磁共振在前列腺特异性抗原低于20μg／L患者中诊断前列腺癌的影像分级研究

The clinical value of magnetic resonance imaging grading for prostate cancer diagnosis in patients with prostate-specific antigen levels less than 20 μg/L

目的 探讨T2加权像（T2WI）和弥散加权像（DWI）的影像分级在前列腺特异性抗原（PSA）＜20 μg/L的患者中对前列腺癌诊断的意义. 方法 2011年12月至2013年1月PSA＜20μg/L、在我院行前列腺穿刺活检的133例患者.将核磁共振（MRI）上前列腺外周带分为6个分区,评估T2WI和DWI上外周带每个区域的影像级别,以前列腺活检病理结果作为对照,比较两种扫描方式中的分级系统单独或联合应用对于前列腺癌的诊断意义. 结果 60例（45.1％）诊断为前列腺癌.T2WI影像分级中0～5级对应的前列腺癌诊断率分别为2.8％、13.5％、20.4％、34.6％、52.6％和88.9％；T2WI＋DWI中1～5级对应的前列腺癌诊断率分别为11.1％、16.1％、48.5％、71.0％和86.1％.随着预先制定的T2WI和T2WI＋ DWI影像分级的递增,前列腺活检阳性率增加（Z=-9.8552、-13.4148,均P＜0.0001）.受试者工作特征曲线分析发现T2WI联合DWI对前列腺癌的诊断能力优于T2WI独立诊断（AUC=0.743与0.715,P=0.0072）. 结论 T2WI影像分级标准可以预测PSA＜20 μg/L的患者前列腺癌的风险；DWI可以进一步增强对于前列腺癌预测的能力.

Objective To explore the clinical value of image gradings of T2 weighted imaging （T2WI） and diffusion weighted imaging （DWI） for prostate cancer diagnosis in patients with prostate specific antigen （PSA） less than 20 μg/L.Methods A total of 133 patients with PSA〈20 μg/L who received prostate biopsies in our hospital from December 2011 to January 2013 were recruited.The prostate was divided into six regions in MRI images.T2WI and DWI image gradings on each region in peripheral zone were evaluated with reference to histopathological evaluation of prostate biopsies.The significance of grading system for the diagnosis of prostate cancer in the two scanning methods alone or in combination were compared.Results 60 patients were diagnosed as prostate cancer.The positive biopsy rates were 2.8%,13.5%,20.4%,34.6%,52.6% and 88.9%,respectively in grade 0-5 based on T2WI imaging grading.The positive biopsy rates were 11.1%,16.1%,48.5%,71.0% and 86.1%,respectively in grade 1-5 based on T2WI＋ DWI imaging grading.The positive biopsy rate was significantly increased with the increments of pre-established T2WI and T2WI＋DWI image gradings （Z=-9.8552,-13.4148,both P〈0.0001）.Receiver operating characteristic analysis showed that the diagnostic capability was better in T2WI combined with DWI than in T2W1 alone in prostate cancer detection （AUC：0.743 vs.0.715,P=0.0072）.Conclusions T2WI image grading can predict the risk of prostate cancer in patients with PSA〈20 μg/L,and DWI can enhance the ability to predict prostate cancer.