## 1 Introduction  
Despite the high technical and intellectual level of modern medicine, the problem of diagnosis and treatment of hepatopancreatoduodenal organs pathologies is still acute. The significance of this issue is caused by high rate of morbidity, great risk of complications together with steep mortality rate [1; 2]. In recent decades strong interest from research and clinical community is shown towards the introduction of minimally invasive technologies and techniques for diagnosis and treatment in clinical practice. This is caused by decreased surgical injury and the volume of surgical interventions, as well as the substantially reduced number of postoperative complications. This approach features significantly reduced time required for treatment and recovery, especially compared with open surgery [3]. During the minimally invasive operation, the choice of a rational medical tactics strictly depends on the observed syndrome, but usually suffer from lack of information during the procedure, as the surgical site is limited by the field of view of the optical channel. Currently, the integral parts of any minimally invasive intervention are the methods of ultrasound and X-ray examination. They are necessary for determining the allocation of pathological formations (such as neoplasms or abscesses), as well as more complex methods of computer tomography (CT) and magnet resonance imaging (MRI). However, these methods mostly show anatomical and morphological features at the organ level whereas in most cases it is important to assess the type and vitality of tissues at the cellular level. Therefore, obtaining of additional diagnostic information about the properties of the tissues intraoperatively is of particular interest for modern surgery. Speaking of CT and MRI these methods cannot be used immediately during the surgery. Another problem of X-ray and CT methods to be worried about is the harmful effects of the radiation. A gold standard for analysis of state of biological tissues is histological examination, but it takes time to obtain the results. The development of minimally invasive technologies determines the need for development of diagnostic methods that allow for obtaining information in vivo with accuracy comparable to histological data. The implementation of new methods will increase the quality of diagnosis of biological tissues state and nature (healthy, inflamed, malignant, etc.) [4], and consequently improve the quality of treatment. Optical diagnostic methods have been used for many years in various fields of medicine. Currently, the studies of application of spectrometry and imaging in surgery are quickly developing worldwide [5]. One of such methods is fluorescence spectroscopy (FS). The method is sensitive both to the emission of administrated fluorescence contrast [6] as well as endogenous fluorescence of certain tissue biomarkers in vivo [7; 8; 9]. FS is aimed to studying the structure of cells, their properties and ongoing biochemical reactions. In certain cases, such parameters of fluorescence as intensity and lifetime depend on the metabolism conditions in the biological tissues under study. In particular, it is possible to evaluate cell metabolism by studying the ratio of nicotine adenine dinucleotide (NADH) and flavinoadenidine dinucleotide (FAD) coenzymes. These compounds are vital elements of tricarbonate acid cycle. Changes in the content of NADH and FAD influence the intensity of endogenous fluorescence excited by radiation of certain wavelengths. Thus, FS method creates an opportunity for diagnosis and monitoring of tissue metabolic activity in inflammatory processes [10; 11]. Currently fluorescent diagnostics is successfully applied in several areas of medicine [12; 13]. Normal level of blood perfusion in abdominal tissues is highly important for normal oxygenation and nutrition of them at the cellular level. Ischemia, or lack of perfusion, is a common way for tissue death or degeneration.