# Innovative Tool for Automatic Detection of Arterial Stenosis on Cone Beam Computed Tomography
## 1 Introduction  
Image-guided surgical navigation is one of the main technologies used for minimally invasive surgery, which, in turn, is a technique that introduces several advantages over traditional open surgery. This reduces the size and number of incisions that need to be made on the body of the patients, inducing a faster recovery of the patient and a reduced risk of injury-related complications, as well as lower hospitalization costs [1]. On the other hand, minimally invasive surgery often requires computed tomography (CT) and/or magnetic resonance imaging (MRI) of the anatomical area to be combined with the operating scenario. In this context, surgical planning acquires a decisive role as the best outcomes are achieved when surgeons are preoperatively prepared with a deep understanding of the anatomy they will face. To obtain an accurate model of the anatomical part that needs to be studied, some steps need to be performed. First, high-quality images of the anatomical structures of interest must be acquired, followed by segmentation of the parts of interest and rendering the surface or volume using specialized software [2, 3]. The resulting models allow the surgeon to observe the anatomy from different angles and define the best-possible route to reach the area of interest [4, 5]. The realization of models before surgery is spreading more and more. It allows not only the surgeon to gain an idea and act in a more targeted way, but also students to practice and learn techniques of intervention [6]. [PERSON] et al. in their work realized a color-coded 3D model of benign glotto-subglottic stenosis and a control airway using a commercial 3D printer starting from CT scans. They showed how the realization of a 3D model resulted in being the more accurate diagnostic strategy compared to the endoscopy and the CT scan usually used for these diagnoses [7]. Furthermore,Shi et al. showed, as the application of a preoperative planning software to treat the lumbar foraminal stenosis, advantages such as the reduced puncture channel establishment time, operative time, and number of intraoperative fluoroscopic images taken without affecting the clinical outcomes [8]. [PERSON] et al. showed the possibility of making patient-specific models of the anatomic and functional characteristics of severe aortic valve stenosis using 3D stereolithographic printing to convert high-resolution CT images into life-sized physical models. The CT digital data were processed with a computer-aided design (CAD) software and exported to a multi-material 3D printer to create dual-material fused 3D models of severe aortic stenosis. The realized model accurately reflected the anatomy with excellent visual correlation to the corresponding clinical CT. The possibility of obtaining specific tailored models can lead to further advances in surgery [9]. Our study focused on the applications of the 3D model in the field of endovascular surgery, a branch of minimally invasive surgery, with the aim of restoring natural blood flow in pathological conditions affecting the vascular system such as the occluded arteries. Numerous diseases, as well as aging induce pathological changes in vascular structures. One of the most-common alterations consists of a reduction in the diameter of the the vessel, resulting in stenosis of varying severity up to a complete occlusion; this type of alteration leads to changes in blood flow, thus reducing the supply of the normal amount of oxygen-rich blood to the tissues, eventually leading to serious complications [10; 11]. For this reason, the study of the properties of the arterial walls is the subject of several papers, as well as providing important information that can increase the performance of doctors in both the diagnosis and therapy of vascular pathology [12; 13; 14; 15; 16; 17].