TU-E-BRA-07: Post-Operative Eye Plaque Imaging Using Tomotherapy MVCT.

Area of Science:

• Medical Physics
• Radiation Oncology
• Ophthalmology

Background:

• Intra-operative ultrasound is standard for verifying episcleral eye plaque positioning in ocular melanoma treatment.
• Ultrasound imaging can be limited by artifacts and plaque displacement post-surgery, especially for anterior tumors.
• Post-operative imaging is crucial for timely interventions to prevent treatment failure.

Purpose of the Study:

• To investigate the feasibility of using Tomotherapy megavoltage computed tomography (MVCT) for post-implantation verification of eye plaque positioning.
• To assess the image quality and conditions under which MVCT can accurately confirm plaque placement and tumor coverage.

Main Methods:

• Episcleral plaques were placed on preserved cow eyes and imaged using a Tomotherapy linear accelerator's MVCT system.
• Image quality was evaluated visually and quantitatively, using lens visibility as a proxy for tumor visibility.
• Image averaging techniques were employed to simulate higher beam current imaging for improved signal-to-noise ratio.

Main Results:

• The eye plaque, lens, and globe were clearly visible in the MVCT images.
• The contrast-to-noise ratio (CNR) for the lens improved from 5.6 (single image) to 9.2 (10 averaged images).
• The estimated radiation dose was within acceptable limits for image-guided radiotherapy, though scan times were long (up to 240 seconds).

Conclusions:

• Tomotherapy MVCT imaging is a viable option for verifying eye plaque position and tilt after episcleral implantation.
• Standard MVCT images can visualize tumors, but higher beam current imaging would enhance visualization.
• Further human trials are planned to validate these findings in clinical settings.