Phase-domain processing of optical coherence tomography images.

Area of Science:

• Biomedical Optics
• Medical Imaging
• Optical Coherence Tomography

Background:

• Optical coherence tomography (OCT) typically forms images from signal envelopes, losing crucial phase information.
• Envelope calculation is a nonlinear process that discards phase data, limiting image quality and analysis.
• Phase aberrations contribute to speckle noise in OCT images, degrading resolution and contrast.

Purpose of the Study:

• To explore processing OCT interference signals in the complex domain before envelope calculation.
• To investigate the use of phase information for correcting aberrations and reducing speckle noise.
• To evaluate a novel complex-domain speckle reduction technique, the zero-adjustment procedure (ZAP).

Main Methods:

• Developed an OCT system with quadrature demodulation for accurate phase and amplitude recording.
• Implemented and investigated the zero-adjustment procedure (ZAP) for complex-domain signal processing.
• Validated ZAP's speckle-correction properties through mathematical analysis and numerical simulations.

Main Results:

• ZAP effectively reduces speckle contrast in OCT images, particularly in high scatterer density regions.
• The technique expands the dynamic range of gray values within the OCT images.
• Current implementation of ZAP can lead to blurring of sharp boundaries between image features.

Conclusions:

• Complex-domain processing of OCT signals offers a pathway to correct phase aberrations and mitigate speckle noise.
• The ZAP technique demonstrates potential for enhancing OCT image quality by reducing speckle.
• Further refinement of ZAP is needed to address the blurring of image feature boundaries.