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Results for “Surgical simulation”

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At least 415 records · Page 23Linked to original sources

PubMed1991

Development of a computer-aided surgery system: three-dimensional graphic reconstruction for treatment of liver cancer.

Simulation of the needle puncture and volume estimation for the tumors in the liver were carried out with the three-dimensional image reconstruction system, which consists of a medical image acquisition system, a data processing system, and a graphic display. A set of sliced-image data from a computerized tomography and/or a magnetic resonance imaging was used to reconstruct the liver, the vessels, and the tumors of the patients with liver cancer. A good agreement of anatomic locations of both the intrahepatic vessels and the tumors between the reconstructed liver model and the echography done intraoperatively was observed. Surgical simulations with these graphic models clearly indicated safety areas for needle puncture in the laser coagulation therapy. In addition liver volumes were calculated within 3% of error in comparison to the measured values. These results indicate that the computer-aided surgery system is a highly promising method that avoids cumbersome stereoscopic recognition of the anatomical location of the diseased area and the vessels, before and after surgery.

Aged↗

PubMed2005

Developing a model system for teaching goniotomy.

PURPOSE: To design a model-system instruction course to prepare trainees for performing goniotomy on patients. DESIGN: Experimental study. PARTICIPANTS: Three pediatric ophthalmology fellows and 1 recent graduate of the fellowship program. METHODS: We piloted 3 model systems: human cadaver eyes with and without Marty the Surgical Simulator (Iatrotech Inc., Del Mar, CA, hereafter referred to as Marty Head) eye supporting system and artificial eyes in Marty Head. For improving intraocular view in cadaver eyes, we used epithelial scrapping, intracameral viscoelastic, and/or intracameral lubricating jelly. Each trainee underwent a training course, including background reading, didactic lecture, and video review followed by goniotomy on model systems with the operating microscope. MAIN OUTCOME MEASURES: Each trainee evaluated each step of the course using modified 5-point Likert scales. Reading material and videos were evaluated for usefulness, readability/quality, and new information obtained. Each model system was evaluated for visibility, ease of setup, surgical feel, and transferability to live surgery. In the end, each trainee was asked to assess the overall course for usefulness. RESULTS: Trainees rated the reading materials and video highly for their usefulness and quality, yet they believed they did not learn substantial amounts of new information. Visibility and ease of setup was best with artificial eyes in the Marty Head model. Human cadaver eyes in the Marty Head provided somewhat less visibility and ease of setup, but the perceived feel and transferability to live surgery was slightly better than with artificial eyes. Cadaver eyes without the Marty Head got the lowest rating in all categories. At the end of the course, all participants felt more confident and ready to perform goniotomy on patients. All recommended this course as part of pediatric ophthalmology fellowship training programs. CONCLUSIONS: This model system instruction course can assist trainees in learning to perform goniotomy while potentially lessening the risks to patients.

Gonioscopy↗

PubMed1997

Basic technology of simulation system for laparoscopic surgery in virtual environment with force display.

A basic simulation system for laparoscopic surgery was constructed. The system consists of force display in a virtual environment construction system. Recently, laparoscopic surgery has become popular around the world. However, this operation strategy requires very high dexterity, so that only some medical doctors can use it. Doctors can see the human organs in a three-dimensional environment in the case of ordinary operations. On the other hand, in the case of laparoscopic surgery, doctors can only see a narrow space in a two-dimensional environment on a CRT monitor and tactile information is decreased during operation procedures. We therefore developed a basic technology of surgical simulator for laparoscopic surgery. The focus of our research is the presentation of resistance from virtual organs.

Computer Simulation↗

PubMedDate not supplied

Three-dimensional imaging in craniofacial surgery.

