Time-resolved transillumination of turbid media

The suitability and limits of time-resolved transillumination to determine inner details of biological tissues are investigated by phantom experiments. The achievable improvement is demonstrated by using different phantoms (absorbing objects embedded in a turbid medium). By means of line-scans across a sharp edge the spatial resolution and its dependence on temporal resolution can be determined. To demonstrate the physical resolution according to the Rayleigh-criterion, measurements were performed on blackened bead pairs. Investigations with partially transparent beads demonstrate the high sensitivity of time-resolving techniques with respect to variations in scattering or absorption coefficients

Time-gated transillumination of biological tissues and tissuelike phantoms

Abstract: We have performed non-invasive, real-time optical mapping of the piglet brain during a subcortical injection of autologous blood. The time resolution of the optical maps is 192 ms, thus allowing us to generate a real-time video of the growing subcortical hematoma. The increased absorption at the site of blood injection is accompanied by a decreased absorption at the contralateral brain side. This contralateral decrease in the optical absorption and the corresponding time traces of the cerebral hemoglobin parameters are consistent with a reduced cerebral blood flow caused by the increased intracranial pressure