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

Abstract

The human brain develops rapidly during 32-45 postmenstrual weeks (PMW), a critical stage characterized by dramatic increases of metabolic demand. The increasing metabolic demand can be inferred through measurements of regional cerebral blood flow (CBF), which might be coupled to regional metabolism in preterm brains. Arterial spin labeled (ASL) perfusion MRI is one of the few viable approaches for imaging regional CBF of preterm brains, but must be optimized for the extremely slow blood velocity unique in preterm brains. In this study, we explored the spatiotemporal CBF distribution in newborns scanned at the age of 32-45PMW using a pseudo-continuous ASL (pCASL) protocol adapted to slow blood flow in neonates. A total of 89 neonates were recruited. PCASL MRI was acquired from 34 normal newborns and phase contrast (PC) images from 19 newborns. Diffusion tensor images (DTI) were acquired from all 89 neonates for measuring cortical fractional anisotropy (FA), which characterizes cortical microstructure. Reproducible CBF measurements were obtained with the adjusted pCASL sequence. Global CBF measurement based on PC MRI was found to double its value in the 3rd trimester. Regional CBF increases were heterogeneous across the brain with a significantly higher rate of CBF increase in the frontal lobe and a lower rate of CBF increase in the occipital lobe. A significant correlation was found between frontal cortical CBF and cortical FA measurements (p<0.01). Increasing CBF values observed in the frontal lobe corresponded to lower FA values, suggesting that dendritic arborization and synaptic formation might be associated with an elevated local CBF. These results offer a preliminary account of heterogeneous regional CBF increases in a vital early developmental period and may shed the light on underlying metabolic support for cortical microstructural changes during the developmental period of 32-45PMW. Preterm effects and limitations of pCASL techniques in newborns need to be carefully considered for interpretation these results.

Cerebral Perfusion Is Perturbed by Preterm Birth and Brain Injury

“…In another study by the same authors, 27 scanning of 18 PT infants was performed to assess hematocrit variability in the T1b and ASL measurements. Ouyang et al 26 reported higher global CBF and heterogeneous increases in regional CBF during the third trimester in 17 PT infants. Our data are in keeping with these findings; however, our study is the first to characterize quantitative regional CBF in PT infants with BI.…”

“…To the best of our knowledge, only 4 studies have performed ASL-MR imaging at preterm age. 12,[25][26][27] Varela et al 25 scanned Ͻ10 PT infants without BI to quantify the ASL parameters and techniques. De Vis et al 12 scanned 6 PT infants, looking for cerebral perfusion changes with brain maturation.…”

“…13,17 While several ASL-MR imaging studies have been reported in full-term neonates, 13,18-24 only 4 studies have performed ASL-MR imaging in the preterm (PT) period (ie, third trimester of ex utero life), all of which included small sample sizes of preterm infants with no structural BI at the time of the MR imaging. 12,[25][26][27] To date, to our knowledge, no study has examined early CBF in PT infants during the third trimester of ex utero brain development to better ascertain the impact of early-life BI on cerebral perfusion.…”

Regularized-Ncut: Robust and homogeneous functional parcellation of neonate and adult brain networks

“…Neonate dataset and preprocessing: A series of MR sequences including rs-fMRI were conducted on neonates with a Philips 3T Achieva MR scanner Cao et al, 2017a;Ouyang et al, 2017;Song et al, 2017 functional volumes were retained for each subject. After correction for acquisition time delay between slices and head motion between volumes, the rs-fMRI image volumes were then registered to the custom-made template (Cao et al, 2017a).…”

Rest functional brain maturation during the first year of life

“…Therefore, ASL MRI non-invasively assesses brain perfusion and allows for a quantitative measurement of rest CBF without the administration of contrast material or exposure to ionizing radiation (41). This imaging method has been used to study rest CBF in neonates (42, 43), toddlers (44, 45) and older children (46), as well as, more recently, brain injuries in preterm babies (47).…”