Fast measurement of blood T 1 in the human carotid artery at 3T: Accuracy, precision, and reproducibility

Purpose To develop a fast protocol for measuring T 1 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 T 1 in the ICA at 3T. T 1 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 T 1 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 T 1 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 T 1 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