- Email: [email protected]
Rapid Evaluation of Radiation Treatment Plan Quality Using Interactive Treemaps
S880
International Journal of Radiation Oncology Biology Physics
3701
(99.231.90)% and (97.542.90)%, respectively. Mean deviation and gamma passing rate value (Dmed/% of points) is (-0.000.81/ 99.500.71)% for rectum, (0.800.90/99.601.21)% for bladder and (2.842.28/100.000.00)% for penile bulb. Mean deviations and gamma passing rates for right and left femoral heads (Dmed/Dmax/% of points) are (0.030.43/-1.272.35/100.000.00)% and (0.050.38/-1.492.24/ 100.000.00)%, respectively. Conclusions: Deviations are below 1.5% for all parameters and volumes, excepting penile bulb (due to the limited number of contoured slices). 3D gamma passing rates are above 97.5% for all structures, reaching 100.0% in some cases. The tested system is a quick, effective and reliable tool to perform independent TPS-quality dose calculations of complex treatments, such as those used in VMAT techniques. Author Disclosure: F. Clemente Gutierrez: None. C. Perez Vara: None.
Daily Delivery Accuracy of Volumetric Modulated Arc Therapy Treatments Using Linac Log Files G. Li, S. Bai, and Y. Li; Radiation Physics Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, China Purpose/Objective(s): To evaluate the daily delivery accuracy of volumetric modulated arc therapy (VMAT) treatments using Linac log files, and analyze the impact of cancer site for the delivery accuracy. Materials/Methods: All VMAT plans were generated in commercial treatment planning systems, and delivered by Synergy accelerator (with MLCi). When each plan was delivered, Linac parameters, such as gantry angle, MLC leaf position, jaw position, monitor unit (MU), had been recorded in a log file. A total of 2446 VMAT treatments during three weeks have been evaluated using an in-house software. Also the daily delivery stability of accelerator, the impact of cancer sites for the delivery accuracy has been analyzed. Results: The average errors ( standard deviation) of gantry rotational angle, X (GT direction) and Y (AB direction) jaw position, MLC leaf position and dose delivery were 0.490.10 , 0.090.04 and 0.380.04 mm, 0.310.04 mm and 0.050.009 MU, respectively. The standard deviations of the daily delivery errors for the same plan were 0.04 , 0.02 mm, 0.02 mm and 0.005 MU, respectively, for gantry rotational angle, jaw position, MLC leaf position and dose delivery. For the four cancer sites (cervix, nasopharynx, rectum, larynx), the maximum differences of the average errors for the four parameters were 13%, 3%, 5% and 18%, respectively. Conclusions: Daily delivery verification of VMAT can be performed conveniently using Linac log files. Plan-specific affect the delivery accuracy of VMAT for all the four Linac parameters obviously, while cancer sites affect the delivery accuracy of VMAT for only gantry rotational angle and MU. Author Disclosure: G. Li: None. S. Bai: None. Y. Li: None.
3702 3D Secondary Verifications for VMAT Prostate Treatments Based in DVH-Metrics and 3D Gamma Analysis F. Clemente Gutierrez and C. Perez Vara; Hospital Central de la Defensa, Madrid, Spain Purpose/Objective(s): Independent monitor unit (MU) verification of intensity-modulated radiation therapy (IMRT) treatments is traditionally performed with Monte Carlo calculations or comparing point-dose calculations in homogeneous media. Recent verifications systems permit to perform secondary checks of treatment plans calculating dose on patient CT images. Single-point MU check is replaced with 3D treatment plan verification, incorporating DVH-based metrics with clinical relevance to the QA process. This work shows the 3D dosimetric verification of several volumetric modulated arc therapy (VMAT) prostate treatment plans by means of dose-volume parameters comparison with a new 3D treatment plan QA software. Materials/Methods: VMAT prostate plans are generated and delivered with a single VMAT arc technique. DICOM RT information (CT, RT Struct, RT Plan and RT Dose) is transferred from TPS to verification system. This software uses a new independently developed collapsed cone algorithm to calculate dose distributions in CT. A stock reference beam model is used for calculations. Beam data can be fitted with key parameters (PDDs, OFs, OARs). A dosimetric leaf gap of -2 mm is needed to scale the results. 25 prostate plans have been verified using this solution, comparing DVH parameters (Dmed, D90 and eventually Dmax) and performing 3D gamma tests for PTVs (prostate, seminal vesicles, pelvic lymph nodes) and OARs (rectum, bladder, femoral heads, penile bulb). Results: Mean relative deviations (Dmed/D90) are (-0.220.97/0.621.20)% for prostate PTV, (0.290.90/0.560.90)% for seminal vesicles PTV and (1.140.53/0.900.58)% for pelvic lymph nodes PTV. 3D gamma passing rate values for PTVs are (97.993.12)%,
