(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose:
Despite potential benefit of minibeam therapy using particle beams, obstacles remain regarding beam delivery and computational planning tools. The purpose of this work was to demonstrate feasibility of dose calculation for particle minibeam therapy in anatomically realistic patient anatomy and to investigate the ability to treat deeper brain tumors using carbon-ion minibeams instead of proton minibeams.
Methods:
Proton and carbon-ion minibeams were simulated using Monte Carlo software (TOPAS v3.3_beta1) at energies of 115 MeV and 217 MeV/u, respectively. The minibeam arrays were configured as 0.3-mm planar parallel minibeams with 1-mm center-to-center spacing in a 5x5-mm² rectangular array. Irradiations were simulated in both a water phantom and a computed tomographic (CT) image of a brain tumor patient. Peak to valley ratios (PVR) were recorded as a function of beam depth to determine the depths of tissue to which the distinct spatial pattern of minibeams could be preserved.
Results:
For the brain tumor patient, the simulated proton minibeams exhibited PVRs of 115.14 ± 16.69, 6.89 ± 0.32, 1.08 ± 0.06, 1.09 ± 0.20 at depths of 0, 2, 4, and 6 cm. Simulated carbon-ion minibeams had PVRs of 109.27 ± 7.83, 63.88 ± 4.30, 24.13 ± 1.48, 3.28 ± 0.07, respectively. The dose distributions revealed a minibeam merge depth of approximately 4 cm for the protons, compared to 9 cm for carbon ions.
Conclusion:
Our work demonstrates an early step in the development of a Monte Carlo based research treatment planning system for proton and carbon-ion minibeam therapy. The deeper merge depth and relatively higher PVRs at depth for carbon-ion minibeams, compared with protons, may prove to be favorable for deeper brain tumors. Future studies will focus on inverse planning tools needed for minibeam therapy with particle beams.
Keywords
Monte Carlo, Heavy Ions, Protons
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