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Biomedical subjects

P Cinquin

Publications and source records attributed to P Cinquin.

At least 19 recordsLinked to original sources
PubMed1998

Automated 3-dimensional computed tomographic and fluoroscopic image registration.

The registration of 3-dimensional (3-D) anatomical surfaces to sensor data such as intraoperative fluoroscopy is one of the basic problems in computer integrated surgery. The main objective is to find the relationship between 3-D preoperative computed tomographic images and a pair of intraoperative fluoroscopic images. Consequently, surgical navigation devices can use this relationship to provide improved surgical guidance. The proposed registration strategy presents a noninvasive anatomy-based (frameless) method for registration. In this article, we propose a cooperative approach between registration and contour segmentation on fluoroscopy. This approach is based on the duality between registration and segmentation in a model-based vision system. It associates a likelihood value to each pixel that corresponds to the probability that the pixel belongs to the contour of the object of interest. The registration is then achieved between backprojection lines stemming from likely contour pixels and the 3-D surface model of the object of interest. Then, in order to take into account the internal contour points extracted by the cooperative approach, we propose a new line to surface distance computation algorithm to be used during the data to model distance minimization step. Finally, we present the obtained results that demonstrate the validity of the proposed approach in carrying out accurate 3-D and 2-D registration.

Algorithms↗
PubMed1998

Computer-assisted spine surgery.

The aim of this study was to improve the reliability of pedicle screw insertion. Transpedicle screw insertion may cause neurological, vascular, and mechanical complications. Previous studies of surgical procedures have shown a significant rate of incorrect placement of the screw ranging from 10 to 40%. A new technique that combines preoperative computed tomography (CT) imaging with intraoperative passive navigation was used to perform 64 pedicle screw insertions in the thoracolumbar region. At the same time, 64 pedicle screw insertions were performed manually in the same region and on the same vertebral levels. Surgery was followed in all cases by postoperative radiographs and computed tomography examination, which allowed measurements of screw position relative to pedicle position to be performed. A comparison between the two groups showed that six screws in 64 vertebra (9%) had incorrect placement with the computer-assisted technique whereas 28 screws in 64 vertebra (44%) had incorrect placement with manual insertion. The intraoperative accuracy provided by the computer after registration was better than 1 mm. The good results obtained are similar to those reported in the literature. The cortex penetration observed with the computer-assisted technique was not imputed to computer failure. Errors by the surgeon in acquiring data in the pre- and perioperative steps may explain the six incorrect screw placements. This clinical experience confirms that the accuracy and the reliability of this computer-assisted technique are good.

Bone Screws↗
PubMed1998

[Computer-assisted surgery: automated screw placement in the vertebral pedicle].

AIM OF THE STUDY: Previous studies of conventional surgical procedures have shown a significant rate of incorrect pedicle screw placement ranging from 10 to 40%. Transpedicle screw insertion may cause three types of complications: neurologic, vascular and mechanical. The aim of this prospective study is to improve the reliability of pedicle screwing with computer assistance. MATERIAL AND METHODS: A new and original technique that combines preoperative computed tomography imaging with intraoperative passive navigation has been used to perform 48 pedicle screwings in the thoracolumbar region. In the same time, 48 pedicle screwings were performed manually in the same region and on the same vertebral levels. With postoperative X-rays and computed tomography examination, screw position related to pedicle position could be assessed and comparison could be made between the two groups (with and without computer assistance). RESULTS: Two screws in 48 vertebra (4%) had incorrect placement with computer assisted technique whereas 18 screws in 48 vertebra (37%) had incorrect placement with manual insertion. The intraoperative accuracy provided by the computer after registration was better than 1 mm. The difference between the two groups was statistically highly significant (P < 0.0001). The cortex penetration observed with the computer assisted technique was not imputed to computer failures. Errors in acquiring data by the surgeon in the pre and peroperative steps may explain the two incorrect placements of the screws. CONCLUSION: This clinical experience confirms that the accuracy and reliability of this computer assisted technique are very good.

Bone Screws↗
PubMed1998

Registration of real and CT-derived virtual bronchoscopic images to assist transbronchial biopsy.

