Relaxation Properties of Human Umbilical Cord Blood at 1.5 Tesla

Purpose: To characterize the MRI relaxation properties of human umbilical cord blood at 1.5 Tesla. Methods: Relaxometry measurements were performed on cord blood specimens (N - 88, derived from six caesarean deliveries) spanning a broad range of hematocrits (Hct - 0.190.76) and oxygen saturations (sO(2) - 4-100%), to characterize the dependence of T-1 and T-2 on these blood properties. Adult blood data (N - 31 specimens, derived from two volunteers) were similarly studied to validate our experimental methods by comparison with existing literature. Using biophysical models previously developed for adult blood, new model parameters were estimated, which relate Hct and sO(2) to the observed cord blood relaxation times. Results: Fitted biophysical models explained more than 90% of the variation in T-1 and T-2. In general, T-2 relaxation times of cord blood were longer (by up to 35%) than those of adult blood, whereas T-1 relaxation times were slightly shorter ( by up to 10%). Conclusions: The models and fitted parameters presented here can be used for calibration of future MRI investigations of fetal and neonatal blood physiology. This study is an important step in facilitating accurate, noninvasive assessments of fetal blood oxygen content, a valuable diagnostic parameter in the identification and treatment of fetal hypoxia. Magn Reson Med 77: 1678- 1690, 2017. (C) 2016 International Society for Magnetic Resonance in Medicine