High-performance dosimetric gel for low-dose-rate 3D-printed brachytherapy devices

Area of Science:

• Medical Physics
• Radiotherapy Dosimetry
• Biomedical Engineering

Background:

• Traditional gel dosimeters face limitations in low-energy photon brachytherapy due to stability and water equivalency issues.
• Low-dose-rate (LDR) brachytherapy, particularly for eye cancers using isotopes like 125I, requires precise dosimetry.
• Existing dosimetric methods struggle with the specific challenges of LDR brachytherapy applications.

Purpose of the Study:

• To develop and optimize a novel dosimetric gel (MAGIC-pf) for low-energy photon brachytherapy.
• To evaluate the performance of MAGIC-pf gel with 125I radioactive seeds in 3D-printed brachytherapy implants.
• To assess the gel's suitability for precise dose distribution measurements in ocular treatments.

Main Methods:

• Optimized the MAGIC gel formulation using agarose (MAGIC-a) and paraformaldehyde (MAGIC-pf).
• Assessed thermal/temporal stability and self-polymerization using MRI and NMR relaxometry.
• Evaluated water equivalency via Monte Carlo simulations and measured radiation sensitivity to 125I and 192Ir sources.

Main Results:

• MAGIC-pf gel exhibited superior thermal and temporal stability and enhanced MRI readout performance.
• Measured sensitivity of MAGIC-pf to 125I seeds ranged from 0.1 to 0.388 Gy-1.s-1 across 1.5T and 3T MRI.
• 3D-printed implants with 125I seeds demonstrated reproducible, precise dose distributions visualized in 2D and 3D.

Conclusions:

• MAGIC-pf gel offers excellent stability, water equivalency, and compatibility with both LDR and HDR brachytherapy.
• The sub-millimetric dose profiles achieved are ideal for personalized, next-generation 3D-printed brachytherapy implants.
• This novel gel dosimeter advances precision dosimetry for advanced brachytherapy techniques.