Physics and Imaging in Radiation Oncology (Jan 2024)

Survey on fan-beam computed tomography for radiotherapy: Imaging for dose calculation and delineation

  • Esther Decabooter,
  • Guido C. Hilgers,
  • Joke De Rouck,
  • Koen Salvo,
  • Jacobus Van Wingerden,
  • Hilde Bosmans,
  • Brent van der Heyden,
  • Sima Qamhiyeh,
  • Chrysi Papalazarou,
  • Robert Kaatee,
  • Geert Pittomvils,
  • Evelien Bogaert

Journal volume & issue
Vol. 29
p. 100522

Abstract

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Background and purpose: To obtain an understanding of current practice, professional needs and future directions in the field of fan-beam CT in RT, a survey was conducted. This work presents the collected information regarding the use of CT imaging for dose calculation and structure delineation. Materials and methods: An online institutional survey was distributed to medical physics experts employed at Belgian and Dutch radiotherapy institutions to assess the status, challenges, and future directions of QA practices for fan-beam CT. A maximum of 143 questions covered topics such as CT scanner availability, CT scanner specifications, QA protocols, treatment simulation workflow, and radiotherapy dose calculation. Answer forms were collected between 1-Sep-2022 and 10-Oct-2022. Results: A 66 % response rate was achieved, yielding data on a total of 58 CT scanners. For MV photon therapy, all single-energy CT scans are reconstructed in Hounsfield Units for delineation or dose calculation, and a direct- or stoichiometric method was used to convert CT numbers for dose calculation. Limited use of dual-energy CT is reported for photon (N = 3) and proton dose calculations (N = 1). For brachytherapy, most institutions adopt water-based dose calculation, while approximately 26 % of the institutions take tissue heterogeneity into account. Commissioning and regular QA include eleven tasks, which are performed by two or more professions (29/31) with varying frequencies. Conclusions: Dual usage of a planning CT limits protocol optimization for both tissue characterization and delineation. DECT has been implemented only gradually. A variation of QA testing frequencies and tests are reported.

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