This paper describes research work motivated by an innovative medical application: computer-assisted transbronchial biopsy. This project involves the registration, with no external localization device, of a preoperative three-dimensional (3-D) computed tomography (CT) scan of the thoracic cavity (showing a tumor that requires a needle biopsy), and an intraoperative endoscopic two-dimensional (2-D) image sequence, in order to provide assistance in transbronchial puncture of the tumor. Because of the specific difficulties resulting from the data being processed, a multilevel strategy was introduced. For each analysis level, the relevant information to process and the corresponding algorithms were defined. This multilevel strategy, thus, provides the best possible accuracy. Original image processing methods were elaborated, dealing with segmentation, registration and 3-D reconstruction of the bronchoscopic images. In particular, these methods involve adapted mathematical morphology tools, a "daemon-based" registration algorithm, and a model-based shape-from-shading algorithm. This pilot study presents the application of these algorithms to recorded bronchoscopic video sequences for five patients. The preliminary results presented here demonstrate that it is possible to precisely localize the endoscopic camera within the CT data coordinate system. The computer can thus synthesize in near real-time the CT-derived virtual view that corresponds to the actual endoscopic view.

Biopsy, Needle↗
PubMed1997

Computer assisted spine surgery.

When inserting screws into a vertebral pedicle, the surgeon usually exposes the back part of the vertebra and uses his or her anatomic knowledge to align the drill in the proper direction. A slight error in direction may result in an important error in the position of the tip of the screw. This is done with no direct visibility of crucial structures (spinal cord, pleura, vessels). Statistical analysis of a series of surgical procedures has shown that 10% to 40% of the screws are not installed correctly. To reduce the risk of complication, a computer assisted method is proposed that enables the surgeon to place a screw at a position preoperatively defined in 3 dimensions using computed tomography images. This allows the surgeon to align a standard surgical drill with the optimal position and direction. The depth of the pilot hole during drilling also is monitored by the system to prevent penetration of the anterior cortex of the vertebral body. Using this procedure, in vitro tests were performed and showed that an accuracy of less than 1 mm can be obtained. Clinical trials were done in 10 patients who suffered severe scoliosis or spondylolisthesis. The trajectory of the holes drilled in L2, L3, L4, and L5 vertebrae were checked for all clinical tests. Postoperative radiographs and computed tomography scans showed that the screws were well inserted in each plane for each pedicle. This technique also can be used to perform osteosynthesis at the thoracic and cervical levels.

Adult↗
PubMed1996

[Medical imaging and computer-assisted interventions].

Computer science can assist the physician or the surgeon in defining an optimal strategy for an intervention, and then in performing it. This implies introducing new sensors, then processing all the data gathered about the patient, and finally operating systems for guidance of the very act of intervention.

Diagnostic Imaging↗
PubMed1996

Computer-assisted mandibular condyle positioning in orthognathic surgery.

PURPOSE: The correct placement of the mandibular condyle in the glenoid fossa during the osteosynthesis after the sagittal ramus osteotomy is often a problem. This article describes a computer-assisted positioning device. METHODS: The procedure is based on the use of a three-dimensional optical localizer to establish the condylar segment position. The operative procedure is only slightly different from the usual. RESULTS: The system is very easy to use, it does not require preoperative data acquisition, and the accuracy obtained is in fractions of a millimeter.

Bone Nails↗
PubMed1996

Three-dimensional fetal cephalometry.

Craniofacial growth has been the subject of numerous studies in which different techniques have been elaborated aiming to model this dynamic phenomenon in a rational manner. One of the methods employed is cephalometric analysis applied to the fetus. Generally, however, these studies are confined to the exploration of a single spatial plane (sagittal plane), whose orientation is never defined in a rigorous and perfectly reproducible manner. Thus, none of these analyses offers a formal growth model. This has led us to propose a new method of fetal cephalometric study taking into account criteria for proper reproducible analysis: spatial exploration of the head performed through three-dimensional tomodensitometric images and precise location of landmarks and reproducibility of the orientation of each image, which is assured by reference to the vestibular orientation (based on the external semicircular canals), as has been described by Girard and Perez and further developed by Fenart. When the labyrinth is developed, this orientation does not change during the growth stages of the head, even with craniofacial deformities. This permits application of this orientation on fetuses and the superposition of images of different subjects. The methodology is presented using two normal human fetuses, and the advantages of this computerized tool are discussed.

