Comparison of Commercial Pre-Treatment QA Devices for Stereotactic Radiotherapy Plans

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James, Shands
Mostafaei, Farshad
Wang, C.-K. Chris
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Stereotactic radiotherapy methods have become common for the treatment of small tumors in various parts of the body. Small field dosimetry has a unique set of challenges when it comes to the pre-treatment validation of a radiotherapy plan that involves film dosimetry or high-resolution detectors. Film dosimetry is a cost effective method that provides superior spatial resolution in comparison to ion chamber matrices and high-resolution diode arrays. However, film dosimetry is work and time intensive. Alternatives to film dosimetry are devices such as the Sun Nuclear Corporation (SNC) SRS MapCheck, SNC ArcCheck, IBA Matrixx Resolution, the Varian Edge DMI Electronic Portal Imaging Device, and the IBA myQA SRS detector. The goal of this research is to compare commercial quality assurance devices to the film dosimetry method for pre-treatment evaluation of stereotactic radiosurgery, fractionated stereotactic radiotherapy, and stereotactic body radiation therapy treatment plans. Forty stereotactic treatment plans that were planned using volumetric modulated arc therapy (VMAT) or intensity modulated radiotherapy (IMRT) technique with 6x, 6xFFF, 10x, or 10xFFF beam energies for various treatment sites. EBT-XD films were analyzed by RIT software and the commercial devices QA data were analyzed using gamma analysis criteria of 3%/3mm DTA, 2%/2mm DTA, 2%/1mm DTA, and 1%/1 mm DTA using the device's software. The results of the commercial devices are compared to the EBT-XD film dosimetry results for each gamma criteria. Treatment plan characteristics such as modulation factor and target volume were investigated for correlation with the passing rate on these devices.
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