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At least 757 records · Page 42Linked to original sources
PubMed1998

Adaptive canceling of physiological tremor for improved precision in microsurgery.

Physiological hand tremor impedes microsurgery. We present both a novel adaptive algorithm for tremor estimation and a new technique for active real-time canceling of physiological tremor. Tremor is modeled online using the weighted-frequency Fourier linear combiner (WFLC). This adaptive algorithm models tremor as a modulating sinusoid, and tracks its frequency, amplitude, and phase. Piezoelectric actuators move the surgical instrument tip in opposition to the motion of tremor, effectively subtracting the tremor from the total motion. We demonstrate the technique in one dimension using a cantilever apparatus as a benchtop simulation of the surgical instrument. Actual hand motion, prerecorded during simulated surgery, is used as input. In 25 tests, WFLC tremor compensation reduces the rms tip motion in the 6-16 Hz tremor band by 67%, and reduces the rms error with respect to an a posteriori estimate of voluntary motion by 30%. The technique can be implemented in a hand-held microsurgical instrument.

Algorithms↗
PubMedDate not supplied

Computer simulation of arcuate keratotomy for astigmatism.

BACKGROUND: The development of refractive corneal surgery involves numerous attempts to isolate the effect of individual factors on surgical outcome. Computer simulation of refractive keratotomy allows the surgeon to alter variables of the technique and to isolate the effect of specific factors independent of other factors, something that cannot easily be done in any of the currently available experimental models. METHODS: We used the finite element numerical method to construct a mathematical model of the eye. The model analyzed stress-strain relationships in the normal corneoscleral shell and after astigmatic surgery. The model made the following assumptions: an axisymmetric eye, an idealized aspheric anterior corneal surface, transversal isotropy of the cornea, nonlinear strain tensor for large displacements, and near incompressibility of the corneoscleral shell. The eye was assumed to be fixed at the level of the optic nerve. The model described the acute elastic response of the eye to corneal surgery. RESULTS: We analyzed the effect of paired transverse arcuate corneal incisions for the correction of astigmatism. We evaluated the following incision variables and their effect on change in curvature of the incised and unincised meridians: length (longer, more steepening of unincised meridian), distance from the center of the cornea (farther, less flattening of incised meridian), depth (deeper, more effect), and the initial amount of astigmatism (small effect). CONCLUSIONS: Our finite element computer model gives reasonably accurate information about the relative effects of different surgical variables, and demonstrates the feasibility of using nonlinear, anisotropic assumptions in the construction of such a computer model. Comparison of these computer-generated results to clinically achieved results may help refine the computer model.

Animals↗
PubMed1976

Intramural gastric abscess.

Two patients who underwent surgical resection of intramural gastric abscesses are described. Intramural gastric abscesses is a rare problem that simulates more common surgical conditions. The salient features of the symptoms, signs, and findings are reviewed.

Abscess↗
PubMed1986

The computer as a stereotactic surgical instrument.

We have developed methodology and stereotactic software for an operating room computer and imaging system. Patients undergo preoperative CT, MR and DSA imaging with their heads fixed in a stereotactic headholder. Localization systems attach to the headholder during the studies to create reference marks for computer transformation of points and volumes into three-dimensional stereotactic space. At the operating room computer console, the surgeon selects target points, avascular trajectories and tumour boundaries for volume reconstruction. Surgical approaches are simulated and target coordinates calculated. During surgery, the computer interactively monitors the position of stereotactically directed surgical instruments in relationship to the resident database along any viewing angle and conveniently superimposes the multiple data sources. We have found this system useful to provide rapid data acquisition and retrieval, accurate target point calculations, lesion volume reconstructions, and a convenient ability to reformat data from multiple sources in a manner useful to the surgeon and beneficial to the patient.

Angiography↗
PubMed2001

Structured assessment of minor surgical skills (SAMSS) for family medicine residents.

