Abstract 4153: Commissioning and radiobiological verification of the small animal radiotherapy research platform (SARRP)

Abstract

Preclinical radiation biology has become increasingly sophisticated due to the implementation of advanced small animal image guided radiation platforms into laboratory investigation. Small animal radiotherapy devices enable state-of-the-art image guided therapy (IGRT) research to be performed in small animal cancer models by combining high-resolution cone beam computed tomography (CBCT) imaging with an isocentric irradiation system. The technological evolution from simple, broad field irradiation configurations, to more sophisticated dose deliveries for preclinical radiobiology experiments has introduced new dosimetry challenges for preclinical small animal cancer research. Because of this, robust QA and dosimetry techniques are a key part of using novel treatment platforms using very small irradiation fields. In this study, we present a dosimetric study of the small animal radiotherapy research platform (SARRP, Xstrahl Inc.) focusing on the small field dosimetry. Physical dosimetry was assessed using ion chambers and radiochromic film, investigating the impact the beam focus size has on the dose rate output as well as beam characteristics (beam shape and penumbra variations). Two film reading modalities have been used to assess the dose output using the 0.5 mm diameter aperture. This study establishes that FilmQA Pro is a suitable tool for small field dosimetry, with a sufficiently small sampling area (0.1 mm) to ensure an accurate measurement. Furthermore, all small field dosimetry data generated in this study are equally comparable with our Monte Carlo simulations for both focal spot sizes. Overall, it was observed that the small focal spot, while having a lower dose-rate output was shown to produce a more stable and homogenous beam with minimum penumbra over time when compared to the larger focal spot. These findings suggest that when preclinical stereotactic irradiation fields are used, a practical compromise (time to deliver a desired dose and field homogeneity) needs to be considered when deciding the optimum treatment plan and beam configuration used. Citation Format: Jonathan L. Kane. Commissioning and radiobiological verification of the small animal radiotherapy research platform (SARRP) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4153.