MR扩散加权成像在肝癌介入治疗后随访中的图像评价

目的：探讨不同扩散敏感梯度因子（b值）MR扩散加权成像（DWI）对肝癌介入治疗后随访中图像质量的影响。方法：对20例肝癌介入治疗后患者分别进行DWI检查和MRI常规扫描（T1WI和T2WI）。每次取2个扩散敏感梯度值即b=0和／或150、350、500和800s／mm^2利用固定参数组合的自旋回波-平面回波（SE—EPI）序列进行DWI检查。在各成像序列上分别计算病灶信号-噪声比（SNR）、病灶-脏信号对比噪声比（CNR）和病灶的ADC值；与肝脏CT和DSA检查结果进行对比分析，定性评价不同b值DWI对肿瘤内部坏死组织和活组织的鉴别诊断能力。结果：病灶在T2WI、DWI150、DWI350、DWI500和DWI800的SNR分别为：（69．81±18．99）、（59．33±32．66）、（59．23±32．94）、（54．25±19．71）、（39．43士11．67），差异有统计学意义（F＝4．43，P＝0．0024）；病灶-肝脏CNR分别为（19．11±11．33）、（17．69±9．20）、（21．38±10．10）、（19．90±13．75）和（13，24±11．02），差异无统计学意义（F=1．70，P＝0．1556）；b＝150、350、500和800s／mm^2时病灶的ADC分别为（2．35±0．80）×10^-3、（1．95±0．59）×10^-3、（1．78±0．44）×10^-3和（1．54±0．37）×10^-3mm^2／s，差异有统计学意义（F=21．96，P=0．0001）。DWI500和DWI800病灶内部坏死和活性肿瘤组织能有效区分。结论：在肝癌介入治疗后随访检查时，选择合适的扩散梯度系数能够得到较佳的信号对比度，同时也能较准确地区分坏死组织与活性肿瘤。

Evaluation of Different b Value of Diffusion-weighted Imaging in the Follow-up of Liver Cancer after Trans-arterial Chemoembolization

Objective：To assess the impact of different b values on the image quality of MR diffusion-weighted imaging （DWI） in the follow-up of liver cancer after trans-arterial ehemoembolization （TACE）. Methods：DWI and routine non- enhanced MRI （T1WI,T2 WI） were performed in 20 patients with liver cancer after TACE at 1.5T MR scanner. DWI were performed with the same SE EPI sequence and different b values [b=0 and b≠0 （b= 150,350,500 and 800s/mm^2 , respectively）]. The signal noise ratio （SNR） of the lesions after TACE and the contrast noise ratio （CNR） between tumor and liver tissue on DWI with different b values and T2 WI were measured. The lesion apparent diffusion coefficient （ADC） values were measured on functional diffusion maps. The capability of differentiating viable and necrosis tissue in tumor were evaluated qualitatively on DWI with different diffusion coefficient and compared with that of DSA and enhanced CT. Results：The SNR of lesions on T2WI,DWI （b value= 150,350,500 and 800） were 69.81±18.99,59.33±32.66,59.23±32.94,4.25± 19.71,39.43± 11.67 respectively, with significant statistical differences （F= 4.43, P = 0. 0024〈 0.05）. The CNR between the lesion and liver were 19.11 ± 11.33,17.69± 9.20,21.38 ± 10. 10, 19. 90± 13.75 and 13.24 ±11.02 respectively on T2 WI,DWI （b value= 150,350,500 and 800, no statistical differences were existed. （F = 1. 70, P = 0. 1556 〉0.05）. The ADC values of lesions were （2.35±0.80）,（1.95±0.59）,（1.78±0.44）,（1.54±0.37） × 10^-3mm^2/s on functional diffusion maps with b= 150,350,500 and 800s/mm^2 , respectively, with statistical differences （ F = 21.96, P = 0. 0001〈 0.05 ）. The viable and necrosis tissue in tumor could be identified more clearly on DWI （b value= 500 and 800） than b value= 150 and 350. Conclusion： In the follow-up of liver cancer after TACE with MR DWI, high image quality with optimal SNR could be achieved by selecting suitable different diffusion coefficient,viable tumor and