磁共振波谱在老年人前列腺癌和前列腺炎诊断中的应用

The diagnostic value of magnetic resonance spectroscopic imaging in prostate cancer and prostatitis in elderly patients

目的探讨应用磁共振波谱所提供的代谢物质的比值鉴别前列腺癌和前列腺炎的可行性及方法。方法对前列腺外周带经组织病理证实的42个前列腺癌及30个前列腺炎体素的磁共振波谱数据进行回顾性分析。评估每个体素内（胆碱＋肌酐）／枸橼酸盐（CC／C）的比值及体素内胆碱和枸橼酸盐水平的改变。癌体素定义为CC／C大于0．86。t检验用于评估CC／C比值在前列腺癌与前列腺炎鉴别诊断中的价值。结果前列腺癌体素CC／C比值为（1．28±0．41），与前列腺炎体素CC／C比值（1．03±0．40）比较，差异有统计学意义（t=6．45，P〈0．05），主要是由于癌体素内胆碱水平升高。当CC／C≥0．86作为标准时，前列腺癌诊断的敏感性、特异性、准确性分别65．5％、71．4％和66．7％。阳性预测值和阴性预测值分别为90．5％和33．3％。在66．7％前列腺炎体素（30个体素中20个）中，MR波谱数据显示较高的CC／C比值（大于0．86），主要是取决于升高的胆碱水平。当应用枸橼酸盐／正常枸橼酸盐≥0．75作为辅助指标评估前列腺炎时，误诊为前列腺癌的比率降低至26．6％（30个体素中8个体素）。结论代谢物CC／C比值能够鉴别前列腺肿瘤及前列腺炎。当应用枸橼酸盐不降低或轻度降低枸橼酸盐／正常枸橼酸盐≥0．75作为辅助指标评估前列腺炎时，前列腺癌的误诊率降低。

Objective To investigate the feasibility of differentiation between prostate cancer and prostatitis by using metabolic ratios provided by 3D 1H Magnetic Resonance Spectroscopic Imaging （MRSI）. Methods Metabolic changes were evaluated in 42 voxels with prostate cancer and 30 voxels with prostatitis in the peripheral zone using MRSI. The results were based on the pathologic findings by biopsy. The （choline＋ creatine）/Citrate （CC/C） ratio and the changes of choline and citrate levels were evaluated in each voxel with cancer or prostatitis, t test was used to determine the power of the CC/C ratio in differentiation between prostate cancer and prostatitis. Results The CC/C ratio for cancer voxels （1.28 ± 0.41 ） was significantly different from the ratio in the voxles with prostatitis （1.03± 0.40）, t = 6.45, P〈0.05, due to greatly increased choline level in the cancer voxels. When CC/C ratio of 0.8 was taken as the criteria for the diagnois of prostate cancer, the sensitivity, specificity and accuracy were 65.5%, 71.4% and 66.7%, respectively. Positive predictive value （PPV） and negative predictive value （NPV） were 90.5% and 33.3%, respectively. The CC/C ratio was higher than 0.86 in 66.7% voxels with prostatitis （20 voxels of total 30 voxels）, which mostly depended on the level of choline. When citrate level was used as an auxiliary index to evaluate prostatitis （Cit/norm. Cit ≥0. 75）, the misdiagnosis rate of prostate cancer was reduced to 26.6%（8 voxels of total 30 voxels）. Conclusions The metabolic ratio of CC/C can be used to differentiate prostate cancer from prostatitis. The misdiagnosis rate is reduced when citrate is not or slightly decreased relative to normal citrate level （Cit/norm, Cit ≥ 0.75）.