A numerical method to optimise the spatial dose distribution in carbon ion radiotherapy planning

• Published in: Radiation protection dosimetry Vol. 166; no. 1-4; p. 351
• Main Authors: Grzanka, L, Korcyl, M, Olko, P, Waligorski, M P R
• Format: Journal Article
• Language: English
• Published: England 01.09.2015
• Subjects: Algorithms; Animals; Cell Survival - radiation effects; CHO Cells; Computer Simulation; Cricetinae; Cricetulus; Heavy Ion Radiotherapy - standards; Linear Energy Transfer - radiation effects; Models, Theoretical; Monte Carlo Method; Radiometry - methods; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy Planning, Computer-Assisted - standards
• ISSN: 1742-3406
• DOI: 10.1093/rpd/ncv195

The authors describe a numerical algorithm to optimise the entrance spectra of a composition of pristine carbon ion beams which delivers a pre-assumed dose-depth profile over a given depth range within the spread-out Bragg peak. The physical beam transport model is based on tabularised data generated using the SHIELD-HIT10A Monte-Carlo code. Depth-dose profile optimisation is achieved by minimising the deviation from the pre-assumed profile evaluated on a regular grid of points over a given depth range. This multi-dimensional minimisation problem is solved using the L-BFGS-B algorithm, with parallel processing support. Another multi-dimensional interpolation algorithm is used to calculate at given beam depths the cumulative energy-fluence spectra for primary and secondary ions in the optimised beam composition. Knowledge of such energy-fluence spectra for each ion is required by the mixed-field calculation of Katz's cellular Track Structure Theory (TST) that predicts the resulting depth-survival profile. The optimisation algorithm and the TST mixed-field calculation are essential tools in the development of a one-dimensional kernel of a carbon ion therapy planning system. All codes used in the work are generally accessible within the libamtrack open source platform.