Long term OSLD reader stability in the ACDS level one audit

Andrew D C Alves, Jessica Lye, John Kenny, Leon Dunn, Joerg Lehmann, Andrew Cole, Tomas Kron, Duncan Butler, Peter Johnston, Ivan Williams

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The Australian Clinical Dosimetry Service (ACDS) has demonstrated the capacity to perform a basic dosimetry audit on all radiotherapy clinics across Australia. During the ACDS’s three and a half year trial the majority of the audits were performed using optically stimulated luminescence dosimeters (OSLD) mailed to facilities for exposure to a reference dose, and then returned to the ACDS for analysis. This technical note investigates the stability of the readout process under the large workload of the national dosimetry audit. The OSLD readout uncertainty contributes to the uncertainty of several terms of the dose calculation equation and is a major source of uncertainty in the audit. The standard deviation of four OSLD readouts was initially established at 0.6 %. Measurements over 13 audit batches—each batch containing 200−400 OSLDs—showed variability (0.5−0.9 %) in the readout standard deviation. These shifts have not yet necessitated a change to the audit scoring levels. However, a standard deviation in OSLD readouts greater than 0.9 % will change the audit scoring levels. We identified mechanical wear on the OSLD readout adapter as a cause of variability in readout uncertainty, however, we cannot rule out other causes. Additionally we observed large fluctuations in the distribution of element correction factors (ECF) for OSLD batches. We conclude that the variability in the width of the ECF distribution from one batch to another is not caused by variability in readout uncertainty, but rather by variations in the OSLD stock.

Original languageEnglish (US)
Pages (from-to)151-156
Number of pages6
JournalAustralasian Physical and Engineering Sciences in Medicine
Volume38
Issue number1
DOIs
StatePublished - Mar 29 2015
Externally publishedYes

Keywords

  • Level one dosimetric audit
  • Optically stimulated luminescence dosimeter (OSLD)
  • OSLD element correction factor
  • OSLD readout uncertainty
  • Radiotherapy

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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