Observation of Zn-photoprotoporphyrin red Autofluorescence in human bronchial cancer using color-fluorescence endoscopy.

BACKGROUND: We observed red autofluorescence emanating from bronchial cancer lesions using a sensitive color-fluorescence endoscopy system. We investigated to clarify the origin of the red autofluorescence. METHODS: The wavelengths of the red autofluorescence emanating from lesions were measured in eight patients using a spectrum analyzer and compared based on pathologic findings. Red autofluorescence at 617.3, 617.4, 619.0, and 617.1 nm was emitted by normal bronchus, inflamed tissue, tissue exhibiting mild dysplasia, and malignant lesions, respectively. Protoporphyrin, uroporphyrin, and coproporphyrin, the major porphyrin derivatives in human blood, were purchased to determine which porphyrin derivative is the source of red fluorescence when acquired de novo. We synthesized photoporphyrin, Zn-protoporphyrin and Zn-photoprotoporphyrin from protoporphyrin. RESULTS: Coproporphyrin and uroporphyrin emitted only weak fluorescence. Fluorescence was emitted by our synthesized Zn-photoprotoporphyrin at 625.5 nm and by photoprotoporphyrin at 664.0 nm. CONCLUSIONS: From these results, we conclude that Zn-photoprotoporphyrin was the source of the red autofluorescence observed in bronchial lesions. Zn-protoporphyrin is converted to Zn-photoprotoporphyrin by radiation with excitation light. Our results suggest that red autofluorescence emanating from Zn-photoprotoporphyrin in human tissues could interfere with photodynamic diagnosis using porphyrin derivatives such as Photofrin® and Lazerphyrin® with a sensitive endoscopy system, because color cameras cannot differentiate Zn-photoprotoporphyrin red fluorescence from that of other porphyrin derivatives.

Color auto-fluorescence from cancer lesions: improved detection of central type lung cancer.

A fluorescence endoscopic system, PDS-2000, enabled observation of color auto-fluorescence from the human body. We performed a clinical study to determine whether color auto-fluorescence bronchoscopy using PDS-2000 improved the accuracy of central type lung cancer diagnosis, as compared to white light bronchoscopy. White light bronchoscopy followed by auto-fluorescence bronchoscopy was performed in 71 subjects with either bronchogenic cancer, previous lung cancer, bloody sputum or who were at a high risk of developing lung cancer. Findings of white light bronchoscopy and auto-fluorescence bronchoscopy were classified into three categories. Two hundred eighty-eight biopsy specimens were taken from all sites which were considered to be abnormal by white light bronchoscopy as well as by auto-fluorescence bronchoscopy. The pathological findings were classified into nine categories. The sensitivity of only white light bronchoscopy (WLB) regarding the detection of severe dysplasia and cancer was compared with that of only auto-fluorescence bronchoscopy (AFB) and that of WLB+AFB. We quantified color endoscopic fluorescence images and compared the red/green signal intensity ratio (R/G ratio) according to the pathological diagnosis. The pathological diagnosis was normal in 123, inflammation, hyperplasia or metaplasia in 120, mild or moderate dysplasia in 8, severe dysplasia in 14 and cancer in 23. The sensitivity of WLB, AFB and WLB+AFB regarding the detection of severe dysplasia or cancer was 54.1%, 81.1% and 89.2%, respectively. The R/G ratio was significantly increased in the areas with severe dysplasia and cancer.