Système de visualisation pour l'assistance des chirurgies minimalement invasives du rachis

Scoliosis is a complex three-dimensional deformity of the spine that may require surgical treatment. Minimally invasive surgeries, as opposed to conventional surgeries, are done by performing small incisions through which surgical instruments and an endoscopic camera can be inserted within the body. This type of surgery offers numerous known benefits, such as reduction of blood loss, of post-surgery pain, of intensive care unit and hospital stay lengths, of complications, of recovery time and of overall treatment costs. However, it brings new challenges for surgeons. Indirect visualization of surgical sites via a monitor that shows images from the endoscopic camera can be disorienting. Depth perception is lost as the view is monocular and the camera lens is very close to the surgical site. This lens proximity also causes a loss in perception of the global spine shape since only a small part of it is visible at one time. These difficulties make minimally invasive surgeries very complex procedures, especially in the case of spine surgeries, where several critical organs are located near the surgical site. Image-guided surgical assistance tools are increasingly available in various fields such as cardiology, neurology and orthopaedics. For spine surgeries, ionizing imaging modalities such as computed tomography or fluoroscopy, involving radiation for both the patient and the surgical team, are often used. These surgical navigation systems are also generally designed for conventional surgeries requiring long incisions to facilitate access to targeted structures. Thus, metal markers can be screwed into specific vertebral levels, a procedure that is both invasive and hard to perform in a minimally invasive context. Recent minimally invasive surgical assistance approaches try to provide depth cues to the surgeon using only the content of endoscopic images. Methods using a stereoscopic endoscope give unsatisfactory results due to the weak disparity between the two acquired views and to the complexity of feature matching in the two views, caused by the presence of smoke, blood and specular reflections. By the same token, approaches based on shape-from-shading algorithms give, to date, acceptable results in controlled environments but do not perform as well with real images. Hence, this research project's objective is to propose a 3D visualization tool for minimally invasive spine surgery assistance. This tool realizes multimodal fusion of the images acquired from the endoscopic camera with a preoperative 3D model acquired by MRI that has been previously segmented and then registered in a coordinate system linked to the surgical site, in order to display more information than what is available in the endoscopic images alone.