Millimetre-Wave Radiometer in Medical Applications

Human skin covers around 95% of the human body and it plays an important role in temperature and water level regulation. However, human skin is sensitive to external and internal variations [1] and it can be damaged or broken by mechanical, electrical and thermal traumas. The current treatments of assessing and monitoring wound healing is through visual inspection, necessitating the removal of dressing materials used to assist in the wound healing process. The removal of dressing layers can have undesirable effects, such as increasing the probability of infection [2]. Open-ended coaxial probes have been used for measuring the complex dielectric permittivity of healthy skin and skin with second-degree burns [3]. The relative complex permittivity is easily measured using a suitable coaxial probe. This probe must be in contact with the sample under measurement. This requirement prevents use in scenarios where contact is not desirable or not possible. Electromagnetic radiation at Microwave and Millimetre-Wave frequencies can propagate through typical dressing materials with little attenuation and is non-ionising [4]; these bands of the electromagnetic spectrum are promising for assessing wounds through dressing materials. As non-contact screening is often desirable in medical applications and since coaxial probes are unable to provide measurements over large areas without being repeatedly placed in contact with the skin, a radiometric approach is a more appropriate solution. Therefore, two-layer skin model is implemented in this work for predicting the emissivity of healthy skin and damage skin, the simulation results show that, emissivity of healthy skin is 57% and emissivity of second degree burn skin is 56%. There is a more significant difference, 5% to 10% in the emissivity between healthy skin and skin with malignant lesions. These differences in emissivity are due to different water that affected strongly the human skin emissivity. The experimental work in the lab shows that, dressing materials reduce the reflectivity of the skin and as a result, human skin emissivity is increased. Based on the presented results the authors conclude passive Microwave/Millimetre-Wave (MMW) sensing may be used for non-contact diagnosis of skin disease and for monitoring the wound healing under bandages.