optical coherence tomography angiography

#Optical coherence tomography angiography skin#

A short scan time prevents too much patient movement during signal acquisition. One approach to decreasing the influence of movement on signal detection is to shorten the scanning time. Movement introduces a lot of noise into the signal making tiny vessels impossible to distinguish. Greater fluctuations receive a greater decorrelation value and indicate more movement.Ī significant challenge when trying to image the eye is patient movement and saccadic movement of the eye. The equation takes into account fluctuations of the received signal amplitude or intensity over time. The blood vessels are where the most decorrelation occurs allowing them to be visualized, while static tissue has low decorrelation values. The split-spectrum amplitude decorrelation angiography (SSADA) algorithm calculates the decorrelation in the reflected light that is detected by the OCT device. Calculating blood flow Īn algorithm developed by Jia et al., is used to determine blood flow in the retina. Multiple algorithms have been proposed and utilized to contrast such motion signals from static signals in various biological tissues.

To simply put it, the backscattered light reflected back from static samples would remain the same over multiple B-scans while the backscattered light reflected back from moving samples would fluctuate. OCTA detects moving particles ( red blood cells) by comparing sequential B-scans at the same cross-sectional location. Similarly, OCTA was shown to provide more refined information compared to dye-based angiography in other vascular occlusive diseases such as central (or branch) retinal vein occlusion. Thus, OCTA may offer in future the potential to monitor the progression of DR at an earlier, pre-clinical state. Moreover, OCTA was shown to provide a plethora of additional biomarkers including subclinical loss of vessel density. In DR, OCTA was shown to resolve previously established markers of severe disease (i.e., vitreous proliferation). While conventional dye-based angiography is still the common gold standard, OCTA has been evaluated and used across many diseases. This has allowed OCTA to become widely used clinically to diagnose a variety of ophthalmological diseases, such as, age related macular degeneration (AMD), diabetic retinopathy, artery and vein occlusions, and glaucoma.

Recent advancements in OCT acquisition speed have made it possible the required sampling density to obtain a high enough resolution for OCTA. This form of OCT requires a very high sampling density in order to achieve the resolution needed to detect the tiny capillaries found in the retina. To correct for patient movement during scanning, bulk tissue changes in the axial direction are eliminated, ensuring that all detected changes are due to red blood cell movement. OCTA uses low-coherence interferometry to measure changes in backscattered signal to differentiate areas of blood flow from areas of static tissue. OCTA may make use of speckle variance optical coherence tomography.

#Optical coherence tomography angiography skin#

Optical coherence tomography angiography (OCTA) is a non-invasive imaging technique based on optical coherence tomography (OCT) developed to visualize vascular networks in the human retina, choroid, skin and various animal models.