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Multimodal Volumetric Retinal Imaging by Oblique Scanning Laser Ophthalmoscopy oSLO and Optical Coherence Tomography OCT
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Flexible A-scan rate MHz-OCT: efficient computational downscaling by coherent averaging
Tom Pfeiffer1,2, Madita Göb1, Wolfgang Draxinger1
1Institut für Biomedizinische Optik, Universität zu Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany.
Biomedical Optics Express
|December 7, 2020
Summary
Coherent averaging in MHz-OCT systems allows adjustable A-scan rates, enhancing image quality and sensitivity. This technique achieves up to 100x averaging without special hardware, improving optical coherence tomography performance.
Area of Science:
- Biomedical Optics
- Medical Imaging Technology
Background:
- Fast optical coherence tomography (OCT) systems, particularly those using Fourier Domain Mode Locked (FDML) lasers, face challenges in balancing imaging speed with data quality.
- Achieving higher sensitivity and improved image resolution often requires compromises in acquisition rates.
Purpose of the Study:
- To investigate and demonstrate the feasibility of adjustable A-scan rates in MHz-OCT systems through coherent averaging.
- To analyze the technical challenges and solutions for efficient coherent averaging in swept-source OCT.
- To quantify the achievable sensitivity gains and speed reductions using this method.
Main Methods:
- Acquisition of OCT image data using a MHz-OCT system based on an FDML laser.
- Implementation of software-based coherent averaging strategies to reduce the A-scan rate.
- Analysis of technical requirements and solutions for coherent averaging in swept-source OCT.
- In vivo imaging of a human finger knuckle joint for comparison.
Main Results:
- Demonstrated that coherent averaging is achievable at MHz OCT speeds without specialized interferometer designs or digital phase stabilization.
- Achieved up to approximately 100x coherent averaging, resulting in a sensitivity increase close to ideal values (20 dB gain).
- Reduced effective imaging speed from 3.3 MHz to 33 kHz while maintaining high sensitivity (121 dB).
- Showcased improved image quality and sensitivity through coherent averaging compared to magnitude averaging.
Conclusions:
- Coherent averaging offers a viable method for adjusting A-scan rates in MHz-OCT systems, enhancing sensitivity and image quality.
- The proposed techniques overcome specific challenges of coherent averaging in swept-source OCT, enabling significant performance improvements.
- This approach provides substantial benefits for low-sensitivity MHz-OCT systems, particularly through computational downscaling.
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