PURPOSE: To develop a valid and reliable examination to assess the technical proficiency of family medicine residents' performance of minor surgical office procedures. METHOD: A multi-station OSCE-style examination using bench-model simulations of minor surgical procedures was developed. Participants were a randomly selected group of 33 family medicine residents (PGY-1 = 16, PGY-2 = 17) and 14 senior surgical residents who functioned as a validation group. Examiners were qualified surgeons and family physicians who used both checklists and global rating scales to score the participants' performances. RESULTS: When family medicine residents were evaluated by family physicians, interstation reliabilities were .29 for checklists and .42 for global ratings. When family medicine residents were evaluated by surgeons, the reliabilities were .53 for checklists and .75 for global ratings. Interrater reliability, measured as a correlation for total examination scores, was .97. Mean scores on the examination were 60%, 64%, and 87% for PGY-1 family medicine, PGY-2 family medicine, and surgery residents, respectively. The difference in scores between family medicine and surgery residents was significant (p < .001), providing evidence of construct validity. CONCLUSION: A new examination developed for assessing family medicine residents' skills with minor surgical office procedures is reliable and has evidence for construct validity. The examination has low reliability when family physicians serve as examiners, but moderate reliability when surgeons are the evaluators.

Ambulatory Surgical Procedures↗
PubMed1984

Giant hyperplasiogenous polyp of the stomach simulating malignant polyp.

A surgical case of giant hyperplasiogenous polyp of the stomach with unusual radiological and pathological findings is presented. Radiological and endoscopical examinations revealed characteristic papillary (villous) features simulating either true adenoma or malignant polyp of the antrum. Complete serial sections from the resected stomach disclosed no malignant area anywhere in and out of the polyp. The pathomorphological nature and radiological characteristics of this rare lesion are discussed.

Aged↗
PubMed1994

Assessing medical students' and surgery residents' clinical competence in problem solving in surgical oncology.

BACKGROUND: We sought to determine the competence of medical students and surgery residents in evaluating clinical problems (using both real and simulated patients) in surgical oncology. METHODS: Forty-five third-year medical students, 23 first postgraduate year (PGY-1) residents, and seven second postgraduate year (PGY-2) residents were presented with the same four clinical problems (breast evaluation, prostate nodule, colon cancer, and mole evaluation). The two resident groups were presented with two additional patients (breast cancer options and thyroid mass). RESULTS: Mean performance scores for the problems were generally poor (32-72%); most students and residents failed almost all of the problems. Level of training was of some importance; the overall mean scores of the PGY-2 residents were superior to those of the medical students and the PGY-1 residents (p = 0.049). However, in many areas of information gathering, diagnosis, and management, training level appeared to have no impact. Numerous important performance deficits were identified in all groups. CONCLUSION: Medical students and surgery residents are not receiving adequate training in diagnosing and treating important problems in surgical oncology.

Analysis of Variance↗
PubMedDate not supplied

[Measurement of the development of psychomotor abilities in surgical endoscopy training with the use of a simulator and biological pieces].

INTRODUCTION: Learning laparoscopic surgery skills using a simulator board is one of the new acquired teaching methods. This work seeks an evaluation method to assess, by objective means, the development of psychometric skills during a simulated workshop with biological pieces. MATERIAL AND METHODS: During a 2-month period, 15 students from an endoscopic surgery seminar were evaluated using a simulator board with the objective to assess four specific skills: object mobilization, cutting pattern, sutures and intracorporeal knots. Eight practice procedures with biological pieces were performed in the simulator. Time and precision were measured in the four assignments. RESULTS: Students improved significantly in object mobilization (p = 0.02), precision in cutting pattern (p < 0.01) and suture (p = 0.02), and time and precision to realize intracorporeal knots (p < 0.01). CONCLUSIONS: This method allows the objective evaluation of the degree of development of surgical skills using a simulator board. It is inexpensive and easy to perform, which makes it useful for other institutions.

Computer Simulation↗
PubMed2003

Healing of periapical lesions with complete loss of the buccal bone plate: a histologic study in the canine mandible.

