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Practical approach for pretreatment verification of IMRT with flattening filter‐free (FFF) beams using Varian portal dosimetry
Patient‐specific pretreatment verification of intensity‐modulated radiation therapy (IMRT) or volumetric‐modulated arc therapy (VMAT) is strongly recommended for all patients in order to detect any potential errors in treatment planning process and machine deliverability, and is thus performed routi...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5689987/ https://www.ncbi.nlm.nih.gov/pubmed/25679149 http://dx.doi.org/10.1120/jacmp.v16i1.4934 |
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author | Min, Soonki Choi, Young Eun Kwak, Jungwon Cho, Byungchul |
author_facet | Min, Soonki Choi, Young Eun Kwak, Jungwon Cho, Byungchul |
author_sort | Min, Soonki |
collection | PubMed |
description | Patient‐specific pretreatment verification of intensity‐modulated radiation therapy (IMRT) or volumetric‐modulated arc therapy (VMAT) is strongly recommended for all patients in order to detect any potential errors in treatment planning process and machine deliverability, and is thus performed routinely in many clinics. Portal dosimetry is an effective method for this purpose because of its prompt setup, easy data acquisition, and high spatial resolution. However, portal dosimetry cannot be applied to IMRT or VMAT with flattening filter‐free (FFF) beams because of the high dose‐rate saturation effect of the electronic portal imaging device (EPID). In our current report, we suggest a practical QA method of expanding the conventional portal dosimetry to FFF beams with a QA plan generated by the following three steps: 1) replace the FFF beams with flattening filtered (FF) beams of the same nominal energy; 2) reduce the dose rate to avoid the saturation effect of the EPID detector; and 3) adjust the total MU to match the gantry and MLC leaf motions. Two RapidArc plans with 6 and 10 MV FFF beams were selected, and QA plans were created by the aforementioned steps and delivered. The trajectory log files of TrueBeam obtained during the treatment and during the delivery of QA plan were analyzed and compared. The maximum discrepancies in the expected trajectories between the treatment and QA plans were within 0.002 MU for the MU, 0.06° for the motion of gantry rotation, and 0.006 mm for the positions of the MLC leaves, indicating much higher levels of accuracy compared to the mechanical specifications of the machine. For further validation of the method, direct comparisons of the delivered QA FF beam to the treatment FFF beam were performed using film dosimetry and show that gamma passing rates under 2%/2 mm criteria are 99.0%–100% for the all four arc beams. This method can be used on RapidArc plans with FFF beams without any additional procedure or modifications on the conventional portal dosimetry of IMRT and is, therefore, a practical option for routine clinical use. PACS numbers: 87.53.Kn, 87.55.T‐, 87.56.bd, 87.59.‐e |
format | Online Article Text |
id | pubmed-5689987 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-56899872018-04-02 Practical approach for pretreatment verification of IMRT with flattening filter‐free (FFF) beams using Varian portal dosimetry Min, Soonki Choi, Young Eun Kwak, Jungwon Cho, Byungchul J Appl Clin Med Phys Radiation Oncology Physics Patient‐specific pretreatment verification of intensity‐modulated radiation therapy (IMRT) or volumetric‐modulated arc therapy (VMAT) is strongly recommended for all patients in order to detect any potential errors in treatment planning process and machine deliverability, and is thus performed routinely in many clinics. Portal dosimetry is an effective method for this purpose because of its prompt setup, easy data acquisition, and high spatial resolution. However, portal dosimetry cannot be applied to IMRT or VMAT with flattening filter‐free (FFF) beams because of the high dose‐rate saturation effect of the electronic portal imaging device (EPID). In our current report, we suggest a practical QA method of expanding the conventional portal dosimetry to FFF beams with a QA plan generated by the following three steps: 1) replace the FFF beams with flattening filtered (FF) beams of the same nominal energy; 2) reduce the dose rate to avoid the saturation effect of the EPID detector; and 3) adjust the total MU to match the gantry and MLC leaf motions. Two RapidArc plans with 6 and 10 MV FFF beams were selected, and QA plans were created by the aforementioned steps and delivered. The trajectory log files of TrueBeam obtained during the treatment and during the delivery of QA plan were analyzed and compared. The maximum discrepancies in the expected trajectories between the treatment and QA plans were within 0.002 MU for the MU, 0.06° for the motion of gantry rotation, and 0.006 mm for the positions of the MLC leaves, indicating much higher levels of accuracy compared to the mechanical specifications of the machine. For further validation of the method, direct comparisons of the delivered QA FF beam to the treatment FFF beam were performed using film dosimetry and show that gamma passing rates under 2%/2 mm criteria are 99.0%–100% for the all four arc beams. This method can be used on RapidArc plans with FFF beams without any additional procedure or modifications on the conventional portal dosimetry of IMRT and is, therefore, a practical option for routine clinical use. PACS numbers: 87.53.Kn, 87.55.T‐, 87.56.bd, 87.59.‐e John Wiley and Sons Inc. 2014-01-08 /pmc/articles/PMC5689987/ /pubmed/25679149 http://dx.doi.org/10.1120/jacmp.v16i1.4934 Text en © 2015 The Authors. This is an open access article under the terms of the Creative Commons Attribution (http://creativecommons.org/licenses/by/3.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Radiation Oncology Physics Min, Soonki Choi, Young Eun Kwak, Jungwon Cho, Byungchul Practical approach for pretreatment verification of IMRT with flattening filter‐free (FFF) beams using Varian portal dosimetry |
title | Practical approach for pretreatment verification of IMRT with flattening filter‐free (FFF) beams using Varian portal dosimetry |
title_full | Practical approach for pretreatment verification of IMRT with flattening filter‐free (FFF) beams using Varian portal dosimetry |
title_fullStr | Practical approach for pretreatment verification of IMRT with flattening filter‐free (FFF) beams using Varian portal dosimetry |
title_full_unstemmed | Practical approach for pretreatment verification of IMRT with flattening filter‐free (FFF) beams using Varian portal dosimetry |
title_short | Practical approach for pretreatment verification of IMRT with flattening filter‐free (FFF) beams using Varian portal dosimetry |
title_sort | practical approach for pretreatment verification of imrt with flattening filter‐free (fff) beams using varian portal dosimetry |
topic | Radiation Oncology Physics |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5689987/ https://www.ncbi.nlm.nih.gov/pubmed/25679149 http://dx.doi.org/10.1120/jacmp.v16i1.4934 |
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