Time-gated transillumination of biological tissues and tissuelike phantoms

The applicability and limits of time-resolved transillumination to
determine the internal details of biological tissues are
investigated by phantom experiments. By means of line scans across
a sharp edge, the spatial resolution (Ax) and its dependence on the
time-gate width (At) can be determined. Additionally, measurements
of completely absorbing bead pairs embedded in a turbid medium
demonstrate the physical resolution in a more realistic case. The
benefit of time resolution is especially high for a turbid medium
with a comparatively small reduced scattering coefficient of
approximately pL,' = 0.12 mm-1. Investigations with partially
absorbing beads and filled plastic tubes demonstrate the high
sensitivity of time-resolving techniques with respect to spatial
variations in scattering or absorption coefficients that are due to
the embedded disturber. In particular, it is shown that time gating
is sensitive to variations in scattering coefficients. Key words:
Time-resolved transillumination, turbid media, light scattering,
streak camera.