Dose error from deviation of dwell time and source position for high dose-rate 192Ir in remote afterloading system

Hiroyuki Okamoto, Ako Aikawa, Akihisa Wakita, Kotaro Yoshio, Naoya Murakami, Satoshi Nakamura, Minoru Hamada, Yoshihisa Abe, Jun Itami

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The influence of deviations in dwell times and source positions for 192Ir HDR-RALS was investigated. The potential dose errors for various kinds of brachytherapy procedures were evaluated. The deviations of dwell time ΔT of a 192Ir HDR source for the various dwell times were measured with a well-type ionization chamber. The deviations of source position ΔP were measured with two methods. One is to measure actual source position using a check ruler device. The other is to analyze peak distances from radiographic film irradiated with 20 mm gap between the dwell positions. The composite dose errors were calculated using Gaussian distribution with ΔT and ΔP as 1σ of the measurements. Dose errors depend on dwell time and distance from the point of interest to the dwell position. To evaluate the dose error in clinical practice, dwell times and point of interest distances were obtained from actual treatment plans involving cylinder, tandem-ovoid, tandem-ovoid with interstitial needles, multiple interstitial needles, and surface-mold applicators. The ΔT and ΔP were 32 ms (maximum for various dwell times) and 0.12 mm (ruler), 0.11 mm (radiographic film). The multiple interstitial needles represent the highest dose error of 2%, while the others represent less than approximately 1%. Potential dose error due to dwell time and source position deviation can depend on kinds of brachytherapy techniques. In all cases, the multiple interstitial needles is most susceptible.

Original languageEnglish
Pages (from-to)780-787
Number of pages8
JournalJournal of radiation research
Volume55
Issue number4
DOIs
Publication statusPublished - Jul 2014
Externally publishedYes

Keywords

  • dose error
  • dwell time
  • RALS
  • source position

ASJC Scopus subject areas

  • Radiation
  • Radiology Nuclear Medicine and imaging
  • Health, Toxicology and Mutagenesis

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