<abstract xmlns="http://www.w3.org/1999/xhtml">

<italic>Introduction:</italic> The objectives of this study were to construct a very robust in-house cylindrical ionization chamber from locally available materials to minimize cost, and to assess its suitability for use in a clinical setting.
<italic>Materials and Methods:</italic> The entire body of the constructed IC was composed of Perspex (PMMA). Other components of the IC were made from locally available materials, such as paper and discarded items. The in-house IC was made waterproof by passing the triaxial cable connecting its various electrodes through a plastic tube which once served as a drainage tube of a urine bag. This connection was made such that the chamber was vented to the environment. The completed in-house IC was evaluated for: polarity effect, ion recombination, ion collection efficiency, stability, dose linearity, stem effect, leakage current, angular, dose rate and energy dependences.
<italic>Results:</italic> Although the pre-evaluation results confirmed that the in-house IC satisfied the stipulated international standards for ICs, there was a need to enhance the stem effect and leakage current characteristics of the IC. The in-house IC was found to have an absorbed dose to water calibration coefficient of 4.475 x 107 Gy/C (uncertainty of 1.6%) for cobalt 60 through a cross-calibration with a commercial 0.6 cc cylindrical IC with traceability to the Germany National Dosimetry Laboratory. Using a Jaffé diagram, the in-house IC was also found to have a recombination correction factor of 1.0078 when operated at the calibration voltage of + 400 V. In terms of beam quality correction factors for megavoltage beams, the in-house IC was found to exhibit characteristics similar to those of Scanditronix-Wellhofer IC 70 Farmer type IC.
<italic>Conclusion:</italic> The constructed in-house Farmer-type IC was able to meet all the recommended characteristics for an IC, and therefore, the in-house IC is suitable for beam output calibration in external beam radiotherapy.
</abstract>

Introduction: The objectives of this study were to construct a very robust in-house cylindrical ionization chamber from locally available materials to minimize cost, and to assess its suitability for use in a clinical setting.
Materials and Methods: The entire body of the constructed IC was composed of Perspex (PMMA). Other components of the IC were made from locally available materials, such as paper and discarded items. The in-house IC was made waterproof by passing the triaxial cable connecting its various electrodes through a plastic tube which once served as a drainage tube of a urine bag. This connection was made such that the chamber was vented to the environment. The completed in-house IC was evaluated for: polarity effect, ion recombination, ion collection efficiency, stability, dose linearity, stem effect, leakage current, angular, dose rate and energy dependences.
Results: Although the pre-evaluation results confirmed that the in-house IC satisfied the stipulated international standards for ICs, there was a need to enhance the stem effect and leakage current characteristics of the IC. The in-house IC was found to have an absorbed dose to water calibration coefficient of 4.475 x 107 Gy/C (uncertainty of 1.6%) for cobalt 60 through a cross-calibration with a commercial 0.6 cc cylindrical IC with traceability to the Germany National Dosimetry Laboratory. Using a Jaffé diagram, the in-house IC was also found to have a recombination correction factor of 1.0078 when operated at the calibration voltage of + 400 V. In terms of beam quality correction factors for megavoltage beams, the in-house IC was found to exhibit characteristics similar to those of Scanditronix-Wellhofer IC 70 Farmer type IC.
Conclusion: The constructed in-house Farmer-type IC was able to meet all the recommended characteristics for an IC, and therefore, the in-house IC is suitable for beam output calibration in external beam radiotherapy.

Construction and pre-evaluation of an in-house cylindrical ionization chamber fabricated from locally available materials

Department of Radiography, School of Biomedical and Allied Health Sciences

College of Health Sciences, University of Ghana

Department of Radiation Oncology, National Centre for Radiotherapy and Nuclear Medicine

Department of Health and Technology Support Service- Division of Physical Asset Management

Polish Journal of Medical Physics and Engineering

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Introduction: The objectives of this study were to construct a very robust in-house cylindrical ionization chamber from locally available materials to minimize...

Construction and pre-evaluation of an in-house cylindrical ionization chamber fabricated from locally available materials

Published Online: Nov 17, 2022

Page range: 188 - 199

Received: Jun 26, 2022

Accepted: Oct 23, 2022

DOI: https://doi.org/10.2478/pjmpe-2022-0022

Keywords
in-house ionization chamber, beam output calibration, Perspex, stem effect, leakage current

© 2022 Samuel Nii Adu Tagoe et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Construction and pre-evaluation of an in-house cylindrical ionization chamber fabricated from locally available materials

Published Online: Nov 17, 2022

Page range: 188 - 199

Received: Jun 26, 2022

Accepted: Oct 23, 2022

DOI: https://doi.org/10.2478/pjmpe-2022-0022

Keywordsin-house ionization chamber, beam output calibration, Perspex, stem effect, leakage current

© 2022 Samuel Nii Adu Tagoe et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Keywords
in-house ionization chamber, beam output calibration, Perspex, stem effect, leakage current