SU-E-T-93: High Dynamic Range Scanning for Optical-CT in 3D Dosimetry.

Area of Science:

• Medical Physics
• Radiation Oncology
• Imaging Science

Background:

• 3D dosimetry is crucial for radiation therapy quality assurance.
• Optical-computed tomography (optical-CT) offers high-resolution 3D dosimetry potential.
• Imaging strongly attenuating dosimeters presents challenges for accuracy.

Purpose of the Study:

• To present a novel optical-CT acquisition method for improved 3D dosimetry.
• To enhance accuracy when imaging strongly attenuating dosimeters.
• To improve signal-to-noise ratio in challenging dosimetry scenarios.

Main Methods:

• Acquired optical-CT projection images with increased light source intensity, avoiding detector saturation.
• Addressed saturation issues in flood-field images by using reduced shutter times.
• Scaled non-saturated flood-field images using shutter time ratios and investigated signal linearity.

Main Results:

• Demonstrated high linearity between signal and shutter time, validating the method's foundation.
• Achieved high agreement (<1% deviation) with standard methods for moderately attenuating dosimeters.
• Significantly improved signal-to-noise (2-3x) in dark regions and eliminated artifacts for strongly attenuating dosimeters.

Conclusions:

• The new optical-CT method improves signal-to-noise for 3D dosimetry in strongly attenuating dosimeters.
• The method enhances convenience and practicality by eliminating the need for fluid tinting in the optical-CT water-bath.
• This advancement strengthens quality assurance in radiation therapy.