Reference dosimetry at the neutron capture therapy facility at Studsvik

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Neutron Therapy

Background:

• Neutron capture therapy (NCT) relies on precise dose delivery.
• Epithermal neutron beams are utilized in NCT, requiring accurate dosimetry.
• Reference dosimetry methods for these beams need thorough evaluation.

Purpose of the Study:

• To present and evaluate reference dosimetry methods for epithermal neutron beams.
• To calibrate the epithermal neutron beam at the Studsvik NCT facility.
• To determine absorbed doses and neutron fluence with associated uncertainties.

Main Methods:

• Measurements conducted in a PMMA phantom and in air.
• Utilized ionization chambers and activation probes for calibration.
• Employed Monte Carlo methods for beam-dependent detector calibration factors.

Main Results:

• Determined photon, neutron, and total absorbed dose to PMMA with uncertainties of +/- 5.0%, +/- 25%, and +/- 5.5% (2 SD), respectively.
• Photon absorbed dose uncertainty is comparable to conventional radiotherapy.
• Thermal neutron group fluence determined with an uncertainty of +/- 2.8% (2 SD), deemed acceptable.

Conclusions:

• The presented methodology allows for the determination of absorbed doses in epithermal neutron beams.
• Current methods yield higher uncertainty for neutron absorbed dose compared to photon absorbed dose.
• The achieved uncertainty in thermal neutron fluence is suitable for dosimetry applications in epithermal neutron beams.