Radiological properties of the PRESAGE and PAGAT polymer dosimeters

Area of Science:

• Medical Physics
• Radiotherapy Dosimetry
• Polymer Science

Background:

• Accurate dosimetry is crucial for effective radiotherapy treatment planning and delivery.
• Polymer gel dosimeters offer potential advantages for 3D dose verification.
• Assessing the radiological water equivalence of dosimeters is essential for their clinical application.

Purpose of the Study:

• To investigate and compare the radiological properties and water equivalence of PRESAGE and PAGAT polymer dosimeters.
• To determine the suitability of these dosimeters for radiotherapy dosimetry applications.
• To identify which polymer formulation exhibits better water equivalence.

Main Methods:

• Comparison of photon and electron interaction cross-sections from 10 keV to 20 MeV.
• Monte Carlo modeling of depth dose using the BEAMnrc software package.
• Evaluation of effective Z-value, mass density, photoelectric interaction probability, stopping power ratios, and scattering power ratios.

Main Results:

• PAGAT showed a mass density 2.6% higher than water, with stopping and scattering power ratios <1%.
• PRESAGE had higher effective Z-value and mass density, with significant differences in photoelectric interaction probability.
• Depth dose comparisons showed PAGAT with <1% absolute and <2.5% relative difference to water, while PRESAGE had <2% absolute and <8% relative difference.

Conclusions:

• The PAGAT polymer gel formulation is more radiologically water equivalent than PRESAGE.
• PRESAGE, despite not being as water equivalent, offers usability benefits and can be corrected with dosimetric factors.
• PAGAT is a more suitable candidate for accurate radiotherapy dosimetry due to its superior water equivalence.