Abstract
Purpose: This work investigated the accuracy of prowess treatment planning system (TPS) in dose calculation in a homogenous phantom for symmetric and asymmetric field sizes using collapse cone convolution / superposition algorithm (CCCS). Methods: The measurements were carried out at source-to-surface distance (SSD) set to 100 cm for 6 and 10 MV photon beams. Data for a full set of measurements for symmetric fields and asymmetric fields, including inplane and crossplane profiles at various depths and percentage depth doses (PDDs) were obtained during measurements on the linear accelerator. Results: The results showed that the asymmetric collimation dose lead to significant errors (up to approximately 7%) in dose calculations if changes in primary beam intensity and beam quality. It is obvious that the most difference in the isodose curves was found in buildup and the penumbra regions. Conclusion: The results showed that the dose calculation using Prowess TPS based on CCCS algorithm is generally in excellent agreement with measurements.
Highlights
The dose calculation algorithm must accurately model for all beam configurations normally used in the clinic
In crossplane direction the maximum difference was found at (X1 = 1, X2 = 3 & Y1 = 2, Y2 = 2), it equals to 5.5%
The results showed that most data gave a high passing rate (>97%) for the gamma index for Prowess TPS approved the suitability of collapse cone convolution/superposition algorithm (CCCS) algorithm for incorporation into a treatment planning system for asymmetric opened fields
Summary
The dose calculation algorithm must accurately model for all beam configurations normally used in the clinic. Radiation therapy treatment planning for many clinical situations requires asymmetric field size correctly modeled in the treatment planning computer system. This includes verifying the accuracy of both the isodose distributions and the monitor units (MUs) generated by the treatment planning system.[1,2,3] The degree of success achieved by the optimization process is largely dependent on the cost function used by the algorithm (which in turn depends on the structures defined by the user) and the algorithm used for minimization.[4] Several authors have conducted the evaluation of dose calculation algorithms for external beam radiation therapy.[5,6,7]. Since asymmetric fields are the simplest case of irregular fields, others have approached this problem using appropriate algorithms that utilize the data available for symmetric fields.[9]
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