Cephalometry↗
PubMed1995

Computer-assisted knee anterior cruciate ligament reconstruction: first clinical tests.

Anterior cruciate ligament reconstruction is a delicate task. The procedure of choice is the patellar tendon bone autograft, but an anisometric position of this tendon often leads to failure. We allows positioning of the central part of the ligament graft at the least anisometric sites. The system uses a workstation and a three-dimensional optical localizer to create images that represent knee kinematics. The surgeon uses these images to guide the surgery. This technique has been validated on eight cadavers and 12 patients.

Anterior Cruciate Ligament↗
PubMed1995

Computer-assisted spine surgery: a technique for accurate transpedicular screw fixation using CT data and a 3-D optical localizer.

The computer-assisted spine surgery system presented in this paper follows the basic ideas which have been developed for computer-assisted medical interventions (CAMI) in our lab since 1985. There are three steps to insert a linear tool inside vertebral pedicles. First, the surgeon defines an optimal trajectory on pre-operative computed tomography. Second, this trajectory is reported in the operating room coordinate system using an intra-operative sensor and a registration algorithm. Third, a guiding system helps the surgeon follow the selected trajectory. In this paper, we present an implementation of this method that uses only a 3-dimensional optical localizer. Results on cadaver specimens and on the first seven patients are presented.

Bone Screws↗
PubMed1995

Patient setup optimization for external conformal radiotherapy.

The aim of conformal radiotherapy is to deliver precisely a specific dose of radiation to a planning target volume, concurrently radiating as little healthy tissue and organs as possible. This can be accomplished only with the accurate positioning of the patient with respect to the radiotherapy system. In this paper, we describe a system to achieve a higher overall accuracy in the delivery of a prostatic radiation boost for treatment of carcinoma of the prostate. The system is based on the use of ultrasound images for measuring the actual position of the patient's prostate just before the radiation. Since these images are registered with pretreatment computed tomography or magnetic resonance imaging, the position and orientation of the planning target volume are computed with respect to the radiotherapy system and can be corrected as needed. This system is under clinical evaluation.

Computer Simulation↗
PubMed1995

Computer-assisted bronchoscopy: aims and research perspectives.

The introduction of spiral computed tomography (CT) of the thoracic cavity has allowed the development of new visualization tools. These tools provide a three-dimensional (3-D) endoluminal reconstruction of the tracheobronchial tree, as it would be viewed through a fibroscopic instrument. However, 3-D reconstruction techniques cannot replace conventional fibroscopy, which remains indispensable for obtaining histological samples. Furthermore, when CT-detected mediastinal or parenchymal lesions are not seen during fiberoptic bronchoscopy, guiding transbronchial needle biopsy is a major challenge. Computer-guided transbronchial biopsy involves the fusion of image data from both CT slices and bronchoscopic video sequences. This fusion is described in this paper in two parts. First, we present a segmentation process, using mathematical morphology operators, in order to analyze the video sequence and localize the bronchoscopic camera within the tracheobronchial tree. Second, we present tools used to match this localization knowledge with CT data. Finally, we produce images that create a bronchoscopic augmented reality, using elements extracted from the CT examination.

Biopsy, Needle↗
PubMed1995

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.

Biomechanical Phenomena↗
PubMed1995

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.

Algorithms↗
PubMed1995

Computer generated visual assistance during retroperitoneoscopy.

In this paper we present a system of computer assisted surgery, the function of which is to enhance the real time feedback between the patient's body, the surgical tools and the surgeon. We show using such a system during some surgical operations--in our case, retroperitoneoscopy. After giving the requirements for such a system, we describe the components currently used in our experiments. We detail the different problems and our current solutions; photographs of an experiment carried out on a cadaver and of classical operations are shown in this paper.

Computer Simulation↗