Quantitative lateral and axial flow imaging with optical coherence microscopy and tomography

Abstract

Optical coherence tomography (OCT) and optical coherence microscopy (OCM) allow the acquisition of quantitative three-dimensional axial flow by estimating the Doppler shift caused by moving scatterers. Measuring the velocity of red blood cells is currently the principal application of these methods. In many biological tissues, blood flow is often perpendicular to the optical axis, creating the need for a quantitative measurement of lateral flow. Previous work has shown that lateral flow can be measured from the Doppler bandwidth, albeit only for simplified optical systems. In this work, we present a generalized model to analyze the influence of relevant OCT/OCM system parameters such as light source spectrum, numerical aperture and beam geometry on the Doppler spectrum. Our analysis results in a general framework relating the mean and variance of the Doppler frequency to the axial and lateral flow velocity components. Based on this model, we present an optimized acquisition protocol and algorithm to reconstruct quantitative measurements of lateral and axial flow from the Doppler spectrum for any given OCT/OCM system. To validate this approach, Doppler spectrum analysis is employed to quantitatively measure flow in a capillary with both extended focus OCM and OCT.

Full-Field Optical Coherence Tomography as a Diagnosis Tool: Recent Progress with Multimodal Imaging

“…To our knowledge, the contrast revealed by D-FF-OCT is therefore quite unique. Similar dynamic measurements in OCT mainly focus on the blood flow velocity [116,133,134], even with high transverse resolution [135] similar to ours, but, to our knowledge, they never directly show dynamic signals coming from intracellular dynamics. We are wondering whether it comes from a loss in the signal collection due to the use of lower NA illumination, from a difference in the algorithms used (if only blood flow was expected), or from a difference in the exposure time per pixel.…”

Development and Application of Optical Coherence Tomography (OCT)

“…Since the RNFL is damaged in glaucoma-the second leading cause of blindness worldwide [132]-and since RNFL birefringence is connected to layer integrity [133,134], the polarization properties of the RNFL were investigated as potential diagnostic markers for glaucoma. PS-OCT based assessment of the RNFL's birefringent properties might be particularly interesting since it was shown that polarization changes in experimental glaucoma can be observed earlier than RNFL thickness changes [135].…”

Label-free fast 3D coherent imaging reveals pancreatic islet micro-vascularization and dynamic blood flow

“…These parameters are extracted by adapting a joint Spectral and Time domain approach (jSTD) to get the axial and transversal velocities [35,36]. C-scans of 128x4096x1024 pixels were acquired by scanning laterally over 200x200 µm.…”

“…Vessels were segmented by applying thresholding and morphological operators. Blood velocity was computed using the axial and transversal velocity components to get the so-called total velocity [36,37]. The median flow velocities over vessel cross-sections were performed to get an estimated velocity.…”