Improving spatial resolution in skin-contact thermography: comparison between a spline based and linear interpolation

A wearable device for skin-contact thermography [Giansanti D, Maccioni G. Development and testing of a wearable integrated thermometer sensor for skin contact thermography. Med Eng Phys 2006 [ahead of print]] using a 2-D array of 4x4 integrated silicon sensors has been designed and constructed. The thermal resolution was equal to 0.03 degrees C and the spatial resolution equal to 1.6x10(-5)m(2) in the range 25-41 degrees C. The improvement of spatial resolution is strongly needed in several medical correlated applications of skin-contact thermography such as the breast cancer monitoring and the feature recognition. A cubic-spline interpolation procedure has been designed to improve the spatial resolution. The performances have been investigated in a significant medical application. Results were compared to those ones obtained by means of an infrared digital video camera and a linear based interpolation procedure. The comparison showed that: (1) the spline based interpolation procedure permitted to improve the spatial resolution of the device to 1.5x10(-8)m(2) with an interpolating number of pixels equal to 128x. (2) The accuracy of the thermal reconstruction obtained by means of the spline interpolation in each one of the pixels was better than the one obtained by a pure linear interpolation; in particular the maximal error was equal to, 81x10(-3) degrees C.