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Absorbed dose in water. Comparison of several methods using a liquid ionization chamber
O Mattsson1, H Svensson, G Wickman
1Department of Radiation Physics, Sahlgrenska Sjukhuset, Göteborg, Sweden.
Acta Oncologica (Stockholm, Sweden)
|January 1, 1990
Summary
A liquid ionization chamber accurately measures absorbed dose in water using cobalt-60 gamma rays. This new method shows excellent agreement (0.2%) with established dosimetry techniques, confirming consistency in absorbed dose determination.
Area of Science:
- Medical Physics
- Radiation Dosimetry
Background:
- Accurate absorbed dose determination in water is crucial for radiotherapy.
- Established dosimetry methods include air-ionization chambers, water calorimetry, and ferrous-sulphate dosimetry.
Purpose of the Study:
- To evaluate a liquid ionization chamber as a transfer instrument for absorbed dose in water.
- To compare its performance against established dosimetry techniques.
- To investigate the impact of updated air kerma standards on dosimetry.
Main Methods:
- Utilized a liquid ionization chamber with a cobalt-60 gamma-ray beam.
- Compared measurements with air-ionization chamber dosimetry, water calorimetry, and ferrous-sulphate dosimetry.
- Analyzed the effect of the 1986 BIPM air kerma standard.
Main Results:
- The liquid ionization chamber demonstrated excellent agreement (within 0.2%) with other dosimetry methods.
- Consistency in absorbed dose determination was confirmed.
- Differences in air kerma standards did not affect cobalt-60 beam dosimetry results.
- The ferrous-sulphate dosimeter's epsilon mG value is applicable to cobalt-60 beams.
Conclusions:
- The liquid ionization chamber is a reliable transfer instrument for absorbed dose in water.
- Current dosimetry methods for cobalt-60 beams are consistent.
- The new air kerma standard has no net impact on cobalt-60 dosimetry.
- Ferrous-sulphate dosimetry recommendations are applicable across different radiation types.