MR Imaging of the Preterm Brain: safer better faster stronger

__Abstract__ Human brain development and maturation consist of complex processes that span from the first trimester of pregnancy to adult life. These processes include: 1) neuronal proliferation, characterized by generation of neurons in the dorsal subventricular zone and ventral germinative epithelium of the ganglionic eminence; 2) migration, where neurons move from these zones to specific sites where they will reside for life; 3) organization, in which neurons differentiate to subplate neurons, align, orientate and connect through their axons and dendrites. Glial cells differentiate into astrocytes, oligodendrocytes and microglia, and 4) myelination, where oligodendrocytes produce myelin that will be deposited around axons. Preterm infants are born in this critical period, in which the brain is particularly vulnerable to exogenous and endogenous events. Perinatal hypoxia-ischemia, hyperoxia, infection and hypocarbia can result in fluctuations in cerebral blood flow, inflammation, increased excitotoxicity and oxidative stress, all of which can affect normal brain ontogenesis and cause irreversible injury. In general, the two most commonly recognized variants of preterm brain injury are: periventricular white matter (WM) injury and hemorrhage in the germinal matrix and lateral ventricle. These injury patterns will be discussed separately in the following sections

Data quality in diffusion tensor imaging studies of the preterm brain: a systematic review

Background: To study early neurodevelopment in preterm infants, evaluation of brain maturation and injury is increasingly performed using diffusion tensor imaging, for which the reliability of underlying data is paramount. Objective: To review the literature to eva

Safety of routine early MRI in preterm infants

Background: Cerebral MRI performed on preterm infants at term-equivalent 30 weeks' gestational age (GA) is increasingly performed as part of standard clinical care. Objective: We evaluated safety of these earlyMRI procedures. Materials and methods We retrospectively collected data on patient safety of preterm infants who underwent early MRI scans. Data were collected at fixed times before and after the MRI scan. MRI procedures were carried out according to a comprehensive guideline. Results: A total of 52 infants underwent an MRI scan at 30 weeks' GA. Although no serious adverse events occurred and vital parameters remained stable during the procedure, minor adverse events were encountered in 26 infants (50%). The MRI was terminated in three infants (5.8%) because of respiratory instability. Increased respiratory support within 24 h after the MRI was necessary for 12 infants (23.1%) and was significantly associated with GA, birth weight and the mode of respiratory support. Hypothermia (core temperature < 36°C) occurred in nine infants (17.3%). Temperature dropped significantly after the MRI scan. Conclusion: Minor adverse events after MRI procedures at 30 weeks GA were common and should not be underestimated. A dedicated and comprehensive guideline for MRI procedures in preterm infants is essential

Data quality in diffusion tensor imaging studies of the preterm brain : a systematic review

BACKGROUND: To study early neurodevelopment in preterm infants, evaluation of brain maturation and injury is increasingly performed using diffusion tensor imaging, for which the reliability of underlying data is paramount. OBJECTIVE: To review the literature to evaluate acquisition and processing methodology in diffusion tensor imaging studies of preterm infants. MATERIALS AND METHODS: We searched the Embase, Medline, Web of Science and Cochrane databases for relevant papers published between 2003 and 2013. The following keywords were included in our search: prematurity, neuroimaging, brain, and diffusion tensor imaging. RESULTS: We found 74 diffusion tensor imaging studies in preterm infants meeting our inclusion criteria. There was wide variation in acquisition and processing methodology, and we found incomplete reporting of these settings. Nineteen studies (26%) reported the use of neonatal hardware. Data quality assessment was not reported in 13 (18%) studies. Artefacts-correction and data-exclusion was not reported in 33 (45%) and 18 (24%) studies, respectively. Tensor estimation algorithms were reported in 56 (76%) studies but were often suboptimal. CONCLUSION: Diffusion tensor imaging acquisition and processing settings are incompletely described in current literature, vary considerably, and frequently do not meet the highest standards

Serial cranial ultrasonography or early MRI for detecting preterm brain injury?

OBJECTIVE: To investigate detection ability and feasibility of serial cranial ultrasonography (CUS) and early MRI in preterm brain injury. DESIGN: Prospective cohort study. SETTING: Level III neonatal intensive care unit. PATIENTS: 307 infants, born below 29 weeks of gestation. METHODS: Serial CUS and MRI were performed according to standard clinical protocol. In case of instability, MRI was postponed or cancelled. Brain images were assessed by independent experts and compared between modalities. MAIN OUTCOME MEASURES: Presence of preterm brain injury on either CUS or MRI and discrepant imaging findings on CUS and MRI. RESULTS: Serial CUS was performed in all infants; early MRI was often postponed (n=59) or cancelled (n=126). Injury was found in 146 infants (47.6%). Clinical characteristics differed significantly between groups that were subdivided according to timing of MRI. 61 discrepant imaging findings were found. MRI was superior in identifying cerebellar haemorrhage; CUS in detection of acute intraventricular haemorrhage, perforator stroke and cerebral sinovenous thrombosis. CONCLUSIONS: Advanced serial CUS seems highly effective in diagnosing preterm brain injury, but may miss cerebellar abnormalities. Although MRI does identify these lesions, feasibility is limited. Improved safety, better availability and tailored procedures are essential for MRI to increase its value in clinical care