Hyperpolarized 13C MRS cardiac metabolism studies in pigs: comparison between surface and volume radiofrequency coils

Cardiac metabolism assessment with hyperpolarized 13C Magnetic Resonance Spectroscopy in pig models requires the design of dedicated coils capable of providing large field of view with high Signal-to-Noise Ratio (SNR) data. This work presents a comparison between a commercial 13C quadrature birdcage coil and a home-made 13C circular coil both designed for hyperpolarized studies of pig heart with a clinical 3T scanner. In particular, the simulation of the two coils is described by developing an SNR model for coil performance prediction and comparison. While coil resistances were calculated from Ohm’s law, the magnetic field patterns and sample induced resistances were calculated using a numerical Finite-Difference Time-Domain (FDTD) algorithm. After the numerical simulation of both coils, the results are presented as Signal-to-Noise Ratio (SNR)-vs-depth profiles using experimental SNR extracted from the [1-13C]acetate phantom chemical shift image (CSI) and with a comparison of metabolic maps acquired by hyperpolarized [1-13C]pyruvate injected in a pig. The accuracy of the developed SNR models was demonstrated by good agreement between the theoretical and experimental coil SNR-vs-depth profiles.