CT模拟血管分布个体化三维设计盆腔照射野初探

Use of CT Simulation With Vessel Contouring as a Guide for Lymph Node Localization to Design the Pelvic Fields

目的初步探讨根据盆腔血管个体化分布作为淋巴结位置导向,CT模拟三维设计盆腔照射野。方法5例直肠癌和5例宫颈癌患者通过CT模拟扫描,并在三维治疗计划系统逐层勾画小肠,腹主动脉、髂总动脉、髂内外动脉、相应血管外扩20 mm定义为PTV,利用数字重建影像(DRR)技术显示盆腔骨骼和靶区,根据个体化血管位置分布设计盆腔照射野。结果与传统按骨性标志设计的盆腔照射野边界一对一比较,按血管分布设计的照射野有明显的个体差异,其前后对穿野的侧界和侧野的前界分别波动在传统野边界的+7^-5 mm和+5^-6 mm之间。照射野内小肠的体积由202.4±65.7cm3减少为77.5±21.2 cm3。结论模拟盆腔血管分布进行盆腔照射野三维设计有可能达到个体化最优的目的,能较大程度减少小肠照射体积。

Objective To evaluate the optimal individual pelvic irradiation field design, with contoured pelvic vessels on simulation computed tomography as a guide for lymph node location. Method Pelvic arteries were contoured on contrast - enhanced CT simulation images of 5 cases of rectal and 5 cases of cervical cancer patients. The PTV was defined as pelvic arteries expanded with 20mm margins. The lateral border of the A - P and P - A fields and the anterior border of the lateral fields were individually placed at the edge of the PTV respectively, the other borders were the same as the conventional fields based on the bony landmarks. The conventional pelvic fields were also outlined on those digitally reconstructed radiographs （DRR）. The borders of those two kinds of fields design were displayed and compared case by case. Results The lateral borders of the vessels - based A- P and P - A fields were located around the borders of the convention fields ranged from ＋ 7 mm to - 5 mm, and the anteri- or border of the lateral fields ranged from ＋ 5 mm to - 6mm, which indicated the field borders were individually located with their respective vessel distribution. The volume of the small bowel within the irradiation fields reduced from 202.4 ± 65.7 cm^3 to 77.5 ±21.2 cm^3, with evident reduction favored for the vessels - based pelvic fields. Conclusion CT simulation with vessel contouring as a guide for lymph node localization may provide more precise and individualized field delineation and may exclude more small bowel within the irradiation fields compared with the conventional pelvic fields based on bony landmarks.