Cone-beam optical computed tomography for gel dosimetry II: imaging protocols

Area of Science:

• Medical Physics
• Radiation Dosimetry

Background:

• Accurate radiation dose measurement is crucial in radiotherapy.
• Fricke-xylenol orange-gelatin (FXG) dosimeters offer potential for 3D dose verification.
• Existing imaging protocols require optimization for FXG dosimeters.

Purpose of the Study:

• To develop and validate imaging protocols for improved dose readout of FXG gel dosimeters.
• To enhance the accuracy and reliability of dose measurements using optical CT.

Main Methods:

• Utilized a commercial cone-beam optical computed tomography (CT) scanner.
• Established optimal warm-up times and light source management for scanner stability.
• Implemented precise temperature control (±0.2 °C) to mitigate thermochromic effects.
• Defined a standard post-irradiation wait time (30 min) to minimize diffusion uncertainties.

Main Results:

• Scanner warm-up (2 h) and continuous light source operation improved stability.
• Temperature control procedures effectively reduced thermochromic artifacts.
• A 30-minute post-irradiation wait time minimized measurement uncertainties.
• Stray light was identified but deemed manageable through calibration, not additional imaging protocols.

Conclusions:

• Optimized imaging protocols significantly improve dose readout accuracy for FXG dosimeters.
• Temperature control and standardized wait times are critical for reliable FXG dosimetry.
• Future improvements may involve dosimeter modification and inter-jar calibration.