Millimetre wave radiation interacts with the human body down to a depth of around half a millimetre into the skin at 100 GHz; less than this depth at higher frequencies, with greater penetration at lower frequencies. Interaction is exclusively with the skin, including the first layers of living tissue, and is therefore the ideal probe for the largest organ of the human body.
Spatial resolutions of measurements are down to half a wavelength in the skin, so range from 0.1 mm to 5 mm.
The medical applications of millimetre wave sensing technology are relatively undeveloped. This is due to the subtlety of signatures and the absence of commercially available systems to efficiently measure and generate high quality calibrated data. However, likely applications will be those associated with assessing skin cancers, skin moles, Raynaud's disease, psoriasis, sclerosis, eczema and any other medical conditions involving the skin.
Moving to lower frequencies around 10 GHz will enable penetration to ~2 mm enabling signatures to be measured associated with circulatory disorders.
Potentially these measurements could be made of the whole of the human body in a period of seconds, enabling a new type of whole body screening.
Millimetre wave sensors to image specifically the human skin could complement the existing portfolio of imaging systems (ultra-sound, CT, MRI, PET) that are used to monitor health and diagnose diseases and conditions in other parts of the body.