Improvement of imaging of skin thermal properties by successive thermographic measurements at a stepwise change in ambient radiation temperature.

Imaging of skin thermal properties was attempted by successive thermographic measurements of the skin surface with a stepwise change in ambient radiation temperature. In order to produce the stepwise change in ambient radiation temperature, two hoods maintained at different temperatures, 20 degrees C and 60 degrees C, were mechanically switched. A total of 65 thermograms were taken from 2 s before to 32 s seconds after the hood switching. Images of skin emissivity, emissivity-corrected skin temperature and thermal inertia were obtained by least-squares fitting at each pixel of 64 thermograms. Measurements were performed on the forehead, cheek, forearm, palm and back of the hand of 10 healthy male subjects. Differences in emissivity between sites and subjects were insignificant. Significant differences were observed in thermal inertia values between sites. Great improvements in the imaging of thermal inertia have been achieved by applying least-squares fitting to 64 thermograms instead of by computations from only two thermograms as in the previous study. Non-contact measurement and visualization of skin thermal properties are significant advantages of this method.