namic induced apoptosis. Post photodynamic therapy extracted normal rat liver tissue usually shows a fraction
of surviving cells, the photodynamic resistant cells, residing in the necrotic region. To treat these photodynamic
resistant cells a technique has been proposed based on fractionated drug administration of diluted photosensi-
tizer, keeping the net concentration (5 mg/kg) constant, and subsequently varying drug light interval (DLI).
Flourescence measurements were made for the presence of photosensitizer in a tissue. For qualitative analysis
both histological and morphological studies were made. Although preliminary aim of this approach was not
achieved but there were some interesting observation made i.e. for higher dilution of photosensitizer there was
a sharp boundary between necrotic and normal portion of tissue. An increase in the absorption coefficient (
) from 2.7
2.9 was observed as photosensitizer was diluted while the corresponding threshold dose (Dth) per-sistently decreases from (0.10
0.02) J/cm2 when irradiated with a 635 nm laser fluence of 150 J/cm2.