Purpose: To evaluate planning quality and dosimetric differences of clinically deliverable 3D conformal plans generated from Tomotherapy with TomoDirectTM (TD) and conventional field-in-field approach in prone breast ...Purpose: To evaluate planning quality and dosimetric differences of clinically deliverable 3D conformal plans generated from Tomotherapy with TomoDirectTM (TD) and conventional field-in-field approach in prone breast treatment. Materials and methods: Total of twelve randomly selected early stage left breast patients who went through lumpectomy and were previously treated on traditional Linear Accelerator (LINAC) have been re-planned and tested on Tomotherapy TomoDirect module. Baseline prescription dose was chosen at 50.4 Gy (1.8 Gy × 28 fractions) to cover ≥95% of PTV for planning criteria with other critical structure dose constraints in the thoracic region. Planning outcomes such as D95 (95% of volume of PTV receiving the prescribed dose), D5 and D1, heart, both lungs as well as the contralateral breast were simultaneously evaluated. Conformity of the prescription isodose/volume to PTV was evaluated as conformity index (CI) and dose uniformity was also evaluated with homogeneity index (HI) in the same study series. All outcome parameters were analyzed and summarized to evaluate dosimetric impact of planning qualities between these two planning platforms. Results: The planning results indicate that CI, HI, D95, D5 and D1 of PTV, critical structures such as heart, ipsilateral and contralateral lungs as well as contralateral breast doses were comparable but with better overall statistical end points from TD plans. The D95, D5 and D1 of PTV for TD plans were superior in dosimetric analysis and more uniform than those plans generated from PinnacleTM field-in-field planning technique. Overall, TD plans have superior planning quality than the conventional method does, with straightforward and automated planning process once the beam delivery parameters were established. Conclusions: From the clinical treatment planning results, plans from TD in general achieved better uniform tumor coverage with fewer hot spots while sparing more critical structures were based upon isodose distribution and Dose Volume Histogram (DVH) analysis. Image guidance of TD delivery automates the setup within the treatment bore without tedious verification process compared to the process with LINAC. Though all plans are deliverable, TD planning possesses dosimetric advantages due to its modulated optimization pattern. However, TD did present a challenge during the simulation if a patient is oversized with long pendulant breast which is hard to fit into the Tomotherapy ring structure. From our analysis, TD plans reserve superior dosimetric outcome with CI, HI, D95, D5, and D1 of PTV, and better sparing contralateral lung and breast doses.展开更多
Aim: In prone breast treatments, a carbon fiber support device resides under the contralateral breast. Tangent beams are designed to encompass the treated breast and these often pass through the board at a shallow ang...Aim: In prone breast treatments, a carbon fiber support device resides under the contralateral breast. Tangent beams are designed to encompass the treated breast and these often pass through the board at a shallow angle, resulting in significant attenuation. Our planners account for this attenuation by adding field-in-field dose to the deep part of the breast, through the board. Concern was raised about how accurate the treatment delivery is when the inherent uncertainties of patients’ positions are accounted for. Furthermore, transmission measurements are usually carried out perpendicular to the board, a non-clinical situation. The goal of this study is to evaluate the dosimetric effect of the board and the robustness of the plan to positional uncertainty. Materials and Methods: Twenty-two breast patients treated on a commercial prone breast board between 2017 and 2020 were selected for this retrospective study. To evaluate the board’s attenuation, we compared the plans with the board removed from the dose calculation. To quantify the robustness of this technique, we moved the beam isocenter with respect to the patient and board. Results: Our results showed that when the breast board is removed from a plan which was designed to account for the board attenuation, the average point dose increases by 7.48%, with a maximum of 