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Dose-rate considerations for the INTRABEAM electronic brachytherapy system: Report from the American association of physicists in medicine task group no. 292.

Authors
  • Culberson, Wesley S1
  • Davis, Stephen D2
  • Gwe-Ya Kim, Grace3
  • Lowenstein, Jessica R4
  • Ouhib, Zoubir5
  • Popovic, Marija6
  • Waldron, Timothy J7
  • Safigholi, Habib8
  • Simiele, Samantha J4
  • Rivard, Mark J9
  • 1 Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin, Madison, WI, 53705, USA.
  • 2 Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 33176, USA.
  • 3 Department of Radiation Medicine and Applied Science, University of California - San Diego, La Jolla, CA, 92093-5004, USA.
  • 4 Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
  • 5 Department of Radiation Oncology, Lynn Regional Cancer Center, Delray Beach, FL, 33484, USA.
  • 6 Department of Medical Physics, McGill University Health Center, Montreal, QC, H4A 3J1, Canada. , (Canada)
  • 7 Department of Radiation Oncology, University of Iowa Hospital & Clinics, Iowa City, IA, 52242-1009, USA.
  • 8 Carleton Laboratory for Radiotherapy Physics, Physics Department, Carleton University, Ottawa, ON, K1S 5B6, Canada. , (Canada)
  • 9 Department of Radiation Oncology, Rhode Island Hospital, Brown University, Providence, RI, 02903, USA.
Type
Published Article
Journal
Medical Physics
Publisher
Wiley (John Wiley & Sons)
Publication Date
Aug 01, 2020
Volume
47
Issue
8
Identifiers
DOI: 10.1002/mp.14163
PMID: 32246456
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

The purpose of this report is to provide detailed guidance on the dosimetry of the INTRABEAM® (Carl Zeiss Medical AG, Jena, Germany) electronic brachytherapy (eBT) system as it stands at the present time. This report has been developed by the members of American Association of Physicists in Medicine (AAPM) Task Group 292 and endorsed by the AAPM. Members of AAPM Task Group 292 on Electronic-Brachytherapy Dosimetry have reviewed pertinent publications and user manuals regarding the INTRABEAM system dosimetry and manufacturer-supplied dose calculation protocols. Formal written correspondence with Zeiss has also provided further clarification. Dose-rate calculations for the INTRABEAM system are highly dependent on choice of dosimetry protocol. Even with careful protocol selection, large uncertainties remain due to the incomplete characterization of the ionization chambers used for verification with respect to their energy dependence as well as manufacturing variations. There are two distinct sets of dose-rate data provided by Zeiss for the INTRABEAM system. One dataset (Calibration V4.0) is representative of the physical dose surrounding the source and the other dataset (TARGIT) has been adjusted to be consistent with a clinical trial named TARGIT (TARGeted Intraoperative RadioTherapy). The adjusted TARGIT doses are quite dissimilar to the physical doses, with differences ranging from 14% to 30% at the surface of a spherical applicator, depending on its diameter, and up to a factor of two at closer distances with the smaller needle applicators. In addition, ion chamber selection and associated manufacturing tolerances contribute to significant additional uncertainties. With these substantial differences in dose rates and their associated uncertainties, it is important for users to be aware of how each value is calculated and whether it is appropriate to be used for the intended treatment. If users intend to deliver doses that are the same as they were in 1998 at the onset of the TARGIT trial, then the TARGIT dose-rate tables should be used. The Calibration V4.0 dose rates may be more appropriate to use for applications other than TARGIT trial treatments, since they more closely represent the physical doses being delivered. Users should also be aware of the substantial uncertainties associated with the provided dose rates, which are due to beam hardening, chamber geometry, and selection of the point-of-measurement for a given ionization chamber. This report serves to describe the details and implications of the manufacturer-recommended dosimetry formalism for users of the INTRABEAM system. © 2020 American Association of Physicists in Medicine.

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