Ekaterina Borisova, Tsanislava Genova, Aleksandra Zhelyazkova, Latchezar Avramov, Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
Momchil Keremedchiev, Nikolay Penkov, Borislav Vladimirov, Queen Jiovanna-ISUL University Hospital, 8, Bialo More str., 1527 Sofia, Bulgaria
In this report we will present our recent investigations of the fluorescence properties of lower part gastrointestinal tissues using excitation-emission matrices and synchronous fluorescence spectroscopy measurement modalities. The spectral peculiarities observed will be discussed and the endogenous sources of the fluorescence signal will be addressed.
For these fluorescence spectroscopy measurements the FluoroLog 3 system (HORIBA Jobin Yvon, France) was used. It consists of Xe lamp (300 W, 200-850 nm), scanning double monochromators, and PMT detector with high performance in the region 220-850 nm. Autofluorescence signals were detected in the form of excitation-emission matrices for the samples of normal mucosa, dysphasia and colon carcinoma and specific spectral features for each tissue were found.
Autofluorescence signals from the same samples are observed through synchronous fluorescence spectroscopy, which is a novel promising modality for fluorescence spectroscopy measurements of bio-samples. It is one of the most powerful techniques for multicomponent analysis, because of its sensitivity. In the SFS regime, the fluorescence signal is recorded while both excitation λexc and emission wavelengths λemm are simultaneously scanned. A constant wavelength interval is maintained between the λexc and λemm wavelengths throughout the spectrum. The resulted fluorescence spectrum shows narrower peak widths, in comparison with EEMs, which are easier for identification and minimizes the chance for false determinations or pretermission of specific spectral feature. This modality is also faster, than EEMs, a much smaller number of data points are required. 
In our measurements we use constant wavelength interval Δλ in the region of 10-100 nm. Measurements are carried out in the terms of finding Δλ, which resulting a spectrum with most specific spectral features for comparison with spectral characteristics observed in EEM.
Implementing synchronous fluorescence spectroscopy in optical methods for analyzing biological tissues could result in a better differentiation between normal and dysplastic tissue. Thus could improve fluorescence imaging like diagnostic modality among optical techniques applied in clinical practice.
Acknowledgements: This work is supported by the National Science Fund of Bulgarian Ministry of Education and Science under grant #DMU-03-46/2011 “Development and introduction of optical biopsy for early diagnostics of malignant tumors” and grant DO-02-112/2008 “National Center on Biomedical Photonics”
 Quan Liu, Kui Chen, Matthew Martin, Alan Wintenberg, Roberto Lenarduzzi, Masoud Panjehpour, Bergein F. Overholt, and Tuan Vo-Dinh, “Development of a synchronous fluorescence imaging system and data analysis methods”, OPTICS EXPRESS, Vol. 15, No. 20, (2007)
Dr. Ekaterina Georgieva Borisova
Institute of Electronics, Bulgarian Academy of Sciences, Associate Professor
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