22%. Comparing results with a mixed Analysis of Variance (ANOVA) and a least-square means analysis, our robustness evaluation indicates that anterior shifts at every magnitude (1 mm through 5 mm) make a significant difference in all dose statistics (D95, max, 95% prescription coverage and homogeneity index) investigated. In/out and right/left shifts resulted in an insignificant change in dose statistics. Conclusion: Prone breast boards can add significant dosimetric uncertainty into the treatment delivery process. Accounting for plan robustness in the design of the plan is highly recommended. A prone breast board design with support moved away from the beam path is warranted.展开更多
目的:通过比较分析早期左乳腺癌保乳术后仰卧位和俯卧位两种不同固定方式的调强治疗计划,评价不同计划方案在剂量学上的差异性,确定患者选择合适的体位固定方式。方法:对22例早期左侧乳腺癌保乳术后患者分别制定仰卧位和俯卧位两种不同...目的:通过比较分析早期左乳腺癌保乳术后仰卧位和俯卧位两种不同固定方式的调强治疗计划,评价不同计划方案在剂量学上的差异性,确定患者选择合适的体位固定方式。方法:对22例早期左侧乳腺癌保乳术后患者分别制定仰卧位和俯卧位两种不同固定方式的调强治疗计划,对两种计划的靶区剂量分布和危及器官的保护进行评估。结果:俯卧位固定方式的调强治疗计划的以下指标优于相应的仰卧位治疗计划:(1)差异均有统计学意义(P<0.05):PTV异质性指数(HI由12.89上升到26.03);左肺)Dmean由1415.80 c Gy降到859.19 c Gy、V5由84.99%降到56.98%、V20由20.79%降到10.19%);心脏(Dmean由1537.67 c Gy降到1135.78 c Gy、V10由70.78%降到42.78%、V20由26.87%降到14.78%、V30由9.49%降到3.98%);左心室(Dmean由1749.67 c Gy降到1175.99 c Gy、V10由80.89%降到49.12%、V20由29.56%降到15.45%);冠状动脉左前降支(Dmean由3069.95 c Gy降到2627.42 c Gy、V20由75.12%降到67.13%)。(2)差异无统计学意义(P>0.05):PTV参数(Dmean由5039.9 c Gy上升到5059.5 c Gy、D95由4779.6 c Gy上升到4811.4 c Gy);适形指数(CI由0.791降到0.692);右肺(Dmean由438.98 c Gy降到259.01 c Gy、V5由38.01%降到10.43%);心脏(V40由2.51%降到1.30%);左心室(V30由14.67%降到5.87%、V40由3.98%降到0.88%);冠状动脉左前降支(V10由89.97%降到76.97%、V30由54.79%降到41.12%、V40由30.75%降到21.65%);右侧乳腺(Dmax由810.12 c Gy降到590.89 c Gy、Dmean由259.86 c Gy降到217.69 c Gy)。结论:与仰卧位固定方式相比,俯卧位固定方式的调强治疗计划能够有效降低危及器官的高剂量区,提高靶区剂量的均匀性,在保护肺、心脏、心脏亚结构等正常器官方面显示出较明显的优势,为靶区剂量提升创造了空间。展开更多
文摘Purpose: To evaluate planning quality and dosimetric differences of clinically deliverable 3D conformal plans generated from Tomotherapy with TomoDirectTM (TD) and conventional field-in-field approach in prone breast treatment. Materials and methods: Total of twelve randomly selected early stage left breast patients who went through lumpectomy and were previously treated on traditional Linear Accelerator (LINAC) have been re-planned and tested on Tomotherapy TomoDirect module. Baseline prescription dose was chosen at 50.4 Gy (1.8 Gy × 28 fractions) to cover ≥95% of PTV for planning criteria with other critical structure dose constraints in the thoracic region. Planning outcomes such as D95 (95% of volume of PTV receiving the prescribed dose), D5 and D1, heart, both lungs as well as the contralateral breast were simultaneously evaluated. Conformity of the prescription isodose/volume to PTV was evaluated as conformity index (CI) and dose uniformity was also evaluated with homogeneity index (HI) in the same study series. All outcome parameters were analyzed and summarized to evaluate dosimetric impact of planning qualities between these two planning platforms. Results: The planning results indicate that CI, HI, D95, D5 and D1 of PTV, critical structures such as heart, ipsilateral and contralateral lungs as well as contralateral breast doses were comparable but with better overall statistical end points from TD plans. The D95, D5 and D1 of PTV for TD plans were superior in dosimetric analysis and more uniform than those plans generated from PinnacleTM field-in-field planning technique. Overall, TD plans have superior planning quality than the conventional method does, with straightforward and automated planning process once the beam delivery parameters were established. Conclusions: From the clinical treatment planning results, plans from TD in general achieved better uniform tumor coverage with fewer hot spots while sparing more critical structures were based upon isodose distribution and Dose Volume Histogram (DVH) analysis. Image guidance of TD delivery automates the setup within the treatment bore without tedious verification process compared to the process with LINAC. Though all plans are deliverable, TD planning possesses dosimetric advantages due to its modulated optimization pattern. However, TD did present a challenge during the simulation if a patient is oversized with long pendulant breast which is hard to fit into the Tomotherapy ring structure. From our analysis, TD plans reserve superior dosimetric outcome with CI, HI, D95, D5, and D1 of PTV, and better sparing contralateral lung and breast doses.
