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 »
- Authors:
-
- Radiofisica. Hospital Universitario Virgen Macarena, Sevilla (Spain) and Departamento de Fisiologia Medica y Biofisica, Facultad de Medicina, Universidad de Sevilla, Sevilla (Spain)
- Abt Medizinische Physik in der Strahlentherapie, Deutsches Krebsforschungszentrum, Heidelberg (Germany)
- Departamento de Fisica de Particulas, Facultade de fisica, Universidade de Santiago de Compostela, Santiago de Compostela (Spain)
- Nuclear Data Section, International Atomic Energy Agency, Vienna (Austria)
- Fisica Sanitaria, Arcispedale S. Maria Nuova, Reggio Emilia (Italy)
- 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}
}