Absolute dosimetry on a dynamically scanned sample for synchrotron radiotherapy using graphite calorimetry and...

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Synchrotron Radiation Applications

Background:

• Accurate dose measurement is critical for radiation therapy and medical imaging.
• The Australian Synchrotron's Imaging and Medical Beamline (IMBL) requires precise dosimetry for its dynamically scanned beams.
• Existing dosimetry methods need validation against primary standards for synchrotron applications.

Purpose of the Study:

• To measure the absolute dose delivered by the IMBL at the Australian Synchrotron.
• To establish a graphite calorimeter as a primary standard for synchrotron dosimetry.
• To compare calorimeter measurements with ionization chambers and a free-air chamber.

Main Methods:

• Absolute dose measurement using a graphite calorimeter.
• Comparison with a free-air chamber (FAC) and two ionization chambers (PTW 31014 Pinpoint and PTW 34001 Roos).
• Monte Carlo (MC) simulations (EGSnrc code) and AAPM TG-61 protocol for dose conversion.
• Calibration of ionization chambers against the Australian primary standard for air kerma.

Main Results:

• Agreement of 2% or better was achieved between the graphite calorimeter and ionization chambers.
• The free-air chamber measured a dose 3-5% higher than the calorimeter, within uncertainties.
• The calorimeter provides a reliable method for absolute dose determination at the IMBL.

Conclusions:

• The graphite calorimeter is suitable for establishment as a primary standard for synchrotron dosimetry.
• The study validates dosimetry protocols for scanned beams at the IMBL.
• Precise dose delivery is confirmed, supporting clinical applications of synchrotron radiation.