Can we use 1H MRS shimming values to obtain 31P spectra?

The perfect shimming of ³¹P magnetic resonance spectroscopy (MRS) is not easy in vivo. The purpose of this study was to examine the feasibility of using ¹H MRS shimming values to obtain ³¹P spectra in a same sequence. Both phantom and volunteer studies were carried out in this study. Phantom was a sphere filled with physiological metabolites of brain. In vivo study was performed on 4 healthy volunteers. The studies were performed on a 3-T GE scanner. A same localizer and a same cursor were used for both ¹ H and ³¹P scans. A spin echo MRS sequence was utilized for both ¹H scans with a standard head coil and ³¹P scans with a GE service coil. ¹H scan was performed using first and automatic shimming and water linewidth (FWHM) of 3 Hz for phantom and 5 Hz for the volunteer were obtained. Shimming values of ¹H scan in x, y, z directions were copied to ³¹P scan. A routine procedure of ³¹P scan without value coping was also performed. Spectra were analyzed using SAGE/IDL program. Signal to noise ratio (SNR) was defined as the ratio of the signal height / maximum noise height. Good ¹H spectra and ³¹P spectra were obtained for both phantom and volunteer studies. The ³¹P spectra with ¹H MRS shimming values were similar with the ³¹P spectra obtained with routine procedure. Lower SNRs of ³¹P spectra were obtained in phantom with ¹H MRS shimming values, compared with routine procedure scan. Average SNR for Pi of ³¹P spectra was 7.45:1 in the volunteer study with routine procedure, and 7.275:1 with ¹ H MRS shimming values. ¹H MRS shimming values can be used to obtain useful ³¹P spectra in a same sequence