Impact of Prematurity on the Tissue Properties of the Neonatal Brain Stem: A Quantitative MR Approach.

ABSTRACT

BACKGROUND AND PURPOSE: Preterm birth interferes with regular brain development. The aim of this study was to investigate the impact of prematurity on the physical tissue properties of the neonatal brain stem using a quantitative MR imaging approach. MATERIALS AND METHODS: A total of 55 neonates (extremely preterm [n = 30] <28 + 0 weeks gestational age; preterm [n = 10] 28 + 0-36 + 6 weeks gestational age; term [n = 15] ≥37 + 0 weeks gestational age) were included in this retrospective study. In most cases, imaging was performed at approximately term-equivalent age using a standard MR protocol. MR data postprocessing software SyMRI was used to perform multidynamic multiecho sequence (acquisition time 5 minutes, 24 seconds)-based MR postprocessing to determine T1 relaxation time, T2 relaxation time, and proton density. Mixed-model ANCOVA (covariate gestational age at MR imaging) and the post hoc Bonferroni test were used to compare the groups. RESULTS: There were significant differences between premature and term infants for T1 relaxation time (midbrain P < .001; pons P < .001; basis pontis P = .005; tegmentum pontis P < .001; medulla oblongata P < .001), T2 relaxation time (midbrain P < .001; tegmentum pontis P < .001), and proton density (tegmentum pontis P = .004). The post hoc Bonferroni test revealed that T1 relaxation time/T2 relaxation time in the midbrain differed significantly between extremely preterm and preterm (T1 relaxation time P < .001/T2 relaxation time P = .02), extremely preterm and term (T1 relaxation time/T2 relaxation time P < .001), and preterm and term infants (T1 relaxation time P < .001/T2 relaxation time P = .006). CONCLUSIONS: Quantitative MR parameters allow preterm and term neonates to be differentiated. T1 and T2 relaxation time metrics of the midbrain allow differentiation between the different stages of prematurity. SyMRI allows for a quantitative assessment of incomplete brain maturation by providing tissue-specific properties while not exceeding a clinically acceptable imaging time.