Localized 4.7 T Proton Magnetic Resonance Spectroscopy in Neonatal Encephalopathy: Implementation, Safety and Preliminary Interpretation of Results

Summary Magnetic resonance (MR) techniques have revolutionized the assessment of brain development and injury in the newborn. MR studies at 3 T or above are becoming widespread; however, given the high cost and complexity of high‐field MR systems, it is important to assess their benefits and limitations for clinical practice. MR spectroscopy (MRS) studies at high field carry potential benefits such as improved signal‐to‐noise ratio (SNR) and chemical shift dispersion compared with 1.5 T. However, safety is a very important consideration as radiofrequency (RF) tissue heating and acoustic noise also increase with field strength. Furthermore, increased chemical‐shift dependence of the position of the volume of interest (VOI), shorter transverse and longer longitudinal relaxation times constitute additional challenges. We describe the first in‐vivo , proton MRS studies of newborn human brain at 4.7 T. Nine infants with neonatal encephalopathy, all ventilated and with continuous physiological monitoring, were studied. We used L‐FOCI localization, mostly with a VOI centred on the thalami. The absence of 4.7 T results from healthy infants made it impossible to interpret pathological metabolite peak‐area ratios. However, concentration ratios and concentrations should be field‐strength independent and interpretable using control values acquired at lower field. Of eight infants with concentration‐ratio measurements, seven had low [ N ‐acetylaspartate (NAA)]/[choline (Cho)] and three increased [lactate]/[NAA]. Of the two infants with ‘concentration’ measurements both had low [NAA] and one reduced [creatine]. We used an adult coil and consequent RF power restrictions had repercussions for the minimum magnetization recovery time (TR). A smaller, neonatal coil should improve SNR and, with less RF power, relax TR constraints thereby enabling fuller exploitation of the potential of high‐field MRS.