Dosimetric verification of IMAT delivery with a conventional EPID system and a commercial portal dose image prediction tool

Mauro Iori, Elisabetta Cagni, Marta Paiusco, Peter Munro, Alan E. Nahum

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: The electronic portal imaging device (EPID) is a system for checking the patient setup; as a result of its integration with the linear accelerator and software customized for dosimetry, it is increasingly used for verification of the delivery of fixed-field intensity-modulated radiation therapy (IMRT). In order to extend such an approach to intensity-modulated arc therapy (IMAT), the combined use of an EPID system and a portal dose image prediction (PDIP) tool has been investigated. Methods: The dosimetric behavior of an EPID system, mechanically reinforced to maintain its positional stability during the accelerator gantry rotation, has been studied to assess its ability to measure portal dose distributions for IMAT treatment beams. In addition, the PDIP tool of a commercial treatment planning system, commonly used for static IMRT dosimetry, has been validated for simulating the PDIs of IMAT treatment fields. The method has been applied to the delivery verification of 23 treatment fields that were measured in their dual mode of IMRT and IMAT modalities. Results: The EPID system has proved to be appropriate for measuring the PDIs of IMAT fields; additionally the PDIP tool was able to simulate these accurately. The results are quite similar to those obtained for static IMRT treatment verification, although it was necessary to investigate the dependence of the EPID signal and of the accelerator monitor chamber response on variable dose rate. Conclusions: Our initial tests indicate that the EPID system, together with the PDIP tool, is a suitable device for the verification of IMAT plan delivery; however, additional tests are necessary to confirm these results.

Original languageEnglish
Pages (from-to)377-390
Number of pages14
JournalMedical Physics
Volume37
Issue number1
DOIs
Publication statusPublished - 2010

Keywords

  • Electronic portal imaging device
  • EPID
  • IMAT
  • IMAT-SIM
  • Intensity-modulated arc therapy
  • Portal dosimetry

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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