基于DWI及^(18)F-FDG PET-CT勾画胸段食管癌大体肿瘤体积变化与比较

Comparison of spatial location and dynamic changes of functional parameters of primary tumors of thoracic esophageal cancer based on DWI and 18F-FDG PET-CT before and during radiotherapy

目的探讨基于食管癌原发肿瘤弥散加权像(DWI)高信号区域指导个体化局部加量放疗的可行性。方法对比32例胸段食管癌患者放疗前和放疗第15次时增强3DCT、18F-FDG PET-CT及增强MRI定位扫描图像,基于放疗前和放疗中3DCT、PET-CT及基于MRI的DWI与T2WI融合图像勾画食管癌大体肿瘤体积(GTV)并分别定义为GTV_(CTpre)和GTV_(CTdur)、GTV_(PETpre)和GTV_(PETdur)、GTV_(DWIpre)和GTV_(DWIdur),分别测量放疗前及放疗中标准摄取值(SUV)、代谢肿瘤体积(MTV)、病灶糖酵解总量(TLG)、表观弥散系数(ADC)并计算其变化。结果治疗前与治疗中基于PET-CT和DWI图像所勾画食管癌GTV体积及其变化与相应增强3DCT之间均呈正相关(均P<0.001);SUV、MTV、TLG、ADC差异均有统计学意义(均P<0.001);无论治疗前还是治疗中GTV的SUV与ADC、△SUV与△ADC均无相关性(均P>0.05);GTV_(PETpre)与GTV_(DWIpre)间适形指数(CI)明显高于GTV_(PETdur)与GTV_(DWIdur)间的CI(P<0.001);基于DWI的GTV最大径退缩率及体积退缩率均>基于PET者(24%∶14%,P=0.017;60%∶41%,P<0.001)。结论无论放疗前还是放疗中食管癌SUV与ADC值、△SUV与△ADC均无相关性;放疗中期基于PET-CT图像高FDG摄取区勾画的GTV与基于DWI高信号区勾画者空间位置差异明显,且后者GTV退缩率明显大于前者。因此,放疗中基于DWI高信号区的变化进行放疗后程食管癌局部加量照射的可行性并不明确。

Objective To evaluate the spatial position and functional parameters of18F-FDG PET-CT and diffusion-weighted imaging(DWI)before and during radiotherapy(RT)based on the medium of 3DCT in patients with esophageal cancer and to explore whether the high-signal area derived from DWI can be used for individualized definition of the volume in need of dose-escalation for esophageal cancer.Methods Thirty-two patients with esophageal cancer treated with concurrent chemoradiotherapy or neoadjuvant chemoradiation sequentially underwent repeated 3DCT,18F-FDG PET-CT and enhanced MRI scans before RT and at the 15th time of RT.All images were fused with the 3DCT images by deformable registration.The gross tumor volume(GTV)was delineated based on PET Edge on the first and second 3DCT,PET-CT and DWI and corresponding T2-weighted MRI(T2W-MRI)fused images,and defined as GTV_(CTpre) and GTV_(CTdur),GTV_(PETpre),GTV_(PETdur),GTV_(DWIpre) and GTV_(DWIdur),respectively.SUV(SUVmax,SUVmean,SUVpeak),MTV,TLG,ADC(ADCmin and ADCmean)values and△SUV(△SUVmax,△SUVmean,△SUVpeak),△MTV,△TLG,△ADC(△ADCmean and△ADCmin)of lesions were measured before and during RT.Results The differences in SUV(SUVmax,SUVmean,SUVpeak),MTV,TLG,ADCmean and ADCmin of the GTV before and during RT were statistically significant(all P<0.001).The tumor ADC and SUV values before and during RT showed no significant correlation,and there was no correlation between△ADC and△SUV(both P>0.05).The conformity index(CI)of GTV_(PETpre) to GTV_(DWIpre) was significantly higher than that of GTV_(PETdur) to GTV_(DWIdur)(P<0.001).The shrinkage rate of maximum diameter(△LDDWI)(24%)and the shrinkage rate of tumor volume(VRRDWI)(60%)based on DWI during RT were significantly greater than the corresponding PET-based△LDPET(14%)and VRRPET(41%)(P=0.017 and P<0.001).Conclusions The location of high residual FDG uptake based on PET-CT yields poor spatial matching compared with the area with residual high signal based on DWI during RT.Tumor ADC and SUV values may play complementary roles as imaging markers for prediction of patterns of failure and for definition of the volume in need of dose-escalation.In addition,the shrinkage rates of tumor maximum diameter/volume based on DWI during RT are significantly faster than those based on PET-CT.Therefore,the feasibility of selecting boosting of the high signal area derived from DWI for individualized definition of the volume for esophageal cancer is not clear.