Development of Next-Generation Low-Cost Optical Coherence Tomography (OCT) Systems: Advancing Retinal Imaging for Clinical Applications

Academic Background

Optical Coherence Tomography (OCT) is a non-invasive, high-resolution imaging technology widely used in ophthalmology, particularly for diagnosing retinal diseases. However, existing commercial OCT systems are expensive (ranging between $40,000 and $150,000), limiting their use in resource-limited settings. To increase the accessibility of OCT technology, researchers are dedicated to developing low-cost OCT systems that can provide high-quality retinal imaging at the point-of-care. This study introduces a next-generation low-cost OCT system that significantly improves imaging performance through hardware design and image processing algorithm enhancements, making it highly competitive for clinical applications.

Source of the Article

This paper, authored by Hillel B. Price, Ge Song, Wan Wang, and others from the Department of Biomedical Engineering at Duke University, was published in the February 1, 2025 issue of Biomedical Optics Express (Volume 16, Issue 2). The research was supported by funding from the U.S. National Institutes of Health (NIH).

Research Workflow and Details

1. System Design and Hardware Improvements

The research team developed three generations of low-cost OCT systems (Gen 1, Gen 2, Gen 3), each featuring significant upgrades in hardware and software. The Gen 1 system reduced costs through 3D printing and custom electronics but lagged in imaging performance compared to commercial systems such as the Heidelberg Spectralis. The Gen 2 system introduced hardware improvements such as stable superluminescent diode (SLD) output power, a higher A-line rate (40 kHz), and an improved spectrometer design. The Gen 3 system further incorporated balanced detection technology, significantly enhancing signal recovery and noise suppression.

• Gen 1 System: Used an SLD light source without thermal control and a 3D-printed spectrometer housing, costing $5,037.
• Gen 2 System: Featured a thermally controlled SLD and a faster camera, costing $6,097.
• Gen 3 System: Added a second spectrometer and balanced detection, bringing the cost to $9,522.

2. Image Processing Algorithm

To enhance image quality, the research team developed a self-referenced histogram matching (HM) algorithm. This algorithm generates a reference histogram through image blurring and matches it to the original image histogram, improving the contrast-to-noise ratio (CNR) without sacrificing resolution. In addition, the Gen 3 system introduced depth-dependent background noise correction, further enhancing image quality.

3. Clinical Studies

Clinical trials were conducted at Duke University to evaluate the imaging performance of the Gen 2 and Gen 3 systems. The Gen 2 system was tested on 12 healthy participants, while the Gen 3 system was tested on 14 healthy participants. By comparing CNR values across different systems, the researchers found that the Gen 3 system achieved significantly higher CNR values than both Gen 1 and Gen 2 systems, and in some cases, even outperformed commercial systems.

• Gen 1 System: CNR of 1.69 ± 0.27 (average across 2 B-scans).
• Gen 2 System: CNR of 1.74 ± 0.07 (average across 2 B-scans), increasing to 1.93 ± 0.08 with 9-scan averaging.
• Gen 3 System: CNR of 2.01 ± 0.39 (average across 9 B-scans), significantly surpassing the commercial system’s 1.80 ± 0.33.

4. Spectrometer Performance

The Gen 3 system demonstrated notable improvements in spectrometer performance, achieving a dynamic range of 114 dB for single-channel detection and nearing 120 dB for balanced detection, comparable to some swept-source OCT systems. Moreover, the Gen 3 system redesigned its spectrometer to use a lens instead of an off-axis parabolic (OAP) mirror, reducing power losses and improving efficiency.

Major Findings

• Improved Image Quality: The balanced detection and HM algorithms of the Gen 3 system significantly enhanced image quality, yielding a 73% increase in CNR compared to single-channel detection.
• Enhanced Clinical Usability: The inclusion of an external fixation target and an upgraded pupil camera in the Gen 3 system enabled operators to acquire retinal images more quickly and accurately.
• Cost-Effectiveness: Although the Gen 3 system’s cost increased ($9,522), it achieved significantly better performance than its predecessors while still being priced far below commercial systems.

Conclusions and Implications

The third-generation low-cost OCT system demonstrated remarkable progress in imaging performance, operational ease, and cost-effectiveness. By incorporating balanced detection, optimized spectrometer design, and self-referenced histogram matching algorithms, the Gen 3 system achieved retinal image quality comparable to commercial systems. This development offers new possibilities for diagnosing retinal diseases in resource-limited settings, particularly for point-of-care applications.

Research Highlights

1. Hardware Innovations: The Gen 3 system introduced balanced detection and an improved spectrometer design, significantly enhancing signal recovery and noise suppression.
2. Algorithmic Innovations: The self-referenced histogram matching algorithm improved image contrast without sacrificing resolution.
3. Clinical Applications: The incorporation of an external fixation target and upgraded pupil camera improved operational convenience and imaging accuracy.
4. Cost-Effectiveness: Despite a moderate cost increase, the Gen 3 system outperformed its predecessors and remained far more affordable than commercial alternatives.

Additional Valuable Information

The research team also explored future directions for optimization, including real-time image processing algorithm development and large-scale production to further reduce costs. Furthermore, the Gen 3 system’s design provides a reference framework for other OCT applications, such as diagnosing neurodegenerative diseases.

This study establishes an important theoretical and practical foundation for the development of low-cost OCT technology, offering broad scientific and application value.