Abstract
Purpose :
To develop a new dual-channel VIS-OCT to achieve micron-level resolution, extended imaging range, and shot-noise limited imaging.
Methods :
We designed and implemented three engineering solutions. First, a linear-in-K spectrometer for VIS-OCT is developed to overcome the wavelength-dependent roll-off in VIS-OCT and improve the overall roll-off performance. Second, we introduced a reference pathlength modulation to achieve full-range VIS-OCT by introducing phase modulation within B-scans. A retro-refelctor was installed in the reference arm allowing real time modulation of the reference pathlength. The reference modulation was also used to maintain the retina within the imaging depth range. Third, an active noise cancellation was used by recording the reference spectrum per A-line to effectively remove the excessive noise from the Supercontinnum generation.
Results :
The linear-in-K spectrometer achieved 7.2dB roll-off over the entire imaging depth range (Fig. 1a), ~50% of the state-of-the-art, within which the axial resolution is characterized at 1.3-1.7 μm in water. The spectral coverage is from 500-640nm. Full-range VIS-OCT doubled the imaging range to 1.74 mm in water by the reference pathlength modulation within B-scans (Fig. 1c). The imaging system is operating at 100kHz. The power on corneal is ~0.22-0.24mW. The active noise cancellation achieved the shot-noise imaging performance, characterzied by linear relation between pixel value and variance, suppressing the excessive noise by 4-folds at the zero-delay line (Fig. 1b). The dual-channel design includes a conventional near-infrared (NIR) channel, facilitating the initial alignment without excessive visible light exposure. The dual-channel design makes VIS-OCT compatible with Doppler OCT and OCT angiography (OCTA) by NIR-OCT.
Conclusions :
The second generation dual-channel VIS-OCT alleviates the trade-off between micron-level axial resolution and imaging depth, improving the practical use in clinical setting. The linear-in-K spectrometer, reference pathlength modulation and active noise cancellation dramatically improved the viability of VIS-OCT in clinical settings.
This abstract was presented at the 2023 ARVO Imaging in the Eye Conference, held in New Orleans, LA, April 21-22, 2023.