Optical Coherence Tomography Angiography (OCTA)

 

In the early nineties, a new optical method based on low-coherence interferometry called Optical Coherence Tomography (OCT) [1] was developed. This non-invasive imaging method has been widespread in ophthalmology over the past decades thanks to its ability to visualize ocular structures at high resolution in lateral and axial direction.

To further improve axial resolution, the use of an ultra-broadband source is needed such as a supercontinuum source from NKT Photonics. Although this system is able to provide good visual structural data, doctors want more by asking to add different kinds of information. Therefore, there is a strong pull for OCT to move from structural imaging to functional imaging to add additional information to the morphological information, like polarization sensitive OCT, spectroscopic OCT, elastographic OCT and so forth.
Age-related macular degeneration, glaucoma and diabetic retinopathy are the three main causes for visual field loss and blindness. These diseases have an impact on blood vessels such as the presence of choroidal neovacularization, a reduction or complication in retinal blood flow. Currently, the gold standard for imaging the vasculature network is Fluorescein Angiography (FA) and Indocyanine Green Angiography (IGA). However, both are invasive and require intravenous dye injections.

OCT angiography is a solution providing superficial and deep vascular plexuses. This method solves the previous mentioned issues from FA and IGA. In this project, different methods from phase sensitivity OCT to speckle variance OCT are investigated [2],[3],[4].

Software was developed to isolate the fluid in a tube to simulate blood flow. Figure 1 presents a B-scan and an angiography image of the sample used, which is a tube connected to a pump to create flow. To highlight the flow, two successive B-scans are recorded and the correlation is calculated. By combining B-scans and angiography images, flow can be separated from the static features giving doctors access to structural and functional information.

 

angio

Figure 1: (a) B-scan, (b) Angiography image and (c) combination of B-scan and angiography image of a tube with fluid on a cardboard

References:

[1] J.G. Fujimoto, J.G and Drexler, W., 2008, Springer-Verlag

[2] Sultan Mahmud,M., Cadotte, D.W., Vuong, B., Sun, C., Luk, T.W.H., Mariampillai, A. and Yang, V.X.D., 2013, Journal of Biomedical Optics, 18(5)

[3] Anqui, Z., Qinqin, Z., Chieh-Li, C., and Ruikang, K.W., 2015, Journal of Biomedical Optics, 20(10)

[4] Gorczynska, I., Migacz, J.V., Zawadzki, R.J., Capps, A.G. and Werner, J.S., 2016, BIOMEDICAL OPTICS EXPRESS, 7(3)

Leave a Reply

Your email address will not be published. Required fields are marked *