skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Uncertainty Estimation in Intensity-Modulated Radiotherapy Absolute Dosimetry Verification

Abstract

Purpose: Intensity-modulated radiotherapy (IMRT) represents an important method for improving RT. The IMRT relative dosimetry checks are well established; however, open questions remain in reference dosimetry with ionization chambers (ICs). The main problem is the departure of the measurement conditions from the reference ones; thus, additional uncertainty is introduced into the dose determination. The goal of this study was to assess this effect systematically. Methods and Materials: Monte Carlo calculations and dosimetric measurements with five different detectors were performed for a number of representative IMRT cases, covering both step-and-shoot and dynamic delivery. Results: Using ICs with volumes of about 0.125 cm{sup 3} or less, good agreement was observed among the detectors in most of the situations studied. These results also agreed well with the Monte Carlo-calculated nonreference correction factors (c factors). Additionally, we found a general correlation between the IC position relative to a segment and the derived correction factor c, which can be used to estimate the expected overall uncertainty of the treatment. Conclusion: The increase of the reference dose relative standard uncertainty measured with ICs introduced by nonreference conditions when verifying an entire IMRT plan is about 1-1.5%, provided that appropriate small-volume chambers are used. The overall standardmore » uncertainty of the measured IMRT dose amounts to about 2.3%, including the 0.5% of reproducibility and 1.5% of uncertainty associated with the beam calibration factor. Solid state detectors and large-volume chambers are not well suited to IMRT verification dosimetry because of the greater uncertainties. An action level of 5% is appropriate for IMRT verification. Greater discrepancies should lead to a review of the dosimetric procedure, including visual inspection of treatment segments and energy fluence.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [2];  [6];  [6]
  1. Radiofisica. Hospital Universitario Virgen Macarena, Sevilla (Spain) and Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla (Spain)
  2. Abt Medizinische Physik in der Strahlentherapie, Deutsches Krebsforschungszentrum, Heidelberg (Germany)
  3. Departamento de Fisica de Particulas, Facultade de fisica, Universidade de Santiago de Compostela, Santiago de Compostela (Spain)
  4. Nuclear Data Section, International Atomic Energy Agency, Vienna (Austria)
  5. Fisica Sanitaria, Arcispedale S. Maria Nuova, Reggio Emilia (Italy)
  6. Radiofisica. Hospital Universitario Virgen Macarena, Sevilla (Spain)
Publication Date:
OSTI Identifier:
20951646
Resource Type:
Journal Article
Journal Name:
International Journal of Radiation Oncology, Biology and Physics
Additional Journal Information:
Journal Volume: 68; Journal Issue: 1; Other Information: DOI: 10.1016/j.ijrobp.2006.11.056; PII: S0360-3016(06)03655-8; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0360-3016
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; CALIBRATION; CORRECTIONS; DOSIMETRY; IONIZATION CHAMBERS; MONTE CARLO METHOD; QUALITY ASSURANCE; RADIATION DOSES; RADIOTHERAPY; VERIFICATION

Citation Formats

Sanchez-Doblado, Francisco, Hartmann, Guenther H, Pena, Javier, Capote, Roberto, Paiusco, Marta, Rhein, Bernhard, Leal, Antonio, Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla, Lagares, Juan Ignacio, and Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla. Uncertainty Estimation in Intensity-Modulated Radiotherapy Absolute Dosimetry Verification. United States: N. p., 2007. Web. doi:10.1016/j.ijrobp.2006.11.056.
Sanchez-Doblado, Francisco, Hartmann, Guenther H, Pena, Javier, Capote, Roberto, Paiusco, Marta, Rhein, Bernhard, Leal, Antonio, Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla, Lagares, Juan Ignacio, & Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla. Uncertainty Estimation in Intensity-Modulated Radiotherapy Absolute Dosimetry Verification. United States. https://doi.org/10.1016/j.ijrobp.2006.11.056
Sanchez-Doblado, Francisco, Hartmann, Guenther H, Pena, Javier, Capote, Roberto, Paiusco, Marta, Rhein, Bernhard, Leal, Antonio, Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla, Lagares, Juan Ignacio, and Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla. 2007. "Uncertainty Estimation in Intensity-Modulated Radiotherapy Absolute Dosimetry Verification". United States. https://doi.org/10.1016/j.ijrobp.2006.11.056.
@article{osti_20951646,
title = {Uncertainty Estimation in Intensity-Modulated Radiotherapy Absolute Dosimetry Verification},
author = {Sanchez-Doblado, Francisco and Hartmann, Guenther H and Pena, Javier and Capote, Roberto and Paiusco, Marta and Rhein, Bernhard and Leal, Antonio and Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla and Lagares, Juan Ignacio and Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla},
abstractNote = {Purpose: Intensity-modulated radiotherapy (IMRT) represents an important method for improving RT. The IMRT relative dosimetry checks are well established; however, open questions remain in reference dosimetry with ionization chambers (ICs). The main problem is the departure of the measurement conditions from the reference ones; thus, additional uncertainty is introduced into the dose determination. The goal of this study was to assess this effect systematically. Methods and Materials: Monte Carlo calculations and dosimetric measurements with five different detectors were performed for a number of representative IMRT cases, covering both step-and-shoot and dynamic delivery. Results: Using ICs with volumes of about 0.125 cm{sup 3} or less, good agreement was observed among the detectors in most of the situations studied. These results also agreed well with the Monte Carlo-calculated nonreference correction factors (c factors). Additionally, we found a general correlation between the IC position relative to a segment and the derived correction factor c, which can be used to estimate the expected overall uncertainty of the treatment. Conclusion: The increase of the reference dose relative standard uncertainty measured with ICs introduced by nonreference conditions when verifying an entire IMRT plan is about 1-1.5%, provided that appropriate small-volume chambers are used. The overall standard uncertainty of the measured IMRT dose amounts to about 2.3%, including the 0.5% of reproducibility and 1.5% of uncertainty associated with the beam calibration factor. Solid state detectors and large-volume chambers are not well suited to IMRT verification dosimetry because of the greater uncertainties. An action level of 5% is appropriate for IMRT verification. Greater discrepancies should lead to a review of the dosimetric procedure, including visual inspection of treatment segments and energy fluence.},
doi = {10.1016/j.ijrobp.2006.11.056},
url = {https://www.osti.gov/biblio/20951646}, journal = {International Journal of Radiation Oncology, Biology and Physics},
issn = {0360-3016},
number = 1,
volume = 68,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}