Abstract
In super-continuum (SC) source based spectral domain optical coherence tomography (SC-SDOCT), the stability of the power spectral density (PSD) has a significant impact on OCT system sensitivity and image signal to noise ratio (SNR). High speed imaging decreases the camera's exposure time, thus each A-scan contained fewer laser pulse excited SC wideband emissions, resulting in a decrease of SNR. In this manuscript, we present a buffer-averaging SC-SDOCT (BASC-SDOCT) to improve the system's performance without losing imaging speed, taking advantage of the excess output power from typical SC sources. In our proposed technique, the output light from SC was passed through a fiber based light buffering and averaging system to improve the PSD stability by averaging 8 SC emissions. The results showed that 6.96 µs of SC emission after buffering and averaging can achieve the same PSD stability equivalent to a longer exposure time of 55.68 µs, despite increasing the imaging speed from 16.8 kHz to 91.9 kHz. The system sensitivity was improved by 8.6 dB, reaching 100.6 dB, which in turn improved SNR of structural imaging, Doppler OCT velocity measurement, and speckle variance OCT (SVOCT) angiographic imaging as demonstrated by phantom and in vivo experiments.
Highlights
Optical coherence tomography (OCT) [1] technique is an emerging imaging modality for medical diagnostics and treatments
In addition to microstructural imaging, OCT microvasculature images are widely used in medical imaging and play an increasingly important role with algorithms for extracting blood flow information such as optical Doppler tomography (ODT) [2,3] or color Doppler OCT (CDOCT) [4] which are able to calculate the axial velocity component of moving scattering particles
As axial resolution in OCT is determined by bandwidth and center wavelength, SC offers an important option for super-high resolution OCT [13,14,15,16,17], such as the axial resolution of 0.88 μm achieved in Lichtenegger's recent work [14]
Summary
Optical coherence tomography (OCT) [1] technique is an emerging imaging modality for medical diagnostics and treatments. An exception has been Yuan et al [16], who reported system sensitivity of 108 dB for structural imaging at exposure time of approximately 14.3 μs and center wavelength of 900 nm This was achieved using high seed laser frequency of 325 MHz, which meant there were 4,647 pulses per camera exposure. At a comparatively low seed frequency of 80 MHz, a sensitivity of 100.6 dB was achieved with an A-line rate of 91.9 kHz at camera exposure time of 6.96 μs (approximately 4,454 seed laser pulses per exposure) To our knowledge, this is the fastest A-scan rate and shortest exposure time achieved with a comparable sensitivity, using a low-cost, passively buffered-averaging SC-SDOCT (BASC-SDOCT) technique to improve system performance and maintained high imaging speed
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