Abstract
This study aims to investigate the quality difference of short echo time (TE) breathhold 1H magnetic resonance spectroscopy (MRS) of the liver at 3.0T using the body and phased array coils, respectively. In total, 20 pairs of single-voxel proton spectra of the liver were acquired at 3.0T using the phased array and body coils as receivers. Consecutive stacks of breathhold spectra were acquired using the point resolved spectroscopy (PRESS) technique at a short TE of 30 ms and a repetition time (TR) of 1500 ms. The first spectroscopy sequence was “copied” for the second acquisition to ensure identical voxel positioning. The MRS prescan adjustments of shimming and water suppression, signal-to noise ratio (SNR), and major liver quantitative information were compared between paired spectra. Theoretical calculation of the SNR and homogeneity of the region of interest (ROI, 2 cm×2 cm×2 cm) using different coils loaded with 3D liver electromagnetic model of real human body was implemented in the theoretical analysis. The theoretical analysis showed that, inside the ROI, the SNR of the phase array coil was 2.8387 times larger than that of body coil and the homogeneity of the phase array coil and body coil was 80.10% and 93.86%, respectively. The experimental results showed excellent correlations between the paired data (all r > 0.86). Compared with the body coil group, the phased array group had slightly worse shimming effect and better SNR (all P values < .01). The discrepancy of the line width because of the different coils was approximately 0.8 Hz (0.00625 ppm). No significant differences of the major liver quantitative information of Cho/Lip2 height, Cho/Lip2 area, and lipid content were observed (all P values >0.05). The theoretical analysis and clinical experiment showed that the phased array coil was superior to the body coil with respect to 3.0T breathhold hepatic proton MRS.
Highlights
Hepatic magnetic resonance spectroscopy (MRS) is an evolving technique with potential capability for improving the diagnostic accuracy of tissue characterization
RF coil serves as the immediate interface between the complex chain of MRS hardware and the patient; its performance characteristics are crucial in determination of image quality as measured by the signal-to noise ratio (SNR) related to the receiver coil and the radio frequency field homogeneity related to the transition coil
This study aims to answer the following questions: 1) Are there any significant differences among shimming, water suppression, and SNR using different RF coils?; 2) Are there any significant differences on the major liver metabolite concentrations of choline peak (Cho)/Lip2 height, Cho/Lip2 area, and lipid content using different RF coils?; and 3) Which kind of coil is more suitable for 3.0T hepatic proton MRS?
Summary
Hepatic MRS is an evolving technique with potential capability for improving the diagnostic accuracy of tissue characterization. The acquisition of high-quality hepatic proton spectra is technically demanding. No consensus on the concepts or detailed criteria of quality assessment for MR spectra has been reached among experts [3,4,5,6]. The diagnostic value is directly related to the quality of abdominal MRS, which relies on adequate technical factors, such as prescan adjustments of shimming and effective water suppression [3,5]. Strong resonance signals in prescan from the hydrogens in water molecules may interfere with the signals from the lower concentration compounds of interest. The water signal may be suppressed to better discern the resonance signals of the compounds of interest [7,8,9]
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