RESUMO
PURPOSE: Monaco treatment planning system (TPS) version 5.1 uses a Monte-Carlo (MC)-based dose calculation engine. The aim of this study is to verify and compare the Monaco-based dose calculations with both Pinnacle3 collapsed cone convolution superposition (CCCS) and Eclipse anisotropic analytical algorithm (AAA) calculations. MATERIALS AND METHODS: For this study, 18 previously treated lung and head-and-neck (HN) cancer patients were chosen to compare the dose calculations between Pinnacle, Monaco, and Eclipse. Plans were chosen from those that had been treated using the Elekta VersaHD or a Novalis Tx linac. All of the treated volumetric-modulated arc therapy plans used 6 MV or 10 MV photon beams. The original plans calculated with CCCS or AAA along with the recalculated ones using MC from the three TPS were exported into Velocity software for intercomparison. RESULTS: To compare the dose calculations, Planning target volume (PTV) heterogeneity indexes and conformity indexes were calculated from the dose volume histograms (DVH) of all plans. While mean lung dose (MLD), lung V5 and V20 values were recorded for lung plans, the computed dose to parotids, brainstem, and mandible were documented for HN plans. In plan evaluation, percent differences of the above dosimetric values in Monaco computation were compared against each of the other TPS computations. CONCLUSION: It could be concluded through this research that there can be differences in the calculation of dose across different TPSs. Although relatively small, these differences could become apparent when compared using DVH. These differences most likely arise from the different dose calculation algorithms used in each TPS. Monaco employs the MC allowing it to have much more detailed calculations that result in it being seen as the most accurate and the gold standard.
RESUMO
The partition function of a grafted polymer brush was calculated as a sum over all possible configurations, each of them being an ensemble of n1, n2, ...n(i), ... loops having 2, 4, ..., 2i, ... segments. A system of equations for the most likely configuration has been obtained, and it was concluded that no solution exists for an infinite chain, with nonvanishing interactions between segments and surface. This implies that an infinite chain is either collapsed on the surface (for attractive interactions) or is forming a stretched brush (for repulsive interactions). However, for finite chains, a solution could be found. When the attractive segment-surface interaction becomes sufficiently strong, the brush collapses on the surface (the "loops" to "trains" transition). When the interaction is repulsive and sufficiently strong, the brush becomes stretched, with most segments belonging to open loops which do not return to the surface (the "loops" to "tails" transition). The critical values of the segment-surface interaction, for which the above transitions occur, depend on the length of the polymer chain as well as on other physical properties of the brush, such as the segment-segment and segment-solvent interactions and the grafting density.