This review highlights time-resolved fluorescence kinetics and photon transport in tissues and other biomedical media with a special emphasis on ultrafast measurements of key optical parameters. Measurements of fluorescence decay lifetimes from human breast and atherosclerotic artery tissues in the uv and visible region are described after a brief description of fundamentals of fluorescence kinetics. A time-dependent diffusion model for photon migration and various ultrafast methods for time-resolved light scattering measurements to obtain key optical parameters of tissues and other model turbid media are presented. The usefulness of optical parameters as markers in optical diagnostics and imaging is considered. Time-gated measurements of ballistic and snake photons to obtain shadowgrams and an inverse numerical reconstruction of the interior map of a turbid medium from time-resolved data in the context of optical tomography are presented.

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The MgO in blast furnace slag provides an optimum condition in terms of both good flowability and desulphurisation. The mode of its addition to the blast furnace changed from, initially, as raw flux in the form of dolomite, to via sinter, with the argument that raw flux demands energy for its decomposition inside the blast furnace. Thus, the decomposition reaction was diverted from the blast furnace to the sintering bed, and the energy source for decomposition was changed from costly blast furnace coke to a relatively cheap coke breeze. Now olivine/dunite/serpentine is being used as a source of MgO, where energy for decomposition is not required; this also provides a source of SiO 2 , which 1 Influence of MgO on productivity RESULTS AND DISCUSSIONMr Jena are at sinter plants BB and SP2, Tata Steel, Jamshedpur,

The image of an object hidden in highly scattering media was reconstructed using a fast, noiseresistant algorithm newly applied to diffusion tomography. A pulsed light source producing scattered and transmitted light is examined at multiple times. Multiple source detector pairs around the medium are used to obtain data in many different directions. An inverse scattering algorithm with nonuniform regularization achieves rapid inversion convergence.Probing internal structures of highly scattering media using ultrafast optical sources in the visible and near infrared spectral region has many medical, biological, and industrial applications. Radiation in this spectral region is non-ionizing and safe, which is particularly important for medical applications. Images of objects in highly scattering media obtained using conventional steady-state transillumination shadowgram techniques are blurred by strong multiple scattering. These photons are randomized in the scattering media, and the paths they take to traverse through the media are tortuous and lack a clear well-defined pattern. Over the past 10 years, many methods and techniques have been proposed and tested to overcome the multiple scattering problem. With the rapid advance of laser technology and detection techniques, various gating techniques were demonstrated to selectively detect the first and early arriving photons that travel through the turbid medium along and near the straight line path connecting the source and detector, referred to as ballistic and snake signals (1, 2). Frequency domain techniques using intensity modulated (up to 1 GHz) diode laser sources have also been demonstrated for imaging a simple object hidden in a highly scattering medium with limited success (3). The limitation of these methods is that for thick highly scattering media, the useful signal is weak. In highly scattering media, the diffused signal is predominant with intensities many orders of magnitude stronger than the early image carrying light. These methods require many measurements in many directions to obtain a threedimensional image that may be difficult in practical applications. One alternative method proposed to overcome this problem is to solve an inverse problem using scattered light profiles measured around the media. Diffusion tomography is used since diffusive scattering is the dominant factor in the problem. Both time-resolved data and frequency domain data can be used for reconstruction.In this paper, we present a fast inversion approach to reconstruction of hidden objects in a highly scattering medium by taking time slices over a large time range of the temporal profiles measured by many source-detector (S-D) pairs around the medium.Using multi-time-slices from the temporal profiles increases information data by a large factor so that the number of experimental measurements can be greatly reduced. Thus, the advantage of using time resolved data is clear. Time-resolved measurements can give much more information for image reconstruction with better spatia...

Cypate-octreote peptide analogue conjugate (Cytate) was investigated as a prostate cancer receptortargeted contrast agent. The absorption and fluorescence spectra of Cytate were ranged in the nearinfrared "tissue optical window." Time-resolved investigation of polarization-dependent fluorescence emitted from Cytate in solution as well as in cancerous and normal prostate tissues was conducted. Polarization preservation characteristics of Cytate in solution and tissues were studied. Fluorescence intensity emitted from the Cytate-stained cancerous prostate tissue was found to be much stronger than that from the Cytate-stained normal prostate tissue, indicating more Cytate uptake in the former tissue type. The polarization anisotropy of Cytate contained in cancerous prostate tissue was found to be larger than that in the normal prostate tissue, indicating a larger degree of polarization preservation in Cytate-stained cancerous tissue. The temporal profiles of fluorescence from Cytate solution and from Cytate-stained prostate tissue were fitted using a time-dependent fluorescence depolarization model. The photoluminescence imaging of Cytate-stained cancerous and normal prostate tissues was accomplished, showing the potential of Cytate as a fluorescence marker for prostate cancer detection.

A translucent object hidden in a highly scattering medium is shown to be visible when the early portion of the transmitted diffuse pulse (snake photons) is detected. The use of the snake scattered photons to image objects depends on the scattering characteristics along a quasi-straight-line path that the photons traverse across the medium. A translucent object with different scattering characteristics compared with its surrounding medium will change the intensity of the snake photons. By scanning the medium across the laser beam and detecting only the snake photons, a translucent object hidden in a highly scattering medium could be located.

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