Purpose: Preclinical studies in radiation oncology have a major impact on the design of human clinical trials. Accordingly, similar standards are required to ensure reliable and reproducible workflow and dose delivery for preclinical irradiations on murine subjects. Here we present findings from our four year experience on daily, weekly, monthly, and annual quality assurance (QA) of an orthovoltage preclinical small animal radiation research platform (SARRP, Xstrahl).
Methods: Irradiations on the SARRP can be performed both in vitro and in vivo, with the latter being implemented as image-guided radiation therapy (IGRT) using the integrated cone beam computed tomography system (CBCT). Thus, QA tasks are performed three-fold: (i) Radiation dosimetry is measured using two independent systems using ion chamber and EBT3 radiochromic films. (ii) Geometric and mechanical accuracy tests are performed to evaluate alignment and targeting of a region of interest on the couch with CBCT, radiation beam, and the setup lasers. (iii) Imaging quality parameters are assessed in terms of spatial resolution.
Results: Dosimetric output constancy measurements showed monthly variations within 2.5% over a course of four years. A cross-check to a clinical 6MV beam showed a difference of 1.1% to the SARRP beam. Dosimetric characteristics of the different collimators - including percentage depth dose (PDD), beam profile, symmetry, and flatness - were found consistent with results obtained at commissioning. Geometric and mechanical accuracy are confirmed on a weekly basis. Imaging QA revealed a slow decline in spatial resolution over time, which was corrected by a CBCT calibration resulting in improved image quality compared to commissioning.
Conclusion: The results showed the successful implementation and importance of rigorous QA for preclinical irradiators. Solutions for challenges associated with implementation of clinical protocols on preclinical irradiators, which often operate on different energies and differ in their physical setup, are highlighted.
Not Applicable / None Entered.