3703 Rapid Evaluation of Radiation Treatment Plan Quality Using Interactive Treemaps E.S. Paulson and D.E. Prah; Medical College of Wisconsin, Milwaukee, WI Purpose/Objective(s): Evaluation of radiation treatment plan quality using dose-volume (DV) constraints can be time consuming for treatment plans containing large numbers of structures or constraints. Treemaps are a new class of intuitive data visualization techniques for rapidly evaluating large amounts of time-varying data, particularly in financial services applications. The goal of this work was to investigate whether treemaps offer advantages for plan quality evaluation in radiation therapy. Materials/Methods: A retrospective, proof-of-principle study was performed on three patients with high-risk intact prostate cancer. Dose-volume histogram (DVH) data was exported from multi-arc VMAT plans generated for the patients. Treemaps were generated using DV constraints based on QUANTEC data. The treemap is a color-coded, equal-aspect, 2D array containing nested cells for each structure. The area of each cell represents the structure volume at a particular dose. The color of each cell indicates whether the structure fell above or below the DV constraint at that dose. For example, if rectum V45 exceeded 50%, the rectum cell would be colored red, otherwise it would remain green. The treemap dose can be fixed, or can be changed interactively by the user during plan evaluation. Six treemaps were generated using the prostate DVH data for doses of 45, 50, 60, 70, 75.6, and 83.2 Gy. These treemaps were displayed simultaneously in a 3x2 mosaic in order of increasing dose for plan quality evaluation. In addition, patient contours were transferred from planning CT images to one daily CT-on-rails image acquired for IGRT. In this case, two treemaps were generated: one using planning CT structures and the other using daily CT structures. A slider was used to dynamically adjust the dose level during comparison of the two treemaps. Results: Interactive changes in dose resulted in a re-tessellation of the treemap as cell areas were updated with the latest DV results. As dose was increased, cell areas of critical structures became smaller and targets became larger. At doses above 70 Gy, the planning target volume (PTV) demonstrated the largest cell area. Color differentiation of cells was effective at rapidly identifying structures failing to meet DV constraints at a particular dose. Differences in cell areas at a given dose facilitated rapid comparison between planning and daily DV results, demonstrating the utility of treemaps for online adaptive radiation therapy. These results suggest a natural human factors advantage of treemaps over conventional DVH analysis. Conclusions: We have introduced a novel method for rapidly evaluating radiation treatment plan quality using treemaps, with DV constraints based on embedded QUANTEC data. The method can be employed for both pretreatment plan quality evaluation as well as evaluation of daily DV results for online adaptive radiation therapy. Author Disclosure: E.S. Paulson: None. D.E. Prah: None.
International Journal of Radiation Oncology Biology Physics
3701
(99.231.90)% and (97.542.90)%, respectively. Mean deviation and gamma passing rate value (Dmed/% of points) is (-0.000.81/ 99.500.71)% for rectum, (0.800.90/99.601.21)% for bladder and (2.842.28/100.000.00)% for penile bulb. Mean deviations and gamma passing rates for right and left femoral heads (Dmed/Dmax/% of points) are (0.030.43/-1.272.35/100.000.00)% and (0.050.38/-1.492.24/ 100.000.00)%, respectively. Conclusions: Deviations are below 1.5% for all parameters and volumes, excepting penile bulb (due to the limited number of contoured slices). 3D gamma passing rates are above 97.5% for all structures, reaching 100.0% in some cases. The tested system is a quick, effective and reliable tool to perform independent TPS-quality dose calculations of complex treatments, such as those used in VMAT techniques. Author Disclosure: F. Clemente Gutierrez: None. C. Perez Vara: None.
Daily Delivery Accuracy of Volumetric Modulated Arc Therapy Treatments Using Linac Log Files G. Li, S. Bai, and Y. Li; Radiation Physics Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, China Purpose/Objective(s): To evaluate the daily delivery accuracy of volumetric modulated arc therapy (VMAT) treatments using Linac log files, and analyze the impact of cancer site for the delivery accuracy. Materials/Methods: All VMAT plans were generated in commercial treatment planning systems, and delivered by Synergy accelerator (with MLCi). When each plan was delivered, Linac parameters, such as gantry angle, MLC leaf position, jaw position, monitor unit (MU), had been recorded in a log file. A total of 2446 VMAT treatments during three weeks have been evaluated using an in-house software. Also the daily delivery stability of accelerator, the impact of cancer sites for the delivery accuracy has been analyzed. Results: The average errors ( standard deviation) of gantry rotational angle, X (GT direction) and Y (AB direction) jaw position, MLC leaf position and dose delivery were 0.490.10 , 0.090.04 and 0.380.04 mm, 0.310.04 mm and 0.050.009 MU, respectively. The standard deviations of the daily delivery errors for the same plan were 0.04 , 0.02 mm, 0.02 mm and 0.005 MU, respectively, for gantry rotational angle, jaw position, MLC leaf position and dose delivery. For the four cancer sites (cervix, nasopharynx, rectum, larynx), the maximum differences of the average errors for the four parameters were 13%, 3%, 5% and 18%, respectively. Conclusions: Daily delivery verification of VMAT can be performed conveniently using Linac log files. Plan-specific affect the delivery accuracy of VMAT for all the four Linac parameters obviously, while cancer sites affect the delivery accuracy of VMAT for only gantry rotational angle and MU. Author Disclosure: G. Li: None. S. Bai: None. Y. Li: None.