This study evaluated periapical healing of induced apical lesions with concomitant loss of the buccal bone plate in a dog model using four foxhounds. In an initial surgery, pulp cavities of mandibular premolars were exposed to induce apical lesions. In the same session, the cortical bone covering the buccal root surfaces was surgically removed to simulate buccal bone loss. After radiographic confirmation of the development of apical lesions, sites were reentered for surgical treatment. Following apical and buccal debridement, root-end resection, and root-end filling, sites were subjected to three different treatment modalities: (1) flap readaptation (controls); (2) placement of a collagen membrane covering the apical defect and denuded root surface; or (3) placement of an anorganic bovine bone filler into the apical defect and onto the exposed buccal root surface, with additional application of a collagen membrane. Animals were sacrificed 7 months following the second surgery. Step sections were analyzed histometrically and morphometrically for periapical healing. Sites with membrane + filler showed a statistically significantly lower mean percentage of new bone formation within the former defect compared to both membrane-alone and control sites. No significant differences were found for tissue components deposited on the cut root face across treatment groups. Formation of a continuous thin layer of new cementum covering the exposed dentin surface and root-end filling material was a frequent finding. Analysis of the tissue regeneration on the buccal root aspect as well as the clinical periodontal parameters will be presented in a separate article.

Absorbable Implants↗
PubMed1996

Using human factor analysis and VR simulation techniques for the optimization of the surgical worksystem.

The introduction of minimal invasive operating techniques into the conventional surgical worksystem, requires a fundamental analysis of the resulting problems. Based on ergonomic investigations, concerning working postures, static holding work and task sequence analysis, bottlenecks of workplace design can be demonstrated. As a contribution to the optimization of workplace design, the development of a CAD-based VR simulation environment with an integrated anthropometric man-model, as a very useful tool for anthropometric system design is presented.

Computer Simulation↗
PubMedDate not supplied

Biomechanics of soft tissues.

Recent developments in Computer-Integrated and Robot-Aided Surgery (in particular, the emergence of automatic surgical tools and robots (as well as advances in Virtual Reality techniques, call for closer examination of the mechanical properties of very soft tissues (such as brain, liver, kidney, etc.). Moreover, internal organs are very susceptible to trauma. In order to protect them properly against car crash and other impact consequences we need to be able to predict the organ deformation. Such prediction can be achieved by proper mathematical modelling followed by a computer simulation. The ultimate goal of our research into the biomechanics of these tissues is development of corresponding, realistic mathematical models. This paper contains experimental results of in vitro, uniaxial, unconfined compression of swine brain tissue obtained by the author in Mechanical Engineering Laboratory, Japan, and discusses liver and kidney in vivo compression experiments conducted in Highway Safety Research Institute and the Medical Centre of The University of Michigan. The stress-strain curves for investigated tissues are concave upward for all compression rates containing no linear portion from which a meaningful elastic modulus might be determined. The tissue response stiffened as the loading speed increased, indicating a strong stress (strain rate dependence. As the step in the direction towards realistic computer simulation of injuries and surgical procedures, this paper presents two mathematical representations of brain, liver and kidney tissue stiffness. Biphasic and single-phase models are discussed. The biphasic model is shown to be inappropriate due to its inability to account for strong stress-strain relationship. Agreement between the proposed single-phase models and experiment is good for compression levels reaching 30% and for loading velocities varying over five orders of magnitude. Presented mathematical models can find applications in computer and robot assisted surgery, e.g. the realistic simulation of surgical procedures (including virtual reality), control systems of surgical robots, and non-rigid registration, as well as ergonomic design for injury prevention.

Animals↗
PubMed2004

Performance evaluation of two published closed-loop control systems using bispectral index monitoring: a simulation study.

