A laser plantar pressure sensor for the diabetic foot

  • Rowland Hughes

    Student thesis: Doctoral Thesis

    Abstract

    This thesis is concerned with the design and building of a foot pressure system capable of measuring the pressure distribution underneath the diabetic foot. The system is developed to have a higher resolution and be more cost-effective than existing commercial systems.

    The biomechanics of the foot and ankle is explained in detail, providing an explanation for the relationship between high pressures and ulcerations. Various techniques of measuring foot pressure are reviewed, providing a thorough understanding of the advantages and disadvantages of each technique.

    The system developed uses the technique of interferometry, which is discussed in detail, explaining why the Fizeau Interferometer technique was chosen over other interferometer techniques. A number of materials were tested as to their suitability to be used as the pressure plate in the system i.e. compression/force relationship. From the results 'Perspex' was found to be the most suitable material. Two fringe-processing software packages were tested i.e. Fringe Processor 2 and Fringe Pattern Analysis (FRAN), with Fringe Processor 2 being chosen for this research. A graphical user interface for image display was created in order to display and analyse the various pressure images.

    Three prototypes were implemented. The first used a variation on the Fizeau interferometer, the second used a variation on the Twyman Green interferometer, whilst the third improved on the use of the variation of the Fizeau interferometer. By analysing the advantages and disadvantages of each prototype, the 3 rd prototype was chosen as the most suitable for achieving the aims and objectives of this research. This prototype was subjected to various tests i.e. resolution, measurable area, repeatability, calibration, short term reliability and sensitivity to heat. Various normal and pathological foot measurements were taken and analysed, and the effectiveness of the image display graphical user interface tested.

    The main contribution of this thesis is the use of interferometry to measure pressure. This in turn provides a foot pressure system, which has extremely high resolution and accuracy. The simple nature of the new pressure system also means that the entire system is very cost effective.
    Date of AwardNov 2000
    Original languageEnglish
    SupervisorHefin Rowlands (Supervisor)

    Keywords

    • Interferometry

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