A Novel Small Animal FLASH Irradiator (SAFI) Based On Distributed KV X-Ray Sources
Y Tan*, S Zhou, Q Chen, T Mazur, A Darafsheh, T Zhang, Washington University School of Medicine, St. Louis, MO
Presentations
WE-D-BRA-2 (Wednesday, 7/13/2022) 10:15 AM - 11:15 AM [Eastern Time (GMT-4)]
Ballroom A
Purpose: A small animal irradiator that can deliver FLASH-RT treatments similar to clinical RT treatments is needed for preclinical studies of FLASH-RT. We designed and optimized a novel small animal FLASH irradiator (SAFI) based on the distributed x-ray technology.
Methods: The SAFI system comprises a distributed x-ray source with 51 focal spots equally distributed on a 20 cm diameter ring, which are used for both FLASH-RT and inverse-geometry micro-CT imaging. In FLASH-RT mode, a custom-designed multi-aperture collimator (MAC) is positioned in the beam path, and all sources are activated simultaneously according the treatment plan. In imaging mode, the MAC is replaced with a small area detector and another imaging MAC that rotate about the animal together while the x-ray sources within the field-of-view are activated sequentially at each projection angle. Monte Carlo simulation was performed to characterize the dosimetric characteristics of the SAFI treatment beams. The system parameters necessary to achieve UHDR, including geometry, kVp, tube current, focal spot size, and beam-on duration, were determined. Inverse-geometry micro-CT acquisition was simulated, and the images were reconstructed using an iterative reconstruction algorithm.
Results: At 160 kVp, with 51 focal spots each in the dimension of 2×20 mm² and 10° anode angle, the SAFI system can produce up to 120 Gy/s maximum continuous (DC) irradiation at the center of a 4 cm cylindrical water phantom. The system can also deliver FLASH-RT in pulse mode with a greater instantaneous dose rate. The maximum doses that can be delivered in each pulse at different dose rates were determined using finite element thermal analysis. We further demonstrated forward and inverse FLASH-RT planning, as well as inverse-geometry micro-CT via numerical simulations.
Conclusion: The SAFI with integrated inverse-geometry micro-CT is capable of delivering conformal FLASH-RT to small animals.
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