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Use of a commercial ion chamber detector array for the measurement of high spatial‐resolution photon beam profiles

Linear accelerator (linac) commissioning and quality assurance measurements are time‐consuming tasks that often require a water tank scanning system to acquire profile scans for full characterization of dosimetric beam properties. To increase efficiency, a method is demonstrated to acquire variable...

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Autores principales: Karimnia, Vida, Belley, Matthew D., Rodgers, Robert, Price, Michael
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6236837/
https://www.ncbi.nlm.nih.gov/pubmed/30284378
http://dx.doi.org/10.1002/acm2.12466
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author Karimnia, Vida
Belley, Matthew D.
Rodgers, Robert
Price, Michael
author_facet Karimnia, Vida
Belley, Matthew D.
Rodgers, Robert
Price, Michael
author_sort Karimnia, Vida
collection PubMed
description Linear accelerator (linac) commissioning and quality assurance measurements are time‐consuming tasks that often require a water tank scanning system to acquire profile scans for full characterization of dosimetric beam properties. To increase efficiency, a method is demonstrated to acquire variable resolution, photon beam profile data using a commercially available ion chamber array (0.5 cm detector spacing). Field sizes of 2 × 2, 5 × 5, 10 × 10, and 15 × 15 cm(2) were acquired at depths in solid water of d (max), 5 cm, and 10 cm; additionally, beam profiles for field sizes of 25 × 25 and 40 × 40 cm(2) were acquired at 5 cm depth in solid water at x‐ray energies of 6 and 23 MV. 1D composite profiles were generated by combining discrete point measurements made at multiple couch positions. The 1D composite profile dataset was evaluated against a commissioning dataset acquired with a 3D water tank scan system utilizing (a) 0.125 cc ion chamber for 5 × 5, 10 × 10, 15 × 15, 25 × 25, and 40 × 40 field sizes and (b) a solid state detector for 2 × 2 cm(2) field size. The two datasets were compared to the gamma criteria at 1%/1 mm and 2%/2 mm tolerance. Almost all pass rates exceeded 95% at 2%/2 mm except for the 6 MV 2 × 2 cm(2) field size at d (max). Pass rates at 1%/1 mm ranged from 51% to 99%, with an average pass rate of 82%. A fourfold reduction in MU was achieved for scans larger than 15 × 15 cm(2) using this method compared to the water tank scans. Further, dynamic wedge measurements acquired with the ion chamber array showed reasonable agreement with the treatment planning system. This method opens up new possibilities for rapid acquisition of variable resolution 2D–3D dosimetric data mitigating the need for acquiring all scan data with in‐water measurements.
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spelling pubmed-62368372018-11-20 Use of a commercial ion chamber detector array for the measurement of high spatial‐resolution photon beam profiles Karimnia, Vida Belley, Matthew D. Rodgers, Robert Price, Michael J Appl Clin Med Phys Technical Notes Linear accelerator (linac) commissioning and quality assurance measurements are time‐consuming tasks that often require a water tank scanning system to acquire profile scans for full characterization of dosimetric beam properties. To increase efficiency, a method is demonstrated to acquire variable resolution, photon beam profile data using a commercially available ion chamber array (0.5 cm detector spacing). Field sizes of 2 × 2, 5 × 5, 10 × 10, and 15 × 15 cm(2) were acquired at depths in solid water of d (max), 5 cm, and 10 cm; additionally, beam profiles for field sizes of 25 × 25 and 40 × 40 cm(2) were acquired at 5 cm depth in solid water at x‐ray energies of 6 and 23 MV. 1D composite profiles were generated by combining discrete point measurements made at multiple couch positions. The 1D composite profile dataset was evaluated against a commissioning dataset acquired with a 3D water tank scan system utilizing (a) 0.125 cc ion chamber for 5 × 5, 10 × 10, 15 × 15, 25 × 25, and 40 × 40 field sizes and (b) a solid state detector for 2 × 2 cm(2) field size. The two datasets were compared to the gamma criteria at 1%/1 mm and 2%/2 mm tolerance. Almost all pass rates exceeded 95% at 2%/2 mm except for the 6 MV 2 × 2 cm(2) field size at d (max). Pass rates at 1%/1 mm ranged from 51% to 99%, with an average pass rate of 82%. A fourfold reduction in MU was achieved for scans larger than 15 × 15 cm(2) using this method compared to the water tank scans. Further, dynamic wedge measurements acquired with the ion chamber array showed reasonable agreement with the treatment planning system. This method opens up new possibilities for rapid acquisition of variable resolution 2D–3D dosimetric data mitigating the need for acquiring all scan data with in‐water measurements. John Wiley and Sons Inc. 2018-10-04 /pmc/articles/PMC6236837/ /pubmed/30284378 http://dx.doi.org/10.1002/acm2.12466 Text en © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Technical Notes
Karimnia, Vida
Belley, Matthew D.
Rodgers, Robert
Price, Michael
Use of a commercial ion chamber detector array for the measurement of high spatial‐resolution photon beam profiles
title Use of a commercial ion chamber detector array for the measurement of high spatial‐resolution photon beam profiles
title_full Use of a commercial ion chamber detector array for the measurement of high spatial‐resolution photon beam profiles
title_fullStr Use of a commercial ion chamber detector array for the measurement of high spatial‐resolution photon beam profiles
title_full_unstemmed Use of a commercial ion chamber detector array for the measurement of high spatial‐resolution photon beam profiles
title_short Use of a commercial ion chamber detector array for the measurement of high spatial‐resolution photon beam profiles
title_sort use of a commercial ion chamber detector array for the measurement of high spatial‐resolution photon beam profiles
topic Technical Notes
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6236837/
https://www.ncbi.nlm.nih.gov/pubmed/30284378
http://dx.doi.org/10.1002/acm2.12466
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