NEWS
Early warning
3D measuring system aims to detect malignant melanomas without invasive treatment
THE DETECTION of skin cancer could be further
improved with a new technology that aims to
help dermatologists find subtle changes in the
shape and size of moles.
The development — from researchers at
Photometrix Imaging, a spin-out from Glamorgan
University’s Medical Imaging Laboratories
— could also be used by the cosmetics and
computer gaming sectors.
The technology, called Measurement of Area
and Volume Instrument System (MAVIS) II, captures
and measures 3D images of dermatological
anomalies, such as malignant melanomas, using
a high-resolution camera, a stereo adapter and
a computer.
Peter Plassmann, chairman of Photometrix,
said that moles become a cause for concern
when they develop a 3D structure and no longer
lay flat on the skin.
‘With our technology we can spot that
moment in time and say “now it’s time to do
something about it”,’ he said.
Currently, non-invasive assessments are
made by doctors who observe the anomaly
directly or look at digital images of it. Subtle
changes, which can indicate a melanoma is
malignant, can be missed unless invasive testing
is carried out.
The MAVIS technique, which is completely
non-contact, produces 3D images using specialised
software based on a technique known
as stereophotogrammetry.
The technique operates on the principle that
human eyes are placed slightly apart, and when
a person’s eyes observe the same object, each
will produce subtly different images because the
object is shown at slightly different lateral positions.
MAVIS uses a normal digital camera fitted
with a dual lens for taking stereo photographs.
Two tube-shaped LED projectors on the base of
the camera produce two beams of light, forming
a single spot of light when the camera is held at
the right angle and distance from the subject.
The picture is taken and the photo file is
loaded into a computer via a memory card. The
lateral displacement is a measure of the distance
between the object and the ‘eyes’ of the camera.
The software program processes the data to
identify common points on the image taken from
both the left and the right. Within minutes, an onscreen
3D map of the object is built up.
The technology was originally designed to
monitor the kind of chronic wound that either
heals very slowly or becomes deep, resembling
a crater in the skin.
Plassmann and his team realised that doctors
14
needed a highly accurate monitoring system so
they could determine whether the treatment of
such wounds was producing any effect.
Existing techniques involve measuring either
the area or volume of wounds. The current
method of measuring the area is to place a transparent
acetate sheet on to the wound and trace
its perimeter. The tracing is then placed on to
graph paper and the number of squares is
counted. This method of determining the area of
a wound can lead to inaccuracies.
Similarly, there are two main methods for
measuring the volume of a wound. The first is to
fill it with a saline solution. The volume
dispensed from the syringe equals the
volume of the wound. The main
source of error is that the
wound absorbs the saline.
The second method is to
fill the wound with an
alginate or siliconebased
paste and
weigh the amount of
material used.
The main problem
with these measurements
is they require
contact with the
wound, which may be
painful to the patient
and incur the risk of
infection, a situation the
non-contact MAVIS system
is able to avoid.
The National Physical
Laboratory conducted
tests on the accuracy of
MAVIS and found it
achieves a measurement
precision of five
per cent or better,
which is higher than
existing techniques.
The MAVIS developers
plan to incorporate wireless
image transfer in the
future.
In addition to skin cancer
detection and wound monitoring,
Photometrix is also targeting
its 3D measurement technology at
the cosmetics and plastic surgery
sector. The company is in talks with
manufacturers and service providers in
the sector to develop a device that could,
for example, determine the effectiveness
of products for wrinkle reduction.
The technology could also be used for
full-body scanning with computer games like
Second Life where the production of a 3D model
of a player’s virtual ‘real-life’ appearance, or
‘avatar,’ is currently a time-consuming and
expensive manual task.
‘Our main problem is there are virtually
hundreds of applications out there and we just
need strong partners to help us to exploit that,’
said Plassmann.
Siobhan Wagner
the EnGIneeR 21 APRIL–4 MAY 2008
Face of the future:
the new camera can
capture and measure
subtle anomalies
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