Angiography debuts as latest upgrade to high-definition OCT platform

Take-home message: OCT angiography (AngioPlex OCT Angiography) is now available as an upgrade to the CIRRUS 5000 HD-OCT platform (Carl Zeiss Meditec). The technology allows visualization of the blood flow and microvasculature in the retina, choriocapillaris, and choroid with the ease of noninvasive imaging.

By Cheryl Guttman Krader, Reviewed by Philip J. Rosenfeld, MD, PhD

AngioPlex OCT Angiography, now available as an upgrade on the CIRRUS 5000 HD-OCT platform (Carl Zeiss Meditec), is the first OCT angiography system available in the United States, and it is expected to provide clinicians and researchers with valuable new information about the blood flow and microvasculature in the retina, choriocapillaris, and choroid.

“AngioPlex OCT Angiography affords visualization of microvascular abnormalities and perfusion defects with the ease of obtaining a routine non-invasive OCT scan,” said Philip J. Rosenfeld, MD, PhD, professor of ophthalmology, Bascom Palmer Eye Institute, University of Miami, Miami, FL.

“The processing time is a little longer than with traditional OCT, and clinicians will need to spend more time reviewing the images, but this is time well spent. I’m learning something new every day and the images are breathtaking. Unlike traditional angiography, OCT angiography avoids the need for injections of contrast dye so that the experience for the patient is the same as with standard OCT imaging, and the clinician gets more information that is bound to be helpful,” he said.

AngioPlex OCT Angiography uses the fast spectral-domain imaging of the CIRRUS 5000 HD-OCT platform (68,000 A-scans/sec) and generates two-dimensional structural, intensity, and flow images by averaging 4 B-scans taken in rapid sequence at the same location of the retina. It scans an area of 3mm x 3mm or 6mm x 6mm and uses a proprietary real-time tracking system (FastTrac) that reduces artifacts from eye motion and increases scan success for poorly fixating patients.

Image processing is done using proprietary algorithms (Optical Micro Angiography, OMAG) that analyze changes in both intensity and phase signals within sequential B-scans to determine blood flow.

“With the OCT angiography upgrade, there is higher scan density than with conventional CIRRUS B-scan imaging, and image quality is improved because of the averaging of the 4 B-scans at each location. So, the quality of the standard OCT structural image is better with the angiography upgrade than with the standard CIRRUS imaging,” Dr. Rosenfeld said.

“Consequently, it is a win-win situation for users. We get blood flow images along with higher quality structural images.”

The images also can be manipulated with different segmentation patterns so that the microvasculature can be viewed in different layers within the retina as well as in the choriocapillaris and choroid. In addition, there are benefits of the enface intensity algorithms that Zeiss offers in its standard CIRRUS instrument.

“There is some signal roll-off below the retinal pigment epithelium since this is an SD-OCT system. Nevertheless, the Zeiss system has excellent algorithms and flexibility for segmentation,” Dr. Rosenfeld said.

“The ability to move the boundary lines enables evaluation of different tissues in different patients as needed depending on their disease, and the layers can be visualized not only as thickness maps, but also in enface intensity and flow images.”

Applications

Dr. Rosenfeld said AngioPlex OCT angiography is ideal for studying the microvasculature in diseases that affect the central macula, such as age-related macular degeneration (AMD), diabetic maculopathy, retinal vein occlusions, and macular telangiectasia type 2. In addition, there is interest in using OCT angiography to look at the microvasculature around the optic nerve in glaucoma and other optic nerve diseases.

“The scanning area can be moved out to the periphery, but the system is not able to do widefield angiography out to the periphery,” Dr. Rosenfeld said.

Since OCT angiography is so new, further investigation is needed to determine how clinicians will incorporate the information into patient management. In the meantime, since OCT angiography imaging has no impact on workflow, Dr. Rosenfeld encouraged clinicians to start acquiring and studying the images to help them learn more about the technology, about the diseases, and about how they may use the technology in clinical care.

Dr. Rosenfeld said that OCT angiography will clearly be a valuable tool for researchers aiming to understand the progression of diabetic retinopathy; the development, growth, and treatment-induced regression of AMD-related neovascularization; changes in the choriocapillaris in dry AMD; and occlusions and vascular abnormalities in eyes with retinal vein occlusions.

“OCT angiography will be an invaluable tool for use in clinical trials. It provides better visualization of the microvasculature than traditional angiography, and by enabling more frequent serial imaging, we will now be better able to study disease evolution and the effects of therapeutic intervention,” said Dr. Rosenfeld.

“In fact, we already have proof at our center that OCT angiography will fulfill its promise. Using a prototype of the Zeiss platform at our center, we were able to identify recurrent neovascularization in AMD before we could detect it using traditional OCT.”

Philip J. Rosenfeld, MD PhD 

E: prosenfeld@med.miami.edu

Dr. Rosenfeld receives research support from Carl Zeiss Meditec through a research relationship the company has with the University of Miami. He has no other relevant financial interests to disclose.