文摘Aim: In prone breast treatments, a carbon fiber support device resides under the contralateral breast. Tangent beams are designed to encompass the treated breast and these often pass through the board at a shallow angle, resulting in significant attenuation. Our planners account for this attenuation by adding field-in-field dose to the deep part of the breast, through the board. Concern was raised about how accurate the treatment delivery is when the inherent uncertainties of patients’ positions are accounted for. Furthermore, transmission measurements are usually carried out perpendicular to the board, a non-clinical situation. The goal of this study is to evaluate the dosimetric effect of the board and the robustness of the plan to positional uncertainty. Materials and Methods: Twenty-two breast patients treated on a commercial prone breast board between 2017 and 2020 were selected for this retrospective study. To evaluate the board’s attenuation, we compared the plans with the board removed from the dose calculation. To quantify the robustness of this technique, we moved the beam isocenter with respect to the patient and board. Results: Our results showed that when the breast board is removed from a plan which was designed to account for the board attenuation, the average point dose increases by 7.48%, with a maximum of 22%. Comparing results with a mixed Analysis of Variance (ANOVA) and a least-square means analysis, our robustness evaluation indicates that anterior shifts at every magnitude (1 mm through 5 mm) make a significant difference in all dose statistics (D95, max, 95% prescription coverage and homogeneity index) investigated. In/out and right/left shifts resulted in an insignificant change in dose statistics. Conclusion: Prone breast boards can add significant dosimetric uncertainty into the treatment delivery process. Accounting for plan robustness in the design of the plan is highly recommended. A prone breast board design with support moved away from the beam path is warranted.
文摘目的:通过比较分析早期左乳腺癌保乳术后仰卧位和俯卧位两种不同固定方式的调强治疗计划,评价不同计划方案在剂量学上的差异性,确定患者选择合适的体位固定方式。方法:对22例早期左侧乳腺癌保乳术后患者分别制定仰卧位和俯卧位两种不同固定方式的调强治疗计划,对两种计划的靶区剂量分布和危及器官的保护进行评估。结果:俯卧位固定方式的调强治疗计划的以下指标优于相应的仰卧位治疗计划:(1)差异均有统计学意义(P<0.05):PTV异质性指数(HI由12.89上升到26.03);左肺)Dmean由1415.80 c Gy降到859.19 c Gy、V5由84.99%降到56.98%、V20由20.79%降到10.19%);心脏(Dmean由1537.67 c Gy降到1135.78 c Gy、V10由70.78%降到42.78%、V20由26.87%降到14.78%、V30由9.49%降到3.98%);左心室(Dmean由1749.67 c Gy降到1175.99 c Gy、V10由80.89%降到49.12%、V20由29.56%降到15.45%);冠状动脉左前降支(Dmean由3069.95 c Gy降到2627.42 c Gy、V20由75.12%降到67.13%)。(2)差异无统计学意义(P>0.05):PTV参数(Dmean由5039.9 c Gy上升到5059.5 c Gy、D95由4779.6 c Gy上升到4811.4 c Gy);适形指数(CI由0.791降到0.692);右肺(Dmean由438.98 c Gy降到259.01 c Gy、V5由38.01%降到10.43%);心脏(V40由2.51%降到1.30%);左心室(V30由14.67%降到5.87%、V40由3.98%降到0.88%);冠状动脉左前降支(V10由89.97%降到76.97%、V30由54.79%降到41.12%、V40由30.75%降到21.65%);右侧乳腺(Dmax由810.12 c Gy降到590.89 c Gy、Dmean由259.86 c Gy降到217.69 c Gy)。结论:与仰卧位固定方式相比,俯卧位固定方式的调强治疗计划能够有效降低危及器官的高剂量区,提高靶区剂量的均匀性,在保护肺、心脏、心脏亚结构等正常器官方面显示出较明显的优势,为靶区剂量提升创造了空间。
