Properties of liquid ionization chambers at LDR brachytherapy dose rates

Phys Med Biol. 1995 Apr;40(4):575-87. doi: 10.1088/0031-9155/40/4/006.

Abstract

Properties such as sensitivity, general recombination and reproducibility of liquid-filled parallel-plate ionization chambers for dosimetry in low-dose-rate brachytherapy radiation fields have been evaluated. Two different dielectric liquids, isooctane (C8H(1)8) and tetramethylsilane (Si(CH3)4), have been used as sensitive media in chambers having a coin-shaped sensitive volume of 3 mm in diameter and 1 mm thickness. An electric field strength of 300 kV m-1 was found to be optimal with respect to sensitivity, leakage current and general recombination. At absorbed dose rates from 0.1-100 mGy min-1 the ionization charge measurements at an irradiation time of 1 min showed a reproducibility better than 1%, and a general recombination not exceeding 0.5%. The calibration--absorbed dose to water against ionization charge at a 60Co reference source--did not show any significant change over an observation time of one year for any of the chambers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Brachytherapy / instrumentation*
  • Brachytherapy / methods
  • Half-Life
  • Humans
  • Octanes
  • Radiation Dosage*
  • Silanes
  • Technetium
  • Trimethylsilyl Compounds

Substances

  • Octanes
  • Silanes
  • Trimethylsilyl Compounds
  • tetramethylsilane
  • Technetium
  • 2,2,4-trimethylpentane