Using Foot Temperature To Assess Foot Health
Podium Device
A lightweight and robust thermography scanner for the plantar foot:
- Intuitive thermal images
- Left/right thermal symmetry comparison histogram analysis
- Standardised photographs that visualise pressure areas
- Highly portable in convenient carrying case
Podium App
Running on an industry-standard tablet, the Podium App acts as the primary information input system for patient scans:
- Drives the Podium Device
- Displays the thermal scans & photographs
- Customisable patient questionnaire
- Patient scans at multiple clinic episodes
- Patient notes facility
- Automatically buffers session and uploads to Podium Portal when wifi connection available
Podium Portal
The Podium Portal provides a window into the Podium data repository for organisations and individual clinicians:
- Review new and historical patient information
- Access for multi-multidisciplinary support teams
- Track, review & intervene in patient treatment pathways
- PDF exports to centralised patient administration systems
- Print, export & share information
- Patient & clinician administration
Podium Deployment
Virtual Healthcare: Bring podiatry, diabetic, renal vascular, and other teams together – digitally
- Displays accurate thermal and white light images
- Enables all MDT members to view patient records remotely via the portal
- Helps to make the referral process quicker and more efficient to other specialties
Virtual Healthcare: Patient tracking system
- The Podium Portal enables multidisciplinary team members to view scans and clinic notes remotely
- See where and when patients were last assessed, and by whom
- Check for early signs of inflammation
- Additional measure to support clinical assessment
- Monitor progress of pathology or current interventions
- Compare the progress of different treatments
- Aid in decision making
Increase Healthcare Capacity
- Provides additional information for management decisions in between face to face clinic episodes:
- thermal image – temperature information
- histogram analysis – symmetry information
- visual image – pressure, foreign bodies, skin cracks, appearance
- Enables monitoring of ulcers with consistent and comparable images
- Reduce the burden on overbooked or currently reduced clinics
- Scanning can be performed by patients or non-clinical staff
Digital Community Care
- Highly portable in convenient carrying case
- Help increase community patient management
- Monitor at risk patients remotely and more often through digital imaging
- Scan patients at multiple clinic episodes
- Review concerning signs in the multidisciplinary teams virtually
- Enable shared decision-making with community and hospital professionals
- Provide support and informed advice to colleagues remotely
Increase Patient Involvement
- Involve patients in their own care
- View images with patients: explain and show effect of interventions
- Empower patients to monitor their feet and improve self-care
- Improve compliance, using Podium images
Foot Thermography Background Information
- Foot temperature assessment – a review – normal foot temperature, 4 approaches to identify problems, examples, literature references PDF poster
- An introduction to foot temperature assessment – why, what and how PowerPoint slides
- Thermography of the diabetic foot – a PDF white paper on how micro-angiopathy, macro-angiopathy, and neuropathy appear in a plantar foot thermal image
- Interpreting Podium foot scans How-to Guide
- Video – How temperature assessment can inform patient care – a 37 minutes, MP4 video
- Audio – Podium, the background story. Interview on UK Health Radio – The Diabetes Show 50 minutes, MP3 audio
- How Podium is used in clinical practice 3 minute video
Key Features in Thermal Assessment
The Colour Scale
- The colour scale must be interpreted
- Absolute scale:
- a fixed scale with the same range for all thermograms (here: 18℃ to 35℃)
- advantage: same for all thermograms so different scans can be directly compared
- disadvantage: contrast of colours may be low if foot has a narrow range of temperatures only
- Dynamic scale:
- colours are optimised for temperature range of current image (here 16℃ to 27℃)
- advantage: high contrast, easy to spot small differences in temperature
- disadvantage: colours can mislead when comparing scans: same colour ≠ same temperature
It is important to note that a contact making device such as Podium is not thermometric, i.e. it does not measure the absolute temperature of the foot. On contact with the thermal sheet the foot cools (if the sheet is colder than the foot) or warms (if it is warmer). As a result the absolute foot temperature changes. This is often advantageous, e.g. when cooling provides a mild “cold stress” that can serve to highlight areas of inflammation. Relative temperature patterns are thus preserved or emphasised which may be helpful when interpreting the resulting thermograms.
The Histogram
- Shows the distribution of temperatures in a thermogram
- Sorts image pixels with the same temperature into “bins”
- Each bin is represented by a horizontal line
- The longer the line, the bigger the area of that temperature
- Two histograms are shown side by side:
- one for the left foot
- one for the right foot
- allows assessment of left/right temperature symmetry (see further below)
As outlined above Podium thermograms are non-thermometric by design. The numbers on the histogram scale are therefore provided as relative indications and do not represent absolute temperature values.
The Healthy Foot
- Plantar foot temperature of healthy people is characterised by:
- medial arch being between 0℃ to 7℃ warmer than the toes
- left-right (contralateral) mirror-symmetry better than 1.8℃ (>2.2℃ is frequently seen as a warning sign)
- the 2nd to 5th toe have approximately the same temperature
- there are no hot spots
- the average foot temperature is around 26℃ at the toes and 29℃ at the medial arch
The image shows the average plantar foot temperature of 103 healthy subjects who were resting at 22℃ for 10 minutes after taking their socks and shoes off. Reproduced from Kluwe B., Early detection of diabetic foot ulcers using thermal imaging, PhD Thesis, University of South Wales, July 2018
Thermal Variability
- Healthy feet are thermally symmetrical but different between individuals and over time
- The lowest variation, i.e. the most stable temperature region, is the medial arch
- The most variable parts are the toes and the heel
The image shows the variation of temperatures in the 103 healthy individuals within a 1 standard deviation interval. It is noticeable that the temperature at the toes is far more variable between individuals than that of the medial arch. Reproduced from Kluwe B., Early detection of diabetic foot ulcers using thermal imaging, PhD Thesis, University of South Wales, July 2018
Thermal Symmetry
- Healthy feet are thermally highly symmetrical
- Asymmetry may be an early sign of pathology
- May be useful to pick up early signs of pathology
- Additional measure to support clinical assessment
- Provides an objective indicator of inflammation
The figure shows a histogram of the left-right differences at 33 distinct points in the feet of 103 healthy subjects (resulting in 3,399 data points). The width of the interquartile range (IQR) is 0.9℃, i.e. 50% of all aspects in one foot differ by less than 0.45℃ from those of the other foot, 99% less than 1.8℃. Reproduced from Macdonald A., Petrova N. et al.