Individual A-scan signal normalization between two spectral domain optical coherence tomography devices

Area of Science:

• Ophthalmology
• Medical Imaging
• Biomedical Engineering

Background:

• Spectral-domain optical coherence tomography (SD-OCT) is crucial for eye imaging.
• Variations between SD-OCT devices can hinder direct comparison of imaging data.
• Standardization is needed to enhance the reliability of OCT-based measurements.

Purpose of the Study:

• To develop and validate a signal normalization method for two specific SD-OCT devices (Cirrus HD-OCT and RTVue).
• To increase the comparability of OCT signal profiles obtained from different spectral-domain OCT devices.
• To improve the accuracy of OCT image analysis and measurements across various platforms.

Main Methods:

• Eyes from healthy and glaucoma subjects were scanned using two SD-OCT devices.
• A-scan signals were acquired and registered relative to the foveola.
• Data underwent oversampling, rescaling, speckle noise reduction, and amplitude normalization.
• Mean absolute difference in A-scan profile amplitude was calculated before and after normalization.

Main Results:

• Signal normalization significantly reduced the mean residual A-scan profile amplitude (12.7% to 6.2%, P < 0.0001).
• Statistically significant reductions were observed in all four measured quadrants.
• Normalized differences were smaller than those between repeated scans on the same device.
• No performance differences were noted between healthy and glaucomatous eyes.

Conclusions:

• The developed signal normalization method effectively reduces A-scan profile differences between SD-OCT devices.
• This processing enhances the direct comparability of OCT data across different instruments.
• The method holds potential for improving multi-device OCT image analysis and measurement consistency.