匀场效果对3.0T质子磁共振波谱水抑制及代谢物定量的影响

Effect of shimming on water suppression and metabolites concentrations of 3.0T proton spectrum

目的探讨匀场线宽对谱线信噪比(SNR)、NAA/Cr、Cho/Cr及抑水效果的影响。方法使用GESignaExciteHD3.0T超导磁共振扫描仪,采用8通道头颈联合相控阵线圈,单体素PRESS序列1H-MRS采集,共得到49条谱线。检查参数为TR1500ms,TE30ms,NSA128。记录自动匀场半高全宽(FWHM)和抑水率,把受检者按是否抑水分为匀场较好组(FWHM<10Hz)和匀场较差组(FWHM≥10Hz)。采用两独立样本t检验比较两组的Cr_SNR、NAA/Cr、Cho/Cr、抑水率和感兴趣容积(VOI)。结果匀场较好组较匀场较差组的平均Cr_SNR好(t=5.976,P<0.001),NAA/Cr比值(t=2.469,P=0.017)更大,Cho/Cr(t=-4.460,P<0.001)更小,VOI(t=3.862,P<0.001)更大,水抑制更有效(t=3.704,P=0.001)。结论头部单体素3.0T1H-MRS采集时,较小VOI更易匀场,匀场好的谱线信噪比及主要代谢物相对比值较高,且水抑制效果好。

Objective To observe the effect of full width half max （FWHM） on spectra signal-to-noise ratio （SNR）, NAA/Cr, Cho/Cr and water suppression at 3.0T MR. Methods GE Signa Excite HD 3.0T MR scanner with 8 channel phrased-array head and neck coil was used. The respective study of liver 1 H-MRS was performed using PRESS sequence. A total of 49 spectrums were obtained with parameters of TR 1500 ms, TE 30 ms, NSA 128. FWHM and water suppression were recorded automatically and the subjects were divided into better shimming group （FWHM〈10 Hz） and worse shimming group （FWHM≥10 Hz）. Independent t test was used to analyze the Cr_SNR, NAA/Cr, Cho/Cr, water suppression and volume of interest （VOI）. Results Compared with worse shimming group, better shimming group could provide better Cr_SNR （t=5. 976, P〈0. 001）, higher NAA/Cr （t=2. 469, P=0. 017）, lower Cho/Cr （t=-4. 460, P〈0. 001） and smaller VOI （t=3. 862, P〈0. 001）. Conclusion When single voxel proton spectroscopy of head is adopted with 3.0T MR, small VOI is easy to achieve effective shimming, and better shimming is helpful to improve SNR, the ratio of main metabolites as well as water suppression.