MRI evaluation and safety in the developing brain

Abstract

Magnetic resonance imaging (MRI) evaluation of the developing brain has dramatically increased over the last decade. Faster acquisitions and the development of advanced MRI sequences, such as magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), perfusion imaging, functional MR imaging (fMRI), and susceptibility-weighted imaging (SWI), as well as the use of higher magnetic field strengths has made MRI an invaluable tool for detailed evaluation of the developing brain. This article will provide an overview of the use and challenges associated with 1.5-T and 3-T static magnetic fields for evaluation of the developing brain. This review will also summarize the advantages, clinical challenges, and safety concerns specifically related to MRI in the fetus and newborn, including the implications of increased magnetic field strength, logistics related to transporting and monitoring of neonates during scanning, and sedation considerations, and a discussion of current technologies such as MRI conditional neonatal incubators and dedicated small-foot print neonatal intensive care unit (NICU) scanners.

Introduction

The use of magnetic resonance imaging (MRI) in evaluation of the developing brain is well established. MRI has proven itself as a beneficial modality in the evaluation of fetal and neonatal neurological conditions due to its unsurpassed sensitivity and excellent tissue contrast.1, 2, 3, 4, 5, 6 Fetal MRI, which was first introduced in the 1980s, was not widely accepted until nearly a decade later due to long imaging times and limited availability. Even with long imaging times, MRI demonstrated improved anatomic detail, better sensitivity for white matter lesions, and consistently detected abnormalities that were not identified on prenatal ultrasound, such as cortical malformations, heterotopias, and posterior fossa abnormalities6, 7, 8, 9, 10, 11 (Fig. 1). MRI has become an important adjunct to transcranial ultrasound in the evaluation of neonates, especially in preterm and very low-birth-weight infants. The development of faster imaging acquisitions has made imaging of the moving fetus and neonate more feasible.12, 13, 14, 15, 16 MRI conditional neonatal incubators, specially designed neonatal head coils and dedicated neonatal intensive care (NICU) MRI magnets, have increased the accessibility and feasibility of MRI in the neonatal population.16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 Advanced imaging techniques, such as magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), perfusion imaging, functional magnetic resonance imaging (fMRI), and susceptibility-weighted imaging (SWI), combined with higher clinically applicable static magnetic field strengths have provided new insights into brain development and increased sensitivity for a wider variety of pathology in the developing brain.16, 24, 27, 28, 29, 30