G Cui*, J Duan, F Yin, Duke University Medical Center, Durham, NC

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  G Cui

PO-GePV-T-377 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

ePoster Forums

Purpose: Current pre-treatment verification of single-isocenter multiple-target (SIMT) SRS plans typically checks one to two targets in 2D measurement, which can lead to “false positive” results because not all targets are verified. It is ideal to verify all targets but would be time-consuming. It is also challenging to verify in 3D fashion due to limitations in measurement devices. This study explored a Monte Carlo (MC)-powered verification tool that enables 3D gamma analysis of each target and comparative DVH review in SIMT SRS plans.

Methods: MyQA iON software (IBA Dosimetry GmbH, Schwarzenbruck, Germany) was explored for this purpose. It provides an independent secondary 3D dose based on MC calculation. It compares the MC dose map and that of a treatment planning system (TPS) and gives the dose map difference, as well as 3D gamma analysis of each target. Twelve SIMT SRS plans with 37 targets were tested. All plans were created in the Eclipse TPS (Varian Medical systems, Palo Alto, CA) using 6 MV flattening filter free photon beam. The 3D gamma index analysis was performed for each individual target as well as the plan using 3%/2 mm criteria with a 10% dose threshold. The mean dose to each target was extracted from the DVH and compared between the MC and TPS.

Results: The 3D gamma passing rates for all 37 targets range from 61.2% to 100%. The average gamma-passing rate for all targets is 95.6%, while that for 12 plans is 99.8%. The mean and standard deviation of the percentage difference of the mean dose to individual target between the MC and TPS is (-3.6 ± 1.8)%.

Conclusion: MyQA iON software was explored for pre-treatment verification of SIMT SRS plans. It is shown to be promising for 3D plan QA but needs to be further evaluated for individual target analysis.

Funding Support, Disclosures, and Conflict of Interest: This study is partially funded by IBA Dosimetry GmbH (Schwarzenbruck, Germany).

Keywords

Stereotactic Radiosurgery, Quality Assurance, Monte Carlo

Taxonomy

TH- External Beam- Photons: intracranial stereotactic/SBRT

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