Novel approaches to GRID therapy: Electron GRID and photon minibeams
Szalkowski, Gregory A.
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This dissertation describes a study into the dosimetric properties of several new forms of spatially fractionated radiation therapy, commonly referred to as SFRT or GRID; small beam electron GRID, radioisotope-based photon minibeam GRID, and megavoltage photon minibeam GRID. For each methodology, a combination of Monte Carlo simulation (using the Monte Carlo code MCNP6) and physical measurements (using EBT3 radiochromic film) was used to characterize the dose rate and peak-to-valley dose ratio (PVDR) of each of the proposed methods. This presented work shows the calculated and/or measured in-phantom dose distributions from each of these new modalities. In all cases, beam definition similar to or exceeding that of clinically used GRID therapy techniques was achieved, as defined by the PVDR. In addition, the photon-based minibeam modalities were able to effectively produce beams below 5 mm in diameter, which could be expected to significantly improve healthy tissue recovery. Also in this work, the limitations and challenges of each of these techniques are discussed, namely the reduced dose rate that corresponds to the small beam size. However, each method has some conditions under which it can effectively be used, and with further development in specified areas, aspects of this work could be applied clinically.