Biophysics, Invited Lecture

FLUORESCENCE SPECTROSCOPY OF GASTROINTESTINAL TUMORS – ADVANTAGES AND DRAWBACKS

E. Borisova(1), B. Vladimirov(2), R. Ivanova(3), L. Avramov(1)
1) Institute of Electronics, Bulgarian Academy of Sciences
2) Clinic of Gastroenterology, University Hospital Queen Joanna - ISUL
3) Laboratory of clinical pathology, University Hospital “St. Ivan Rilski”, Sofia, Bulgaria

ABSTRACT

The limitations of standard endoscopy for detection of cancerous changes in gastrointestinal tract are significant challenge for development of new diagnostic modalities. The majority of gastrointestinal malignancies, especially adenocarcinoma, arise from epithelial surfaces. A common phenotype of all epithelial cancers is the progression from normal mucosa, through a stage of dysplasia, to cancer. The diagnosis of dysplasia based on standard endoscopy with multiple biopsies is still very limited and significant inter-observer disagreement between pathologists in diagnosing dysplasia is occurred. Technological advances in fiber optics, light sources, detectors, and molecular biology have stimulated the development of numerous optical methods that promise to significantly improve our ability to visualize and evaluate human epithelium in vivo. Different methods such as chromoendoscopy, magnifying endoscopy, and optical-based spectroscopic and imaging modalities can increase the possibility to detect endoscopically precursor lesions and early stage of gastrointestinal cancer with combination of target biopsies. They have the potential to overcome the limitations of standard endoscopic procedures by assessing wide neoplastic regions. These modalities may also provide a more accurate assessment of the extent of neoplastic lesions than conventional endoscopy, which is critical for success of the new endoscopic therapy, such as endoscopic mucosal resection. Nevertheless, all of these new techniques are also associated with various limitations and standardization.
Fluorescence spectroscopy, which is one of the most sensitive optical techniques applied for tissue detection and evaluation of tumors with different localizations using endoscopic equipment, is analyzed. The aim of our study is to evaluate the fluorescence spectroscopy diagnosis of dysplasia and tumors of esophagus and stomach during endoscopic examinations using endo- and exogenous fluorophores. Delta-aminolevulinic acid/Protoporphyrin IX (5-ALA/PpIX) is used as exogenous fluorescent marker. High-power light-emitting diode at 405 nm was used as an excitation source. Measurements of the fluorescence spectra were made using fibre-optic spectrometer and 2-D visualization and record of fluorophore distribution in the mucosa was made using video system of the endoscopic equipment. Standard histology was used as a “gold” standard. The fluorescence detected from tumor sites consisted of blue-green autofluorescence signal from mucosa and red fluorescence when exogenous fluorophore are applied. The lack of fluorescence peaks in the red spectral area for normal mucosa was observed and it was an indication for selective accumulation of 5-ALA/PpIX only in abnormal sites. The neovascularisation of tumors was also clearly pronounced in all dysplastic and tumor sites investigated. Results achieved show very good correlation between fluorescence signals and histology examination of the lesions investigated. Rapid lesions border determination using exogenous fluorescence signal is also obtained.

Representing author

photo

Dr. Ekaterina Georgieva Borisova

Institute of Electronics, Bulgarian Academy of Sciences, Associate Professor
Sofia, Bulgaria

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