One of the latest technologies in medicine is optical imaging. Optical imaging is the use of technology to look at structures of the body using visible light and photons. Unlike x-rays, optical imaging uses non-ionizing radiation, which greatly reduces the patient’s radiation exposure. Optical imaging techniques can differentiate between healthy soft tissues and those which might be cancerous, and the technology is non-invasive, meaning no surgical cuts or biopsies are needed to make a diagnosis. These new techniques can be particularly useful in skin cancer detection, as well as aiding in the diagnosis of other skin conditions.1,2
How does optical imaging work?
The non-ionizing radiation that is used in optical imaging includes the visible, ultraviolet, and infrared light. These forms of light create images of bodily structures without causing damage to the cells, which can occur with ionizing radiation used in other imaging techniques. Many optical imaging techniques use lasers that produce short light pulses, which reflect back the different structures to create a picture.1
Cancer cells have different properties than healthy cells, including how they reflect light. While this can’t be seen with the naked eye, optical imaging techniques can provide high-resolution images of skin lesions and can differentiate between structures like pigmented skin lesions (like moles), skin cancers, margins of tumors, and inflammatory skin conditions.3
What types of optical imaging can be used in dermatology?
There are several different optical imaging techniques that are currently being used or investigated for their use in skin cancer diagnosis, including:
Dermoscopy uses polarized light and a high-quality magnifying lens to create a microscopic, real-time image that can detect abnormalities in the epidermis and superficial dermis layers of the skin. Research has proven that dermoscopy can be effective in diagnosing a variety of lesions, including melanoma, basal cell carcinoma, squamous cell carcinoma, and actinic keratosis.4
Confocal microscopy uses a powerful microscope and light delivered by a laser to create a real-time image of the intracellular structures of different layers of the skin. Despite its high cost, the confocal microscope is gaining popularity due to its ability to non-invasively diagnose skin diseases. Confocal microscopy is especially useful in differentiating between atypical moles (nevi) and melanoma and diagnosing basal cell carcinoma, squamous cell carcinoma, and actinic keratosis.4
Cross-polarized light and florescence photography can help doctors identify lesions that may be invisible to the naked eye, including actinic keratosis and basal cell carcinoma. 4
Optical coherence tomography (OCT) is a technique that creates real-time images of structures on or just below the skin. OCT has been used in ophthalmology since 1991 and is emerging as a useful tool in dermatology to diagnose skin conditions like basal cell carcinoma, squamous cell carcinoma, and actinic keratosis.4
High-frequency ultrasound uses ultrasonic waves that travel through the layers of the skin and reflect an image back that helps doctors see the different layers and deeper structures for the diagnosis and treatment of skin conditions, including non-melanoma skin cancers.4
Potential to change the diagnosis process
Currently, most skin cancers are first examined visually by a doctor during a skin examination and suspicious areas are then biopsied. Skin biopsy is the gold standard for diagnosis of skin cancers, allowing doctors to remove the suspicious lesion and examine the tissue under a microscope with special stains that can distinguish between cancerous and healthy tissue. However, biopsies are invasive, possibly painful, and can cause scarring. Optical imaging techniques offer a non-invasive in-depth skin examination, and the ongoing advancements in these technological advancements offer doctors and patients a new tool in diagnosing and treating skin cancers.4
In addition, optical imaging techniques can be helpful in skin cancer removal procedures, such as Mohs surgery. Mohs surgery is the most effective technique for the removal of skin tumors, including basal cell carcinoma and squamous cell carcinoma, and involves removing the tumor layer by layer and examining the layers under a microscope to ensure all the cancerous cells have been removed. Optical imaging techniques, like confocal microscopy, can be used to speed up the process, because the frozen sectioning and processing time needed for a traditional microscope isn’t necessary with the confocal microscope.4
Optical imaging technology provides a new tool to diagnose skin cancers early, when they are most treatable. These new tools require training to gain expertise in identifying different lesions.4
Optical imaging. National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health. Available at https://www.nibib.nih.gov/science-education/science-topics/optical-imaging. Accessed 1/30/18.
Tkaczyk ER. Innovations and developments in dermatologic non-invasive optical imaging and potential clinical applications. Acta Derm Venereol. 2017;Suppl 218:5-13. Epub ahead of print.
A clearer look at optical imaging. The Dermatologist. Available at https://www.the-dermatologist.com/article/2418. Accessed 1/31/18.
Malvehy J, Pellacani G. Dermoscopy, confocal microscopy and other non-invasive tools for the diagnosis of non-melanoma skin cancers and other skin conditions. Acta Derm Venerol. 2017 Jul;Suppl 218:22-30. doi: 10.2340/00015555-2720. Epub ahead of print.