(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: Patient specific QA devices such as Arccheck have been used to perform QA measurements for IMRT plans and Vmat plans which may include plans using small fields such as SRT and SBRT plans. This study is to explore the field size limit that an Arccheck can be used to perform plan QA measurements.
Methods: An Arccheck phantom was used to measure output factors for small field sizes from 0.7x0.7cm² to 2x2 cm² for 6X and 6FFF beams for a True Beam linac and compared against the results measured with a microDiamond detector. The Arccheck readings were obtained from a single detector centered to the radiation fields. All output results were daisy-chain corrected.
Results: The output factors measured by Arccheck for 6X for 0.7, 1, 1.5 and 2 cm fields are 15.4%, 5.3%, 1.0% and 0.2% higher than those measured with a microDiamond detector. Those for 6FFF are 12.3%, 4.1%, 0.5% and 0% higher compared to microDiamond results.
Conclusion: Arccheck should be used for patient specific QA measurements for plans with field sizes no smaller than 1.5x1.5 cm². If field sizes are below this limit the response of detectors in the phantom will be too high and not acceptable. This approach can be used to evaluate similar patient specific QA products before they are used for plans with small fields.
Keywords
Small Fields, Treatment Verification
Taxonomy
TH- Radiation dose measurement devices: Multi-dimensional diode/chamber arrays
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