Development of a second-generation fiber-optic on-line image verification system

Area of Science:

• Medical Physics
• Radiological Imaging
• Biomedical Engineering

Background:

• Fiber-optic fluoroscopic systems are used for on-line imaging in radiation therapy.
• Existing systems have limitations including grid artifacts and insufficient resolution due to fiber dimensions.
• These artifacts and limitations can hinder accurate visualization and treatment verification.

Purpose of the Study:

• To develop solutions for reducing grid artifacts in fiber-optic fluoroscopic systems.
• To improve the spatial resolution of on-line imaging systems used in radiation therapy.
• To enhance the overall quality of images for clinical purposes.

Main Methods:

• Investigated magnetic field effects on camera scanning mechanisms and implemented mu-metal shielding.
• Replaced Newvicon cameras with charge-coupled-device (CCD) cameras to mitigate magnetic interference.
• Constructed a high-resolution prototype using smaller input fibers (0.8 mm x 0.8 mm) with a 250x250 array.
• Tested prototype performance using phantom studies.

Main Results:

• Both mu-metal shielding and CCD camera replacement effectively reduced grid artifacts.
• High contrast resolution improved significantly, with the modulation transfer function (MTF) 30% value increasing from 0.3 to 0.7 line pairs/mm.
• The high-resolution prototype showed enhanced detail but had reduced effectiveness in low contrast object detection due to transmission non-uniformity.

Conclusions:

• The implemented methods successfully reduced grid artifacts and improved high contrast resolution in fiber-optic fluoroscopic systems.
• Challenges remain in low contrast detection, attributed to prototype fiber non-uniformity and light collection efficiency.
• Findings inform the development of next-generation clinical on-line image verification systems.