Medical thermography

Skin surface temperature distributions portrayed by infra-red imaging techniques can be used to identify areas of thermal abnormality, to monitor disease processes and to monitor the efficacy of treatment procedures. Technology, originally developed for military purposes, is now being utilised in medical imaging equipment. InSb and CdHgTe (CMT) detectors are used most frequently in these systems, but linear arrays of PbTe are also suitable. The detector characteristics and scanning optics of typical commercial and experimental systems are described and evaluated for medical work. The more complex systems are capable of portraying real-time images with spatial resolutions better than 0.5 mrad and an MRTD < 0.1¿¿C. To achieve this performance, array detectors or multiple SPRITE configurations are necessary. Equipment of this type, designed specifically for medical thermography, is being evaluated currently. The need for alternative cheaper equipment has led to the further development of compact, robust, pyroelectric and singleelement InSb and CMT detector systems for routine medical investigations. With inferior spatial resolution and typically with an MRTD of 0.2¿¿C to 0.3¿¿C, these machines are less suitable for physiological research studies but are adequate for most clinical work. Liquid-crystal plate thermography is also available as a contact method for mapping temperature patterns, but undue pressure over the skin surface can affect the very temperature that is being measured. Contact microwave antennas capable of detecting 1¿¿3 GHz radiation from within the patient are also being used to monitor subcutaneous and deep body temperatures. The conjoint use of surface and deep body temperature measuring techniques will extend the usefulness of medical thermal imaging.