OCT angiography moves beyond ophthalmic applications

10 May 2016

Wasatch Photonics platform brings the technique to a broader range of bioimaging uses.

A new imaging platform launched by Wasatch Photonics aims to widen the range of applications for high-resolution optical coherence tomography angiography, and enhance the versatility of the technique for both researchers and OEM manufacturers.

OCT angiography has already made inroads into clinical ophthalmology, where its non-invasive ability to provide both structural and blood-flow information via functional OCT without the need for fluorescent markers offers an attractive way to map retinal and choroidal vasculature.

Wasatch Photonics, a developer of spectroscopy components and systems including conventional OCT platforms, has designed its MicroAngio system to now expand the use of OCT angiography into new medical research applications, including animal model imaging in dermatology and oncology.

The MicroAngio platform can be equipped with 800, 1050 or 1300 nm OCT, depending on the intended application - the two shorter wavelengths are known to suit retinal applications, while the longest is suitable for examination of the skin or small animal brain imaging.

"The existing commercial OCT angiography systems are dedicated to ophthalmology, but MicroAngio is the first system designed for more general clinical use and a wider array of applications." commented Nishant Mohan, Director Product Management and Marketing at Wasatch Photonics.

"This comes from our flexibility in both choice of algorithms and image acquisition methods. The requirements for creating an angiography map in the human retina are very different from those needed in a mouse retina or in human skin, and we have created a suite of algorithms able to provide angiographic data from all major image acquisition methods. This makes MicoAngio a general purpose OCT angiography system."

The path to adoption of the technique in ophthalmology has been relatively smooth, not least because of the well-established use of conventional OCT in that particular field. But the fresh biomedical applications envisaged for MicroAngio posed some new challenges for Wasatch to solve.

One particular hurdle is unwanted movement, either of the entire specimen or just the area being examined, which interferes with the goal of separating out motion within the blood vessels from that arising from other unconnected sources. Different physical methods to stabilize the specimen and limit movement are needed, depending on exactly where and on what type of target the imaging is being performed.

Another issue is the different information being sought in particular applications, even within the general envelope of angiographic data.

"Each application may have its own requirements in regards to the information of interest, which can vary significantly from what is relevant in ophthalmology," noted Mohan. "If we are studying tumor models, then we are very interested in the health of the blood vessels, while studies of drug effectiveness may be concerned with the vessels' disappearance. These different requirements can be accommodated through modifications to the data acquisition modes and the sample stabilization methods, and our system brings all these together."

An open data model
The advantages of OCT angiography over alternatives such as optical fluorescence and X-ray fluoroscopy include its ability to provide 3D localized information, and the lack of external contrast agents involved in the process - agents which can interfere with the sample physiology. The latter could be a particular factor when comparing OCT angiography to the dye-based angiography commonly used in tumor models, where the naturally leaky vessels present in the tumors inherently create a significant background signal.

Dermatology may prove to be a key application, as OCT angiography is potentially able to define the exact margins of a tumor when excising skin cancer, or assess the success of implants and skin grafts. Studies of nephrology in kidney transplants or of vascular changes in patients suffering from diabetes or sepsis are also likely to benefit.

With such a range of different bioimaging applications potentially opening up, the MicroAngio platform is intended to allow researchers and clinicians more freedom to apply the technique as widely as possible and discover exactly where it might lead. As part of this philosophy it also offers users open access to the data collected by the system, so that subsequent analysis or the application of new algorithms could be used to mine fresh information from the data set, an approach Mohan describes as a conceptual shift in the ways that clinicians might approach an angiography evaluation.

"Our ultimate goal is to expand the applications of OCT angiography and exploit the advantages it can bring over other angiography methods," he commented. "It should be treated as a new imaging modality, and at the moment we can only guess where this technique will prove to be most successful."

About the Author

Tim Hayes is a contributor to Optics.org.