Two-dimensional transillumination imaging of tissues using 1250 nm light from a tunable chromium-doped forsterite laser

Summary form only given. In this presentation, the authors report on near-infrared (NIR) imaging of objects hidden inside bovine, chicken, and porcine and, more importantly, normal and cancerous human breast tissues of different thicknesses using a Cr/sup 4+/:forsterite laser that operates over the 1150- to 1350-nm spectral range and a Nd:YAG (yttrium aluminum garnet) laser operating at 1064 nm. Fourier space and polarization gates were used to discriminate against the image-blurring scattered light. The experimental arrangement used for NIR imaging is displayed schematically in a figure. The output beam of a Cr/sup 4+/:forsterite laser with an average power of 100 mW was expanded to a 10-mm-diameter beam to illuminate the sample. Light from the Nd:YAG laser with the similar beam diameter and average power was also used to image the object through the same set of tissue samples for comparison. The samples were placed between two movable parallel glass plates that slightly compressed them. A 1.5-mm diameter black metal bar was used as the object. A 4fFourier space gate with a 1.5-mm diameter aperture was used to reduce the off-axis multiple-scattered light. The transmitted image-bearing light was monitored by a 128/spl times/128 pixels InGaAs NIR area camera. A polarization gate was implemented using a linear polarizer before the camera to measure the components of the transmitted light polarized parallel and perpendicular to that of the incident light. No time gate was used.