## 3 Results  
### OCT and H&E Histology Comparative Analysis  
Before performing the analysis, it was important to consider that some anatomical differences exist between human colon and murine colon structure. According to [61], in human and rats species, the colon maintains the same mural structure as the rest of the gastrointestinal tract: mucosa, submuc, and inner circular and outer longitudinal tunica muscularis and serosa. The mucosa and submuc layers in mice are relative thin in comparison with the human ones. Furthermore, human mucosa has transverse folds through the entire colon, whereas in mice it varies for each part of the colon. At the occup and proximal colon, mouse mucosa has transverse folds, in the mid colon is flat, and in the distal colon has longitudinal folds. However, in both species the mucosa is composed of tubular glands. Taking this into account and considering that the database used in this work consists of murine (rat) samples, it was expected that the model also learn these anatomical differences present in the mucosa, especially for the healthy samples. A detailed comparison of the anatomical differences (extracted from reference [61]) is provided in Table 11.  
According to previous studies analyzing features on OCT images [18; 19; 20; 21], in normal tissue, well-defined layers can be visualized with uniform intensity. In the presence of hyperplasia, thickening of the mucosa layer occurs, but the intensity is similar to healthy tissue and tissue layers are still visible. However, in the case of adenomatous polyps, both thickening of the mucosa and reduced intensity must be observed. Finally, adenocarcinoma lesions should show blurred boundaries and non-uniform intensity. In the presence of large polyps, the disappearance of the boundaries should be clearly observed, independently from the lesion nature.  
Visual inspection of dataset images was performed to look for the features previously mentioned. Figures 4 and 5 provide a detailed analysis of the visible features on the OCT images (of Figure 1 samples) with respect to the histopathological hematoxylin-eosin (H&E) images annotated by a pathologist (scanned at 5x). Regions of interest (with the same FOV of OCT images in mm) were extracted from H&E slides images and later rescaled to fit axial and lateral resolution of the OCT images for better comparison. In these figures, it can be observed that the main features present in H&E images can also be observed in the OCT images. On the one hand, Figure 4, representing healthy tissue, illustrates (as indicated by arrows and manual segmentation lines on the B-scans on the left, Figure 4A,B) that the mucosa layers can be very clearly observed, confirming what has been reported before in previous studies. Muscularis mucosae and sub-mucosa layers are also observed, although clear differentiation in all parts of the image is tougher. On the other side, when analyzing Figure 5 containing neoplastic lesions, it is also possible to confirm that the boundaries of the layers have totally disappeared, making it impossible to find any difference among them. Differences in the noise pattern are also observed. In addition, as indicated using circles and arrows on the B-scans (Figure 5A,B), new underlying structures appeared in the mucosa and can be identified as bright spots or dark areas in the images. These new structures (in comparison with healthy tissue) are also clearly observed in the corresponding annotated histopathology images (Figure 5C,D), where cystic crypts (CC)have been identified by the pathologist and appear as dark spots in the B-scan and tumoral glands (TG) clusters as bright spots.