific measurement, we recommend the use of 1908 ms and 1785 ms for healthy women and men, respectively, or 1841 ms for adults in general. Magn Reson Med 77:2296–2302, 2017. © 2016 International Society for Magnetic Resonance in Medicine

Current T(1) values for blood at 3T largely came from in vitro studies on animal blood or freshly drawn human blood. Measurement of blood T(1) in vivo could provide more specific information, e.g., for individuals with abnormal blood composition. Here, blood T(1) at 3T was measured rapidly (