Scott B Crowe1, Bess Sutherland2, Rachael Wilks3, Venkatakrishnan Seshadri4, Steven Sylvander3, Jamie V Trapp5, Tanya Kairn6. 1. Royal Brisbane and Women's Hospital, Butterfield Street, Herston QLD 4029, Australia and Science and Engineering Faculty, Queensland University of Technology, 2 George Street, Brisbane QLD 4000, Australia. 2. Genesis Cancer Care Queensland, 1/40 Chasely Street, Auchenflower QLD 4066, Australia. 3. Royal Brisbane and Women's Hospital, Butterfield Street, Herston QLD 4029, Australia. 4. Princess Alexandra Hospital, 199 Ipswich Road, Woolloongabba QLD 4102, Australia. 5. Science and Engineering Faculty, Queensland University of Technology, 2 George Street, Brisbane QLD 4000, Australia. 6. Genesis Cancer Care Queensland, 1/40 Chasely Street, Auchenflower QLD 4066, Australia and Science and Engineering Faculty, Queensland University of Technology, 2 George Street, Brisbane QLD 4000, Australia.
Abstract
PURPOSE: The aim of this work was to use a multicenter audit of modulated radiotherapy quality assurance (QA) data to provide a practical examination of gamma evaluation criteria and action level selection. The use of the gamma evaluation method for patient-specific pretreatment QA is widespread, with most commercial solutions implementing the method. METHODS: Gamma agreement indices were calculated using the criteria 1%/1 mm, 2%/2 mm, 2%/3 mm, 3%/2 mm, 3%/3 mm, and 5%/3 mm for 1265 pretreatment QA measurements, planned at seven treatment centers, using four different treatment planning systems, delivered using three different delivery systems (intensity-modulated radiation therapy, volumetric-modulated arc therapy, and helical tomotherapy) and measured using three different dose measurement systems. The sensitivity of each pair of gamma criteria was evaluated relative to the gamma agreement indices calculated using 3%/3 mm. RESULTS: A linear relationship was observed for 2%/2 mm, 2%/3 mm, and 3%/2 mm. This result implies that most beams failing at 3%/3 mm would also fail for those criteria, if the action level was adjusted appropriately. Some borderline plans might be passed or failed depending on the relative priority (tighter tolerance) used for dose difference or distance to agreement evaluation. Dosimeter resolution and treatment modality were found to have a smaller effect on the results of QA measurements than the number of dimensions (2D or 3D) over which the gamma evaluation was calculated. CONCLUSIONS: This work provides a method (and a large sample of results) for calculating equivalent action levels for different gamma evaluation criteria. This work constitutes a valuable guide for clinical decision making and a means to compare published gamma evaluation results from studies using different evaluation criteria. More generally, the data provided by this work support the recommendation that gamma criteria that specifically prioritize the property of greatest clinical importance for each treatment modality of anatomical site should be selected when using gamma evaluations for modulated radiotherapy QA. It is therefore suggested that departments using the gamma evaluation as a QA analysis tool should consider the relative importance of dose difference and distance to agreement, when selecting gamma evaluation criteria.
PURPOSE: The aim of this work was to use a multicenter audit of modulated radiotherapy quality assurance (QA) data to provide a practical examination of gamma evaluation criteria and action level selection. The use of the gamma evaluation method for patient-specific pretreatment QA is widespread, with most commercial solutions implementing the method. METHODS: Gamma agreement indices were calculated using the criteria 1%/1 mm, 2%/2 mm, 2%/3 mm, 3%/2 mm, 3%/3 mm, and 5%/3 mm for 1265 pretreatment QA measurements, planned at seven treatment centers, using four different treatment planning systems, delivered using three different delivery systems (intensity-modulated radiation therapy, volumetric-modulated arc therapy, and helical tomotherapy) and measured using three different dose measurement systems. The sensitivity of each pair of gamma criteria was evaluated relative to the gamma agreement indices calculated using 3%/3 mm. RESULTS: A linear relationship was observed for 2%/2 mm, 2%/3 mm, and 3%/2 mm. This result implies that most beams failing at 3%/3 mm would also fail for those criteria, if the action level was adjusted appropriately. Some borderline plans might be passed or failed depending on the relative priority (tighter tolerance) used for dose difference or distance to agreement evaluation. Dosimeter resolution and treatment modality were found to have a smaller effect on the results of QA measurements than the number of dimensions (2D or 3D) over which the gamma evaluation was calculated. CONCLUSIONS: This work provides a method (and a large sample of results) for calculating equivalent action levels for different gamma evaluation criteria. This work constitutes a valuable guide for clinical decision making and a means to compare published gamma evaluation results from studies using different evaluation criteria. More generally, the data provided by this work support the recommendation that gamma criteria that specifically prioritize the property of greatest clinical importance for each treatment modality of anatomical site should be selected when using gamma evaluations for modulated radiotherapy QA. It is therefore suggested that departments using the gamma evaluation as a QA analysis tool should consider the relative importance of dose difference and distance to agreement, when selecting gamma evaluation criteria.
Authors: Bryce C Allred; Jie Shan; Daniel G Robertson; Todd A DeWees; Jiajian Shen; Wei Liu; Joshua B Stoker Journal: J Appl Clin Med Phys Date: 2021-03-29 Impact factor: 2.102
Authors: Michela Esposito; Chris Waltham; Jonathan T Taylor; Sam Manger; Ben Phoenix; Tony Price; Gavin Poludniowski; Stuart Green; Philip M Evans; Philip P Allport; Spyros Manolopulos; Jaime Nieto-Camero; Julyan Symons; Nigel M Allinson Journal: Phys Med Date: 2018-11-09 Impact factor: 2.685
Authors: Liting Yu; Timothy L S Tang; Naasiha Cassim; Alexander Livingstone; Darren Cassidy; Tanya Kairn; Scott B Crowe Journal: J Appl Clin Med Phys Date: 2019-10-15 Impact factor: 2.102