5-ALA/PpIX fluorescence detection of esophageal and stomach neoplasia - effects of autofluorescence background from normal and inflammatory areas

摘要

Delta-aminolevulinic acid / protoporphyrin IX is applied for exogenous fluorescent tumor detection in the upper part of gastrointestinal tract. The 5-ALA is administered per os six hours before measurements at dose 20mg/kg weight. High-power light-emitting diode at 405 nm is used as a source and the excitation light is passed through the light-guide of standard video-endoscopic system to obtain 2-D visualization. Through endoscopic instrumental channel a fiber is applied to return information about fluorescence to microspectrometer. In such way 1-D detection and 2-D visualization of the lesions' fluorescence are received. The results from in vivo detection show significant differentiation between normal and abnormal tissues in 1-D spectroscopic regime, but only moderate discrimination in 2-D imaging. In the case of 2-D video visualization the problem of relatively high levels of the autofluorescence signal in the red spectral region gives low contrast between normal and abnormal mucosa when standard CCD camera of the endoscope is applied. Sensitized inflammatory areas also give to the observer in 2-D mode low contrast between malignant areas and benign tissues and finally the emission signals are additionally altered from the re-absorption of the chromophores accumulated in the tissue investigated. The possibilities for proper discrimination between normal, inflammatory and malignant tissues using 5-ALA/PpIX and both - advantages and limitations of 1-D and 2-D fluorescent detection modes are discussed in relation to their clinical applicability.