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Monte Carlo Study of a Compact Distributed X-Ray Source Microbeam Radiation Therapy Research Irradiator

E Schreiber

E Schreiber*, S Chang, UNC School of Medicine, Chapel Hill, NC

TU-C-BRB-3 Tuesday 10:30:00 AM - 12:30:00 PM Room: Ballroom B

Purpose: Microbeam radiation therapy (MRT) is a promising experimental treatment modality produced by large synchrotron facilities. Using carbon-nanotube (CNT) field emission based x-ray generation as an enabling technology, we propose a compact MRT small animal irradiator. We report on a Monte Carlo feasibility study of the proposed device.

Methods: A prototype 160 kVp CNT MRT device was simulated using EGSnrc-based codes. Dosimetry for 100-micron thick planar beams at 160 mm SSD was calculated in a 30 mm diameter cylindrical water target. In contrast to single source synchrotron MRT systems, the proposed CNT-MRT system has multiple linear x-ray sources were arranged in a ring surrounding the target. The planar dosimetry from the MRT was simulated by using 12-24 equally spaced identical linear x-ray source segments. Dosimetry for the full MRT array was generated by combining circular planar dose distributions in parallel planes separated by 150-1000 microns. The resulting configurations were analyzed for isocentric dose rate, dose to normal tissue, and peak-to-valley ratio.

Results: The peak-to-valley dose ratio varied from 10 to 100 as the spacing between adjacent parallel microbeams was increased from 150 to 1000 microns. The dose rate at the center of the phantom was calculated to be 700 Gy/A/min per linear source segment. An expected maximum current per source segment of 1 A (due to anode heating) projects a maximum dose rate of 280 Gy/sec at isocenter for a 24-source segment configuration. The dose rate falls by 80% within 5 mm of the edge of the target area in the center of the phantom, providing significant normal tissue sparing compared with single-direction MRT techniques.

Conclusions: Monte Carlo simulations show that it is feasible for the proposed MRT device to produce the dose rate and peak-to-valley characteristics needed to conduct MRT research.

This work is supported by NCI grant 1U54CA151652

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