肝脏磁共振扩散成像技术实验研究

目的　探讨肝脏最佳磁共振扩散加权成像(DWI)技术。材料与方法　新西兰大白兔15只,用3%戊巴比妥钠麻醉后,在其他参数不变条件下分别用不同扫描线圈与FOV行常规MRI扫描;用SE EPI序列不同b值、TR值以及层厚2mm与5mm分别行DWI扫描,以ADC值、质量指数、信噪比为指标进行统计分析。结果　(1)随着b值的增大,肝脏平均ADC值与质量指数均变小(P <0 .0 1) ,但b =10、5 0、10 0三者图像的质量指数差别较小(P >0 .0 5 ) ,b =80 0质量指数与信噪比均较差。(2 )TR值逐渐增大时,图像的质量指数与信噪比以及肝脏ADC值变化均很小(P >0 .0 5 )。(3)层厚为2mm时,图像的质量指数较层厚为5mm高,信噪比则较后者低(P <0 .0 1)。(4)膝关节线圈扫描较头部线圈图像的信噪比有明显增大,而图像的质量指数反而有所减小(P <0 .0 1)。(5 )随着FOV的增大,信噪比增大,但质量指数先增加后下降(P <0 .0 1)。结论　在高场强磁共振中,头部线圈、b值10 0、层厚2mm、适中的FOV与TR值以及深度麻醉、较大NEX等能获得较高质量的DWI图像。

Experimental Study on Liver MR Diffusion-weighted Imaging

Objective To study the optimal technology of MR diffusion-weighted imaging on the normal rabbit's liver. Materials and Methods After 15 New Zealand white rabbits were anaesthetized, diffusion-weighted imaging (DWI) was performed respectively with SE EPI using different b values, repetition times (TR) or thickness (2mm and 5mm) under the condition of different field of views (FOV) and different coils at 1.5T MR (GE Signa Twinspeed, USA) when other parameter were same. Apparent diffusion coefficient (ADC), quality index or signal-noise ratio (SNR) were analyzed by SPSS10.0.Results (1)With b value increased, the ADC, quality index and SNR decreased at the same time (P<0.01), but the distinction of quality index among DWI with b=10, b=50 or b=100 was insignificant (P>0.05), quality index and SNR were not satisfied. (2)The ADC, quality index and SNR hadn't significant distinction among DWI with TR increased. (P>0.05). (3)The quality index of DWI with 2mm-thickness was better than that of 5mm-thickness (P<0.01), but SNR of DWI with 2mm-thickness was decreased. (4)The SNR of MRI with knee coil was obviously better than that with brain coil, but the quality index decreased on the contrary (P<0.01). (5)When FOV and SNR increased, the quality index firstly increased, then decreased (P<0.01). Conclusion Appropriate b value (b=100), thickness (2mm), brain coils, FOV, TR, deep anaesthetized and big NEX are very important in DWI scanning to get high quality imaging on high field MR.