Carles Muñoz-Montplet1, Jordi Marruecos2, Maria Buxó3, Diego Jurado-Bruggeman4, Ingrid Romera-Martínez5, Marta Bueno6, Joan C Vilanova7. 1. Medical Physics and Radiation Protection Department, Institut Català d'Oncologia, Avda. França s/n, 17007 Girona, Spain; Department of Medical Sciences, University of Girona, C/Emili Grahit 77, 17003 Girona, Spain. Electronic address: cmunoz@iconcologia.net. 2. Department of Medical Sciences, University of Girona, C/Emili Grahit 77, 17003 Girona, Spain; Radiation Oncology Department, Institut Català d'Oncologia, Avda. França s/n, 17007 Girona, Spain. Electronic address: jmarruecos@iconcologia.net. 3. Girona Biomedical Research Institute (IDIBGI), Parc Hospitalari Martí i Julià, Edifici M2, Salt, 17190 Girona, Spain. Electronic address: mbuxo@idibgi.org. 4. Medical Physics and Radiation Protection Department, Institut Català d'Oncologia, Avda. França s/n, 17007 Girona, Spain. Electronic address: djurado@iconcologia.net. 5. Medical Physics and Radiation Protection Department, Institut Català d'Oncologia, Avda. França s/n, 17007 Girona, Spain. Electronic address: iromera@iconcologia.net. 6. Laboratoire de dosimétrie des rayonnements ionisants, Institut de Radioprotection et de Sûreté Nucléaire, 31 Avenue de la Division Leclerc, 92260 Fontenay-aux-Roses, France. Electronic address: marteta.3@gmail.com. 7. Department of Medical Sciences, University of Girona, C/Emili Grahit 77, 17003 Girona, Spain; Department of Radiology, Clínica Girona, Institut de Diagnòstic per la Imatge, C/Lorenzana 36, 17002 Girona, Spain. Electronic address: kvilanova@comg.cat.
Abstract
PURPOSE: To assess the dosimetric impact of switching from the Analytical Anisotropic Algorithm (AAA) to Acuros XB (AXB) for both dose-to-medium (Dm) and dose-to-water (Dw) in VMAT for H&N patients. To study whether it should be linked to a change in the dose prescriptions to the PTVs and in the constraints to the OARs. METHODS: 110H&N patients treated with VMAT were included. Calculations were performed with AAA and AXB. PTV54, PTV60, PTV70, spinal cord, brainstem, brain, larynx, oral cavity, cochleas, parotid glands and mandible were delineated. Clinically-relevant dose-volume parameters were compared. Paired t-tests were used to analyze the differences in mean values. The Pitman-Morgan dispersion test was computed to evaluate inter-patient variability of these differences. RESULTS: AAA overestimated all dose-volume parameters compared to AXB Dm (0.2 Gy to 2.4 Gy). No systematic trend was observed in the differences between AAA and AXB Dw (-5.3 Gy to 0.6 Gy). Dose-volume parameters were significantly higher for AXB Dw compared to AXB Dm (0.1 Gy to 6.6 Gy). In all cases, the largest absolute differences (4%-14%) were found for maximum absorbed doses to the cochleas and the mandible. The number of parameters with significant inter-patient variability was greater when switching from AAA to AXB Dw than from AAA to AXB Dm. CONCLUSIONS: There are important differences between AXB and AAA in VMAT planning for H&N cancer. The systematic differences and their inter-patient variability identified may help to facilitate decision-making about the dose prescriptions to the PTVs and the constraints to the OAR.
PURPOSE: To assess the dosimetric impact of switching from the Analytical Anisotropic Algorithm (AAA) to Acuros XB (AXB) for both dose-to-medium (Dm) and dose-to-water (Dw) in VMAT for H&N patients. To study whether it should be linked to a change in the dose prescriptions to the PTVs and in the constraints to the OARs. METHODS: 110H&N patients treated with VMAT were included. Calculations were performed with AAA and AXB. PTV54, PTV60, PTV70, spinal cord, brainstem, brain, larynx, oral cavity, cochleas, parotid glands and mandible were delineated. Clinically-relevant dose-volume parameters were compared. Paired t-tests were used to analyze the differences in mean values. The Pitman-Morgan dispersion test was computed to evaluate inter-patient variability of these differences. RESULTS:AAA overestimated all dose-volume parameters compared to AXBDm (0.2 Gy to 2.4 Gy). No systematic trend was observed in the differences between AAA and AXB Dw (-5.3 Gy to 0.6 Gy). Dose-volume parameters were significantly higher for AXB Dw compared to AXBDm (0.1 Gy to 6.6 Gy). In all cases, the largest absolute differences (4%-14%) were found for maximum absorbed doses to the cochleas and the mandible. The number of parameters with significant inter-patient variability was greater when switching from AAA to AXB Dw than from AAA to AXBDm. CONCLUSIONS: There are important differences between AXB and AAA in VMAT planning for H&N cancer. The systematic differences and their inter-patient variability identified may help to facilitate decision-making about the dose prescriptions to the PTVs and the constraints to the OAR.
Authors: Vladimir Feygelman; Kujtim Latifi; Mark Bowers; Kevin Greco; Eduardo G Moros; Max Isacson; Agnes Angerud; Jimmy Caudell Journal: J Appl Clin Med Phys Date: 2022-02-25 Impact factor: 2.243