S James^{1, 2}*, A Al-Basheer¹, E Elder^2,3,J Barrett¹, F Mostafaei¹, (1) Augusta University, Augusta, GA, (2) Georgia Institute of Technology (3) Emory University

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  S James

PO-GePV-T-357 (Sunday, 7/25/2021)   [Eastern Time (GMT-4)]

Purpose: The goal of this research is to compare commercial quality assurance (QA) devices to the EBTXD film dosimetry method for pre-treatment evaluation of stereotactic body radiation therapy(SBRT) & Intracranial stereotactic radiosurgery(SRS) treatment plans.

Methods: SBRT & SRS plans were created using IMRT or VMAT technique with varying target volumes (smallest volume of 11.98cc and largest of 40.01 cc) were created using Eclipse 15.6 treatment planning system. Plans were delivered using a Varian Edge LINAC and measured on QA devices at beam energies of 6 MV and 10 MV with and without flattening filter. The QA plans measured using EBTXD film on a 15cm solid water phantom and a A1SL ion chamber, SNC ArcCHECK (0.64mm2 detector area with 10mm spacing) and Varian DMI EPID. Results analyzed at 3%/3mm, 2%/2mm, 2%/1mm, and 1%/1mm for each QA method.

Results: EBTXD films were scanned using an Epson10000XL flatbed scanner and analyzed using RIT software and had average gamma analysis passing rates of 97.42%, 93.42%, 84.52%, and 76.07% for 3%/3mm, 2%/2mm, 2%/1mm, and 1%/1mm gamma criteria, respectively. The Varian DMI EPID produced an average gamma analysis passing rates of 99.46%, 99.90%, 99.29%, and 97.92% for 3%/3mm, 2%/2mm, 2%/1mm, and 1%/1mm gamma criteria, respectively. The SNC ArcCheck produced an average gamma analysis passing rates of 96.82%, 90.84%, 78.18%, and 70.80% for 3%/3mm, 2%/2mm, 2%/1mm, and 1%/1mm gamma criteria, respectively.

Conclusion: Passing rates decreased for all devices as gamma criteria becomes stricter. EBTXD film and ArcCHECK show agreement within 3.5% for 3%/3mm and 2%/2mm gamma criteria and begin to diverge from agreement as criteria becomes more stringent. In contrast, the EPID system resulted in high pass rates regardless of target size, modulation factor, and gamma criteria. To further study this topic, an SNC SRS MapCheck and IBA myQA SRS will also be used in the comparison.

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Keywords

Not Applicable / None Entered.

Taxonomy

TH- Radiation Dose Measurement Devices: diodes/solid state

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