NEW: Breakthrough 3-D optical imaging possible in vivo
Breakthrough 3-D optical imaging possible in vivo
Publish date: May 1, 2011
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Source: Dermatology Times
National report — A series of technological innovations has led to near-real-time, in vivo, three-dimensional optical imaging of skin up to a depth of 1 mm – with potentially a depth of up to 2 mm with clearing methods.
The resolution is approaching that of histology biopsy. Initial use is likely to be in a research setting; broad clinical use will require both validation and the marketing of a device that is economically competitive with biopsy.
This breakthrough in optical coherence tomography (OCT) imaging was achieved by a team at the University of Rochester Institute of Optics.
"We leveraged emerging technology that is coming out of cell phones, like liquid lenses, and developed a new way to record the data using a spectrometer and dynamic focusing," says team leader Jannick P. Rolland, Ph.D.
A liquid lens is made of water and oil on an electrode. When voltage is applied, the surface of the electrode becomes less hydrophobic.
"By changing the voltage, you can make things more or less hydrophobic and have the water being repulsed or attracted toward the electrode," Dr. Rolland says. "The oil-water interface changes and you create bending, the different curvature at the interface" which serves as the lens. Changing the voltage changes the focus, she says.
Quicker response
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The advantage is that without the moving parts of a traditional lens, researchers can refocus much more quickly and without the potential for mechanical jarring of the device. This reduces the chances of blurring an image.
Dr. Rolland uses a near-infrared light source (either 800 or 1,300 nanometers) to get deep into the tissue. "You go a little deeper with 1,300, but it is harder to get the high resolution," she says.
A custom-designed spectrometer "records an entire spectrum of all of the light that is back-scattered from all of the different layers" of cell scans, which are performed at multiple focal points, about 1 per 100 microns of depth, she says. The entire process can last a fraction of a second or up to several seconds, if a larger area is being examined.
A software algorithm on a powerful computer then "sections out all of the out-of-focus zones from each scan" and stitches the in-focus portions together into a single coherent high-resolution image, she says.
The device is contained in a cylindrical probe that is pressed against the skin to examine the morphology of the lesion.
"Right now we can get a 2 microns (2µm) lateral resolution over maybe a 2 mm working depth," Dr. Rolland says. Perhaps that is sufficient to guide diagnosis of cancerous lesions and procedures such as Mohs surgery, she says.
There is a bit of friendly rivalry between two of her post-doctoral students as to who has the more photogenic fingers in these early studies, she says. Their initial preference is for "thin" skin to demonstrate images of deeper penetration through the various layers of types of cells.
Still in development
Dr. Rolland says she looks forward to validating the technique in a variety of skin types, ages and disease states. She is tinkering with the mechanics to see whether resolution can be further improved, and looking to determine what resolution really is needed for clinical application.
It might make sense to maintain the current resolution for scanning broader areas of skin but add the capacity to zoom in to a particular area with higher resolution, she says.
She is currently working on coupling the device with Doppler technology to map blood vessels and measure the speed of blood flow under the skin.
Technique 'holds promise'
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That impresses Daniel Mark Siegel, M.D., professor of dermatology at State University of New York Downstate Medical Center College of Medicine, Brooklyn, N.Y. "OCT holds a lot of promise, and I think this brings it a step forward," he says. "I think it is great that people are pushing the technology."
However, "Will it replace biopsy? I'm not sure yet," he says.
Dr. Siegel says the current resolution is sufficient to identify individual cells, but, "Are we seeing basal cell carcinoma? Are we seeing melanoma? Are we seeing squamous cell carcinoma? Or are we simply seeing thickened epidermis because we have psoriasis?" he says.
He says he awaits studies that demonstrate how the tool might replace biopsy in clinical use.
Dr. Siegel says the ultimate goal is a device that probably will contain "OCT, confocal microscopy, and destructive modalities where you can home in on something, determine a diagnosis, have machine-aided confirmation of that, and then destroy it then and there. Right now we are in the primitive stage when a variety of machines just do one bit or the other."
Dr. Rolland presented her research in February at the annual meeting of the American Association for the Advancement of Science. Earlier stages of the research have been published and a paper on the latest findings is in press in the journal Optics Letters.
Disclosures: The New York State Foundation for Science, Technology and Innovation (NYSTAR) and other noncommercial entities supported the research. Dr. Rolland recently has begun discussions with companies about possible commercial applications of these tools. Dr. Siegel is an unpaid consultant to Michelson Diagnostics and is using equipment provided by the company to better define Mohs surgery margins and tumor morphology.
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