Image quality in time-resolved transillumination of highly scattering media

Abstract

Using a photon-counting setup and a streak-camera arrangement with time resolutions of 35 and 6 ps, respectively, we have investigated the spatial resolution of a time-gated transillumin tion technique applied to turbid media. In the case of large relative amounts of unscattered light, it is found that small detection angles improve the spatial resolution. For large concentrations of scatterers and large sample thicknesses, i.e., when the amount of unscattered light is negligible, the best time-gate position is found to be at times that are later than the minimum transit time. In this case (minimum transit time), temporal resolutions from small values up to approximately 50 ps yield almost the same image resolution. The only advantage of measuring systems with a higher than 50-ps temporal resolution is their ability to distinguish the diffused from the unscattered light, when a significant amount of the latter is present.

Computer simulation of time-resolved optical imaging of objects hidden in turbid media

“…without image processing) is possible [82]. Diffusive light imaging can be performed in the frequency domain [39,[83][84][85][86] or in the time domain [23][24][25]38,87]. In the former case a continuous intensity-modulated light source is used to generate diffusive monochromatic light-intensity waves in the medium.…”

“…The source emits a Gaussian light distribution of width 2 mm, centered around (0, 36, 25) mm during a time of 0.06 ps. R denotes the distance between the source and the detector [23] "1.128 mm\;conc and "0.12 mm\;conc at "780 nm; [23] "1.4 mm\; conc and "0.5 mm\;conc at "633 nm; [67] "0.888 mm\;conc at "632.8 nm [162]. The abbreviation conc denotes the concentration of intralipid in percent.…”

Tissue characterization with ballistic photons: counting scattering and/or absorption centres

“…Without it the power value for a given point (x, y) would correspond to a specific gray value: transmitted power at time t = 0 in Eq. (11). Due to the phase−offset f 0 , the modulation term would, therefore, be decreased from its highest value.…”

“…Biomedical diagnosis is often based on the characterization of tissue samples using the optical tech− niques, such as the response to the coherent or non-coherent illumination, including reflection (optical coherence tomog− raphy), transmission [4,5], absorption, and scattering [6][7][8][9], in either time−integrated or time−resolved applications [10][11][12][13][14][15].…”

Advanced optical microscopy methods for in vivo imaging of sub-cellular structures in thick biological tissues

“…This is achieved using an ultrashort-pulsed laser and an ultra-fast time gate, such as a streak camera. [4][5][6][7][8] The time resolution available is usually not su±cient for microscopic imaging.…”