## 1 Introduction
The mentioned ex vivo studies using this technology have revealed significant morphological differences between healthy and cancerous tissue. However, the interpretation of MPM images by clinicians also remains a challenge and relies on their expertise in histopathology. In contrast, OCT provides sub-surface structural information of the lesion under a label-free approach, with reported resolutions less than 10 \(\upmu\)m and penetration capacities up to 2 mm. OCT can be used in combination with MPM, as both technologies provide complementary information useful for diagnosis assessment. While RCM and MPM 2D images are obtained horizontally in the transversal plane (also called \"en-face\"), OCT 2D images (B-scan) are obtained axially in depth in the coronal or sagittal plane. Furthermore, since OCT also allows obtaining 3D images (C-scan), lesions can be studied volumetrically from different points or axes of visualization. Although OCT images have less resolution than RCM and MPM images, the penetration capacity is higher, and the acquisition time is generally lower. This OCT aspect is of great importance to evaluate lesion margins and tumor infiltration into the mucosa under real-time situations in clinical environments. OCT technology capabilities in the diagnosis of colon polyps have been investigated in the latest years with promising results on the future adoption in clinical practice. Several studies [18; 19; 20; 21], both in murine and human models, have reported the identification of tissue layers and the discrimination capacities of the technology on the differentiation of different types of benign (including healthy) and malignant tissue. When analyzing 44 polyps from 24 patients [18], endoscopists detected fewer subsurface structures and a lower degree of light scattering in adenomas, and that, in comparison, hyperplastic polyps were closer in structure and light scattering to healthy mucosa. The scattering property was calculated by a computer program applying statistical analysis (Fisher-Freeman-Halton test and Spearman rank correlation test), confirming the previous appreciation. A comparison of OCT images with respect to histopathological images was performed in [19] using previously defined criteria for OCT image interpretation on the identification of tissue layers. Upon the observations, hyperplastic polyps are characterized by a three-layer structure (with mucosa thickening) whereas adenomas are characterized by the lack of layers. Then, under these assumptions, measured over a group of 116 polyps from patients, lesions could be visually differentiated in OCT images with 0.92 sensitivity and 0.84 specificity. Later, a fluorescence-guided study performed on 21 mice [20] after administrating a contrast agent showed the OCT ability to differentiate healthy mucosa, early dysplasia, and adenocarcinoma. Visual analysis of normal tissue revealed that the submuc layer is very thin in some specimens and not always well appreciated in the OCT images, although the tissue boundaries remain distinguishable. In adenoma polyps, a thickening of the mucosa (in first stages) or disappearance of the boundary between layers is detected, whereas in the case of adenocarcinoma, the OCT images showed a loss of tissue texture, absence of layers, and the presence of dark spots caused by the high absorption in necrotic areas. In the latest study [21], they go beyond and propose a diagnosis criterion over micro OCT images with some similarities to the Kudo pit pattern [22] and demonstrate the diagnosis capacity of the OCT technology as clinicians can reach 0.9688 sensitivity and 0.9231 specificity on the identification of adenomas over 58 polyps from patients. Both the cross sectional and the en-face images have been shown to provide clinically relevant information in the mentioned studies, and the combination of both views for the detailed study of tissue features suggests an important advance [23; 24; 25].