A simple procedure to plan, verify and implement craniospinal irradiation（CSI） with patients supine is presented. Treatment is conducted with a single posterior spinal field abutting two lateral cranial fields. The ...A simple procedure to plan, verify and implement craniospinal irradiation（CSI） with patients supine is presented. Treatment is conducted with a single posterior spinal field abutting two lateral cranial fields. The opposed lateral fields are half-blocked and the inferior line is perpendicular. The posterior field uses some fixed field parameters so that the cephalad edge of the posterior field is coplanar with the caudal edges of the lateral fields and it is independent of the height of the couch. A steel-shot ball is used to measure the size of overlap or gap at the junction using portal images of an electron portal image device or portal films. The results of analyzing the portal images show that the errors of the junction are within ± 1 mm. The dose-volume histograms （DVHs）show that there are not unbearable hot or cold spots in the clinic target volumes （CTVs）. Supine craniospinal treatment is a reliable and convenient alternative to treatment in the prone position and avoids the technical difficulties of the latter. The use of fixed field geometry greatly facilitates treatment planning and effectively reduces the amount of time of setup, verification and treatment.展开更多
Objective: The objective of this work was to establish adequate tolerance limits based on a certain defined institutional indices and generate published data presenting our results to the radiotherapy community. Metho...Objective: The objective of this work was to establish adequate tolerance limits based on a certain defined institutional indices and generate published data presenting our results to the radiotherapy community. Methods: One hundred paediatric patients were treated using 6-MV X-ray beams produced by Siemens ONCOR Expression linear accelerator. The clinical step-and-shoot intensity-modulated radiation therapy (IMRT) treatment plans were designed using KonRad release 2.2.23. For two treatment sites (abdomen, head and neck), the fluence maps generated by the treatment planning system were all delivered for the quality assurance (QA) which included absolute dose verification for all treatment fields, relative dose verification for each treatment field. Results: The 724 fluence maps were analyzed at three different criteria using the gamma index tool. The 3% dose difference of local prescribed dose /3 mm was considered adequate. The passing rate for all fields of all plans always exceeded 70%. The dose differences between the measured and calculated doses ranged from -2.2% to +4% [mean and standard deviation (s): 1.4 ± 1.5] for the abdominal case, and from -3.3% to +5.6% (1.3 ± 1.6) for head and neck case with total confidence limit 0.046 (4.6%). The 14/100 (14%) of the absolute point dose measurements were out of ±3% from the dose predicted by the treatment planning system. Only two cases were below -3%, while 12 cases over +3%. Conclusion: At 3% dose difference of local prescribed dose /3 mm criteria, a 75% passing a gamma criterion and 3% for absolute point dose can be achieved for abdomen and head and neck treatments site. We considered the tolerance limits based on these indices for IMRT QA adequate.展开更多
目的∶研究肺癌立体定向放射治疗(stereoactic body raliotherapy,SBRT)计划设计过程中,等中心位置的选择对验证计划Gamma通过率的影响。方法∶选取2018年1月至2019年3月间的13例肺部SBRT病例,分别通过Pinnacle9.10计划系统设计两个对...目的∶研究肺癌立体定向放射治疗(stereoactic body raliotherapy,SBRT)计划设计过程中,等中心位置的选择对验证计划Gamma通过率的影响。方法∶选取2018年1月至2019年3月间的13例肺部SBRT病例,分别通过Pinnacle9.10计划系统设计两个对应不同等中心的SBRT计划,其中A组的13例计划等中心选在计划靶区(plan-ingtugt wum,PTV)的中心,B组的13例计划等中心选在CT模拟定位的中心,并分别制作对应的验证计划共26例,通过MapClheck分析软件分别采用3%/2 mm和2%/2 mm的Gamma通过率标准对这26例验证计划进行评估,记录A组中SBRT计划的验证通过率γA和B组中SBRT计划的验证通过率γB,并对以上Gamma通过率做统计分析。结果∶当采用3%/2mm的Gamm通过率标准时,γA为99.32%±0.68%,γB为95.07%±2.09%,γA与γB差异具有统计学意义(t=7.128,P<0.001);当采用2%/2 mm的Gamma通过率标准时,γA为97.88%±2.04%,γB为87.71%±5.47%,γA与γB差异具有统计学意义(1=5.733,P<0.001)。结论∶等中心位置的选择不同影响了肺部SBRT验证计划Gamma通过率,且当采用更严格的通过率标准时,影响更显著。展开更多
文摘A simple procedure to plan, verify and implement craniospinal irradiation（CSI） with patients supine is presented. Treatment is conducted with a single posterior spinal field abutting two lateral cranial fields. The opposed lateral fields are half-blocked and the inferior line is perpendicular. The posterior field uses some fixed field parameters so that the cephalad edge of the posterior field is coplanar with the caudal edges of the lateral fields and it is independent of the height of the couch. A steel-shot ball is used to measure the size of overlap or gap at the junction using portal images of an electron portal image device or portal films. The results of analyzing the portal images show that the errors of the junction are within ± 1 mm. The dose-volume histograms （DVHs）show that there are not unbearable hot or cold spots in the clinic target volumes （CTVs）. Supine craniospinal treatment is a reliable and convenient alternative to treatment in the prone position and avoids the technical difficulties of the latter. The use of fixed field geometry greatly facilitates treatment planning and effectively reduces the amount of time of setup, verification and treatment.
文摘Objective: The objective of this work was to establish adequate tolerance limits based on a certain defined institutional indices and generate published data presenting our results to the radiotherapy community. Methods: One hundred paediatric patients were treated using 6-MV X-ray beams produced by Siemens ONCOR Expression linear accelerator. The clinical step-and-shoot intensity-modulated radiation therapy (IMRT) treatment plans were designed using KonRad release 2.2.23. For two treatment sites (abdomen, head and neck), the fluence maps generated by the treatment planning system were all delivered for the quality assurance (QA) which included absolute dose verification for all treatment fields, relative dose verification for each treatment field. Results: The 724 fluence maps were analyzed at three different criteria using the gamma index tool. The 3% dose difference of local prescribed dose /3 mm was considered adequate. The passing rate for all fields of all plans always exceeded 70%. The dose differences between the measured and calculated doses ranged from -2.2% to +4% [mean and standard deviation (s): 1.4 ± 1.5] for the abdominal case, and from -3.3% to +5.6% (1.3 ± 1.6) for head and neck case with total confidence limit 0.046 (4.6%). The 14/100 (14%) of the absolute point dose measurements were out of ±3% from the dose predicted by the treatment planning system. Only two cases were below -3%, while 12 cases over +3%. Conclusion: At 3% dose difference of local prescribed dose /3 mm criteria, a 75% passing a gamma criterion and 3% for absolute point dose can be achieved for abdomen and head and neck treatments site. We considered the tolerance limits based on these indices for IMRT QA adequate.