Over the past decade, three-dimensional (3-D) imaging has been developed to such a stage of perfection and to such a level of interactive selective imaging of specific anatomic and pathologic structures that craniofacial surgeons can now use this technique effectively in the planning of complicated reconstructive surgery. In addition, modeling techniques have been devised that can be used in surgical simulation and in the manufacture of implants and prosthetic devices. The technical aspects of 3-D imaging are discussed in relation to their applications in craniofacial surgery, and reference is made to the literature describing these techniques in full detail. The results are illustrated with cases that the authors have processed by means of: (a) a clinical research program that was developed on a general purpose computer which provided full flexibility in changing and improving the reconstruction algorithms (Lobregt algorithms and DEC VAX 750 computer), (b) a system under development (Pixar PICS 2000), and (c) a commercial system (Cemax 1500X). Finally, a number of emerging techniques are discussed such as surgical stimulation (electronic sculpting), and trends such as multimodality imaging.

Face↗

PubMed2006

Bovine polymerized hemoglobin versus Hextend resuscitation in a swine model of severe controlled hemorrhagic shock with delay to definitive care.

To compare the efficacy of low-volume resuscitation with bovine polymerized hemoglobin (HBOC-201) versus hetastarch (HEX) in an intermediate severity combat-relevant hemorrhagic shock swine model with a simulated delay to hospital care. Twenty-four anesthetized pigs were hemorrhaged 55% estimated blood volume in conjunction with a 5-min rectus abdominus crush. At 20 min, pigs were resuscitated with 10 mL/kg of HBOC-201 or HEX or nothing (NON); resuscitated pigs received additional infusions (5 mL/kg) at 30, 60, 120, or 180 min if hypotension or tachycardia persisted. Pigs were monitored for a 4-h "prehospital" period. At 4-h, hospital arrival was simulated: surgical sites were repaired, blood, or saline provided, and pigs were recovered from anesthesia. Pigs were monitored for 72 h and then killed for histological evaluation. One hundred percent (8/8) of HBOC-201-, 75% (6/8) of HEX-, and 25% (2/8) of NON-resuscitated pigs survived to 72 h (P = 0.007 overall, HBOC vs. HEX P > 0.05). Mean arterial pressure and mean pulmonary arterial pressure were highest in the HBOC-201 group (P < 0.001), and HR was lowest (P < 0.001). HBOC-201- and HEX-resuscitated pigs had comparable cardiac index and prehospital fluid requirements. HBOC-201 pigs had higher transcutaneous tissue oxygen tension, P < 0.001) and lower urine output (P < 0.001). At simulated hospital arrival, no HBOC-201 pigs required additional fluids or blood transfusion. In contrast, 100% of HEX pigs required blood transfusions (P < 0.01). In this swine model of controlled hemorrhage with low-volume resuscitation and delayed definitive care, HBOC-201 pigs had improved hemodynamics, transcutaneous tissue oxygen tension, and transfusion avoidance compared with HEX.

Animals↗

PubMed2005

Developing assessments of surgical skills for the GMC Performance Procedures.

INTRODUCTION: The objectives were to: (i) establish how 'typical' consultant surgeons perform on 'generic' (non-specialist) surgical simulations before their use in the General Medical Council's Performance Procedures (PPs); (ii) measure any differences in performance between specialties; and (iii) compare the performance of group of surgeons in the PPs with the 'typical' group. VOLUNTEERS AND METHODS: Seventy-four consultant volunteers in gastrointestinal surgery (n=21), vascular surgery (n=11), urology (n=10), orthopaedics (n=15), cardiothoracic surgery (n=10) and plastic surgery (n=7), plus 9 surgeons undertaking phase 2 of the PPs undertook 7 simple simulations in the skills laboratory. The scores of the volunteers were analysed by simulation and specialty using ANOVA. The scores of the volunteers were then compared with the scores of the surgeons in the PPs. RESULTS: There were significant differences between simulations, but most volunteers achieved scores of 75-100%. There was a significant simulation by specialty interaction indicating that the scores of some specialties differed on some simulations. The scores of the group of surgeons in the PPs were significantly lower than the reference group for most simulations. CONCLUSIONS: Simple simulations can be used to assess the basic technical skills of consultant surgeons. The simulation by specialty interaction suggests that whilst some skills may be generic, others are not. The lower scores of the surgeons in the PPs suggest that these tests possess criterion validity, i.e. they may help to determine when poor performance is due to lack of technical competence.

