基于3DCT食管癌GTV手动勾画与系统生成CTV及PTV的比较研究

Comparative study of the CTV and PTV derived separately from automatic extension and manually delineation based on the GTV of the mid-thoracic esophageal cancer

目的:基于胸中段食管癌三维CT(3DCT)模拟定位扫描图像,在原发肿瘤大体肿瘤体积(GTV)勾画的基础上,比较手动勾画与系统生成原发肿瘤临床靶体积(CTV)及计划靶体积(PTV)的差异。方法:选择在山东省肿瘤医院放疗科拟行三维适形放疗(3DCRT)的胸中段食管癌患者10例,基于3DCT扫描图像勾画原发肿瘤GTV,在GTV勾画基础上,计划系统自动上下外扩3cm、左右及前后外扩1cm生成CTVauto,按相同外扩范围由放疗医生手动勾画生成CTVmanu;基于CTVauto及CTVmanu系统自动上下外扩1.5cm、左右及前后外扩0.5cm生成PTVauto及PTVmanu。比较CTVauto与CTVmanu、PTVauto与PTVmanu的体积大小、靶区重合度及相对位移。结果:10例患者系统自动生成的CTVauto体积为(384.51±92.21)cm3,手动勾画生成的CTVmanu体积为(286.0±56.19)cm3,差异有统计学意义,t=7.265,P=0.005;PTVauto的体积为(653.17±141.63)cm3,PTVmanu的体积为(583.56±122.84)cm3,差异有统计学意义,t=4.390,P=0.005;CTVauto与CTVmanu的重合度为(75.08±5.49)%,PTVauto与PTVmanu的重合度为(89.46±7.51)%,两者差异有统计学意义,t=9.640,P=0.005;CTVauto与CTVmanu中心点在x、y轴方向上的偏移分别为(0.57±0.19)cm和(0.86±0.52)cm。PTVauto与PTVmanu中心点在x、y轴方向上的偏移分别为(0.52±0.24)cm和(0.99±0.48)cm。结论:由于食管头脚方向走行的非直线性,计划系统自动外扩生成食管原发肿瘤的CTV是不可靠的,胸中段食管癌头脚方向外扩均应基于GTV手动勾画形成。

OBJECTIVE：Based on the three-dimensional computed tomography （3DCT） simulation images,to com- pare the differences of the clinical target volume （CTV） and planning target volume （PTV） derived separately from auto- matic extension and manually delineation based on the gross tumor volume （GTV） of the mid-thoracic esophageal cancer. METHODS.. Ten patients with mid-thoracic esophageal cancer, who were planned to be treated by three-dimensional con- formal radiotherapy,were collected. The GTV was delineated based on the 3DCT images, on basis of GTV, and CTV was automatically created by the planning system with the extended margin of 3 cm in cranial-caudal（CC） direction and lcm in left right（LR） and anterior-posterior（AP） directions,CTV was created by manually delineation with the same extended margin in the same direction as CTV Based on CTV and CTV PTV and PTV were automatically created by the planning system with the extended margin of 1.5 cm in CC direction and 0.5 cm in LR and AP directions. The volume of the targets, the target contact ratios and the relative displacement of the targets between CTVauto and CTV PTVauto and PTVmanu were compared. RESULTS：The volumes of CTVauto and CTVmanu were （384.51±92.21） cm3 and （286.0± 56.19） cm3 , respectively, and the difference of the volumes between CTV and CTVmanu was statistically significant （t=7. 265,P=0. 005）. the volumes of PTV and PTV were （653. 17± 141. 63） cm3 and （583. 56±122. 84） cm3, andthe difference of the volumes between PTV and PTV was statistically significant （t= 4. 390,P= 0. 005）. The contact ratio between CTV and CTV was （75.08±5.49） % ,and it was （89.46±7.51） % between PTV and PTV the difference of the contact radios was not statistically significant （t= 9. 640 ,P= 0. 005）. The displacements between the cen- troids of CTV and CTV in the directions of LR and AP directions were （0.57±0.19） cm and （0.86±0.52） cm,re- spectively; and the displacements between the centroids of PTVau,o and PTV in the directions of LR and AP directions were （0.52 ± 0. 24） cm and （0.99 ± 0. 48） cm, respectivey. CONCLUSION=Because of the non-linear line feed of the e- sophagus along CC direction,it is unreliable for the CTV of primary cancer of the esophagus to be created by automatic extension by planning system, and the extension margins along CC direction should be produced by manual delineation based on the GTV.