Interactions of ultrafast laser pulses with biologic tissues

摘要

Ultra-short IR laser pluses were transmitted through excised female breast tissue. The resulted signal was recorded by a streak camera with a time resolution of the order of a few ps. Experimental data of the temporal spread of the ultra- short pulse during the transmission through the tissue have been analyzed using the Patterson analytical expression derived from the diffusion theory. This resulted in the calculation of the absorption and scattering coefficients, which are related to the optical characteristics of each type of tissue. A streak camera has detected early arriving photons of 100 fs laser pulses transmitted through highly scattering media. Due to their partial spatial coherence they are affected by diffraction caused by small hidden discontinuities. Experimental data of the patterns are analyzed using Fresnel diffraction theory and then corrected accordingly. Sum-mm hidden objects were scanned and imaged. Diffraction correction resulted in a significantly improved contrast of the hidden object's image.