We strive to stay at the forefront of innovation by leveraging our experience and using the latest equipment, techniques and technology – including optical coherence tomography (OCT).
Read on to discover what OCT is, how it works, which OCT device we use at SGS, and most importantly, why OCT is so useful.
What is OCT?
OCT is a real-time, non-invasive imaging technology based on low-coherence interferometry. It allows for cross-sectional evaluation of biological tissues, including skin roughness (Ra and Rz) and epidermal thickness, using a laser with a wavelength of 1305 nm and an A-scan frequency of 10 kHz. OCT scans can be used to visualize skin structures 2 mm beneath the skin surface, including the epidermis, with a resolution of around 10 µm.
While similar to confocal laser microscopy (CLM) – another non-invasive technology that provides high resolution, real-time imaging of both the epidermis and upper dermis at cellular resolution – OCT is a newer, more modern technique.
How does it work?
Approximately 90% of the light that interacts with skin is either absorbed or scattered within the skin. With conventional imaging, light that scatters multiple times creates large angles and can contribute to background noise and interference in the image quality.
OCT imaging offers a solution to this challenge. It is an interferometric procedure based on light reflectance. With OCT, the skin is exposed to broadband light from superluminescent diodes (or an oscillating/tunable laser). The light that it reflects back will only interfere with the light in the reference arm, provided that both travel the same path length. In other words, if they happen to cross paths within the short coherence length, OCT measures the photons and produces high quality, high resolution, real-time cross sectional images of the skin. These have a penetration depth of 1-1.5 mm, are several millimeters long and have a resolution of less than 10 μm. By moving the scanning head laterally, we can combine the images to create three dimensional blocks, allowing us to simultaneously display horizontal images as well.
Which OCT device does SGS use?
We use VivoSight (Michelson Diagnostics Ltd, Kent, England). This is the only commercially available and CE-certified OCT device that has been examined in large-scale studies – and which has a diagnostic accuracy that has been tangibly proven.
Why is OCT so useful?
At SGS, we use OCT to measure skin roughness, epidermal thickness, and blood flow. OCT is a valuable tool for visualizing blood flow because it provides excellent non-invasive images of the vascular network. When using dynamic OCT (a horizontal view), blood vessels clearly appear as a color coded red network. Over the last several years, skin researchers have been trying to identify technology that can be used to visualize sub-surface structures non-invasively. Their focus has most recently turned toward the vascular network, making OCT particularly relevant today.
OCT is especially useful because it allows us to visualize and quantify even the smallest change in blood flow. Therefore, we use OCT in clinical studies to identify the impact of cosmetic related products, capturing changes in blood flow as well as vascular images that demonstrate how products impact their users’ blood vessels.
For instance, the technique has been used to reveal vasoconstriction of superficial blood vessels on the cheeks following topical treatment and has been used to evaluate and monitor inflammatory skin conditions.
For further information about SGS’s cosmetics and hygiene expertise, please contact:
t: +1 201 508 3000
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