A validation study of a dedicated software for an automated in vivo dosimetry control in radiotherapy

A. Piermattei, F. Greco, M. Grusio, S. Menna, L. Azario, G. Stimato, E. Placidi, S. Teodoli, S. Cilla, A. Porcelli, L. Alberico, A. Fidanzio

Research output: Contribution to journalArticlepeer-review

Abstract

In vivo dosimetry (IVD) is the last step of a radiotherapy quality control program aimed to ensure that the dose delivered is in agreement with that prescribed. IVD procedures based on single detectors are time-consuming and impossible to use for the modern radiotherapy techniques, based on static or kinetic beams (modulated in intensity fluence); this means that more efficient and practical methods are highly recommended. The practical method SOFTDISO, based on the use of electronic portal image device (EPID), provides two tests (i) the R ratio between the reconstructed and the planned isocenter doses to verify an agreement within 5% and (ii) the γ-analysis of the EPID images, to verify γ% ≥ 90% and γmean ≤ 0.4. This paper reports the results of 11,357 IVD tests carried out for 823 patients treated by three-dimensional conformal radiation therapy and volumetric modulated arc therapy techniques. In particular, the dose disagreements are reported distinguishing two kinds of causes, those of (i) class 1 that includes the errors due to inadequate quality controls and (ii) the class 2, due to patient morphological changes. About the tests out of tolerance, 6% were by VMAT and 21% by 3DCRT, but taking into account the only class 1 of errors, i.e., removing the causes of class 2, only 7% of patients examined presented at least one of the three mean indexes out of tolerance. The workload for IVD on 9 patients/day per linac is about 52 min/day but recently, a new automated SOFTDISO version has been implemented to reduce the time to about 34 min/day.

Original languageEnglish
Pages (from-to)1939-1947
Number of pages9
JournalMedical and Biological Engineering and Computing
Volume56
Issue number10
DOIs
Publication statusPublished - Oct 1 2018

Keywords

  • Dosimetry
  • Quality controls in radiotherapy
  • Radiotherapy in vivo dosimetry

ASJC Scopus subject areas

  • Biomedical Engineering
  • Computer Science Applications

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