Effect of body mass and BMI on proton hepatic MRS water suppression at 3.0T MR / 中国医学影像技术

Objective To explore the effect of body mass and body mass index (BMI) on proton hepatic MRS water suppression at 3.0T. Methods The prospective study of hepatic proton MRS was performed with GE Signa Excite HD 3.0T system and eight-channel torso phased-array coils using PRESS sequence in 44 healthy subjects. Liver spectra were collected with TR of 1500 ms, TE of 30 ms, VOI of 2 cm×2 cm×2 cm and NSA of 64 times. Areas and heights for metabolites resonances were caulculated. Results Group with small mass has lower height ([161.2±8.5] cm vs [167.7±6.2])cm, lower BMI ([20.8±2.3] kg/m~2 vs [25.6±2.6]kg/m~2), better water suppression effect (min-max: 90-96 vs 65-94;median: 94 vs 93), smaller height (min-max: 1.41×10~4-5.76 ×10~5 vs 3.45×10~4-1.75×10~6;median: 9.00×10~4 vs 2.58×10~5) and integrated area (min-max: 4.27×10~4-2.00×10~7 vs 1.24×10~5-5.00×10~7;median: 2.64×10~5 vs 1.19×10~6)of Lip2 than larger weight group. Standardized lipid content (min-max: 0-0.11 vs 0-0.96;median: 0.01 vs 0.04) was less. Group with lower BMI had lower weight ([55.2±8.2]kg vs [71.2±7.8]kg), smaller age ([33.2±11.9]years vs [45.6±9.4]years), better water suppression effect(min-max: 90-96 vs 65-95;median: 94 vs 93) smaller of height (min-max: 1.41×10~4-5.76×10~5 vs 3.45×10~4-1.75×10~6;median: 7.37×10~4 vs 2.11×10~5) and integrated area (min-max: [4.27×10~4-2.00×10~7] vs [1.24×10~5 -5.00×10~7];median: 2.64×10~5 vs 1.19×10~6) of Lip2 than larger weight group. Standardized lipid content (min-max: 0-0.08 vs 0.01-0.96;median: 0.01 vs 0.04) was less. There was significant correlation among water suppression, weight (r=-0.478, P=0.001) and BMI (r=-0.494, P=0.001). Conclusion Lipid accumulation in the liver may be the result of increased fat portion of the body depending on mass and BMI, and hinder to achieve effective water suppression.

Multiple linear stepwise regression of fiver lipid levels: proton MR spectroscopy study in vivo at 3.0 T / 中华放射学杂志

Objective To analyze the correlations between liver lipid level determined by liver 3.0 T 1H-MRS in vivo and influencing factors using multiple linear stepwise regression. Methods The prospective study of liver 1H-MRS was performed with 3.0 T system and eight-channel torso phased-array coils using PRESS sequence. Forty-four volunteers were enrolled in this study. Liver spectra were collected with a TR of 1500 ms ,TE of 30 ms, volume of interest of 2 cm ×2 cm ×2 cm, NSA of 64 times. The acquired raw proton MRS data were processed by using a software program SAGE. For each MRS measurement, using water as the internal reference, the amplitude of the lipid signal was normalized to the sum of the signal from lipid and water to obtain percentage lipid within the liver. The statistical description of height, weight, age and BMI, Line width and water suppression were recorded, and Pearson analysis was applied to test their relationships. Multiple linear stepwise regression was used to set the statistical model for the prediction of Liver lipid content. Results Age (39.1 ± 12. 6) years, body weight (64.4 ± 10. 4) kg,BMI (23.3 ±3.1) kg/m2, linewidth (18.9 ±4.4) and the water suppression (90.7 ±6.5)% had significant correlation with liver lipid content (0.00 to 0.96%, median 0. 02% ), r were 0.11,0. 44,0. 40,0. 52, - 0. 73 respectively(P < 0. 05 ). But only age, BMI, line width, and the water suppression entered into the multiple linear regression equation. Liver lipid content prediction equation was as follows: Y =1.395-(0.021 × water suppression) + (0.022 × BMI) + (0.014 × line width) - ( 0. 064 × age),and the coefficient of determination was 0.613, corrected coefficient of determination was 0.59. Conclusion The regression model fitted well, since the variables of age, BMI, width, and water suppression can explain about 60% of liver lipid content changes.

Reproducibility of normal hepatic proton MRS at 3.0T / 中国医学影像技术

Objective To explore the reproducibility of normal hepatic MRS at 3.0T. Methods The hepatic proton MRS was performed with GE Signa Excite HD 3.0T system and eight-channel torso phased-array coils using PRESS sequence. Thirty-one healthy individuals were enrolled in this study. Liver spectra were collected with TR of 1500 ms, TE of 30 ms, ROI of 2 cm×2 cm×2 cm, NSA of 64 times. The outcomes were statistically analyzed with Wilcoxon signed ranks test and Spearman correlation test.Results There was no significant difference of signal to noise ratio (Z=-0.535,P=0.593), baseline stability (Z=-0.333, P=0.739), linewidth of automatic shimming (Z=-0.305, P=0.761), water suppression (Z=-1.232, P=0.218), height of lipid peak (Z=-0.558,P=0.557), area under the lipid peak (Z=-1.195,P=0.232), height of water peak (Z=-0.647,P=0.518) and area under the warter peak (Z=-0.118, P=0.906) between first examination and second examination. Correlation coefficient of the former and the later measurements of lipid area and water area were 0.784 (P<0.001) and 0.799 (P<0.001), respectively.Conclusion The reproducibility is good for in vivo liver proton MRS at 3.0T.

Reliability and correlation of in vivo heptic shimming of liver and water suppression with 3.0T proton MRS / 中国医学影像技术

Objective To assess the reliability of auto-shimming line width (LW) and water suppression rate (WS), and the correlation between them. Methods GE Signa Excite HD 3.0T system and eight-channel torso phased-array coils with PRESS sequence were performed in 38 volunteers. Liver spectra were collected with TR of 1500 ms, TE of 30 ms, VOI of 2 cm×2 cm×2 cm, NSA of 64 times. Spectroscopy routine auto-shimming pre-scanning program was executed and the values of LW and WS were recorded. Then another spectroscopy routine auto-shimming pre-scanning program was performed repeatedly and 38 groups of data were obtained totally. Intra-class correlation coefficients (ICC), coefficient of variation (CV) and significance test were conduced on 38 groups of LW and WS data. Spearman rank correlation analysis was used to assess the correlation of LW and WS. Results ①The ICC of LW and WS was 0.862 and 0.961 (both P＜0.0001), respectively, while the value of CV was 0.20, 0.18, 0.09 and 0.08, respectively. Significant difference was not observed; ②The value of correlation coefficient was -0.659, -0.485 (both P＜0.0001), respectively. Conclusion ①The reliability is excellent for in vivo liver 3.0T 1H-MRS and WS appears relatively stable; ②Indexes of LW correlate with WS moderately, and it seems the smaller the value of LW is, the easier to achieve higher WS.