BACKGROUND: Although automated closed-loop control systems may improve quality of care, their safety must be proved under extreme control conditions. This study describes a simulation methodology to test automated controllers and its application in a comparison of two published controllers for Bispectral Index (BIS)-guided propofol administration. METHODS: A patient simulator was developed to compare controllers. Using input scripts to dictate patient characteristics, target BIS values, and the time course of surgical events, the simulator continuously monitors the infusion pump under control and generates BIS values as a composite of modeled response to drug, perceived stimulation, and random noise. The simulator formats the output stream of BIS data as input to the controller under test to emulate the serial output of the actual BIS monitor. A published model-based controller and a classic proportional integral derivative controller were compared when using the BIS value as a controlled variable. Each controller was tested using a set of 10 virtual patients undergoing a fixed surgical profile that was repeated with BIS targets set at 30, 50, and 70. Controller performance was assessed using median (absolute) prediction error, divergence, wobble, and percentage time within BIS target range metrics. RESULTS: The median prediction error was significantly smaller for the proportional integral derivative controller than for the model-based controller. The median absolute prediction error was smaller for the model-based controller than for the proportional integral derivative controller for each BIS target, reaching statistical significance for targets 30 and 50. CONCLUSIONS: When simulating closed-loop control of BIS using propofol, the use of a patient-individualized, model-based adaptive closed-loop system with effect site control resulted in better control of BIS compared with a standard proportional integral derivative controller with plasma site control. Even under extreme conditions, the modeled-based controller exhibited no behavioral problems.

Algorithms↗
PubMed1995

Primary leptomeningeal melanoma simulating a meningioma.

A surgically confirmed primary leptomeningeal malignant melanoma (PLMM) discovered at the parietal region is reported in a 72-year-old male. He developed progressive right hemiparesis and speech disorders caused by a parietal large mass that simulated a growing meningioma. A well-defined, dark-black tumor was removed completely and was histopathologically diagnosed as a malignant melanoma. No melanomas were detected by systemic clinical and radiological examination, including dermatological and ophthalmologic examinations. Follow-up examination 18 months postoperatively showed no evidence of recurrence of the tumor. The patient gradually became bedridden probably because of decreased general activity possibly due to brain atrophy and died of cardiac failure without any evidence of recurrence. Because of the absence of other systemic localizations, we consider this melanoma as primary. A favorable outcome was obtained by surgical treatment alone.

Aged↗
PubMed2002

Virtual reality simulators: current status in acquisition and assessment of surgical skills.

Medical technology is currently evolving so rapidly that its impact cannot be analysed. Robotics and telesurgery loom on the horizon, and the technology used to drive these advances has serendipitous side-effects for the education and training arena. The graphical and haptic interfaces used to provide remote feedback to the operator--by passing control to a computer--may be used to generate simulations of the operative environment that are useful for training candidates in surgical procedures. One additional advantage is that the metrics calculated inherently in the controlling software in order to run the simulation may be used to provide performance feedback to individual trainees and mentors. New interfaces will be required to undergo evaluation of the simulation fidelity before being deemed acceptable. The potential benefits fall into one of two general categories: those benefits related to skill acquisition, and those related to skill assessment. The educational value of the simulation will require assessment, and comparison to currently available methods of training in any given procedure. It is also necessary to determine--by repeated trials--whether a given simulation actually measures the performance parameters it purports to measure. This trains the spotlight on what constitutes good surgical skill, and how it is to be objectively measured. Early results suggest that virtual reality simulators have an important role to play in this aspect of surgical training.

Clinical Competence↗
PubMed1995

Preserving plantar flexion strength after surgical treatment for contracture of the triceps surae: a computer simulation study.

Contractures of the triceps surae commonly are treated by surgical lengthening of the gastrocnemius aponeurosis or the Achilles tendon. Although these procedures generally relieve contractures, patients sometimes are left with dramatically decreased plantar flexion strength (i.e., decreased capacity to generate plantar flexion moment). The purpose of this study was to examine the trade-off between restoring range of motion and maintaining plantar flexion strength after surgical treatment for contracture of the triceps surae. A computer model representing the normal moment-generating characteristics of the triceps surae was altered to represent two conditions: isolated contracture of the gastrocnemius and contracture of both the gastrocnemius and the soleus. The effects of lengthening the gastrocnemius aponeurosis and the Achilles tendon were simulated for each condition. The simulations showed that nearly normal moment-generating characteristics could be restored when isolated gastrocnemius contracture was treated with lengthening of the gastrocnemius aponeurosis. However, when isolated gastrocnemius contracture was treated with lengthening of the Achilles tendon, the moment-generating capacity of the plantar flexors decreased greatly. This suggests that lengthening of the Achilles tendon should be avoided in persons with isolated gastrocnemius contracture. Our simulations also suggest that neither lengthening of the gastrocnemius aponeurosis nor lengthening of the Achilles tendon by itself is an effective treatment for combined contracture of the gastrocnemius and soleus. Lengthening the gastrocnemius aponeurosis did not decrease the excessive passive moment developed by the contracted soleus. Lengthening the Achilles tendon restored the normal passive range of motion but substantially decreased the active force-generating capacity of the muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Achilles Tendon↗
PubMed1990

The effects of phonosurgery on laryngeal vibration: Part I. Theoretic considerations.

