|
It is a new physical diagnostic technology to identify tumor by using laser-induced fluorescence. The fundamental is that porphyrins can accumulate i tumor because of their specific affinity to tumor tissues. However the concentration in normal tissue is very low. Being excited by some light with special wavelength, porphyrins can emit red fluorescence, whose peak wavelength is at 630nm and 690nm. The difference of fluorescence intensity between tumor and normal tissue can indicate where tumor is located. After injecting exogenic porphyrin to the patient, we can differentiate tumor from normal tissue by analyzing fluorescence of an organ. Hematoporphyrin derivative (HPD) has been used to diagnose and treat different tumors for a long time [1 ,2.Itis well known that when examined with endoscope, the early tumor in bronchial gastrointestinal and urinary tract, being very small, can't be easily diagnosed. After HPD being injected into the patient, the tumor will emit red fluorescence when irradiated by laser. By analyzing the spectrum of fluorescence with optical mutichannel analyzer (OMA), we can indicate the location of tumor and sample the tissue for biopsy. So the diagnostic accuracy is enhanced. The clinical suggested dose of HPD is 5mg/kg. Photosensitivity reaction is the main side effect of HPD. When patient who has been injected with HPD irradiated by sunlight, erythematous vesicles may occur on the his skin [3]. To avoid the side effect, the patient has to be protected from powerful light for about a month. It is annoying matter to patient. If photosensitivity drug isn't used, the demand to exciting light is very strict because the autofluorescence emitted by tumor tissue is faint. In order to diagnosing tumor, we have intravenously injected small dose of HPD into patients and analyzed the fluorescence with OMA. The time that patients have to be protected from powerful light was reduced from a month to three days. Meanwhile, the demand of exciting light was cut down. So we can outmostly use the instrument now available. Because experiment on animal had showed that small dose of HPD (2mg/kg) can do favor to diagnosing cancer and there isn't statistical difference between the diagnostic accuracy of small dose and that of larger dose, we gave patients the dose of 2mg/kg.
|
