SUMMARY

Spatially fractionated radiation therapy (SFRT) utilizes multiple radiation beams to combine areas of low and high dose within the treatment volume. Organ-at-risk (OAR) tolerance with SFRT is greater than traditional techniques, with increasing benefits as the beam size decreases. Minibeam radiation therapy (MBRT) is a form of SFRT with beam sizes on the order of 1 mm, which is achievable utilizing standard techniques, but MBRT has yet to be implemented in human treatments.

The primary objective of this work is to develop a technique as the basis of future studies employing MBRT. A pair of collimators have been fabricated and validated to deliver low energy photon MBRT with a commercially available research platform. In vitro cell survival studies were performed for comparison with conventional broad beam (BB) irradiation. A simulation study is proposed to develop a delivery technique that can deliver a BB dose distribution in the target region while delivering a MBRT dose distribution in normal tissue, thus combining the OAR tolerance benefits of SFRT with conventional target coverage goals.

MBRT collimators were fabricated for use with the X-RAD SmART radiation therapy research platform. Beam characteristics were measured with film dosimetry and validated with Monte Carlo (MC) simulations. In vitro cell survival curves were created, and additional MC simulations will be performed to develop a novel technique to provide a desirable dose distribution utilizing the same delivery platform.

Most work in SFRT has focused on larger beams that provide limited benefits or very small beams that are too impractical for clinical use. SFRT dose distributions are desirable outside of the target volume where normal tissue toxicity is improved, but a uniform dose distribution in the target volume is needed to achieve desired treatment responses. This work aims to combine these two traits and lay the groundwork for future studies.