M Rezaee*, J Wong, Johns Hopkins University, School of Medicine, Department of Radiation Oncology and Molecular Radiation Sciences, Baltimore, MD

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  M Rezaee

PO-GePV-T-177 (Sunday, 7/25/2021)   [Eastern Time (GMT-4)]

Purpose: Recent trend of preclinical research on highly conformal radiotherapy, motion management, and FLASH irradiation compels the need for a new generation of advanced preclinical irradiation system. Here, we study the feasibility of a novel x-ray irradiation cabinet system employing medical imaging x-ray sources with rotating anode technology, as an enabling technology to enhance preclinical research capabilities.

Methods: The proposed system employs two commercially available high-capacity 150kVp fluoroscopy x-ray sources with rotating anode technology. The tubes have independent gantry rotational and radial motions. Simulation was performed for parallel-opposed and angled beam arrangements with Geant4 (v.10.04) Monte-Carlo platform. Simulated dosimetric properties were characterized for output, uniformity and field size as a function of SSD, beam current, exposure time, and filters. Additionally, dose, dose-rate, and cross-plane profiles were measured from a single kV x-ray fluoroscopy source using radiochromic films to validate the Monte-Carlo models.

Results: The irradiator can deliver FLASH and conventional dose-rate irradiations with the fields of 25-200 mm in length. Doses over 50 Gy can be delivered to a 20-mm thick water equivalent medium at FLASH dose-rates of 40–240 Gy/s in a parallel-opposed arrangement at SSDs <50mm. A uniform depth dose-rate within ±5% deviation is achieved over 8-12 mm in phantom central region. At extended SSD, conventional dose-rates (< 0.1Gy/s) can be achieved with the depth-dose uniformity improved to a 27-mm thickness in a 40-mm thick water phantom. Beam angling reduces high surface doses up to 39% and provides a first order capability of conformal irradiation for the parallel-opposed beam arrangement.

Conclusion: It is feasible to irradiate small animals and cell cultures with a wide range of doses and dose-rates, including FLASH and conventional irradiation with kV x-rays from rotating anode x-ray sources in the parallel-opposed and angled beam arrangements. The system will greatly enhance basic and translational researches in the laboratory setting.

Keywords

X Rays, Conformal Radiotherapy, Dosimetry

Taxonomy

TH- Small Animal RT: Development (new technology and techniques)

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