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.
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.
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.
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.