肝外胆管癌磁共振扩散加权成像中b值的选择

目的 评价不同b值磁共振扩散加权成像(DWI)对肝外胆管癌的显示能力,确定肝外胆管癌DWI的较佳b值;并探讨表观扩散系数(ADC)值与肝外胆管癌分化程度的关系.方法 对25例肝外胆管癌患者术前行DWI (b=100、300、500、800、1000 s/mm2) 和常规MRI.测量肿瘤的ADC值,计算多b值扩散成像和T2WI图像中的信噪比(SNR)、对比噪声比(CNR)及信号强度比(SIR)等数据;对经手术病理证实的患者进行病理分级,比较不同b值时不同分化程度肿瘤的ADC值,并进行统计学分析.结果 23例肝外胆管癌由DWI检出,DWI诊断肝外胆管癌的敏感度为92.00%.随着b值的升高,肿瘤的SNR和肿瘤与正常肝脏的CNR逐渐下降,而肿瘤的SIR逐渐升高.b值为800 s/mm2时DWI图像肿瘤与正常肝脏的CNR、肿瘤的SIR和SNR均高于T2WI图像,差异有统计学意义(P<0.05).随着b值的增高,肿瘤ADC值逐渐变小.结论 b=800 s/mm2是肝外胆管癌扩散加权成像的较佳b值,可以得到良好显示的肝外胆管癌DWI图像;病灶ADC值随着癌组织分化程度的降低而减小.

Determination of b value in diffusion weighted imaging of extrahepatic cholangiocarcinoma

Objective To evaluate the ability of diffusion weighted imaging (DWI) in demonstrating extrahepatic cholangiocarcinoma (EHCC) with different b values, and to investigate the relationship between the apparent diffusion coefficient (ADC) values and cell differentiation degree of EHCC. Methods Twenty-five patients with EHCC underwent DWI (b=100, 300, 500, 800 and 1000 s/mm²,respectinely) and routine MRI before operation. ADC value, signal-noise ratio (SNR), signal intensity ratio (SIR) of tumors, and contrast-noise ratio (CNR) of tumors and normal liver were calculated and compared. ADC values of differen tumors were compared among different b values. Results Twenty-three of 25 extrahepatic cholangiocarcinomas were detected with DWI. The sensitivity of DWI in diagnosing extrahepatic cholangiocarcinomas was 92.00%. SNR of tumors, CNR of tumors and normal liver in DWI decreased with the increase of b values (P<0.05). SIR of tumors in DWI increased with the increase of b values (P<0.05). CNR of tumors and normal liver, SIR and SNR of tumors in DWI (b=800 s/mm²) were higher than those in T2WI (P<0.05). ADC values of tumors decreased with the increase of b values. Conclusion The optimal b value is 800 s/mm² for DWI of EHCC, and the lesions can be displayed better. ADC values of tumors decrease with the decrease of cell differentiation degree of EHCC.