磁共振弥散加权成像在食管癌调强放疗中的应用及影响

[目的]探讨在食管癌调强放疗(IMRT)中,应用磁共振弥散加权成像技术(DWI)与CT融合图像勾画靶区对靶体积及正常肺组织受照剂量的影响,以及应用DWI对于放疗近期疗效评价的影响.[方法]随机选择40例初治食管癌患者,分别依据单纯CT图像、DWI与CT融合图像以及PET-CT与CT融合图像勾画靶区及危及器官.比较三种影像资料下勾画的GTV、PTV体积的大小差异;以及在PTV的处方剂量达到64Gy/32次时,比较三组调强放疗计划中双肺V5、V20、MLD的差异.同时在放疗前、放疗中(放疗开始后的1个月)及放疗后(放疗结束后1个月)各行1次胸部DWI扫描,比较放疗不同阶段、不同b值下所测肿瘤病灶ADC值的差异.[结果] 92.5％(37/40)的病例在DWI融合组以及PET-CT融合组勾画的GTV比在单纯CT组勾画的GTV体积小,差异具有统计学意义(P＜0.05).而DWI融合组勾画的GTV与PET-CT融合组勾画的GTV体积比较,差异无统计学意义(P＞0.05).在GTV基础上外扩得到的PTV,92.5％的病例在DWI融合组以及PET-CT融合组中比在单纯CT组的体积小,差异具有统计学意义(P＜0.05).将三组计划中的双肺V5、V20、MLD进行比较,92.5％的病例在DWI融合组及PET-CT融合组的双肺V5、Va0、MLD均较单纯CT组小,差异有统计学意义(P＜0.05).不同b值条件下,随着放疗的进行,放疗前、中、后所测得的ADC值逐渐升高,前后比较,差异有统计学意义(P＜0.05).[结论]应用DWI定位及融合技术勾画食管癌靶区提高了靶区勾画的精确性,更有利于正常肺组织的保护,降低正常肺组织的照射剂量.同时DWI对于食管癌患者放疗的近期疗效评价具有可靠价值.

Application of Magnetic Resonance Diffusion Weighted Imaging in Intensity Modulated Radiation Therapy for Esophageal Cancer

[Purpose] To evaluate the application of magnetic resonance diffusion weighted imaging (DWI) and CT image fusion in intensity modulated radiation therapy (IMRT) for esophageal cancer.[Methods] Forty patients with esophageal cancer were randomized to 3 groups:the radiation treatment area and organs at risk were planned according to CT images alone,fusion images of DWI and CT,and the PET-CT images fused with CT,respectively.The differences of planned GTV and PTV were compared among three groups.In addition,V5,V20 and MLD in these three groups were also observed when the doses of PTV were reached to 64Gy/32fx.Chest DWI was performed throughout the process of radiotherapy.The difference of ADC values of tumor lesions at different stages of radiotherapy under different b values was examined.[Results] The GTV volumes in fusion images of DWI and CT,and fusion images of PET-CT and CT group were smaller than these of CT images alone in 92.4％ patients(37/40)(P＜0.05);there was no significant difference in GTV between images of DWI and CT,and fusion images of PET-CT and CT (P＞0.05).The result of PTV was consist with that of GTV.The whole lung V5,V20 and MLD of DWI fusion group and PET-CT fusion group were smaller than those of CT group in 92.5％ of the cases (P＜0.05).B values varied in the whole process of radiation therapy,and ADC values increased after radiotherapy.The difference of ADC values in the beginning and the end of radiation therapy was statistically significant (P＜0.05).[Conclusions] Application of DWI fusion technology in placing position and designing target volume can improve the accuracy of target delineation volume,protect the normal lung tissues,and reduce the dose of normal lung tissues.Moreover,DWI is beneficial in the evaluation of the shortterm curative effect of radiotherapy for esophageal cancer.