DWI诊断外伤性椎体压缩骨折优化b值的初步研究

目的 应用1.5T磁共振采用不同b值对骨折椎体行扩散加权成像（DWI）检查,通过数据分析优选最佳b值。方法 根据外伤时间,按T〈7天、14天≤T〈30天将患者分为二组,每组20例,共40例。所有入组病例均行DWI检查,采用单次激发自旋回波平面成像序列,b值分别取200、300、400、500、600、700、800、900、1 000s/mm^2,测量骨折椎体表观扩散系数（ADC）值并对比不同b值下椎体扩散加权成像（DWI）图像质量,应用ROC曲线分析不同b值下ADC值对不同时间段椎体压缩骨折的诊断价值。结果 40例受检者骨折椎体DWI图像,随着b值由200s/mm^2升高至1 000s/mm^2,图像信噪比逐渐降低,b值为300s/mm^2时图像对比噪声比最高;b值为200、300、400、500、600、700、800、900、1000s/mm^2时不同时间段压缩骨折ADC值的差异均有统计学意义（P〈0.01）;b值为300s/mm^2时诊断新近压缩骨折（T〈7天）价值最大,其诊断敏感度、特异度分别为86.76%、81.87%。结论 b值为300s/mm^2时,椎体DWI图像质量佳,所获得的ADC值诊断效能相对较高。

The preliminary study of the suitable B value in diffusion weighted imaging in diagnosis of vertebral compression fractures

Objective To determine reasonable b values in diffusion weighed imaging of vertebra with 1.5 T MR. Methods According to injury time, 40 patients were divided into two groups, one group was less than seven days after the injury, another group was 14 to 30 days after the injury, with 20 cases in each group. All the patients received DWI of vertebra using a single shot EPI SE pulse sequence with different b values （200, 300, 400, 500, 600, 700, 800, 900, 1 000 s/mm^2）. ADC values of vertebra were measured. The image quality of each group of DWI were analyzed and compared. The diagnostic value of ADC values at different b values was analysed to discriminate the time periods of vertebral compression fractures. Results As b values increasing from 200 s/mm^2 to 1 000 s/mm^2 , SNR of vertebra decreased gradual ly, the CNR in b value 300 s/mm^2 was maximum, then decreased gradually. ROC curve was used to discriminate different time periods of vertebral compression fractures in different h value, h value of 300 s/mm^2 had maximum value when the diagnostic sensitivity specificity values were 86.76%, 81.87%. Conclusion The optimal b value is 300 s/mm^2.