The accurate calculation and delivery of dose in radiotherapy patients iscritical in order to maximize dose to the target volume and minimize doseto surrounding normal tissue. Dose calculation errors can lead to normaltissue complications or underdosage of the target volume leading to localrecurrence of disease. The computation of dose from electron therapybeams is particularly difficult, and even the most advanced algorithms canbe in error by 12 with simple tissue inhomogeneities. The clinicalcriteria for acceptable dose calculation accuracy is 3 in all anatomiclocations. This project has the ultimate aim of producing an electrondose computation algorithm whose accuracy lies within the 3 criteria forpatient treatment. An electron propagation algorithm has recently been developed by ourgroup. This algorithm has distinct advantages over other calculationapproaches since; l the program is modular and is usable with anyelectron scattering model, and 2 it calculates both the spatialredistribution and energy loss straggling suffered by the electrons. Because of 2 the algorithm also computes dose without the need formeasured depth dose data as input. This project proposes to develop, improve, implement and verify this newalgorithm in order to reduce electron dose computation errors to anacceptable level of -3. Four main areas of interest are identified: lFurther theoretical development of the algorithm to include; radiativeenergy loss straggling, an improved scattering theory, secondary electrontransport and backscattering. 2 EGS4 Monte Carlo simulation forverification of interim results. 3 Generalization of the algorithm forclinical use by; 3-D implementation, use for irregular fields, modellingof in-air scattering from the accelerator and integration with CTx-raydata. 4 Verification of the complete algorithm by comparison of resultswith measured and Monte Carlo simulation data.
Electron Radiation, Mathematical Model, Model Design Development, Neoplasm Cancer Radiation Therapy, Radiation Therapy Dosage
