Transserosal optical coherence tomography (OCT) with angiography modality (OCTA) provides real-time label-free visualization of the intestinal structure and blood vessels networks with a spatial resolution about 10-15 µm. This method is a perspective for intraoperative use in abdominal surgery, for example, for determining the depth of ischemic damage to the gut. The paper devoted to analysis the quality of OCT/OCTA data obtained from small intestine of 4 subjects - rat, rabbit, minipigs and humans. The subjects have different thickness of intestinal wall and blood circulation conditions. It was shown, that the intestine of small laboratory animals (rats and rabbits) is convenient for studying with OCT/OCTA: it can be easily stabilized by moving the intestine loop outside the body, which, together with a rigidly fixed probe, minimizes the number of possible motion artifacts. Therefore, OCT/OCTA criteria of structural changes in the intestinal wall and microcirculation disorders during ischemia, important for clinical applications, were established on these objects. Large animals (minipigs) and human proved to be a troublesome subjects for obtaining high-quality OCT/OCTA data: powerful peristaltic movements, pronounced pulse wave and the inability to take the object out of the body in order to exclude the influence of respiratory and other types of the body movements led to a sharp increase in the amount of OCT/OCTA images with artifacts (up to 39% in humans). However, in patients and minipigs the microstructure of intestinal layers was more informative than in small animals due to increased thickness. Therefore, it allowed visualize tissues in more detail: in particular, verify peritoneum edema and intramuscular fluid buildup. The study was performed under support of RFBR grant No.19-75-10096.
In the paper we demonstrate the applicability of optical coherence tomography angiography (OCTA) and optical coherence tomography lymphangiography (OCTL) to investigate changes in intramural blood and lymph flow of the small intestine in an experimental model of spinal trauma with sympathetic denervation of the gut. Resection of sympathetic ganglia was performed in rabbits using the retroperitoneal approach. Lymph and blood circulation in the small intestine wall was evaluated before and after the spinal trauma. For OCTL images the signal attenuation coefficient was quantitatively analyzed, and the areas that did not scatter or absorb light in the infrared range were assigned to the lymph. It was shown that the changes in blood microcirulation are significant, hovewer the significance of changes in lymhatic vessels density is hard to estimate due to high variations of data.
Successful gastrointestinal surgery is based on the precise knowledge of the morphological, functional and metabolic state of the bowel wall at a specific time point. Current trends include the development of real-time, minimally invasive, label-free and rapid techniques for tissue assessment in combination with algorithms of data processing. The aim of the study was to evaluate the performance of trans-serous multimodal optical coherence tomography (MM OCT) and FLIM macro-imaging in detecting changes in microstructure, blood circulation and metabolism of intestinal wall caused by acute arterial ischemia in experiment. The study was supported by the Russian Science Foundation, project No. 19-75-10096.
A method, based on optical coherence angiography (OCA), for the intraoperative diagnosis of blood microcirculation in the ischemic intestine has been tested. The pilot clinical study involved 18 patients who had undergone urgent operations for thrombosis of segments II or III of the superior mesenteric artery, as well as for infringement of the bowel and the mesenteric vessels. In the OCA images regions of preserved blood microcirculation in the intestinal wall were characterized by the presence of branched networks of intramural microvessels and a bright background in the OCA images. Regions of the intestine in which the intramural vessels were interrupted or could not be visualized were considered as potentially non-viable. These data were used to determine the boundaries for intestinal resection. In comparison with the traditional method of intraoperative diagnosis of intestinal blood flow, the use of such OCA criteria meant the volume of bowel resection could be decreased by 21.5 [14.1; 36.0]% (p = 0.037). This observation demonstrates the great potential of OСA in the intraoperative detection of the boundaries of damaged and healthy intestinal wall in ischemic bowel disease.
The objective of the research was a multifaceted study of strangulated small intestine to reveal the optical, morphofunctional and biochemical signs of small bowel ischemia. The study was carried out in vivo using an artificially induced strangulation model of the small intestine (together with its mesentery and blood vessels) in 12 Wistar rats. Over a period of 120 minutes following the bowel ligation, changes in the density of the intramural vasculature and intestinal wall microstructure were detected using multimodal optical coherence tomography (MM OCT). Fluorescence lifetime changes of endogenous fluorophores were also measured using macro-FLIM of the strangulated loop and the adjacent segments of the intestine. At the end of the experiment, a morphometric study of the thickness of the layers and the prevalence of necrosis in the intestinal wall was carried out. A comprehensive analysis of the results of the OCT, FLIM and morphometry of the ischemic wall of the small intestine made it possible to determine the correlating morphofunctional and biochemical manifestations that are specific to this model of mesenteric blood flow disturbance.
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