Peter M McCowan1, Ganiyu Asuni2, Eric Van Uytven3, Timothy VanBeek2, Boyd M C McCurdy4, Shaun K Loewen5, Naseer Ahmed6, Bashir Bashir6, James B Butler6, Amitava Chowdhury6, Arbind Dubey6, Ahmet Leylek6, Maged Nashed6. 1. Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba, Canada. Electronic address: pmccowan@cancercare.mb.ca. 2. Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba, Canada. 3. Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba, Canada; Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada. 4. Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba, Canada; Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada; Department of Radiology, University of Manitoba, Winnipeg, Manitoba, Canada. 5. Department of Oncology, University of Calgary, Calgary, Alberta, Canada. 6. CancerCare Manitoba, Winnipeg, Manitoba, Canada.
Abstract
PURPOSE: To report findings from an in vivo dosimetry program implemented for all stereotactic body radiation therapy patients over a 31-month period and discuss the value and challenges of utilizing in vivo electronic portal imaging device (EPID) dosimetry clinically. METHODS AND MATERIALS: From December 2013 to July 2016, 117 stereotactic body radiation therapy-volumetric modulated arc therapy patients (100 lung, 15 spine, and 2 liver) underwent 602 EPID-based in vivo dose verification events. A developed model-based dose reconstruction algorithm calculates the 3-dimensional dose distribution to the patient by back-projecting the primary fluence measured by the EPID during treatment. The EPID frame-averaging was optimized in June 2015. For each treatment, a 3%/3-mm γ comparison between our EPID-derived dose and the Eclipse AcurosXB-predicted dose to the planning target volume (PTV) and the ≥20% isodose volume were performed. Alert levels were defined as γ pass rates <85% (lung and liver) and <80% (spine). Investigations were carried out for all fractions exceeding the alert level and were classified as follows: EPID-related, algorithmic, patient setup, anatomic change, or unknown/unidentified errors. RESULTS: The percentages of fractions exceeding the alert levels were 22.6% for lung before frame-average optimization and 8.0% for lung, 20.0% for spine, and 10.0% for liver after frame-average optimization. Overall, mean (± standard deviation) planning target volume γ pass rates were 90.7% ± 9.2%, 87.0% ± 9.3%, and 91.2% ± 3.4% for the lung, spine, and liver patients, respectively. CONCLUSIONS: Results from the clinical implementation of our model-based in vivo dose verification method using on-treatment EPID images is reported. The method is demonstrated to be valuable for routine clinical use for verifying delivered dose as well as for detecting errors.
PURPOSE: To report findings from an in vivo dosimetry program implemented for all stereotactic body radiation therapy patients over a 31-month period and discuss the value and challenges of utilizing in vivo electronic portal imaging device (EPID) dosimetry clinically. METHODS AND MATERIALS: From December 2013 to July 2016, 117 stereotactic body radiation therapy-volumetric modulated arc therapy patients (100 lung, 15 spine, and 2 liver) underwent 602 EPID-based in vivo dose verification events. A developed model-based dose reconstruction algorithm calculates the 3-dimensional dose distribution to the patient by back-projecting the primary fluence measured by the EPID during treatment. The EPID frame-averaging was optimized in June 2015. For each treatment, a 3%/3-mm γ comparison between our EPID-derived dose and the Eclipse AcurosXB-predicted dose to the planning target volume (PTV) and the ≥20% isodose volume were performed. Alert levels were defined as γ pass rates <85% (lung and liver) and <80% (spine). Investigations were carried out for all fractions exceeding the alert level and were classified as follows: EPID-related, algorithmic, patient setup, anatomic change, or unknown/unidentified errors. RESULTS: The percentages of fractions exceeding the alert levels were 22.6% for lung before frame-average optimization and 8.0% for lung, 20.0% for spine, and 10.0% for liver after frame-average optimization. Overall, mean (± standard deviation) planning target volume γ pass rates were 90.7% ± 9.2%, 87.0% ± 9.3%, and 91.2% ± 3.4% for the lung, spine, and liver patients, respectively. CONCLUSIONS: Results from the clinical implementation of our model-based in vivo dose verification method using on-treatment EPID images is reported. The method is demonstrated to be valuable for routine clinical use for verifying delivered dose as well as for detecting errors.
Authors: Igor Olaciregui-Ruiz; Julia-Maria Osinga-Blaettermann; Karen Ortega-Marin; Ben Mijnheer; Anton Mans Journal: Phys Imaging Radiat Oncol Date: 2022-04-14
Authors: Anton Mans; Roel Rozendaal; Tomas Janssen; Eugène Damen; Jochem Kaas; Anke van Mourik; Ben Mijnheer Journal: Phys Imaging Radiat Oncol Date: 2022-01-20