Development of a 3D-printed canine head phantom for veterinary radiotherapy.

The goal of this work was to develop the Ultimate Phantom Dog for Orthovoltage Glioma treatment (UPDOG), an anatomical canine head phantom for quality assurance (QA) tests of kilovoltage (kV) radiotherapy treatments. A computed tomography (CT) scan of a canine glioma patient was segmented into bone and soft tissue then converted to stereolithographic files and smoothed. A slit to accommodate a radiochromic film (RCF) was added at the location of the tumor. UPDOG was 3D printed using soft tissue and bone-equivalent materials. CT scans of UPDOG were acquired on a clinical CT scanner. An RCF was irradiated with a kV x-ray source from two angles, with the measured dose compared to Monte Carlo (MC) simulations. The contrast between bone and soft tissue was 49, 47 and 50 HU for the 80, 100, and 120 kVp scans, respectively. Irradiations delivered a maximum dose of 284 mGy to the RCF. Along the depth dose curve a mean absolute difference of 3.3 ± 3.3% was measured. Along 1-D dose profiles, a mean peak absolute difference of 2% was measured with a 1.9 mm larger full width at half maximum on the RCF. We have demonstrated that UPDOG is a useful QA tool for kV canine radiotherapy. UPDOG successfully mimicked the dog anatomy with a reduced but measurable bone contrast. Similarly, the dose delivered to the tumor can be successfully measured with an RCF with acceptable dose accuracy along the central axis.