Initial characterization of a novel dual-robot orthovoltage radiotherapy system

Purpose:Adequate access to radiotherapy is a critical global concern affecting low-resource settings such as low- and middle-income countries and rural regions. We propose to reduce this disparity by developing a novel low-cost radiotherapy device that treats using non-coplanar techniques and a 225 kVp x-ray tube.Methods:This novel device has been preliminarily characterized spectrally, via spectrometer measurements, dosimetrically, via percent depth dose curves and 2D profiles, and geometrically, via a coplanar star-shot. Dosimetric and geometric evaluations were then combined by performing a proof of workflow of the KOALA system. Monte Carlo simulations were run in TOPAS to validate dosimetric measurements and the proof of workflow measurement.Results:Spectral results showed excellent agreement between measured and modelled spectra. Dose errors of  < 2% were achieved for PDD curves. Full width at half maximum values for the 2D profiles were, on average, 0.95 mm higher in simulation compared to film. A star-shot test demonstrated the high geometrical accuracy of the system with a 0.3 mm diameter wobble circle. Finally, a mean absolute percent error of 5  ±  5% (1σ) was measured for the proof of workflow test.Conclusions:This initial characterization showcased the strengths and weaknesses of the KOALA system, with excellent isocenter precision and depth dose accuracy while lacking dosimetric accuracy in the 2D profiles. Further improvements on the source-to-collimator distance and treatment couch material can be made to improve the accuracy of a Monte Carlo model of the KOALA system.