胃肿瘤MR扩散加权成像中扩散敏感因子选择的初步研究

目的：初步探讨胃肿瘤MR弥散加权成像（DWI）中合适的扩散敏感因子（b值）的选择。方法：回顾分析32例经手术证实的胃肿瘤性病变患者的MRI原始资料，包括常规MRI及不同b值的DWI（b值为400s/mm2，600s/mm2，800s/mm2，1000s/mm2）。运用GE ADW 4.2工作站，应用Functool2.0软件分析记录不同b值的ADC值及水背景信号强度比（SIR水-背景噪声）。然后把手术标本制成切片，运用图像分析软件计算单位面积内细胞密度。最后运用统计学软件计算分析细胞密度和不同b值时获得胃肿瘤ADC值之间相关性。综合细胞密度与ADC值相关性和SIR水-背景噪声，确定合适的b值。结果：b值为400s/mm2，600s/mm2，800s/mm2，1000s/mm2时，细胞密度和ADC值之间相关性r分别为：-0.3458、-0.3789、-0.5865、-0.5231；P值均小于0.05。水背景信号强度比（SIR水-背景噪声）分别为：2.036、1.541、1.148、1.109（F=40.12，P<0.05）。b值为400s/mm2，600s/mm2，800s/mm2时， SIR水-背景噪声之间有统计学意义（P<0.05），随着b值的增加越接近1；b值为800s/mm2，1000s/mm2时，SIR水-背景噪声接近1，两者之间无统计学意义（P>0.05）。结论：在胃肿瘤MR弥散加权成像中，b值为800s/mm2时ADC值与细胞密度间相关性最高，并且胃内自由水背景噪声比接近1，可近似认为消除了T2透射效应，最能反映水分子的扩散情况，可作为较合适的成像b值。

The optimal b value in DWI of stomach neoplasm: a preliminary study

Objective： To choose the optimal b value in diffusion weighted imaging of stomach neoplasm. Material and Method： Thirty-two cases were proved to be stomach neoplasms by operation and pathology. Four DWI sequences were performed with different b values, including 400s/mm2, 600s/ram2, 800s/mm2, 1000s/mm2. The ADC value of different stomach neoplasm and free water in gastric lumen were measured. SIR of DWI with different b value was evaluated and compared. Then using image analysis software, the density of cells in pathologic specimens were calculated. Finally, use of statistical analysis software, correlation between the density of cell and ADC of stomach tumor under different b value was calculated. According to correlation of the above-mentioned calculations and SIR （ratio water-background noise）, optimal b value was deternfined. Result： When b value was 400s/mm2, 600s/mm2, 800s/mm2, 1000s/mm2, correlation between the density of （：ell and ADC of stomach tumor under different b value was： -0.3458, -0.3789, -0.5865, -0.5231 respectively. There was significant difference between different b value （P〈0.05）. The SIR of different b value was： 2.036, 1.541, 1.148, 1.109 respectively （F= 40.12, P〈0.05）. When b value was 400s/mm2, 600s/mm2, 800s/mm2, there were significant difference between them （P〈0.05）. When b value was 800s/mm2, 1000s/mm2, SIR approximate 1, there were significant difference between them （P〈0.05）. Conclusion： Diffusion weighted imaging for diagnosing gastric tumor is feasible, the best optimal b value is 800s/mm2. as b value as 800s/mm2, correlation between the density of cell and ADC of stomach tumor was the best, and SIR approximate 1. We can approximately think T2 influence was eliminated, and it can reflect the real situation of water molecules diffusion.