ABSTRACT
It is important to establish reliable calculational tools to plan and analyse representative microdosimetry experiments in the context of microbeam radiation therapy development. In this paper, an attempt has been made to investigate the suitability of the MCNP4C Monte Carlo code to adequately model photon/electron transport over micron distances. The case of a single cylindrical microbeam of 25-micron diameter incident on a water phantom has been simulated in detail with both MCNP4C and the code PSI-GEANT, for different incident photon energies, to get absorbed dose distributions at various depths, with and without electron transport being considered. In addition, dose distributions calculated for a single microbeam with a photon spectrum representative of the European Synchrotron Radiation Facility (ESRF) have been compared. Finally, a large number of cylindrical microbeams (a total of 2601 beams, placed on a 200-micron square pitch, covering an area of 1 cm2) incident on a water phantom have been considered to study cumulative radial dose distributions at different depths. From these distributions, ratios of peak (within the microbeam) to valley (mid-point along the diagonal connecting two microbeams) dose values have been determined. The various comparisons with PSI-GEANT results have shown that MCNP4C, with its high flexibility in terms of its numerous source and geometry description options, variance reduction methods, detailed error analysis, statistical checks and different tally types, can be a valuable tool for the analysis of microbeam experiments.
Subject(s)
Monte Carlo Method , Radiometry/methods , Radiotherapy Planning, Computer-Assisted/methods , Radiotherapy/methods , Computer Simulation , Electrons , Protons , Radiotherapy Dosage , Reproducibility of Results , Sensitivity and Specificity , SynchrotronsSubject(s)
Denture Design , Denture Retention , Denture, Complete, Upper , Humans , Palate/anatomy & histologyABSTRACT
This article presents the steps used in fabricating an orbital prosthesis. Major considerations such as selection of the spectacle frame and the artificial eye, eye alignment, and clay modeling are emphasized to ensure an esthetically acceptable prosthesis. A simple technique for construction of wax templates for fabrication of orbital prostheses in acrylic resin also was described.
