85 Initial Experiences of Magnetic Resonance Imaging and Spectroscopy of the Newborn Brain At 4.7 Tesla

Abstract

Background. The potential benefits of high-field magnetic resonance (MR) include increased signal, contrast, and spectral/spatial resolution, however there are specific safety and cost implications. Aims. (i) to explore the feasibility of MR imaging (MRI) and proton (1H) MR spectroscopy (MRS) at 4.7T of the newborn brain; (ii) to assess specific advantages and disadvantages of 4.7T versus low-field MR. Methods. Informed parental consent and ethical approval were obtained. Nine ventilated infants were studied at a median corrected gestational age 41+4 weeks using a whole-body 4.7T MR system with continuous monitoring (skin temperature, pulse oximetry, ECG). Acoustic noise was attenuated with incubator-lining, ear-plugs and mini-muffs. MRI included: T1- and T2-weighted single and multi-echo spin-echo, and 3D gradient-echo. Quantitative T1 and T2 maps were calculated where possible. A modified PRESS sequence was used for 1H-MRS localised to an 8mm3 thalamic voxel (echo times 144 and 288ms). Sequences were programmed to keep RF heating at less than half the recommended adult maximum levels. Results. Physiological indices were stable and no adverse events occurred. As expected, brain water T1 was higher and T2 lower at 4.7T versus lower fields. The T1-weighted images displayed poor contrast, however high spatial resolution T2-weighted imaging with a 4.7T-optimised fast spin-echo technique delivered remarkable contrast and structure differentiation (figure). 1H-MRS detected brain metabolites including lactate. Conclusions. Safety considerations at high-field limit sequence flexibility and rapidity of data acquisition. Nevertheless our initial experience demonstrates the feasibility of scanning sick newborn infants at 4.7T: The quality of T2-weighted images was significantly improved, whilst T1-weighted images and 1H-MRS were not superior at high vs low-field. Further research on the application of high-field MR to the developing brain is imperative as exploitation of specific features and use of dedicated coils may improve the diagnostic and prognostic accuracy of MR techniques.