弥散加权成像b值及表观扩散系数预测膀胱癌侵袭性

Diffusion-weighted imaging b value and apparent diffusion coefficient for predicting invasiveness of bladder cancer

目的探讨磁共振弥散加权成像(DWI)b值和表观扩散系数(ADC)评估膀胱癌侵袭性的价值。方法回顾性分析经病理证实的58例膀胱癌患者(64个病灶),均接受常规MRI和DWI,梯度扩散因子b值分别取0、600、1000和1500 s/mm^2,根据膀胱癌病理表型将其分为低、中、高侵袭性。测量不同b值下的肿瘤ADC值,分析膀胱癌侵袭性与ADC值的相关性;通过ROC曲线评价ADC值在膀胱癌侵袭性上的诊断效能。结果高侵袭性组膀胱癌平均直径(3.37±1.58)cm,显著大于低侵袭性组[(2.18±0.51)cm]和中侵袭性组[(2.32±0.53)cm,P均<0.01];ADC值与膀胱癌侵袭性呈负相关(r=-0.673,P<0.05);b值取1500 s/mm 2时可清晰显示病灶,图像对比度较高;ADC值对于直径<2.5 cm肿瘤的诊断特异度及准确度更好;ROC曲线显示ADC值0.93×10^-3mm^2/s是判断膀胱癌侵袭性的最佳阈值。结论DWI及ADC可用于预测膀胱癌侵袭性,尤其是小直径膀胱癌,并为后期治疗提供临床指导。

Objective To explore the value of diffusion-weighted imaging b value and apparent diffusion coefficient(ADC)in assessment of invasiveness of bladder cancer.Methods Totally 58 bladder cancer patients with 64 lesions confirmed by pathology were retrospectively analyzed.All patients underwent conventional MRI and DWI.The b values were set as 0,600,1000 and 1500 s/mm^2,respectively.The invasiveness of bladder cancer was classified as low-,intermediate-or high-invasiveness according to its pathological phenotype.ADC of bladder cancers with different b value were measured,and the correlation between ADC and invasiveness of bladder cancer was analyzed.The diagnostic efficacy of ADC values for invasive bladder cancer was analyzed by using ROC curve.Results The mean diameter of bladder cancer in high-invasive group([3.37±1.58]cm)was significantly higher than that in low-invasive group([2.18±0.51]cm)and intermediate-invasive group([2.32±0.53]cm,both P<0.01).The invasiveness of bladder cancer was negatively correlated with ADC value(r=-0.673,P<0.05).When b value was set as 1500 s/mm 2,DWI could clearly show the lesion,and image contrast was relative higher.The diagnostic specificity and accuracy of tumor ADC value was better in<2.5 cm tumors.ROC curve showed that ADC value 0.93×10^-3 mm^2/s was optimal cut-off for diagnosis of invasiveness of bladder cancer.Conclusion DWI and ADC can be used to predict the invasiveness of bladder cancer,especially of small-diameter bladder cancer,therefore providing guidance for follow-up treatment.