Non-contact measurement of thermal diffusivity in tissue

We demonstrate the application of an infrared (IR) imaging technique for no n-contact determination of thermal diffusivity in biological materials. The proposed method utilizes pulsed laser excitation to Produce an initial thr ee-dimensional temperature distribution in tissue, and records IR images of subsequent heat diffusion. The theoretical model assumes that the time-dep endent temperature increase following pulsed laser exposure is due to indep endent heat diffusion in longitudinal and lateral directions. A nonlinear l east-squares algorithm is used to compute the lateral thermal point spread function from a pair of recorded IR images and to determine the thermal dif fusivity of a test specimen. The recorded time-sequence of IR images is use d to compute thermal diffusivity as a function of increasing time interval between two IR emission images, Experimental application of the method was demonstrated using tissue phantoms, ex vivo samples of hydrated cartilage a nd in vivo epidermis.