Contrast optimization of Macaca mulatta basal ganglia in magnetic resonance images at 4.7 Tesla

Abstract

To determine whether high field MRI could distinguish among the different regions of the basal ganglia, the brains of two Macaca mulatta monkeys were explored in vivo using a 4.7 T MR imager. Gradient-echo (GE) and spin-echo images were acquired with proton-density, T 1 and T 2(*) weightings. Five GE images with increased susceptibility effects were generated using a GESFID sequence, from which T 2* maps were also reconstructed. The first echo of the GESFID sequence (TE=12.6 ms) produced the best contrast-to-noise ratio (C/N) between the pallidum and the putamen, the pallidum and the thalamus, the substantia nigra and the surrounding white matter, and the substantia nigra and the subthalamic nucleus. An increased T 2 *-weighting (TE=37.2 ms) was necessary to maximize C/N between the putamen and the surrounding white matter, and between the subthalamic nucleus and the surrounding white matter. A dual GE sequence with a short TE (≈10 ms) and a longer one (≈30 ms) thus effectively localizes basal ganglia subregions at 4.7 T.