National dosimetric audit network finds discrepancies in AAA lung inhomogeneity corrections

Leon Dunn, Joerg Lehmann, Jessica Lye, John Kenny, Tomas Kron, Andrew Alves, Andrew Cole, Jackson Zifodya, Ivan Williams

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

This work presents the Australian Clinical Dosimetry Service's (ACDS) findings of an investigation of systematic discrepancies between treatment planning system (TPS) calculated and measured audit doses. Specifically, a comparison between the Anisotropic Analytic Algorithm (AAA) and other common dose-calculation algorithms in regions downstream (≥2. cm) from low-density material in anthropomorphic and slab phantom geometries is presented. Two measurement setups involving rectilinear slab-phantoms (ACDS Level II audit) and anthropomorphic geometries (ACDS Level III audit) were used in conjunction with ion chamber (planar 2D array and Farmer-type) measurements. Measured doses were compared to calculated doses for a variety of cases, with and without the presence of inhomogeneities and beam-modifiers in 71 audits. Results demonstrate a systematic AAA underdose with an average discrepancy of 2.9 ± 1.2% when the AAA algorithm is implemented in regions distal from lung-tissue interfaces, when lateral beams are used with anthropomorphic phantoms. This systemic discrepancy was found for all Level III audits of facilities using the AAA algorithm. This discrepancy is not seen when identical measurements are compared for other common dose-calculation algorithms (average discrepancy -0.4 ± 1.7%), including the Acuros XB algorithm also available with the Eclipse TPS. For slab phantom geometries (Level II audits), with similar measurement points downstream from inhomogeneities this discrepancy is also not seen.

Original languageEnglish (US)
Pages (from-to)435-441
Number of pages7
JournalPhysica Medica
Volume31
Issue number5
DOIs
StatePublished - Jul 1 2015
Externally publishedYes

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Keywords

  • Algorithm
  • Audit
  • Dose
  • Dosimetry
  • Radiotherapy

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging
  • Physics and Astronomy(all)

Cite this

Dunn, L., Lehmann, J., Lye, J., Kenny, J., Kron, T., Alves, A., Cole, A., Zifodya, J., & Williams, I. (2015). National dosimetric audit network finds discrepancies in AAA lung inhomogeneity corrections. Physica Medica, 31(5), 435-441. https://doi.org/10.1016/j.ejmp.2015.04.002