Adult↗

PubMed2006

Point-to-point computer-assisted navigation for precise transfer of planned zygoma osteotomies from the stereolithographic model into reality.

PURPOSE: To evaluate the feasibility and accuracy of a new method for planning and realizing zygomatic osteotomies in cases of established post-traumatic deformities using stereolithographic (SL) models and computer assisted navigation. PATIENTS AND METHODS: In 5 patients, osteotomy and repositioning of the zygomatic complex was planned using SL models. The desired position of the zygoma in the patient was determined by fixing individualized osteosynthesis plates to predefined screw positions. The SL model and the patient were registered to the same 3-dimensional computed tomography data set via an occlusal reference frame on the patient and corresponding reference markers on the model. Prebent osteosynthesis plates from the surgical simulation on the model were fixed to corresponding screw positions on the patient, which were located by computer-assisted navigation. Evaluation of accuracy was performed by image fusion of postoperative computed tomography scans of the model and the patient. RESULTS: Clinical outcome was satisfactory in all cases. The evaluation by image fusion showed alignment of the patient's and the model's zygoma in 4 of 5 cases. Mean measured distance between screw positions in the models and the patients were 1.1 +/- 0.3 mm for 44 screws. In 1 patient the treatment plan was changed intraoperatively because of unforeseen soft tissue limitations. CONCLUSION: Point-to-point navigation is an accurate method to transfer the planning of a complex osteotomy from the SL model to the actual surgical procedure. Surgery is facilitated considerably because repositioning and osteosynthesis are achieved in 1 step.

Adult↗

PubMed2002

Real-time computerized in situ guidance system for ACL graft placement.

A recent consensus within an international society for sports traumatology revealed that approximately 40% of ACL grafts are being surgically misplaced in current clinical practice. To help solve this problem, a computer-assisted system has been developed at the M.E. Müller Institute for Biomechanics to perform intraoperative planning and guidance of ACL replacement. Dynamic reference bases are fixed on the femur and tibia to track the knee's movement. No intraoperative imaging is required, and potential ligament attachment sites can be directly digitized using a computerized palpation hook in a minimally invasive fashion when used in conjunction with standard endoscopic tools. The palpation hook can be used by the surgeon to interactively define various anatomical structures and reference landmarks that are important for proper ligament positioning. The system can input a standard diagnostic X-ray (sagittal view of the femur) and allows intraoperative registration of this image with the patient to provide valuable X-ray landmarks for intraoperative guidance. The computer helps in situ planning of ligament placement by providing the surgeon with a 3D overview of the relevant anatomical landmarks and information on graft impingement and elongation for various simulated surgical insertions and graft sizes. After planning, the computer helps guide placement of the chosen insertion tunnels. This approach provides an augmented 3D view of knee anatomy and ligament function prior to drilling that is not possible with current procedures. The flexibility of the system in permitting surgeon-defined landmarks and free interpretation of functional factors allows it to support a variety of surgical workflows and techniques.

Anterior Cruciate Ligament↗

PubMedDate not supplied

New orthopaedic implant management tool for computer-assisted planning, navigation, and simulation: from implant CAD files to a standardized XML-based implant database.

Computer-Assisted Orthopaedic Surgery (CAOS) has made much progress over the last 10 years. Navigation systems have been recognized as important tools that help surgeons, and various such systems have been developed. A disadvantage of these systems is that they use non-standard formalisms and techniques. As a result, there are no standard concepts for implant and tool management or data formats to store information for use in 3D planning and navigation. We addressed these limitations and developed a practical and generic solution that offers benefits for surgeons, implant manufacturers, and CAS application developers. We developed a virtual implant database containing geometrical as well as calibration information for orthopedic implants and instruments, with a focus on trauma. This database has been successfully tested for various applications in the client/server mode. The implant information is not static, however, because manufacturers periodically revise their implants, resulting in the deletion of some implants and the introduction of new ones. Tracking these continuous changes and keeping CAS systems up to date is a tedious task if done manually. This leads to additional costs for system development, and some errors are inevitably generated due to the huge amount of information that has to be processed. To ease management with respect to implant life cycle, we developed a tool to assist end-users (surgeons, hospitals, CAS system providers, and implant manufacturers) in managing their implants. Our system can be used for pre-operative planning and intra-operative navigation, and also for any surgical simulation involving orthopedic implants. Currently, this tool allows addition of new implants, modification of existing ones, deletion of obsolete implants, export of a given implant, and also creation of backups. Our implant management system has been successfully tested in the laboratory with very promising results. It makes it possible to fill the current gap that exists between the CAS system and implant manufacturers, hospitals, and surgeons.

