Significance of threshold doses for photodynamic therapy of melanotic and amelanotic tumors

摘要

Abstract: The decay of the surviving cell fraction, F, during photodynamic treatment of a cell population, F$-0$/, vs. energy dose obeys an exponential law. The integrated logarithmic form yields a straight line with intercept 0 and slope $MIN@k. The reciprocal slope yields LD$-90$/, i.e., the energy fluence (J/cm$+2$/) necessary to kill 90% of the cell population F$-0$/. In reality there are deviations from this simple set of equations. At low power densities most photosensitizers are unable to kill cells. This leads to an `optical threshold' without cell destruction but frequently with cell stimulating effects, so called `overshots.' This general phenomenon occurs in a very pronounced form with melanotic melanoma cells. !0