Dosimetry with tissue-equivalent ionisation chambers in fast neutron fields for biomedical applications

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Biomedical Applications

Background:

• Tissue-equivalent (TE) ionisation chambers are the standard for absorbed dose determination in mixed neutron-photon fields.
• Accurate dose measurement is critical for biomedical applications.
• Deriving total absorbed dose requires understanding chamber operational characteristics and applying correction factors.

Purpose of the Study:

• To evaluate the operational characteristics of four TE ionisation chambers.
• To assess the accuracy of TE ionisation chambers for absorbed dose determination.
• To present recent findings from high-pressure gas ionisation chamber operation.

Main Methods:

• Investigated ion collection, gas properties (density, composition), wall thickness, and effective point of measurement for TE ionisation chambers.
• Utilized differential fluence measurements and a TE calorimeter for independent verification.
• Conducted experiments with an ionisation chamber operating at high gas pressures (up to 8 MPa).

Main Results:

• Operational characteristics of four TE ionisation chambers were detailed.
• Absorbed doses derived from TE ionisation chambers showed agreement with independent dosimetry methods within uncertainty limits.
• High-pressure gas ionisation chamber results were presented.

Conclusions:

• TE ionisation chambers are a reliable and practical method for absorbed dose determination in mixed fields.
• Careful experimentation and a shared database can achieve dosimetry results with variations below +/- 2%.
• TE ionisation chambers are suitable for precise dosimetry in biomedical applications.