3702 3D Secondary Verifications for VMAT Prostate Treatments Based in DVH-Metrics and 3D Gamma Analysis F. Clemente Gutierrez and C. Perez Vara; Hospital Central de la Defensa, Madrid, Spain Purpose/Objective(s): Independent monitor unit (MU) verification of intensity-modulated radiation therapy (IMRT) treatments is traditionally performed with Monte Carlo calculations or comparing point-dose calculations in homogeneous media. Recent verifications systems permit to perform secondary checks of treatment plans calculating dose on patient CT images. Single-point MU check is replaced with 3D treatment plan verification, incorporating DVH-based metrics with clinical relevance to the QA process. This work shows the 3D dosimetric verification of several volumetric modulated arc therapy (VMAT) prostate treatment plans by means of dose-volume parameters comparison with a new 3D treatment plan QA software. Materials/Methods: VMAT prostate plans are generated and delivered with a single VMAT arc technique. DICOM RT information (CT, RT Struct, RT Plan and RT Dose) is transferred from TPS to verification system. This software uses a new independently developed collapsed cone algorithm to calculate dose distributions in CT. A stock reference beam model is used for calculations. Beam data can be fitted with key parameters (PDDs, OFs, OARs). A dosimetric leaf gap of -2 mm is needed to scale the results. 25 prostate plans have been verified using this solution, comparing DVH parameters (Dmed, D90 and eventually Dmax) and performing 3D gamma tests for PTVs (prostate, seminal vesicles, pelvic lymph nodes) and OARs (rectum, bladder, femoral heads, penile bulb). Results: Mean relative deviations (Dmed/D90) are (-0.220.97/0.621.20)% for prostate PTV, (0.290.90/0.560.90)% for seminal vesicles PTV and (1.140.53/0.900.58)% for pelvic lymph nodes PTV. 3D gamma passing rate values for PTVs are (97.993.12)%,
3703 Rapid Evaluation of Radiation Treatment Plan Quality Using Interactive Treemaps E.S. Paulson and D.E. Prah; Medical College of Wisconsin, Milwaukee, WI Purpose/Objective(s): Evaluation of radiation treatment plan quality using dose-volume (DV) constraints can be time consuming for treatment plans containing large numbers of structures or constraints. Treemaps are a new class of intuitive data visualization techniques for rapidly evaluating large amounts of time-varying data, particularly in financial services applications. The goal of this work was to investigate whether treemaps offer advantages for plan quality evaluation in radiation therapy. Materials/Methods: A retrospective, proof-of-principle study was performed on three patients with high-risk intact prostate cancer. Dose-volume histogram (DVH) data was exported from multi-arc VMAT plans generated for the patients. Treemaps were generated using DV constraints based on QUANTEC data. The treemap is a color-coded, equal-aspect, 2D array containing nested cells for each structure. The area of each cell represents the structure volume at a particular dose. The color of each cell indicates whether the structure fell above or below the DV constraint at that dose. For example, if rectum V45 exceeded 50%, the rectum cell would be colored red, otherwise it would remain green. The treemap dose can be fixed, or can be changed interactively by the user during plan evaluation. Six treemaps were generated using the prostate DVH data for doses of 45, 50, 60, 70, 75.6, and 83.2 Gy. These treemaps were displayed simultaneously in a 3x2 mosaic in order of increasing dose for plan quality evaluation. In addition, patient contours were transferred from planning CT images to one daily CT-on-rails image acquired for IGRT. In this case, two treemaps were generated: one using planning CT structures and the other using daily CT structures. A slider was used to dynamically adjust the dose level during comparison of the two treemaps. Results: Interactive changes in dose resulted in a re-tessellation of the treemap as cell areas were updated with the latest DV results. As dose was increased, cell areas of critical structures became smaller and targets became larger. At doses above 70 Gy, the planning target volume (PTV) demonstrated the largest cell area. Color differentiation of cells was effective at rapidly identifying structures failing to meet DV constraints at a particular dose. Differences in cell areas at a given dose facilitated rapid comparison between planning and daily DV results, demonstrating the utility of treemaps for online adaptive radiation therapy. These results suggest a natural human factors advantage of treemaps over conventional DVH analysis. Conclusions: We have introduced a novel method for rapidly evaluating radiation treatment plan quality using treemaps, with DV constraints based on embedded QUANTEC data. The method can be employed for both pretreatment plan quality evaluation as well as evaluation of daily DV results for online adaptive radiation therapy. Author Disclosure: E.S. Paulson: None. D.E. Prah: None.