Computer-Aided Design↗

PubMed2006

The use of computerized image guidance in lumbar disk arthroplasty.

OBJECTIVES: Surgical navigation systems have been increasingly studied and applied in the application of spinal instrumentation. Successful disk arthroplasty requires accurate midline and rotational positioning for optimal function and longevity. A surgical simulation study in human cadaver specimens was done to evaluate and compare the accuracy of standard fluoroscopy, computer-assisted fluoroscopic image guidance, and Iso-C3D image guidance in the placement of lumbar intervertebral disk replacements. METHODS: Lumbar intervertebral disk prostheses were placed using three different image guidance techniques in three human cadaver spine specimens at multiple levels. Postinstrumentation accuracy was assessed with thin-cut computed tomography scans. RESULTS: Intervertebral disk replacements placed using the StealthStation with Iso-C3D were more accurately centered than those placed using the StealthStation with FluoroNav and standard fluoroscopy. Intervertebral disk replacements placed with Iso-C3D and FluoroNav had improved rotational divergence compared with standard fluoroscopy. Iso-C3D and FluoroNav had a smaller interprocedure variance than standard fluoroscopy. These results did not approach statistical significance. Relative to both virtual and standard fluoroscopy, use of the StealthStation with Iso-C3D resulted in improved accuracy in centering the lumbar disk prosthesis in the coronal midline. CONCLUSIONS: The StealthStation with FluoroNav appears to be at least equivalent to standard fluoroscopy and may offer improved accuracy with rotational alignment while minimizing radiation exposure to the surgeon. Surgical guidance systems may offer improved accuracy and less interprocedure variation in the placement of intervertebral disk replacements than standard fluoroscopy. Further study regarding surgical navigation systems for intervertebral disk replacement is warranted.

Aged↗

PubMed2000

Mechanical properties of brain tissue in-vivo: experiment and computer simulation.

Realistic computer simulation of neurosurgical procedures requires incorporation of the mechanical properties of brain tissue in the mathematical model. Possible applications of computer simulation of neurosurgery include non-rigid registration, virtual reality training and operation planning systems and robotic devices to perform minimally invasive brain surgery. A number of constitutive models of brain tissue, both single-phase and bi-phasic, have been proposed in recent years. The major deficiency of most of them, however, is the fact that they were identified using experimental data obtained in vitro and there is no certainty whether they can be applied in the realistic in vivo setting. In this paper we attempt to show that previously proposed by us hyper-viscoelastic constitutive model of brain tissue can be applied to simulating surgical procedures. An in vivo indentation experiment is described. The force-displacement curve for the loading speed typical for surgical procedures is concave upward containing no linear portion from which a meaningful elastic modulus might be determined. In order to properly analyse experimental data, a three-dimensional, non-linear finite element model of the brain was developed. Magnetic resonance imaging techniques were used to obtain geometric information needed for the model. The shape of the force-displacement curve obtained using the numerical solution was very similar to the experimental one. The predicted forces were about 31% lower than those recorded during the experiment. Having in mind that the coefficients in the model had been identified based on experimental data obtained in vitro, and large variability of mechanical properties of biological tissues, such agreement can be considered as very good. By appropriately increasing material parameters describing instantaneous stiffness of the tissue one is able, without changing the structure of the model, to reproduce experimental curve almost perfectly. Numerical studies showed also that the linear, viscoelastic model of brain tissue is not appropriate for the modelling brain tissue deformation even for moderate strains.

