Intestinal optical coherence tomography (angiography) imaging: a comparison between animal models and humans

Transserosal optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) provide real-time label-free visualization of the intestinal structure and blood vessels networks with spatial resolution 10-15 mu m. This method is promising for intraoperative use in abdominal surgery for determining the depth of ischemic damage to the gut. The paper analyses the quality of OCT/OCTA images obtained from small intestine of 4 subjects - rats, rabbits, minipigs and humans. The subjects have different thickness of intestinal wall and blood circulation conditions. We demonstrate that the intestine of small laboratory animals (rats and rabbits) is well-suited for OCT/OCTA studies: it can be stabilized by moving the intestine loop outside the body, which, together with a rigidly fixed probe, minimizes the number of possible motion artifacts. 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 humans proved to be challenging subjects for obtaining high-quality OCT/OCTA data; powerful peristaltic movements, pronounced pulse waves 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 number of OCT/OCTA images with artifacts (up to 40% in humans). In patients and minipigs the microstructure of intestinal layers was more informative than in small animals due to increased thickness. It allowed visualizing tissues in more detail - verifying peritoneum edema and intramuscular fluid buildup.