磁共振扩散加权成像鉴别诊断鼻腔、鼻窦实性肿块的适宜b值

目的 探讨MR DWI鉴别诊断鼻腔、鼻窦实性肿块的适宜b值。方法 对61例鼻腔、鼻窦肿块患者术前行常规MR及DWI扫描，选取b值为500、1000 s/mm²，测量病变实性部位ROI的ADC值，将结果与组织病理学结果对照。比较良恶性病变ADC值的差异。分别在两种b值下以鼻腔、鼻窦良恶性肿块的ADC值作为临界点绘制ROC曲线，计算曲线下面积（Az），确定诊断阈值，评价诊断效能并进行比较。结果 b=500 s/mm²时，21例恶性肿块和40例良性肿块的平均ADC值为（1.07±0.32）×10^-3 mm²/s、（1.90±0.62）×10^-3 mm²/s（P<0.001），Az为0.929，以ADC值=1.31×10^-3 mm²/s作为预测鼻腔、鼻窦良恶性病变的诊断阈值，其敏感度为85.7%，特异度为95.0%，准确率为91.8%。b=1000 s/mm²时，21例恶性肿块和40例良性肿块的平均ADC值分别为（0.86±0.25）×10^-3 mm²/s、（1.55±0.41）×10^-3 mm²/s（P<0.001），Az为0.963，以ADC值=1.10×10^-3 mm²/s作为预测鼻腔鼻窦良恶性病变的诊断阈值，其敏感度为85.7%，特异度为97.5%，准确率为93.4%。两组b值的Az间差异无统计学意义（P>0.05）。b=500 s/mm²时的图像信噪比明显高于b=1000 s/mm²的信噪比。结论 b=500 s/mm²时在保证更好图像质量的同时具有较好的诊断效能，更适宜鼻腔、鼻窦肿块的鉴别诊断。

Optimal b value on MR diffusion weighted imaging in differential diagnosis of solid sinonasal tumors

Objective To evaluate the optimal b value on MR DWI for differential diagnosis of solid sinonasal tumors. Methods All of 61 patients with sinonasal masses underwent the preoperative routine MR and DWI scan with two b factors of 500 s/mm² and 1000 s/mm², the ADC values were measured in ROI, which compared with histopathological findings. The statistical analysis were made between benign and malignant masses. The ROCs of two b value were constructed using various cut points of ADC for different b values to confirm the diagnostic threshold value, and the differential diagnostic efficacy were evaluated. Results On b=500 s/mm², the mean ADC value in 21 malignant masses and 40 benign masses was (1.07±0.32)×10^-3 mm²/s, (1.90±0.62)×10^-3 mm²/s (P<0.001). The area under the ROC was 0.929. Using an ADC value of 1.31×10^-3 mm²/s as the threshold value for differentiating malignant lesions, the sensitivity, specificity and accuracy was 85.7%, 95.0% and 91.8%. On b=1000 s/mm², the mean ADC value in 21 malignant masses and 40 benign masses was (0.86±0.25)×10^-3 mm²/s, (1.55±0.41)×10^-3 mm²/s (P<0.001). The area under the ROC was 0.963. Using an ADC value of 1.10×10^-3 mm²/s as the threshold value for differentiating malignant lesions, the sensitivity, specificity and accuracy was 85.7%, 97.5% and 93.4%. There was no statistical difference between area under the ROC of two b values (P>0.05). SNR of b=500 s/mm² was significantly higher than that of b=1000 s/mm². Conclusion The proper b value in differential diagnosis of sinonasal masses is 500 s/mm² for the better image quality and the high diagnostic efficacy.