PHOTODYNAMIC THERAPY SYSTEM WITH SINGLET O2 DOSIMETRY

A SYSTEM FOR PHOTODYNAMIC THERAPY (PDT) THAT PROVIDES, IN ADDITION TO THE THERAPEUTIC LIGHT DOSE, A METHOD OF REAL-TIME, INTRAOPERATIVE DOSIMETRY WILL BE ASSEMBLED AND DEMONSTRATED. IN PDT, A PARENTERALLY ADMINISTERED PHOTOACTIVE DYE (DIHEMATOPORPHYRIN ETHER, DHE) LOCALIZES IN MALIGNANT TISSUE. SUBSEQUENT IRRADIATION OF THE DHE-BEARINGTISSUE WITH LIGHT (630NM) PRODUCES, IN COMBINATION WITH OXYGEN, THE CYTOTOXIC REACTION PRODUCT, SINGLET OXYGEN ((1)O2). BY MONITORING THE REAL-TIME-RESOLVED (1)O2 FLUORESCENCE AT 1.27 NM, A SIGNAL PROPORTIONAL TO THE (1)O2 PRODUCTION RATE WILL RESULT, THEREBY PROVIDING DOSIMETRY INFORMATION. THE SYSTEM TO BE DEMONSTRATED EMPLOYS A CW-PUMPED, Q-SWITCHED, FREQUENCY-DOUBLED YAG LASER DRIVING A TUNABLE DYE LASER EMITTING 70-NANOSECOND, 630-NANOMETER WAVELENGTH PULSES AT A 10-KHZ RATE. IN ADDITION TO PROVIDING REAL-TIMEDOSIMETRY INFORMATION, THE SYSTEM ALSO ALLOWS FOR THE STUDY OF A POSSIBLE INCREASE IN THE THERAPEUTIC EFFECT DUE TO THE GENERATION OF THE CYTOTOXIC AGENT (1)O2 IN "BURSTS." TO DATE, THE RECIPROCITY OF THE PDT LIGHT DOSE DOES NOT APPEAR TO HAVE BEEN THOROUGHLY INVESTIGATED. FINALLY, THE INHERENT WAVELENGTH AGILITY OF A TUNABLE DYE LASER MAKES THIS SYSTEM USEFUL WITH NEW PHOTOACTIVE DYES OPERATING BEYOND 630 NM.