Animals↗

PubMed2002

Two surgical cases of internal carotid-ophthalmic artery aneurysms: special reference to the usefulness of three-dimensional CT angiography.

Three-dimensional computerized tomography angiography (3D-CTA) is a noninvasive tool for the diagnosis of cerebral aneurysms. 3D-CTA is helpful in the evaluation of the configuration of aneurysms and their surrounding vessels and anatomical structures. The aim of this study is to assess the usefulness of 3D-CTA for patients with unruptured internal carotid-ophthalmic artery aneurysms. We pre-operatively obtained surgical simulation images using 3D-CTA and 3D reconstruction and then compared them with magnetic resonance angiography (MRA), conventional cerebral angiography and operative findings in the patients. Two patients with unruptured internal carotid-ophthalmic artery aneurysm were selected. These patients underwent direct neck clipping after the optic canal was unroofed through a combined epidural-subdural approach. The cerebral aneurysm was detected by 3D-CTA, MRA and conventional cerebral angiography in each case. Only by 3D-CTA, however, could we easily detect the relationships among the aneurysm neck, ophthalmic artery and optic canal. Based on this information, direct clipping operations were performed safely without any complications. 3D-CTA is an excellent noninvasive diagnostic method not only for detecting cerebral aneurysms, but also for evaluating the relationships between the aneurysms and surrounding structures.

Aged↗

PubMed2005

A model of the upper extremity for simulating musculoskeletal surgery and analyzing neuromuscular control.

Biomechanical models of the musculoskeletal system are frequently used to study neuromuscular control and simulate surgical procedures. To be broadly applicable, a model must be accessible to users, provide accurate representations of muscles and joints, and capture important interactions between joints. We have developed a model of the upper extremity that includes 15 degrees of freedom representing the shoulder, elbow, forearm, wrist, thumb, and index finger, and 50 muscle compartments crossing these joints. The kinematics of each joint and the force-generating parameters for each muscle were derived from experimental data. The model estimates the muscle-tendon lengths and moment arms for each of the muscles over a wide range of postures. Given a pattern of muscle activations, the model also estimates muscle forces and joint moments. The moment arms and maximum moment-generating capacity of each muscle group (e.g., elbow flexors) were compared to experimental data to assess the accuracy of the model. These comparisons showed that moment arms and joint moments estimated using the model captured important features of upper extremity geometry and mechanics. The model also revealed coupling between joints, such as increased passive finger flexion moment with wrist extension. The computer model is available to researchers at http://nmbl.stanford.edu.

Biomechanical Phenomena↗

PubMed2001

Resistance forces acting on suture needles.

Understanding the resistance forces encountered by a suture needle during tissue penetration is important for the development of robotic surgical devices and virtual reality surgical simulators. Tensile forces applied to skin and tendon during suturing were measured. Fresh sheep achilles tendons were tensioned with a static load 4.9 N, 9.8 N or 19.6 N and sheepskin with 0.98 N, 2.9 N or 4.9 N static load. A straight 2/0 cutting suture needle in series with a load cell on a materials testing machine penetrated the tissue at 90 degrees with a velocity of 1, 5 or 10mm/s for each tissue tension (n=5). Continuous load versus displacement data was obtained and penetration load and stiffness were noted. The load versus displacement curve for skin during needle penetration demonstrated two characteristic peaks, corresponding to initial penetration and emergence of needle from the undersurface of the tissue. Increasing the tension within the tissue (skin and tendon) increased the amount of force required to penetrate the tissue with a suture needle (p<0.05). Needle displacement rate did not affect the resistance to needle penetration (p<0.05). This study provides a simple model for measuring force-feedback during needle penetration of soft tissues and is a good starting point for future studies of the penetration resistance properties of human tissues.

Achilles Tendon↗

PubMed2002

Effect of blood transfusion in an experimental sarcoma model.

