A spatial resolution study of a new optical tomography-based polymer gel dosimetry system

Area of Science:

• Medical Physics
• Imaging Technology
• Radiation Dosimetry

Background:

• Polymer gel dosimeters are crucial for 3D radiation dosimetry.
• Accurate spatial resolution is essential for precise dose reconstruction.
• The OCTOPUS-IQ scanner and BANG3-Pro2 gel offer advanced capabilities for 3D dosimetry.

Purpose of the Study:

• To investigate the spatial resolution limits of the OCTOPUS-IQ scanner when used with BANG3-Pro2 polymer gel.
• To assess the impact of scanning parameters on image quality and resolution.
• To determine the effective imaging range of the system for accurate dose mapping.

Main Methods:

• A high-contrast needle phantom with thin needles (0.3 mm diameter) was scanned.
• Scans were performed at various slice spacings (0.25-1.0 mm) and laser beam orientations.
• Optical density profiles, Full Width at Half Maximum (FWHM), Point Spread Function (PSF), and Modulation Transfer Function (MTF) were analyzed.

Main Results:

• The system achieved a spatial resolution of 0.5 mm or less, with measured PSFs having a FWHM of 0.95 mm at the center.
• Image quality showed degradation with increasing off-axis distance due to laser beam defocusing.
• No significant resolution degradation was observed within a 50 mm radius from the center.

Conclusions:

• The OCTOPUS-IQ scanner and BANG3-Pro2 gel combination provides high spatial resolution suitable for 3D dosimetry.
• Careful consideration of scanning parameters and off-axis effects is necessary for optimal results.
• The system is reliable for dose reconstruction within a significant imaging volume.