Abstract

Huorescence measurements using nonimaging photodetection have demonstrated the detection of microscopic residual disease,¹ premalignant lesions,² and lesions undergoing tumor progression.³ Photofrin has been used previously as the tumor localizing photosensitizer with the dual function of emitting red (630 and 690 nm, Φ_f ≈ 0.03) fluorescence after excitation as well as being useful in photodynamic therapy (PDT). Recently, there has been great interest in new photosensitizers that show long wavelength absorption and greater fluorescence yield for use in PDT and diagnosis of solid malignant tumors. Hexylpyropheophorbidea (HPPH, Fig. 1) is a new sensitizer that has shown high antitumor efficacy and rapid clearance from skin in a murine model.⁴ HPPH has a major absorption peak at 665 nm (ϵ = 47,500 M⁻¹cm⁻¹) and an emission peak at 671 nm (Φ_f ≈ 0.3). The fluorescence quantum yield of HPPH is 10 times greater than Photofrin. The extinction coefficient of HPPH is 19 times greater than Photofrin (ϵ = 2,500 M⁻¹cm⁻¹ at 630 nm). Therefore, HPPH may be a promising photosensitizer for the application of photodynamic diagnosis and treatment. The purpose of this study was to estimate HPPH as a fluorescent diagnostic compound for the detection of transformed tissues and metastases of lymph nodes.

© 1995 IEEE