磁共振扩散加权成像应用于食管癌的最佳b值选择及放疗疗效评价

Optimization of b-value in diffusion-weighted imaging for evaluation of radiotherapy efficacy in esophageal cancer

目的:本研究探讨磁共振扩散加权成像(diffusion-weighted imaging,DWI)应用于食管癌的最佳b值选择.并用该b值下的DWI来评价食管癌的放疗疗效.方法:回顾性分析河北肿瘤医院行放射治疗的食管癌患者88例,于放射治疗前1 d及放射治疗结束后1 d分别行磁共振常规扫描(magnetic resonance imaging)和DWI扫描,b值选择为600、800、1000 s/mm2,比较不同b值下DWI图像的信噪比(signal to noise ratio,SNR)、放疗前后的表观扩散系数值(apparent diffusion coefficient,ADC)及病灶长度的变化.结果:放射治疗前b值为600、800和1000 s/mm2时,所测得DWI图像的SNR值分别是11.60±1.50、11.18±1.75、7.15±0.91;所测得ADC值分别为1.66×10-3±0.49×10-3、1.55×10-3±0.41×10-3、1.39×10-3±0.33×10-3 mm2/s;在b值为600、800和1000 s/mm2时,放疗后平均ADC值是2.48×10-3±0.58×10-3、2.16×10-3±0.46×10-3、1.93×10-3±0.35×10-3 mm2/s,放疗后ADC值较放疗前明显升高(P=0.001).选择b值为800 s/mm2时的图像,治疗前后肿瘤病灶长度比较有统计学意义(5.43 cm±1.25 cm vs 2.17 cm±0.95 cm,P=0.001).结论:食管癌放射治疗后ADC值较放射治疗前显著升高;食管癌放射治疗后病灶的长度较放射治疗前显著缩短;b值取800 s/mm2时所得到的DWI图像及ADC图更利于食管癌放射治疗疗效的评价.

AIM：To optimize the b-value in diffusionweighted imaging（DWI） for evaluation of radiotherapy in esophageal carcinoma.METHODS：Eighty-eight patients with esophageal cancer treated by radiotherapy at Hebei Tumor Hospital were included.They received routine magnetic resonance imaging（MRI） and DWI scans one day before and after radiotherapy.Different b values（600,800 and 1000 s/mm2） were used.The differences in signal to noise ratio（SNR） and apparent diffusion coefficient（ADC） values,as well as the tumor length before and after radiotherapy were compared between groups with different b values.RESULTS：Before radiotherapy when the b values were 600,800 and 1000 s/mm^2,the SNRs measured in DWI were 11.60±1.50,11.18±1.75 and 7.15±0.91,respectively;the ADC values were 1.66×10^（-3）±0.49×10^（-3）,1.55×10^（-3）±0.41×10^（-3）and 1.39×10^（-3）±0.33×10^（-3） mm^2/s.After radiotherapy the ADC values were 2.48×10^（-3）±0.58×10^（-3）,2.16×10^（-3）±0.46×10^（-3）and 1.93×10^（-3）±0.35×10^（-）3 mm^2/s,respectively,which were significantly higher than the values before radiotherapy（P = 0.001）.When using the images with the b value of 800 s/mm^2 to measure the tumor length,the length of the lesion was 5.43cm±1.25 cm before radiotherapy and 2.17cm±0.95 cm after radiotherapy,which had a significant difference（P = 0.001）.CONCLUSION：The ADC values after radiotherapy were significantly higher than those before radiotherapy.After radiotherapy,the tumor length was significantly decreased compared with that before radiotherapy.The b value of 800 s/mm^2 is a preferred value for evaluating the efficacy of radiotherapy.