SURGETICA at Grenoble: from computer assisted medical interventions to quality inspired surgery.

Research on "Computer Assisted Medical Interventions" (CAMI) was initiated in Grenoble in 1984, as an attempt to take up the challenge of "Minimally Invasive Interventions", thanks to the introduction of Information and Communication Techniques in the Operating Room. In a first section, we will describe our initial vision. The corresponding achievements will then be presented. A final section will show that the challenge now is to "invert this movement": instead of moving the computer in the Operating Room, we should embed the surgeon (or at least his or her expertise) into the Information Technology based tools he or she uses.

Patient set-up using portal images: 2D/2D image registration using mutual information.

OBJECTIVE: Conformal radiation therapy requires accurate patient set-up for each fraction delivery. Electronic portal imaging devices allow the acquisition of portal images just before and even during dose delivery. However, the quantitative interpretation of these images in determining and correcting the patient's position remains uncertain, and automated methods are therefore being developed. Such methods must be usable for the different radiation therapy techniques. They must be robust and as automated as possible for use in clinical routines. This work was undertaken to establish the feasibility of 2D/2D registration for portal/portal and portal/simulator images in radiotherapy. MATERIALS AND METHODS: This paper describes an automated method based on the combination of calibration algorithms and pixel-based registration algorithms. We present experiments with the different imaging techniques, some of which use a phantom with and without a gold standard. Preliminary results obtained using patient data are also presented and discussed. RESULTS: The results obtained with a phantom demonstrated that this automated method for 2D/2D registration is fast, accurate, and robust, even in the case of blurred images for small treatment fields. CONCLUSIONS: Mutual information is a feasible method for 2D/2D portal/portal and portal/simulator image registration in radiotherapy.

Precise dental implant placement in bone using surgical guides in conjunction with medical imaging techniques.

The use of medical imaging techniques to make a very precise surgical guide for implant placement is described. This template is the combination of a currently used template and a very simple mechanical system designed to transfer a preoperatively defined implant position onto the surgical site. With the planning software, the practitioner determines the implant position according both to the ideal position dictated by the final restorative prosthesis and the available volume of bone. The surgical template then communicates the actual implant position to the surgical site. The template can be used not only in critical anatomical situations but also in placing the implant in an ideal position on bone because it eliminates possible manual placement errors and matches planning to prosthetic requirements.

Fiber-based anterior cruciate ligament model for biomechanical simulations.

Although accurate predictions of the behavior and function of the anterior cruciate ligament would aid in diagnosis and operative treatment, no agreement exists on the best way to model the ligament with a reliable description of its mechanical and geometric features. We propose a new model of the anterior cruciate ligament based on multiple viscoelastic curvilinear fibers. This model was used for quasi-static simulations of the passive motion of eight porcine knees, after registration of the passive trajectories and digitization of the surface of the ligament in flexion. Simulations of anterior cruciate ligament deformations during passive motion predicted a fiber strain of less than 20%, low insertion forces, and isometric anterior fibers. The model explains actions of the ligament fibers, as reported in the literature, better than classic models based on linear fibers and consistent with the mechanical properties of the anterior cruciate ligament.

Building a hybrid patient's model for augmented reality in surgery: a registration problem.

In the field of Augmented Reality in Surgery, building a hybrid patient's model, i.e. merging all the data and systems available for a given application, is a difficult but crucial technical problem. The purpose is to merge all the data that constitute the patient model with the reality of the surgery, i.e. the surgical tools and feedback devices. In this paper, we first develop this concept, we show that this construction comes to a problem of registration between various sensor data, and we detail a general framework of registration. The state of the art in this domain is presented. Finally, we show results that we have obtained using a method which is based on the use of anatomical reference surfaces. We show that in many clinical cases, registration is only possible through the use of internal patient structures.

Computer-assisted dental implant surgery using computed tomography.

Standard planning for dental implants consists of a prosthesis simulation on diagnostic casts and radiographic examination of anatomical structures. The clinician visually locates the planned trajectory on the surgical site in the patient's mouth without direct correlation between the radiographs and the anatomy. We have developed a computer assisted technique to define the optimal position of the bone implant using computed tomography to accurately place the implant in the planned position using a guide drilled into a resin splint.

Mathematical determination of the tibial insertion of the patellar tendon using computed tomography images.

Misalignment of the extensor apparatus is an essential factor in impairment of the patellar-femoral joint. This may be partly or entirely responsible for patellar dislocation or lateral patellar-femoral arthrosis. One surgical method to correct the pathology is medial transposition of the patellar ligament on the tibial tuberosity (anteriorly or posteriorly, distally or ventrally). These interventions correct misalignment of the extensor apparatus relative to statistical norms. We propose a mathematical method based on the use of computed tomography (CT) images to determine the ideal tibial insertion for the patellar tendon. This method is based on biomechanical modeling and the use of equipressure criteria. It is the first step in allowing the use of mathematics to model correctly tibial insertion of the patellar ligament, an entirely new development. This is important because it will allow surgeons greater accuracy in distal correction of extensor apparatus misalignments.