Automatic retinal blood flow calculation using spectral domain optical coherence tomography

Abstract

Optical Doppler tomography (ODT) is a branch of optical coherence tomography (OCT) that can measure the speed of a blood flow by measuring the Doppler shift impinged on the probing sample light by the moving blood cells. However, the measured speed of blood flow is a function of the Doppler angle, which needs to be determined in order to calculate the absolute velocity of the blood flow inside a vessel. We developed a technique that can extract the Doppler angle from the 3D data measured with spectral-domain OCT, which needs to extract the lateral and depth coordinates of a vessel in each measured ODT and OCT image. The lateral coordinates and the diameter of a blood vessel were first extracted in each OCT structural image by using the technique of blood vessel shadowgram, a technique first developed by us for enhancing the retinal blood vessel contrast in the en face view of the 3D OCT. The depth coordinate of a vessel was then determined by using a circular averaging filter moving in the depth direction along the axis passing through the vessel center in the ODT image. The Doppler angle was then calculated from the extracted coordinates of the blood vessel. The technique was applied in blood flow measurements in retinal blood vessels, which has potential impact on the study and diagnosis of blinding diseases like glaucoma and diabetic retinopathy.

Integrating photoacoustic ophthalmoscopy with scanning laser ophthalmoscopy, optical coherence tomography, and fluorescein angiography for a multimodal retinal imaging platform

“…10 Moreover, SD-OCT can measure retinal blood flow by detecting the Doppler shift impinged on the reflected photons. 11 The limitation of SD-OCT, however, is that it is not sensitive to the optical absorption properties of the retina that are strongly associated with various physiological parameters, including oxygen saturation (sO 2 ) and melanin concentration in retinal pigment epithelium (RPE).…”

Quantifizierung von Flussgeschwindigkeiten mit dem Verfahren der Fourier Domain Optische KohärenztomografieFlow Velocity Quantification with Fourier Domain Optical Coherence Tomography

“…Die Phasendifferenz Δϕ wird durch Multiplikation des komplexen A-Scans Γ j+1 (z) mit dem benachbarten, konjugiert komplexen A-Scan Γ * j (z) [9] ermittelt, wie die Gleichung (5) beschreibt: …”

“…Dopplerverschiebung, die durch bewegte Strukturen bei der Bildaufnahme entsteht und wird demzufolge als Doppler FD OCT bezeichnet [7][8][9][10]. Für die Quantifizierung höherer Flussgeschwindigkeiten, bei dem die Doppler FD OCT aufgrund unkorrelierter Phasenbeziehungen benachbarter Tiefensignale limitiert ist, wurde eine zweite Methode entwickelt.…”

Volumetric segmentation of human eye blood vessels based on OCT images

“…The region of intereset for this procedure vary between algorithms. We tested three approaches: two from references [10], [18] and our solution. The main features of these approaches are as follows:…”