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. |
|
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. |
