Time-resolved and quasi-continuous wave three-dimensional tomographic imaging of objects in tissue-like turbid media

Time-sliced and quasi continuous wave two-dimensional (2-D)transillumination imaging methods were used with independent component analysis (ICA) to generate three-dimensional (3-D)tomographic maps of absorbing and scattering inhomogeneities embedded in tissue-like turbid media. The thickness of the turbid media in both the cases was approximately 50 times the transport mean free path. The experimental arrangement for time-sliced optical imaging used 150-fs, 1 kHz repetition-rate, 800-nm light pulses from a Ti:sapphire laser system for sample illumination, and an ultrafast gated intensified camera system (UGICS) providing a minimal gate duration of 80 ps for recording 2-D images. Quasi continuous wave (CW) imaging used 784-nm CW output of a diode laser as the light source and a cooled charge coupled device (CCD) camera for recording 2-D images. Translation stages were used to scan the samples over an array of points in the x-y plane. The temporal profile of the transmitted pulse was used to extract the average optical properties of the media. An independent component separation of the signal, in conjunction with diffusive photon migration theory was used to locate the embedded inhomogeneities. An improved lateral and axial localization of the inhomogeneity over the result obtained by common photon migration reconstruction algorithm is achieved.