Surgical manipulation of the laryngeal framework (phonosurgery) is rapidly gaining interest and attention. To date, however, a comparative objective evaluation of the various phonosurgical techniques has not been reported. A theoretic model of the larynx, a four-mass model based on the work of Ishizaka (J Acoust Soc Am 1976;60:1193-8) and Koizumi et al. (J Acoust Soc Am 1987;82:1179-92), was developed and adapted to simulate laryngeal biomechanical behavior, as understood by current research. The model was then applied to a comparative evaluation of phonosurgical techniques. Input parameters that correlate laryngeal function and model simulation were developed. Surgical procedures were categorized according to their effect on these parameters. A model simulation of these techniques allowed comparison and prediction of the results of phonosurgery and a better understanding of the issues involved with surgical alteration of the voice.

Computer Simulation↗
PubMed2002

ACoA angle measured by computed tomographic angiography and its relevance in the pterional approach for ACoA aneurysms.

The purpose of this study was to analyze the spatial disposition of the anterior communicating artery (ACoA) complex and the orientation of the ACoA plane by computed tomographic angiography with three-dimensional reconstruction (3D-CTA) and to evaluate the relevance of the orientation of the ACoA plane in the planification of the surgical approach to the ACoA complex aneurysms. The dominance of the right or left A1 segment of the anterior cerebral artery, the position of the A1-A2 junction in relation to the transverse plane and the angulation of plane of the ACoA traject were studied using 3D-CTA in 30 patients with subarachnoid hemorrhage. Twelve patients harbored an aneurysm on the ACoA complex and the most relevant anatomic characteristics of these lesions were recorded. In 56.7% of cases both A1 segments were similar in size, whereas in 33.3% of cases the left A1 segment was dominant and in the remaining 10% the right A1 segment was dominant. The position of the left A1-A2 junction was anterior to the transverse plane in 30% of cases with an angulation of the ACoA plane of 42+/-6 degrees. All patients with this anatomical arrangement and left A1 dominance (seven cases) harbored an aneurysm of the ACoA complex located on the left A1-A2 junction. The right A1-A2 junction was anterior to the transverse plane in 13.3% of cases with an angulation of the ACoA plane of 37+/-9 degrees. All patients in this situation and right A1 dominance (three cases) had an aneurysm on the ACoA complex. Finally, in 50% of cases the ACoA plane was on the transverse plane. In this group of cases only two patients harbored an aneurysm located on the ACoA segment. The dominance of an A1 segment of the anterior cerebral artery may develop anatomical changes in the ACoA complex due to the hemodynamic stress. The main result is the advance of the A1-A2 junction point in the dominant side and the angulation of the ACoA plane in relation to the transverse plane as well as the development of aneurismatic lesions. The angulation of the ACoA plane, in combination with the orientation of the aneurysm, must be included among the criteria for the selection of the route of the surgical approach. This information is given by the 3D-CTA. All of these data allows a pre-operative simulation of the surgical approach to the lesion for a safer clipping of the neck of the aneurysm.

Adolescent↗
PubMedDate not supplied

Rapid protyping technology in medicine--basics and applications.

Using medical models built with Rapid Prototyping (RP) technologies represents a new approach for surgical planning and simulation. These techniques allow one to reproduce anatomical objects as 3D physical models, which give the surgeon a realistic impression of complex structures before a surgical intervention. The shift from the visual to the visual-tactile representation of anatomical objects introduces a new kind of interaction called 'touch to comprehend'. As can be seen, from the presented case studies of maxillo-cranio-facial surgery, the RP models are very well suited for use in the diagnosis and the precise preoperative simulation of skeleton modifying interventions.

Acrocephalosyndactylia↗