Brain tissue volumes in preterm infants: prematurity, perinatal risk factors and neurodevelopmental outcome: a systematic review.

OBJECTIVE: To evaluate the clinical value of neonatal brain tissue segmentation in preterm infants according to the literature. METHODS: A structured literature search was undertaken in MEDLINE/Pubmed. This included all publications on volumetric brain tissue assessment in preterm infants at term-equivalent age (TEA) compared to brain tissue volumes of term-born infants, related to perinatal risk factors or related to neurodevelopmental outcome. RESULTS: Sixteen prospective cohort studies, described in 30 articles, fulfilled the criteria. Preterm infants displayed total and regional brain tissue alterations compared to healthy, term-born controls. These alterations seemed more prominent with decreasing gestational age. White matter injury, intraventricular haemorrhage, postnatal corticosteroid therapy, intra-uterine growth retardation and chronic lung disease were frequently associated with volume changes. Associations between volume alterations at TEA and neurodevelopmental outcome in early childhood were shown in a few studies. CONCLUSIONS: Preterm birth is associated with brain tissue volume alterations that become more pronounced in the presence of perinatal risk factors and white matter injury. Moreover, associations between volumetric alterations as early as TEA and long-term neurodevelopmental impairments are scarce.

Observation of a frequency-dependent doublet in the Si-B3 ESR spectrum.

The Si-B3 spectrum, observed in neutron-irradiated p-type silicon after annealing at T(an)≈400 °C, has previously been extensively studied using electron spin resonance (ESR). It has been assigned to a silicon tetra-interstitial (I(4)), based on the symmetry of the defect and resolved hyperfine (hf) structure doublets. However, additional ESR measurements carried out here at three frequency bands show that one of these doublets would not originate from the hf interaction since the doublet spacing is found to be dependent on the applied microwave frequency f. This casts doubt on the previous assignment of the Si-B3 spectrum to I(4) based on ESR data obtained at one observational f. Despite profound investigation, the origin of the f dependence of the satellite doublet could not be traced, disabling any progress on the Si-B3 defect modeling. The observation (re)emphasizes the necessity of the multi-frequency approach in coming to a correct interpretation of ESR parameters and correlated defect modeling.