At CSIE we work on development of new and simple optical systems and tools for better diagnosis, quantification, and assessment of different diseases, complexities and conditions in medicine. We recently developed a pressure mapping system using the concept of frustrated total internal reflection. Here is the story of our on going journey:
Frustrated Total Internal Reflection for Plantar Pressure Mapping
Technology:
In Frustrated Total Internal Reflection, FTIR, light is trapped in a transparent/glass medium. In this condition, if a soft object (foot/skin) contacts the interface, the boundary condition changes and the contacting points become sources of light, enabling an observer or a camera on the other side of medium to see the contacting areas. Applications of FTIR in measurement of plantar pressure maps go back to 1978, when Betts and Duckworth used FTIR using an analogue camera to create contours of the pressure maps (Betts and Duckworth, 1978). This method was investigated for another decade in several studies for analyzing diabetic foot ulcerations; however, applications were limited due to the lack of physical equations required to relate light intensity values captured by the camera to the pressure values. Recently a simplified version of such equations was developed by Sharp et al. that proposes the mathematical relationship between light intensity and mechanical pressure. (Sharp et al., 2018 & Tompkins and Sharp, 2019) Using this equation one can measure pressure maps and therefore Center of Pressure (COP).
We have built several different prototypes of this device to use FTIR and Sharp’s equations and construct plantar pressure maps. The figure below shows one of the early prototypes of the P^2: A) Our prototype; B) design componentsl C) the graphical user interface that was developed by CSIE. We call our device P^2.
One of the main areas of our focus (not limited to) is quantification of human balance using different devices. Therefore, as one of the early studies on the plantar pressure mapping, we investigated the minimum required resolution that is needed to quantify balance using plantar pressure mapping devices. We showed in our recent paper (Detels et al., 2023) that we need submillimeter spatial resolution in order to quantify balance.
Clinical Applications:
Plantar pressure measurement has played a crucial role in a wide range of clinical applications. As the underlying technology and device design of plantar pressure measurement continues to evolve, the opportunities for clinical applications of these devices may grow in proportion. Investigators are encouraged to consider whether such technology may be used to support or enable analyses in novel ways. Plantar pressure mapping technology yields a multitude of parameters, most of which require further investigation. Center of pressure, center of contact areas, peak pressures, and total contact area can be analyzed to provide metrics such as body sway, foot symmetry, left/right weight symmetry and more. Plantar pressures could be further utilized for progress assessment, quantification of functional outcomes after surgery, quantification of risk of fall, early detection of pathologies including dementia and very recently it has been shown that there might be some correlation between plantar pressure mapps and bone density. For a detailed discussion on the clinical applications and available plantar pressure mapping technologies check out out recent review paper (Detels et al., 2023)