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Commissioning of An Xstrahl SARRP in the Novel Micro-RayStation Treatment Planning System

Y Poirier1*, A Anvari1,2, R Nilsson3, A Gerry1, C Johnstone1,4, A Sawant1, (1) University of Maryland School of Medicine, Baltimore, MD, (2) University of Pennsylvania Health System, Philadelphia, PA, (3) RaySearch Laboratories, Stockholm, SE, (4) Princess Margaret Cancer Centre, Toronto, ON, CA

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose:
We commissioned an Xstrahl small animal radiation research platform (SARRP) in µ-RayStation, the first commercially available third-party treatment planning system (TPS) for image-guided small animal irradiators. Unlike manufacturer specific TPS typically commissioned solely by the provider and where few parameters can be modified, µ-RayStation is applicable to any small animal system and can be commissioned according to the Physicist’s customized needs for specific scenarios.

Methods:
Dose distributions for the 220 kVp therapy beam were measured with EBT3 Gafchromic film in the manufacturer’s solid water commissioning jig (~5×5×10 cm³) at depths of 0-8 cm for the 3×3, 5×5, 10×10 mm² standard square applicators at 303.0, 328.3, and 353.3 mm source-to-surface distances. The SARRP spectrum was modeled using SpekCalc to match our 0.58 mm Cu HVL measurements. Literature values confirmed by caliper measurements were used for physical dimensions of the collimator assembly. Dose distributions were calculated in µ-RayStation in a simulated water phantom using a 0.1-0.2 mm grid resolution, 20 million particles/mm², and exported in DICOM-RT format where an in-house MATLAB script extracted central axis depth dose and lateral profiles. The calculated dose distributions were compared to film measurements and used to adjust the µ-RayStation beam model for best agreement.

Results:
Agreement between measured and calculated percent depth dose profiles were within ±3% for all 9 datasets, well within the measurement uncertainty of EBT3 Gafchromic film (2 SD = ±6%). Once normalized to CAX, profiles agreed within 4%/0.15 mm. The generated spectrum was sufficient to commission the SARRP, although best results were obtained with an inner collimator offset by 0.7 mm and tweaked collimator sizes.

Conclusion:
This study represents the first reported commissioning of a commercial third-party clinical TPS at kV energies for the Xstrahl SARRP. Future studies will validate the TPS in heterogeneous geometries, imaging energies, and for TBI.

Download ePoster [PDF]

Funding Support, Disclosures, and Conflict of Interest: This project is possible due to a Material Transfers Agreement between the University of Maryland and RaySearch laboratories where access to the micro-RayStation treatment planning system was provided to the University of Maryland in exchange for technical assistance in commissioning the beam model of the Xstrahl SARRP.

Keywords

Commissioning, Treatment Planning, Radiobiology

Taxonomy

TH- Small Animal RT: Development (new technology and techniques)

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