Cystoscopic fluorescence detector for photodetection of bladder carcinoma with hematoporphyrin derivative

Hematoporphyrin derivative, a fluorogenic substance, tends to accumulate at higher levels in most tumor tissues after intravenous injection. These properties provide a potential application for the detection of malignant tumors. We report the development and in vitro evaluation of an instrument designed to excite and detect low levels of hematoporphyrin derivative fluorescence emitted by tumor cells in the bladder after hematoporphyrin derivative administration. The light source of the instrument for specific hematoporphyrin derivative excitation is at a wavelength of 405 nanometers. Optical fibers for both the excitation and detection of fluorescence were bundled in a single 7 French ureteral catheter which can be inserted into a standard cystoscope. The fluorescence is initially detected as an electrical signal which is amplified and then converted into an audio signal. The interference of the cystoscope illuminating white light to the fluorescence signal is eliminated by a phase-sensitive electronic circuit. The instrument thus allows simultaneous viewing of the bladder and detection of hematoporphyrin derivative fluorescence produced from tumor tissues. In vitro testings using hematoporphyrin derivative solutions on filter paper indicated that the instrument detects as little as 30 nanograms per milliliter of hematoporphyrin derivative and has relatively low noise levels from normal tissues. The utility of this instrument for hematoporphyrin derivative photodetection of small tumors and carcinoma in situ in bladder is currently under clinical evaluation.