Plantar Quad-Zone Analysis: A study of healthy feet
Wright, CJ; Collings, R; Morris, J; et al.Clausen, R; Farress-Gregg, V
Date: 1 October 2020
Article
Journal
Thermology International
Publisher
European Association of Thermology
Abstract
The plantar aspect of the foot is a common site for pathology. Diabetic foot ulceration
(DFU) and peripheral arterial disease (PAD) present the populations with the highest
risk. Many people with diabetes experience foot neuropathy which can result in
extensive skin damage, undetectable to the eye but which is potentially detectable
using ...
The plantar aspect of the foot is a common site for pathology. Diabetic foot ulceration
(DFU) and peripheral arterial disease (PAD) present the populations with the highest
risk. Many people with diabetes experience foot neuropathy which can result in
extensive skin damage, undetectable to the eye but which is potentially detectable
using digital infra-red thermal imaging (DITI). This study aims to present a quad-zone
approach to assess healthy feet for thermal symmetry, and multi-reader reliability, as
a precursor to clinical trials.
A FLIR T650 IR thermal camera (640x480) was used to image the soles of 30
healthy volunteers within a temperature-controlled environment. Five readers blind
analysed the cases: the whole foot; and four regional zones (heel, arch, first ray, and
lateral forefoot); and finally, the individual region of interest (ROI) analysis of the
toes. Inter-operator reliability was assessed for the five readers. Mean values for
each area of interest were assessed for contra-lateral symmetry.
Healthy feet display a wide range of temperatures: left (min=22.60, max=34.00,
mean=27.57, STDEV=2.23) and right (min=22.70, max=34.10, mean=27.63,
STDEV=2.32). Differences between feet or quad-zones of the same individual were
consistently <1
oC. Plantar toes can be significantly cooler than the rest of the foot
and exhibit much greater differences (up to 2.6
oC), however always <1
oC between
adjacent toes on the same healthy foot. No statistically significant differences
between corresponding bilateral areas could be found. ICC=0.990 to 0.998 for all
four quad-zones confirmed excellent inter-operator reliability in blinded assessment
between five readers.
The quad zone technique is easy and time efficient to perform, ideally suited to the
clinical environment, with a very high level of reproducibility. This study of healthy
feet provides the underpinning evidence for further research to determine differences
in the diabetic and/or neuropathic foot and seek correlation with angiographic
findings.
Institute of Health Research
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