Evaluation collapsed cone convolution/superposition (CCCS) algorithms in prowess treatment planning system for calculating symmetric and asymmetric field size

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. 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. The largest 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.Keywords: Symmetric and Asymmetric Fields; Dose Calculation; Treatment Planning System IntroductionThe 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] Commissioning of the dose calculation algorithms of a treatment planning system is generally performed: (i) by entering basic beam data into the system according to the methods and requirements described in the user's manual of the system; and (ii) by comparing the results of dose calculations with the entered data and with data that were measured specifically for this purpose. Most commonly, existing beam data are used as input data. Differences between calculated and actual dose values may be encountered, partly due to uncertainties in the measured data, and partly due to imperfect beam modeling. Criteria for acceptability have to be applied before accepting a treatment planning system for clinical use. Several authors have developed such criteria. 8 Several treatment planning systems calculate asymmetric fields on the assumption that these are equivalent to blocked fields. However, the parameters required for treatment planning implementation depend on the algorithm used, and the method of their derivation is often not explicit. Since asymmetric fields are the simplest case of irregular fields, others have approached this problem using appropriate algorithms that utilize the dat...

Equivalent uniform dose and normal tissue complication probability of acute esophagitis in head-and-neck radiotherapy: Sensitivity to dose calculation accuracy

“…Sasani 4,5 , P. Jafari 6 , R. Fardid 1,3 algorithms can, therefore, be critical (11) . Many studies have evaluated the accuracy of different dose calculation algorithms for a wide range of different parameters and circumstances and have found various magnitudes of differences in the calculated dose depending on the algorithms and the extent and types of tissue heterogeneities and contour irregularities (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) . Radiobiological dose-response relationships are usually nonlinear (23) .…”