目的分析比较Cyberknife实施立体定向放射治疗(Stereotactic Body Radiation Therapy,SBRT)技术治疗椎体转移瘤时在不同方向的剂量跌落趋势。方法利用Cyberknife治疗8例胸椎转移瘤患者,4例患者给予靶区剂量40 Gy/5次,另外4例患者给予靶...目的分析比较Cyberknife实施立体定向放射治疗(Stereotactic Body Radiation Therapy,SBRT)技术治疗椎体转移瘤时在不同方向的剂量跌落趋势。方法利用Cyberknife治疗8例胸椎转移瘤患者,4例患者给予靶区剂量40 Gy/5次,另外4例患者给予靶区剂量33 Gy/3次,用Multi Plan4.0.2治疗计划系统设计优化治疗计划,使其能够满足临床治疗要求。就绝对剂量跌落梯度、相对剂量跌落梯度以及单位距离剂量跌落梯度3个方面统计比较Cyberknife治疗计划中剂量在4个不同方向的跌落趋势。结果在脊髓方向:单位绝对剂量跌落速度为(0.26±0.087)mm/100 c Gy,相对剂量跌落为(0.78±0.416)mm/5%Dmax,单位距离跌落速度为(309.95±127.45)c Gy/mm,且40 Gy组优于33 Gy组。在非脊髓方向,绝对剂量跌落平均速度为(0.725±0.223)mm/100 c Gy,相对剂量跌落为(1.476±0.553)mm/5%Dmax,单位距离跌速度为(217.930±36.493)c Gy/mm,各个方向的跌落速度无统计学差异。结论 Cyberknife治疗椎体转移瘤时,脊髓方向跌落快,加之其独特的追踪系统,对脊髓有较好的保护;而且等剂量线在各方向跌落较均匀,可以在给予大剂量治疗时更好的保护正常组织器官。Cyberknife应用于椎体转移瘤的立体定向放疗安全、有效。展开更多
This work aims to theoretically show the development of a nonequilibrium of radiation-induced bystander effect (RIBE) under steep dose gradient regions that typically occur in the field edges of a beam. We applied the...This work aims to theoretically show the development of a nonequilibrium of radiation-induced bystander effect (RIBE) under steep dose gradient regions that typically occur in the field edges of a beam. We applied the kinetics model proposed by (McMahon et al. 2013) for in vivo conditions coupled with a hypothesis called “Layer-limited bystander signaling (LLBS)” to demonstrate 1) an enhancement in TCP (i.e. Enhanced TCP or ETCP) due to bystander signals, 2) the development of nonequilibrium of RIBE under steep dose gradient regions and 3) the reduction in ETCP in the surface of Clinical Target Volume (CTV) due to the non-equilibrium of RIBE. We incorporated the elements of RIBE directly in the existing Poisson LQ model available in Pinnacle3 TPS (Version 9.10.0) to compute the percentage reduction of ETCP in the tumor surface due to nonequilibrium of RIBE. The percentage improvement in TCP obtained in tumor surface by accounting for RIBE is about 46% lower than that obtained in the interior of the tumor. This suggests that relatively more number of cancerous cells might survive in the vicinity of tumor surface. The result obtained from the study is indicative of an additional uncertainty component associated with radiation treatment. Hence, this paper suggests that the radiation treatments employing steep dose gradients could be biophysically different in many ways.展开更多
文摘This work aims to theoretically show the development of a nonequilibrium of radiation-induced bystander effect (RIBE) under steep dose gradient regions that typically occur in the field edges of a beam. We applied the kinetics model proposed by (McMahon et al. 2013) for in vivo conditions coupled with a hypothesis called “Layer-limited bystander signaling (LLBS)” to demonstrate 1) an enhancement in TCP (i.e. Enhanced TCP or ETCP) due to bystander signals, 2) the development of nonequilibrium of RIBE under steep dose gradient regions and 3) the reduction in ETCP in the surface of Clinical Target Volume (CTV) due to the non-equilibrium of RIBE. We incorporated the elements of RIBE directly in the existing Poisson LQ model available in Pinnacle3 TPS (Version 9.10.0) to compute the percentage reduction of ETCP in the tumor surface due to nonequilibrium of RIBE. The percentage improvement in TCP obtained in tumor surface by accounting for RIBE is about 46% lower than that obtained in the interior of the tumor. This suggests that relatively more number of cancerous cells might survive in the vicinity of tumor surface. The result obtained from the study is indicative of an additional uncertainty component associated with radiation treatment. Hence, this paper suggests that the radiation treatments employing steep dose gradients could be biophysically different in many ways.
