T1 and T2 values of human neonatal blood at 3 Tesla: Dependence on hematocrit, oxygenation, and temperature

Abstract

Purpose Knowledge of blood T1 and T2 is of major importance in many applications of MRI in neonates. However, to date, there has not been a systematic study to examine neonatal blood T1/T2 relaxometry. This present study aims to investigate this topic. Methods Using freshly collected blood samples from human umbilical cord, we performed in vitro experiments under controlled physiological conditions to measure blood T1 and T2 at 3T and their dependence on several factors, including hematocrit (Hct), oxygenation (Y) and temperature. Results The arterial T1 in neonates was 1825±184ms (Hct=0.42±0.08), longer than that of adult blood. Neonatal blood T1 was strongly dependent on Hct (p<0.001) and Y (p=0.005), and the dependence of T1 on Y was more prominent at higher Hct. The arterial T2 of neonatal blood was 191ms at an Hct of 0.42, which was also longer than adult blood. Neonatal blood T2 was positively associated with blood oxygenation and negatively associated with hematocrit level, and can be characterized by an exchange model. Neonatal blood T1 was also positively associated with temperature (p<0.001). Conclusion The values provided in this report may provide important reference and calibration information for sequence optimization and quantification of in vivo neonatal MRI studies.

Heterogeneous increases of regional cerebral blood flow during preterm brain development: Preliminary assessment with pseudo-continuous arterial spin labeled perfusion MRI

“…To better estimate the regional CBF from ASL, future studies will benefit from collecting subject-specific information for tuning these imaging parameters. For example, individual subject's hematocrit can be used for subject-specific blood T1 estimation (Liu et al, 2015). In addition, larger sample size may reveal nonlinear regional CBF change curves instead of simple linear lines used in this study, and longitudinal dataset may remove the effects caused by the individual differences.…”

“…ΔM(x, y, z) is the difference between dynamic-averaged signal intensity in control image and that in the label image at voxel (x, y, z). Here α, the labeling efficiency, is 0.92 according to the relationship of labeling efficiency and blood velocity in the previous study (Aslan et al, 2010) with the blood velocity of 10.77 ± 4.44 cm/sec measured from PC MRI of 14 neonates; λ , the blood-brain partition coefficient, is 0.9 mL/g (Herscovitch and Raichle, 1985); PLD(z), the post labeling delay time at the slice z, is 2500ms for images acquired with 3D GRASE pCASL sequence and 2500+(z-1)*w for images acquired with multi-slice pCASL sequence, where w = 35ms is the slice timing delay between adjacent slices; LabelDur, the labeling duration, is 1650ms; T 1a , T 1 of arterial blood, was obtained for each subject based on blood T1-hematocrit curve (Liu et al, 2015). The subject-specific hematocrit was estimated with the subjects’ age at scan based on the hematocrit-age curve (Jopling et al, 2009).…”

Empirical model of human blood transverse relaxation at 3 T improves MRI T2oximetry

“…into the following subequations: where a 1 , a 2 , a 3 , b 1 , b 2 , and c 1 are empirically determined coefficients . Empirical T 2b calibration models were determined separately for both bovine blood and neonatal, infant cord blood using this method. Overall, the resulting T 2b calibration models were very similar; however, subtle differences were observed particularly at the high oxygen saturation levels.…”

Brain oxygen saturation assessment in neonates using T2-prepared blood imaging of oxygen saturation and near-infrared spectroscopy

“…35 Likewise, the very framework that forms the foundation for estimating SO 2-T2-BIOS also depends on Hct, for example overestimation of Hct would result in underestimation of T 2b . 13,17 Interestingly, correction for Hct of the data removed the statistical significance of the linear association after log-transformation (Figure 4(c) vs. (f)), but it only marginally decreased the limits of agreement (Figure 4(b) and (c) vs. (e) and (f). In this study, the adult calibration curve was used as opposed to the published curve for fetal blood.…”

“…With appropriate knowledge of T 2b , SO 2 can be derived by using previously determined relationships between T 2 and SO 2 . 13,[15][16][17] In this work, we present a method which combines ''intravoxel incoherent motion imaging'' (IVIM) to yield blood volume-weighted images with a standard Malcolm Levitt (MLEV) T 2 preparation. [18][19][20] These two techniques are combined in the ''T 2 -prepared blood imaging of oxygen saturation'' (T 2 -BIOS) sequence, which enables the estimation of T 2b on a voxel-by-voxel basis in a single slice of brain tissue.…”