Photodynamic diagnostics of early gastric cancer:Complexity measures of gastric microcirculation and new model of metastatic adenocarcinoma of rat stomach

The detection of early gastric cancer that often develops asymptomatically is crucial for improving patient survival.The photodynamic diagnosis(PDD)of gastric cancer using 5-aminolevulinic acid/protoporphyrin IX(5-ALA/PpIX)has been reported in several studies.However,the selectivity of PDD of gastric tumor is poor with often false-positive results that require the development of new methods to improve PDD for early gastric cancer.Therefore,a measure of the complexity of gastric microcirculation(multi-scale entropy,MSE)and the detrendedfluctuation analysis(DFA)were applied as additional tools to detect early gastric cancer in rats.In this experimental study,we used our original model of metastatic adenocarcinoma in the stomach of a rat.To induce a gastric tumor,we used a long-term combination(for 9 months,which is 1/2 of the life of rats)of two natural factors,such as chronic stress(overpopulation being typical for modern cities)and the daily presence of nitrites in food and drinks,which are common ingredients added to processed meat andfish to help preserve food.Our results clearly show that both methods,namely,PDD using 5-ALA/PpIX and complexity/correlation analysis,can detect early gastric cancer,which was confirmed by histological analysis.Pre-cancerous areas in the stomach were detected as an intermediatefluorescent signal or MSE level between normal and malignant lesions of the stomach.However,in some cases,PDD with 5-ALA/PpIX produced a false-positivefluorescence of exogenousfluorophores due to its accumulation in benign and inflammatory areas of the mucosa.This fact indicates that the PDD itself is not sufficient for the correct diagnosis of gastric cancer,and the use of additional characteristics,e.g.,complexity measures or scaling exponents,can significantly improve the diagnostic accuracy of PDD of gastric cancer that should be confirmed in further clinical studies and applications.

LIGHT-INDUCED FLUORESCENCE SPECTROSCOPY AND OPTICAL COHERENCE TOMOGRAPHY OF BASAL CELL CARCINOMA

Many up-to-date optical techniques have been developed and applied recently in clinical practice for obtaining qualitatively and quantitatively new data from the investigated lesions.Due to their high sensitivity in detection of small changes,these techniques are widely used for detection of early changes in biological tissues.Light-induced fluorescence spectroscopy(LIFS)is one of the most promising techniques for early detection of cutaneous neoplasia.Increasing number of recent publications have suggested that optical coherence tomography(OCT)also has potential for non-invasive diagnosis of skin cancer.This recent work is a part of clinical trial procedure for introduction of LIFS technique into the common medical practice in National Oncological Medical Center in Bulgaria for diagnosis of non-melanoma skin cancer.We focus our attention here on basal cell carcinoma lesions and their specific features revealed by LIFS and OCT analysis.In this paper we prove the efficiency of using the combined LIFS-OCT method in skin lesions studies by integrating the complimentary qualities of each particular technique.For LIFS measurements several excitation sources,each emitting at 365,385 and 405 nm maxima are applied.An associated microspectrometer detects in vivo the fluorescence signals from human skin.The main spectral features of the lesions and normal skin are discussed and their possible origins are indicated.OCT images are used to evaluate the lesion thickness,structure and severity stage,when possible.The obtained results could be used to develop a more complete picture of optical properties of these widely spread skin disorders.At the same time,our studies show that the combined LIFS-OCT method could be introduced in clinical algorithms for early tumor detection and differentiation between normal/benign/malignant skin lesions.

A special issue on Biophotonics in Europe

Biophotonics is an emerging multidisciplinary research area, embracing all light-based technologies applied to the life sciences and medicine [1-6]. The expression itself is the combination of the Greek syllables ＂bios＂ standing for life and ＂phos＂ standing for light. Photonics is the technical term for all methodologies and technologies utilizing photons over the whole spectrum from X-ray over the ultraviolet, visible and the infrared to the terahertz region, and its interaction with any matter. Beyond this definition, biophotonics is a scientific discipline of remarkable societal importance. As a part of photonics, it has proved to be an important enabling technology for accelerated progress in medicine and biotechnology. It can do so, because it originated at the interface of the most innovative academic disciplines of the last century, i.e., photonics, biotechnology and nanotechnologies. This field of research brings together scientists from different professions, such as physicists, biologists, pharmacists, medical doctors, etc. To work on common projects, they need to understand the ideas and the techniques of their counterparts.