Product Code: JLA_1_2_21

Authors:
A. Edward Profio
T. F. Khoury
Department of Chemical and Nuclear Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106 U.S.A.

Stephen Lam
School of Medicine, University of British Columbia, Vancouver, B.C., Canada

The effective absorbed dose in photodynamic therapy is proportional to the concentration of the photosensitizer, as well as to the radiant energy fluence and concentration of oxygen. The concentration of dihematoporphyrin ether/ester (DHE) has been measured in tissue specimens by chemical extraction followed by spectrofluorimetry against a standard solution, and by an in vivo fluorometer probe calibrated against the extraction method. The emission at 690 nm is measured when excited by either a helium neon laser at 633 nm, or an argon‐dye laser at 630 nm. Background from autofluorescence is subtracted. Because different tissues have different absorption, the probe has to be calibrated for each tissue of interest. An experiment in a phantom indicated that fluorescence is detected from a fairly large volume, hence the average concentration is measured.