Calculation of absorbed dose ratios using correlated Monte Carlo sampling

Chana Mina Ma, Alan E. Nahum

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

A correlated sampling variance reduction technique has been implemented in the EGS4 (Elec-tron Gamma Shower version 4) Monte Carlo code system in order to calculate correction factors for radiation dosimeters. These correction factors are calculated as the ratios of absorbed doses in various geometries irradiated by photon and electron beams. In this paper the efficiency and accuracy of the calculation of the absorbed dose ratios with correlated Monte Carlo sampling is discussed. Theoretical analysis shows that the calculation efficiency and accuracy increases with the degree of correlation between the calculated doses in the individual geometries. Calculations of the absorbed doses in thin slab geometries and in air-filled ionization chambers have been performed. The results show that the gain in computing efficiency is up to a thousand fold for the calculations of the effect of the central electrode material and size on the response of cylindrical ionization chambers. The calculation accuracy (systematic uncertainty) is significantly improved when good correlation exists between the calculated doses in similar thin-slab geometries.

Original languageEnglish
Pages (from-to)1189-1199
Number of pages11
JournalMedical Physics
Volume20
Issue number4
DOIs
StatePublished - Jul 1993
Externally publishedYes

Keywords

  • Carlo
  • EGS4
  • Monte
  • correlated sampling
  • radiation dosimetry
  • variance reduction technique

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