Use of a novel two-dimensional ionization chamber array for pencil beam scanning proton therapy beam quality assurance
| Autor: | Minglei Kang, C. Ainsley, Christian Baeumer, Liyong Lin, Timothy D. Solberg, Thierry Mertens, James McDonough |
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| Rok vydání: | 2015 |
| Předmět: |
Materials science
Quality Assurance Health Care Medizin quality assurance Sensitivity and Specificity Imaging phantom Radiotherapy High-Energy Optics Ionization Proton Therapy Radiation Oncology Physics Radiology Nuclear Medicine and imaging PBS Radiometry Pencil-beam scanning Instrumentation Proton therapy Radiation business.industry Detector Australia Reproducibility of Results Radiotherapy Dosage Equipment Design recombination Equipment Failure Analysis Ionization chamber Laser beam quality business Beam (structure) |
| Zdroj: | Journal of Applied Clinical Medical Physics |
| ISSN: | 1526-9914 |
| DOI: | 10.1120/jacmp.v16i3.5323 |
| Popis: | The need to accurately and efficiently verify both output and dose profiles creates significant challenges in quality assurance of pencil beam scanning (PBS) proton delivery. A system for PBS QA has been developed that combines a new two-dimensional ionization chamber array in a waterproof housing that is scanned in a water phantom. The MatriXX PT has the same detector array arrangement as the standard math formula but utilizes a smaller 2 mm plate spacing instead of 5 mm. Because the bias voltage of the MatriXX PT and Evolution cannot be changed, PPC40 and FC65-G ionization chambers were used to assess recombination effects. The PPC40 is a parallel plate chamber with an electrode spacing of 2 mm, while the FC65-G is a Farmer chamber FC65-G with an electrode spacing of 2.8 mm. Three bias voltages (500, 200, and 100 V) were used for both detectors to determine which radiation type (continuous, pulse or pulse-scanned beam) could closely estimate math formula from the ratios of charges collected. In comparison with the math formula, a significant improvement in measurement of absolute dose with the MatriXX PT was observed. While dose uncertainty of the math formula can be up to 4%, it is math formula for the MatriXX PT. Therefore the math formula should not be used for QA of PBS for conditions in which ion recombination is not negligible. Farmer chambers should be used with caution for measuring the absolute dose of PBS beams, as the uncertainty of math formula can be math formula; chambers with an electrode spacing of 2 mm or smaller are recommended. PACS number: 87.53.Qc OA gold |
| Databáze: | OpenAIRE |
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