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Title: SU-E-I-24: Method for CT Automatic Exposure Control Verification

Abstract

Purpose: Design of a phantom and a simple method for the automatic exposure control (AEC) verification in CT. This verification is included in the computed tomography (CT) Spanish Quality Assurance Protocol. Methods: The phantom design is made from the head and the body phantom used for the CTDI measurement and PMMA plates (35×35 cm2) of 10 cm thickness. Thereby, three different thicknesses along the longitudinal axis are obtained which permit to evaluate the longitudinal AEC performance. Otherwise, the existent asymmetry in the PMMA layers helps to assess angular and 3D AEC operation.Recent acquisition in our hospital (August 2014) of Nomex electrometer (PTW), together with the 10 cm pencil ionization chamber, led to register dose rate as a function of time. Measurements with this chamber fixed at 0° and 90° on the gantry where made on five multidetector-CTs from principal manufacturers. Results: Individual analysis of measurements shows dose rate variation as a function of phantom thickness. The comparative analysis shows that dose rate is kept constant in the head and neck phantom while the PMMA phantom exhibits an abrupt variation between both results, being greater results at 90° as the thickness of the phantom is 3.5 times larger than in themore » perpendicular direction. Conclusion: Proposed method is simple, quick and reproducible. Results obtained let a qualitative evaluation of the AEC and they are consistent with the expected behavior. A line of future development is to quantitatively study the intensity modulation and parameters of image quality, and a possible comparative study between different manufacturers.« less

Authors:
; ; ; ; ; ; ; ; ;  [1]
  1. Complejo Hospitalario de Navarra, Pamplona, Navarra (Spain)
Publication Date:
OSTI Identifier:
22493983
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
07 ISOTOPES AND RADIATION SOURCES; 60 APPLIED LIFE SCIENCES; COMPUTERIZED TOMOGRAPHY; DOSE RATES; ELECTROMETERS; HEAD; HOSPITALS; IMAGES; IONIZATION CHAMBERS; LICENSES; PHANTOMS; PMMA; QUALITY ASSURANCE; THICKNESS; TIME DEPENDENCE; VERIFICATION

Citation Formats

Gracia, M, Olasolo, J, Martin, M, Bragado, L, Gallardo, N, Miquelez, S, Maneru, F, Lozares, S, Pellejero, S, and Rubio, A. SU-E-I-24: Method for CT Automatic Exposure Control Verification. United States: N. p., 2015. Web. doi:10.1118/1.4924021.
Gracia, M, Olasolo, J, Martin, M, Bragado, L, Gallardo, N, Miquelez, S, Maneru, F, Lozares, S, Pellejero, S, & Rubio, A. SU-E-I-24: Method for CT Automatic Exposure Control Verification. United States. https://doi.org/10.1118/1.4924021
Gracia, M, Olasolo, J, Martin, M, Bragado, L, Gallardo, N, Miquelez, S, Maneru, F, Lozares, S, Pellejero, S, and Rubio, A. 2015. "SU-E-I-24: Method for CT Automatic Exposure Control Verification". United States. https://doi.org/10.1118/1.4924021.
@article{osti_22493983,
title = {SU-E-I-24: Method for CT Automatic Exposure Control Verification},
author = {Gracia, M and Olasolo, J and Martin, M and Bragado, L and Gallardo, N and Miquelez, S and Maneru, F and Lozares, S and Pellejero, S and Rubio, A},
abstractNote = {Purpose: Design of a phantom and a simple method for the automatic exposure control (AEC) verification in CT. This verification is included in the computed tomography (CT) Spanish Quality Assurance Protocol. Methods: The phantom design is made from the head and the body phantom used for the CTDI measurement and PMMA plates (35×35 cm2) of 10 cm thickness. Thereby, three different thicknesses along the longitudinal axis are obtained which permit to evaluate the longitudinal AEC performance. Otherwise, the existent asymmetry in the PMMA layers helps to assess angular and 3D AEC operation.Recent acquisition in our hospital (August 2014) of Nomex electrometer (PTW), together with the 10 cm pencil ionization chamber, led to register dose rate as a function of time. Measurements with this chamber fixed at 0° and 90° on the gantry where made on five multidetector-CTs from principal manufacturers. Results: Individual analysis of measurements shows dose rate variation as a function of phantom thickness. The comparative analysis shows that dose rate is kept constant in the head and neck phantom while the PMMA phantom exhibits an abrupt variation between both results, being greater results at 90° as the thickness of the phantom is 3.5 times larger than in the perpendicular direction. Conclusion: Proposed method is simple, quick and reproducible. Results obtained let a qualitative evaluation of the AEC and they are consistent with the expected behavior. A line of future development is to quantitatively study the intensity modulation and parameters of image quality, and a possible comparative study between different manufacturers.},
doi = {10.1118/1.4924021},
url = {https://www.osti.gov/biblio/22493983}, journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}