Imaging and graphing of cortical vasculature using dynamically focused optical coherence microscopy angiography

Abstract

Abstract. Recently, optical coherence tomography (OCT) angiography has enabled label-free imaging of vasculature based on dynamic scattering in vessels. However, quantitative volumetric analysis of the vascular networks depicted in OCT angiography data has remained challenging. Multiple-scattering tails (artifacts specific to the imaging geometry) make automated assessment of vascular morphology problematic. We demonstrate that dynamically focused optical coherence microscopy (OCM) angiography with a high numerical aperture, chosen so the scattering length greatly exceeds the depth-of-field, significantly reduces the deleterious effect of multiplescattering tails in synthesized angiograms. Capitalizing on the improved vascular image quality, we devised and tailored a self-correcting automated graphing approach that achieves a reconstruction of cortical microvasculature from OCM angiography data sets with accuracy approaching that attained by trained operators. The automated techniques described here will facilitate more widespread study of vascular network topology in health and disease.

Multi-Functional OCT Enables Longitudinal Study of Retinal Changes in a VLDLR Knockout Mouse Model

“…This work demonstrates that multi-functional OCT might be a powerful tool for future basic research in ophthalmology and may also have a high impact in other disciplines. For example, Leahy et al [ 46 ] demonstrated the visualization of cortical blood flow in rodents, which shows the potential of OCT in the field of neuro-imaging. The non-invasive characteristic not only allows a direct comparison of individual mice at various ages, it also significantly reduces the numbers of animals used in preclinical research and therefore OCT supports the principles of 3 Rs in basic research which are to replace, to reduce and to refine the use of animals [ 47 ].…”

Investigation of artifacts in retinal and choroidal OCT angiography with a contrast agent

“…As these artifacts are a problem in clinical imaging of choroidal neovascularization, recent research has been directed towards postprocessing algorithms to remove projection artifacts [13,14]. Projection artifacts can also be mitigated by tighter focusing achieved by adaptive optics [29,30], or by using a high NA objective [31] in microscopy. While the multiple scattering theory is plausible based on high RBC forward scattering [32], there is no direct evidence that establishes a causal link in vivo.…”

Mean-Subtraction Method for De-Shadowing of Tail Artifacts in Cerebral OCTA Images: A Proof of Concept

“…Leahy et al employed OCT with a high numerical aperture objective to achieve a shallow depth of field that is much smaller than the scattering length, which essentially blocks multiple scattering, thus mitigating tail artifacts [17]. Despite effectively suppressing the artifacts, the high numerical aperture imaging geometry requires a time-consuming dynamic focusing process to reconstruct OCTA images [17]. You et al intravenously injected an intralipid emulsion into mice, allowing for fewer shadowing effects in mouse somatosensory cortex images [18].…”

“…Recently, Baran et al [23] reported effective suppression of tail artifacts by multiplying an en face OCT structural In order to reduce tail artifacts, a few engineering and software methods have been reported. Leahy et al employed OCT with a high numerical aperture objective to achieve a shallow depth of field that is much smaller than the scattering length, which essentially blocks multiple scattering, thus mitigating tail artifacts [17]. Despite effectively suppressing the artifacts, the high numerical aperture imaging geometry requires a time-consuming dynamic focusing process to reconstruct OCTA images [17].…”