The aim of the study was to observe time-related changes in the optical properties of normal brain tissues as measured using cross-polarization optical coherence tomography (CP OCT). 32 ex vivo tissue samples from 16 animals (rats) were monitored under different external conditions, over a period of 1 hour after excision, to measure time-related optical changes. It was found that the optical properties of white matter were quite stable over the time scales of the experiments, while the optical properties of the gray matter could change significantly. However, these changes could be minimized by using fresh sections from samples that had not been in contact with the air or the saline solution before the CP OCT examination. Such a protocol is suggested to significantly reduce optical changes in the brain tissue samples when ex vivo study is needed.

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Small laboratory animals (rats) are suitable objects for modelling acute mesenteric ischemia (AMI) and monitoring changes in the structural tissue and intramural blood flow using optical coherence tomography (OCT) and OCT angiography methods. Combined with evaluation of blood circulation the prevalence of a necrotic tissue is a key factor in assessing intestine viability during surgery and determining the resection margins. While the assessment of the blood vessels network is commonly performed visually by surgeons, the assessment of the necrosis within individual layers is quite challenging due to small thickness of each intestine layer in small objects. The study demonstrates that the construction of colour-coded maps of the tissue attenuation coefficient estimated from the OCT data, allows quick layer-by-layer evaluation of the intestine wall. Such maps in the AMI model make it possible to track changes separately in the serous-muscular, submucosa and mucosa layers of the intestine wall in vivo and to carry out a differential diagnosis between the inflammation and necrosis in these layers. Colour-coded mapping may be useful in other medical applications where layer-by-layer assessment of structural tissue changes is required in a small range of depths.