SIAscopy understands the way light interacts with skin; the manner in
which it scatters or bounces, the amount absorbed by cells and other
structures as well as the differences changes in wavelength or colour make.
By understanding these interactions and comparing readings as light is
sent into the skin and emerges back out, SIAscopy is able to determine the
nature and position of many of the different cells and structures
within skin.
In particular SIAscopy measures the amount of haemoglobin, melanin,
collagen and whether melanin is in the epidermis or the dermis. The
information is presented in the form of maps called SIAscans, which show
how these measurements vary over the skin.
The light used by SIAscopy is completely safe and painless, which makes it
a perfect technique for monitoring skin conditions.
Contact and non contact SIAscopy
SIAscopy can be used in two forms, contact and non-contact, to assess and monitor many skin conditions including
skin cancers, psoriasis, acne, eczema, skin de-pigmentation, skin aging and scars.
Contact SIAscopy uses a specialised camera that touches the skin and gives very high-resolution images. Being in contact, it can also produce SIAscans for all types of cells and structures, giving the maximum amount of information about an area of skin or a lesion.
Non-contact SIAscopy produces SIAscans from a distance, using a digital camera, allowing an area such as an entire back or face to be imaged. Currently non-contact SIAscopy can image haemoglobin and melanin.
Non-contact SIAscopy is particularly useful for monitoring many moles on a person and looking for moles that are changing, which may require more detailed examination. It is also useful for imaging haemoglobin which disperses if excessive pressure is applied to the skin. |
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Non-contact SIAscan showing the haemoglobin
distribution over a face |
How does SIAscopy work?
Due to the multi-layered structure of the skin, and because the most prominent chromophores have slowly varying
spectral properties, it is possible to generate models which can predict the method of light transport within skin. This
allows us to analyse the skin using broadband spectrophotometric techniques.
Fig1. below shows the skin model structure used in SIAscopy. Four different primary wavelengths of light are shone
into the skin in turn. An imaging chip is then used to record the light remitted from the skin at each pixel, giving an
image representing the amount of light leaving the skin for each of the four wavelengths used. Cross polarisers are
used to remove any scattering from the surface of the skin.
These images are fed into the SIAscopy algorithms which compare them to a mathematical model of the skin. The
outputs of this algorithm are 4 images depicting the concentration of haemoglobin, melanin, collagen and dermal
melanin within the area of skin imaged.
The SIAscopy Model and Algorithms
In order to translate the meaning of reflected light into the condition of the skin, SIAscopy refers to a proprietary
model of the skin which reflects the structure in Fig 1.
Fig1. The analysis of remitted light from the chromophores
In order to generate this model simulations are run for hundreds of thousands of different combinations of
haemoglobin, melanin, collagen and dermal melanin. The result of each simulation represents how the camera would
respond if it was to image the corresponding combination of skin chromophores. This information is stored, and then
interrogated during each scan in order to generate SIAscans. Each SIAscan is a bitmap representing the concentration
of each chromophore on every pixel. There are more than 1.5 million measurements given from each scan.
Contact SIAscopy requires contact with the skin, and measures the skin over a diameter of 11mm. Non-contact
SIAscopy acquires wide field images which are analysed to show the concentrations of haemoglobin and melanin
within the skin.
Non-contact SIAscopy uses a digital camera to capture cross-polarised images of a scene. A flash gun
is used as a light source, providing light over the entire visible spectrum. The camera provides raw
information of the imaging chips response to the light, which results in 3 pictures being produced
from the camera. Red, green and blue images are produced, each covering a different region
of the visible spectrum. These images are then analysed in a similar way to contact SIAscopy,
producing non-contact SIAscans which represent the concentration of haemoglobin and melanin
within the skin.
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