The accurate calculation and delivery of dose in radiotherapy patients is critical in order to maximize dose to the target volume and minimize dose to surrounding normal tissue. Dose calculation errors can lead to normal tissue complications or underdosage of the target volume leading to local recurrence of disease. The computation of dose from electron therapy beams is particularly difficult, and even the most advanced algorithms can be in error by 12% with simple tissue inhomogeneities. The clinical criteria for acceptable dose calculation accuracy is 3% in all anatomic locations. This project has the ultimate aim of producing an electron dose computation algorithm whose accuracy lies within the 3% criteria for patient treatment. An electron propagation algorithm has recently been developed by our group. This algorithm has distinct advantages over other calculation approaches since; (l) the program is modular and is usable with any electron scattering model, and (2) it calculates both the spatial redistribution and energy loss straggling suffered by the electrons. Because of (2) the algorithm also computes dose without the need for measured depth dose data as input. This project proposes to develop, improve, implement and verify this new algorithm in order to reduce electron dose computation errors to an acceptable level of +/-3%. Four main areas of interest are identified: l) Further theoretical development of the algorithm to include; radiative energy loss straggling, an improved scattering theory, secondary electron transport and backscattering. 2) EGS4 Monte Carlo simulation for verification of interim results. 3) Generalization of the algorithm for clinical use by; 3-D implementation, use for irregular fields, modelling of in-air scattering from the accelerator and integration with CT x-ray data. 4) Verification of the complete algorithm by comparison of results with measured and Monte Carlo simulation data.
| Papiez, L; McLellan, J; Sandison, G A et al. (1994) Inclusion of energy straggling in a numerical method for electron dose calculation. Med Phys 21:1591-8 |
| McLellan, J; Sawchuk, S; Battista, J J et al. (1994) A method for the calculation of electron energy-straggling spectra. Med Phys 21:367-78 |
