Thermal Imaging Today and Its Relevance to Diabetes
One great advantage of thermal imaging is
that it is both noncontact and noninvasive. By
remote temperature sensing, the camera is
merely receiving the natural thermal energy
emitted by the body. Since no harmful energy
is used in the imaging process, it is very
suitable for repeated investigations over time.
Thermal Imaging Technique
All medical imaging procedures have
benefited from the use of modern digital
technology. A reliable thermal imaging system
will be used online with a computer that
will be operating specialized software. This
will be able to indicate to the operator when
the camera is stable and ideally will provide
confirmation from a temperature reference
source that the calibration is at the correct
level. The examination should be performed in
a temperature-controlled environment with
a humidity of <50%. The disrobing cubicle
should also be at the constant temperature,
which is typically 22 ºC (70 ºF). A period of
thermal equilibration is required before any
imaging takes place, and this can be variable
depending on whether peripheral or trunk
areas are to be examined. Fifteen minutes is
quite often found to be adequate to at least
achieve a reasonable level of stability in blood
pressure and skin temperature.
In a clinical setting, the ideal camera will
be mounted on a parallax-free stand (not
a tripod) to ensure that positioning is
reproducible and free from unwanted angles
between the patient and the camera.
A series of standard images of the body
regions required for the investigation are
obtained within minutes, since almost all
modern cameras are real time. The images are
stored on the computer to be analyzed by the
image processing software. Standardization
of image capture can be improved by the use
of software masks providing an outline of
the region, e.g., both dorsal hands (Figure 1).
By this means, the camera is moved closer or
farther from the patient until the image fits
the outline mask. Subsequent images from the
same patient will therefore be at a constant
distance and position. A series of such masks
were developed at the University of Glamorgan
to assist practitioners (Figure 2).
After the images have been captured to
the computer, the analysis of temperature
distribution is made by selecting regions of
interest, followed by a statistical measure
of the thermal data. (8) These may also be
preformed in the software, or the operator
draws the region according to protocol,
using anatomical points to delineate the area
required. Drawing regions of interest from
memory can be another source of error, and
when serial images are required, the variance
can be up to 10%, even in so-called expert
thermographers. Most software systems for
thermal imaging provide basic image analysis
"One great advantage of thermal imaging is that it is both noncontact and
noninvasive... Since no harmful energy is used in the imaging process, it is very
suitable for repeated investigations over time."
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