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Objective:To create AAPM TG 119 test plans for intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in order to evaluate the accuracy of the United Imaging Healthcare′s URT treatment planning system (URT-TPS). The plans were delivered to the phantom using the United Imaging Healthcare′s URT-Linac 506C.Methods:The overall accuracy of IMRT and VMAT planning, measurement, and analysis were evaluated for four test geometries provided by American Association of Physicists in Medicine (AAPM) Task Group Report 119(TG-119) on multi-target, prostate, head and neck and C-shape (easy). The dose distributions were measured in the coronal plane. The point measurements were measured by a Farmer type ion chamber and fluence measurements were completed with film and Delta4 phantom, respectively. Measured planar dose distributions were analyzed using gamma index with criteria 3%/3 mm.Results:For IMRT and VMAT plans, the planning results matched the TG-119 planning results. Measured point doses of IMRT and VMAT were within 2.62% and 3.90% of the planned doses, respectively. Measured film dosimetry gamma values of IMRT and VMAT were> 97.50% and> 93.27%, respectively.Conclusion:Based on these analyses which were performed in line with the TG119 recommendations, it is evident that the URT treatment planning system and URT-Linac 506C have commissioned IMRT and VMAT techniques with adequate accuracy.
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Objective KV-CBCT was utilized to evaluate the setup errors in lung SBRT with R624-SCF immobilization equipment,quantitatively analyze the percentage of all types of errors in the cumulative errors and unravel the main sources of setup errors.Methods The CBCT data weekly and QA data monthly from 32 patients diagnosed with lung neoplasms were collected to quantitatively analyze the setup errors.The cumulative errors were calculated by statistical model.The proportion and source of each type of setup error was analyzed.Results All 32 patients received a total of 420 times of CBCT.The setup errors of immobilization equipment in the lateral,supine-inferior,anterior-posterior directions were (0.03±0.72) mm,(0.73± 1.16) mm and (0.21±0.95) mm,respectively.The errors of tumor motion in three directions were (0.71±2.61) mm,(-0.80±2.60) mm and (0.075± 1.77) mm,respectively.According to the calculation formula proposed by Vance Keeling,the proportion of the cumulative error was 54.55％,9.21％ for immobilization equipment,12.97％ for tumor motion,2.55％ for couch sagging,5.70％ for Gantry radiation isocenter,4.73％ for Collimator radiation isocenter,4.61％ for couch radiation isocenter and 5.70％ for Xray field isocenter,respectively.Conclusions The main factors of setup errors during SBRT treatment for lung cancer are setup random,tumor motion,immobilization equipment,couch sagging and machine isocenter.During radiotherapy,targeted control of tumor motion is of significance for minimizing the cumulative errors.
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Objective To evaluate the effect of setup errors on the 2D image projection and image registration, and then propose an improved registration method based on mutual information. Methods An anthropomorphic head phantom was used to simulate the rotational and translational setup errors. The geometric disparities were reflected by the changes of mutual information. Known setup errors were intentionally introduced to twenty cases divided into two groups demarcated by 3 mm translation error and 3° rotation error: ten cases with larger errors and ten with smaller errors. Then the anterior-posterior and lateral portal images were captured by the electronic portal imaging device ( EPID ) , based on which the setup errors were calculated using two mutual information registration method respectively: the vender provided one, and the improved method as proposed. The calculated errors were compared with the actual setup errors to evaluate robustness of the method. Results For the ten cases with smaller setup errors, the average translational registration disparities using the conventional method were 0. 3, 0. 4, and 0. 3 mm in x, y and z directions respectively. The rotational disagreements were 0. 4° in both x and z directions. The average time consumption was 28. 7 s. The corresponding discrepancies analyzed using the improved method were 0. 3, 0. 4, 0. 3 mm, 0. 5° and 0. 4°, respectively. On average, 31. 1 s was needed for registration. For the ten cases with larger setup errors, the mean disparities of the conventional method were 0. 9, 0. 7, 0. 8 mm, 0. 9° and 0. 8°, 29. 9 s taken on average. The corresponding result of the improved method was 0. 5, 0. 4, 0. 5 mm, 0. 6° and 0. 5°, 33. 2 s taken on average. Conclusions Regarding smaller setup errors, the two methods showed little difference and both had good performance in imageregistration accuracy. For larger setup errors, however, the improved mutual information registration method exhibited significantly higher accuracy than the conventional method, at cost of clinically acceptable registration time.
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Objective To evaluate the effect of setup errors on the 2D image projection and image registration, and then propose an improved registration method based on mutual information. Methods An anthropomorphic head phantom was used to simulate the rotational and translational setup errors. The geometric disparities were reflected by the changes of mutual information. Known setup errors were intentionally introduced to twenty cases divided into two groups demarcated by 3 mm translation error and 3° rotation error: ten cases with larger errors and ten with smaller errors. Then the anterior-posterior and lateral portal images were captured by the electronic portal imaging device ( EPID ) , based on which the setup errors were calculated using two mutual information registration method respectively: the vender provided one, and the improved method as proposed. The calculated errors were compared with the actual setup errors to evaluate robustness of the method. Results For the ten cases with smaller setup errors, the average translational registration disparities using the conventional method were 0. 3, 0. 4, and 0. 3 mm in x, y and z directions respectively. The rotational disagreements were 0. 4° in both x and z directions. The average time consumption was 28. 7 s. The corresponding discrepancies analyzed using the improved method were 0. 3, 0. 4, 0. 3 mm, 0. 5° and 0. 4°, respectively. On average, 31. 1 s was needed for registration. For the ten cases with larger setup errors, the mean disparities of the conventional method were 0. 9, 0. 7, 0. 8 mm, 0. 9° and 0. 8°, 29. 9 s taken on average. The corresponding result of the improved method was 0. 5, 0. 4, 0. 5 mm, 0. 6° and 0. 5°, 33. 2 s taken on average. Conclusions Regarding smaller setup errors, the two methods showed little difference and both had good performance in imageregistration accuracy. For larger setup errors, however, the improved mutual information registration method exhibited significantly higher accuracy than the conventional method, at cost of clinically acceptable registration time.