Non-invasive imaging of optical parameters of biological tissues

Abstract

The normalised back-scattered intensity (NBI) profiles at various locations on the forearms of ten human subjects were obtained by moving the multi-probe of a laser reflectometer. The statistical analysis of the NBI data showed that the variation in the NBI was significantly higher at the ulnar region compared with that at other regions. For determination of the scattering (mus) and absorption (mus) coefficients and the anisotropy parameter g at each location on the forearm, these profiles were matched with the NBI profiles simulated by a Monte Carlo procedure (chi(2)0.99). For the reconstruction of images of variation of these parameters, the averaged values of mua, mus, and g at all locations on the forearms of the subjects were determined. The absorption coefficient had a minimum (1.92 cm(-1)) and maximum (2.21cm(-1)) at the wrist and the lateral region of the forearm, respectively. The scattering coefficient had a maximum (194 cm(-1)) at the medial side and near the elbow, and a minimum (186 cm(-1)) at the lateral side of the forearm. Similar changes in the anisotropy parameter were also observed. By interpolation of the data of each parameter on a 100 x 100 image matrix and after median filtering, colour-coded images of the variation in the optical parameters were constructed. These images could be useful for diagnostic and therapeutic applications of lasers.

Non-invasive imaging and characterisation of human foot by multi-probe laser reflectometry and Monte Carlo simulation

“…However, in the foot, the thickness of the epidermis and dermis layers is greater than that in other parts of the body, and their composition is also different, which leads to varying hardness in the sole region (ODLAND, 1991). The placing of the fibres at various locations away from the input fibre means that they collect backscattered photons with a major contribution from the respective depths (CuI and OSTRANDER, 1992;CHACKO and SINGH, 1999;KUMAR and SINGH, 2003a). The variation in the scattering and absorption coefficients and the anisotropy parameter in various regions, except in the epidermis layer, is less (TUCHIN, 1997).…”

Determination of the concentration scaling law of the scattering coefficient of water solutions of Intralipid at 832 nm by comparison between collimated detection measurements and Monte Carlo simulations

“…Analogously to the MC profiles, the experimental transmittance profiles were fitted by the Gaussian function in equation (2). The best fit values of V max , the transmittance peak value, were plotted as a function of the absorption coefficient m a , for each fixed value of the reduced scattering coefficient.…”

Multilayer imaging and compositional analysis of human male breast by laser reflectometry and Monte Carlo simulation

“…These images show the variation of NBI as received from various depths on the tissue surface. Further details of the procedure are given elsewhere [18].…”

“…After converting these into corresponding NBI values, the surface profiles with respect to distance of detectors from beam entrance point were plotted. With an exponential fit, the NBI values, at intermediate locations, were obtained [18].…”

“…However, during photon-tissue interaction, the photons that penetrate deeper into the tissues are backscattered at farther distances from the beam entry point. Thus, the variation in internal structures of tissues located at various depths has been imaged by measurement of backscattered radiation received by placing the output fibers at various distances from the beam entry point [18,32]. Since photon transport is based on the spatial variation of refractive index along the medium, it thoroughly interacts with the tissues at the sub-cellular level.…”