How effective can optical-CT 3D dosimetry be without refractive fluid matching?

Area of Science:

• Medical Physics
• Radiological Imaging
• Computational Science

Background:

• Accurate 3D dosimetry is crucial for radiation therapy.
• Current optical CT dosimetry often requires viscous refractive index (RI) matching fluids, limiting convenience.
• Developing fluid-free or low-viscosity methods enhances practical application.

Purpose of the Study:

• To simulate and evaluate optical CT 3D dosimetry without viscous RI matching fluids.
• To assess the impact of different scanning configurations and refractive media on dosimetric accuracy.
• To determine the feasibility of dry or low-viscosity scanning for specific applications.

Main Methods:

• Software simulation of optical CT 3D dosimetry.
• Investigation of parallel-beam, point, and converging light source geometries.
• Evaluation of three refractive media: air (RI=1.00), water (RI=1.33), and a Presage-matched fluid (RI=1.49).

Main Results:

• Usable dosimeter radius decreased to 68% with water and 31% with air.
• Point source geometry showed slightly better results than other configurations.
• Dry scanning (air) increased detector size by a factor of six, impacting cost.

Conclusions:

• Eliminating viscous matching fluids significantly reduces dosimetric accuracy, particularly in peripheral regions.
• Dry or low-viscosity scanning may be viable for applications not requiring peripheral dose information.
• Further research into optimized scanning geometries and detector configurations is warranted for fluid-free optical CT dosimetry.