Three Dimensional Spectroscopic Imaging in the Prostate with a Surface Combined Endorectal Coil at 7 Tesla

INTRODUCTION: The benefits of performing prostate spectroscopy at 7T include increased spectral and spatial resolution. The potential exists to be able to better quantify individual metabolites, localize smaller volumes of disease and better monitor disease progression or treatment response. However, spectroscopy in the body at 7T faces many challenges including the well described destructive interferences reducing both RF homogeneity and efficiency, increased susceptibility and chemical shift artifacts and an increased concern over local rather than global specific absorption rates (SAR) which would be responsible for local heating. Prostate spectroscopy at 7T has currently been demonstrated through the use of a single-loop transceiver endorectal coil (1). The advantage of such coils are the promise of high SNR on receive and high transmit B1 (B1+), at least close to the prostate, and improved prostate stability and B0 homogeneity as a balloon in the coil is typical inflated with susceptibility matching fluid. Other studies have demonstrated that SAR constraints combined with low achievable B1+ in the prostate limit the applicability of an 8 channel transceiver surface array coil for spectroscopy in the prostate (2). While local SAR is still a limiting factor, we demonstrate that full 3D spectroscopic imaging can be achieved with a surface transmit coil at 7T. To realize the full potential of 7T with respect to SNR, this surface array is combined with a receive-only ERC on reception.