Non-invasive imaging of optical parameters of biological tissues

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 (μ _s ) and absorption (μ _a ) 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 (χ _0.99 ² ). For the reconstruction of images of variation of these parameters, the averaged values ofμ _a ,μ _s 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 (2.21 cm⁻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 100×100 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.