A Quantitative Comparison of 31 P Magnetic Resonance Spectroscopy RF Coil Sensitivity and SNR between 7T and 10.5T Human MRI Scanners Using a Loop-Dipole 31 P- 1 H Probe.

In vivo phosphorus-31 ( 31 P) magnetic resonance spectroscopy (MRS) imaging (MRSI) is an important non-invasive imaging tool for studying cerebral energy metabolism, intracellular nicotinamide adenine dinucleotide (NAD) and redox ratio, and mitochondrial function. However, it is challenging to achieve high signal-to-noise ratio (SNR) 31 P MRS/MRSI results owing to low phosphorus metabolites concentration and low phosphorous gyromagnetic ratio (γ). Many works have demonstrated that ultrahigh field (UHF) could significantly improve the 31 P-MRS SNR. However, there is a lack of studies of the 31 P MRSI SNR in the 10.5 Tesla (T) human scanner. In this study, we designed and constructed a novel 31 P- 1 H dual-frequency loop-dipole probe that can operate at both 7T and 10.5T for a quantitative comparison of 31 P MRSI SNR between the two magnetic fields, taking into account the RF coil B 1 fields (RF coil receive and transmit fields) and relaxation times. We found that the SNR of the 31 P MRS signal is 1.5 times higher at 10.5T as compared to 7T, and the power dependence of SNR on magnetic field strength (B 0 ) is 1.9.