Electron radiotherapy (IOERT) for applications outside of the breast: Dosimetry and influence of tissue inhomogeneities

Michele Avanzo, Andrea Dassie, Prabhu Chandra Acharya, Paola Chiovati, Giovanni Pirrone, Cinzia Avigo, Loredana Barresi, Soai Dang Quoc, Emmanuel Fiagbedzi, Federico Navarria, Elisa Palazzari, Giulio Bertola, Antonino De Paoli, Joseph Stancanello, Giovanna Sartor

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: The purpose of study is to investigate the dosimetry of electron intraoperative radiotherapy (IOERT) of the Intraop Mobetron 2000 mobile LINAC in treatments outside of the breast. After commissioning and external validation of dosimetry, we report in vivo results of measurements for treatments outside the breast in a large patient cohort, and investigate if the presence of inhomogeneities can affect in vivo measurements. Methods and materials: Applicator factors and profile curves were measured with a stereotactic diode. The applicators factors of the 6 cm flat and beveled applicators were also confirmed with radiochromic films, parallel-plate ion chamber and by an external audit performed with ThermoLuminescent Dosimeters (TLDs). The influence of bone on dose was investigated by using radiochromic films attached to an insert equivalent to cortical bone, immersed in the water phantom. In vivo dosimetry was performed on 126 patients treated with IOERT using metal oxide-silicon semiconductor field effect transistors (MOSFETs) placed on the tumor bed. Results: Relatively small differences were found among different detectors for measurements of applicator factors. In the external audit, the agreement with the TLD was mostly within ±0.2%. The largest increase of dose due to the presence of cortical bone insert was +6.0% with energy 12 MeV and 3 cm applicator. On average, in vivo dose was significantly (+3.1%) larger than prescribed dose. Conclusion: IOERT in applications outside the breast results in low discrepancies between in vivo and prescribed doses, which can be also explained with the presence of tissue inhomogeneity.

Original languageEnglish
Pages (from-to)82-89
Number of pages8
JournalPhysica Medica
Volume69
DOIs
Publication statusPublished - Jan 2020

Keywords

  • Dosimetry
  • Electron therapy
  • Intra-operative
  • Radiation therapy
  • Radiochromic film

ASJC Scopus subject areas

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

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