逆向优化算法在宫颈癌三维近距离放疗计划制定中的应用

Application of inverse planning simulated annealing to fomulating three-dimensional radiobrachytherapy plans for cervical cancer

目的探讨逆向优化算法(IPSA)在宫颈癌三维近距离放疗计划制定中的应用价值。方法在60例宫颈癌患者的CT图像上分别完成两种IPSA计划(IPSA1、IPSA2)及正向图形拖拽优化(GRO)计划,其中IPSA2较IPSA1增加了最大体积剂量这一限制函数。分析3种不同计划及不同优化函数对剂量学的影响。结果与GRO计划比较,IPSA1计划提高了靶区覆盖度(D_(90)、D_(100)、V_(100))(P<0.05)。IPSA1与GRO的靶区剂量(V_(150)、V_(200))比较,差异无统计学意义(P>0.05)。与IPSA1比较,IPSA2降低V_(100)、V_(150)、V_(200)、D_(90)、D_(100)及直肠剂量(P<0.05)。3种计划中,IPSA1计划所需时间最短(P<0.05)。结论在宫颈癌三维近距离放疗中,IPSA可以改善正向算法的剂量学结果,并可减少制订计划所需的时间。IPSA可通过限制最大表面剂量降低靶区内高量,但不宜限制最大体积剂量。

Objective To investigate the value of inverse planning simulated annealing（ IPSA） applied to the three-dimensional radiobrachytherapy plans for cervical cancer. Methods Two IPSA plans（ IPSA1 and IPSA2） and forward graphical optimization（ GRO）plan were made based on the CT images of 60 cervical cancer patients. A parameter,maximum volume dose,was added in IPSA2 plan compared to IPSA1 plan. The influences of the three plans and different optimized parameters on dosimetry were analyzed. Results Compared to GRO plan,IPSA1 plan increased the target coverage（ D_（90）,D_（100）） and target dose of V_（100）（ P 0. 05）. There were no significant differences in the target dose（ V150 or V200） between IPSA1 and GRO plans（ P 0.05）. Compared to IPSA1 plan,IPSA2 plan decreased V_（100）,V_（150）,V_（200）,D_（90）,D_（100） and the dose for rectum（ P 0. 05）. Among the three plans,the planning duration of IPSA1 plan was the least（ P 0. 05）. Conclusion In the three-dimensional radiobrachytherapy plans for cervical cancer,IPSA can improve the dosimetric outcomes of forward planning,and decrease the duration for planning. IPSA can decrease the high dose for the target volume by restricting the maximum surface dose,but the maximum volume dose may not be restricted.