OBJECTIVE: To study the effect of allogeneic, syngeneic, and autologous blood transfusion on the growth rate of the KHT tumor in a C3H murine model. DESIGN: Prospective, randomized, and controlled animal study. SUBJECTS: Sixty-one C3H female mice. INTERVENTIONS: The C3H female mice were implanted with 2 x 10(5) cells of KHT, a murine sarcoma. Ten days later, 0.3 mL of blood was removed from a retro-orbital site to simulate surgical blood loss. This blood loss was replaced by blood transfusion through a tail vein with the use of allogeneic (major histocompatibility complex incompatible), syngeneic (major histocompatibility complex compatible), or autologous blood. Tumor growth was measured daily for 14 days. The tumor growth curve for each of the animals was constructed and the mean slope of growth calculated for each group. RESULTS: There were statistically significant differences in tumor growth rate (P =.001) when the allogeneic group (mean slope = 0.232, n = 14), the syngeneic group (mean slope = 0.190, n = 17), and the autologous group (mean slope = 0.202, n = 14) were compared. A t test confirmed that there was no significant difference in the tumor growth rate between the groups transfused with syngeneic and autologous blood (P =.26). However, the rate of tumor growth in the allogeneic group was found to be significantly higher when independently compared with the syngeneic group (P<.001) and the autologous group (P =.02). CONCLUSIONS: In this experimental model of a solid murine sarcoma, allogeneic blood transfusion was associated with an increased rate of tumor growth compared with syngeneic and autologous blood transfusion, likely reflecting immunomodulatory effects incurred by the introduction of major histocompatibility complex-incompatible antigens.

Animals↗

PubMed2006

Photorealistic virtual anatomy based on Chinese Visible Human data.

Virtual reality based learning of human anatomy is feasible when a database of 3D organ models is available for the learner to explore, visualize, and dissect in virtual space interactively. In this article, we present our latest work on photorealistic virtual anatomy applications based on the Chinese Visible Human (CVH) data. We have focused on the development of state-of-the-art virtual environments that feature interactive photo-realistic visualization and dissection of virtual anatomical models constructed from ultra-high resolution CVH datasets. We also outline our latest progress in applying these highly accurate virtual and functional organ models to generate realistic look and feel to advanced surgical simulators.

Adult↗

PubMed2001

Restricted surface matching--numerical optimization and technical evaluation.

Accurate and reliable registration is one of the most important issues in computer-aided surgery, as small errors may have a large influence on the overall accuracy of the system. The restricted surface-matching algorithm (RSM), initially developed for periacetabular osteotomy surgery (PAO), has been improved to become numerically more stable and reliable. To assess the accuracy and sensitivity of registration, a framework is presented that evaluates two aspects of registration: the sensitivity and raw performance of the registration algorithm are tested in a stand-alone environment, and the integration into a CAS system is analyzed by evaluating the accuracy of the complete system. For the latter tests, spherical-headed titanium screws used as fiducial landmarks provide a reference transformation for the registration. This framework was used to analyze the performance of RSM for PAO surgery. The sensitivity analysis showed the algorithm to be insensitive to noise up to a magnitude of 3 mm. Both the sensitivity analysis and simulated surgical environment tests showed that an accuracy can be attained of better than 2 mm in the region of interest, and better than 4 mm far away from the region of interest. This is sufficient for safely assisting PAO surgeries.

Algorithms↗

PubMed2005

Characterization of viscoelastic soft tissue properties from in vivo animal experiments and inverse FE parameter estimation.

Soft tissue characterization and modeling based on living tissues has been investigated in order to provide a more realistic behavior in a virtual reality based surgical simulation. In this paper, we characterize the nonlinear viscoelastic properties of intra-abdominal organs using the data from in vivo animal experiments and inverse FE parameter estimation algorithm. In the assumptions of quasi-linear-viscoelastic theory, we estimated the viscoelastic and hyerelastic material parameters to provide a physically based simulation of tissue deformations. To calibrate the parameters to the experimental results, we developed a three dimensional FE model to simulate the forces at the indenter and an optimization program that updates new parameters and runs the simulation iteratively. We can successfully reduce the time and computation resources by decoupling the viscoelastic part and nonlinear elastic part in a tissue model. The comparison between simulation and experimental behavior of pig intra abdominal soft tissue are presented to provide a validness of the tissue model using our approach.

Animals↗