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At least 361 records · Page 20Linked to original sources

Pickup of visual information by the pilot during a ground control approach in a fighter aircraft simulator.

Before providing the new single-seat fighter aircraft with selective visual information display systems, it is necessary to conduct new studies of the visual behavior of pilots flying these aircraft in order to determine the nature of information to be displayed. The authors describe a modified NAC Eye Mark recorder which can be used in tight spaces without any interfering light source and given an example of its use in an experiment conducted in a Mirage III R training simulator. The reported experiment was designed to analyse the visual behavior of 12 pilots of four different qualification levels who flew a ground control approach (GCA) test each day for five consecutive days. The results show that the pilot's visual behavior is stable, both on an intra- and inter-individual basis. In addition, it is possible to classify the control panel instruments as a function of the number of times and length of time they are checked.

Aerospace Medicine↗

A method of objectively evaluating improvements in laparoscopic skills.

BACKGROUND: In this paper, we explored a quick and inexpensive method to evaluate the improvement in laparoscopic skills gained by residents after attending a formal training course in laparoscopy. METHODS: Surgical residents attending an endoscopic workshop were randomly selected to perform tasks in a training simulator. Each was evaluated qualitatively and quantitatively before and after the workshop. A control group of six residents who did not attend the workshop were selected to perform the same tasks twice in succession. RESULTS: The total mean time improvement for all tasks in the study group was 34.3% and in the control group 7.3% (p = 0.0001). When the data was separated for each task, statistically significant improvement was demonstrated in five of the six tasks. CONCLUSIONS: Residents who attend a formal workshop in endoscopy can gain significant improvement in skills. The methods described in this study can be used to quantitatively measure this improvement throughout a resident's training.

Clinical Competence↗

Heuristic haptic texture for surgical simulations.

Generation of credible force feedback renderings adds the sense of touch crucial for the development of a realistic virtual surgical environment. However, a number of difficulties must be overcome before this can be achieved. One of the problems is the paucity of data on the in-vivo tissue compliance properties needed to generate acceptable output forces. Without this "haptic texture," the sense of touch component remains relatively primitive and unrealistic. Current research in the quantitative analysis of biomechanics of living tissue, including collection of in-vivo tissue compliance data using specialized sensors, has made tremendous progress. However, integration of all facets of biomechanical data in order to transfer them into haptic texture remains a very difficult problem. For this reason, we are attempting to create a library of heuristic haptic textures of anatomical structures. The library of heuristic haptic textures will capture the expert's sense of feel for selected anatomical structures and will be used to convey the sense of touch for surgical training simulations. Once the techniques for converting biomechanical data into haptic texture become more robust, this library can be used as a benchmark to verify theoretical computational models used for generating output forces in haptic devices.

Biomechanical Phenomena↗

Simulation and airway-management training.

PURPOSE OF REVIEW: Simulators can be used to teach simple technical skills or used in more realistic settings to teach or assess various cognitive/affective skills. Although simulators have become widespread, their use and efficacy in these various areas have not been delineated and are still being explored. This review will discuss the present state of using medical simulation for airway-management training. RECENT FINDINGS: Airway management includes both specialized technical skills and higher-order cognitive skills and behaviors. Since no one simulator is capable of covering all the functions necessary to teach these varied skills, medical specialists will need to train on a couple of different simulators. Now widely accepted in medical education, simulator training is being mandated in certain situations at some institutions because of a belief that it alters the physician. In this article its efficacy in teaching the specific psychomotor skills of bronchoscopy were validated but its use in teaching higher cognitive skills remained inconclusive. SUMMARY: Simulators are here to stay. Presently their usage in teaching psychomotor skills has scientific validity in specific tasks but their efficacy for teaching higher-order cognitive skills is still evolving. Future studies will continue to delineate the usage in different areas by studying the outcome in skills training and retention.

Journal Article↗

Computer simulation as a component of catheter-based training.

INTRODUCTION: Computer simulation has been used in a variety of training programs, ranging from airline piloting to general surgery. In this study we evaluate the use of simulation to train novice and advanced interventionalists in catheter-based techniques. METHODS: Twenty-one physicians underwent evaluation in a simulator training program that involved placement of a carotid stent. Five participants were highly experienced in catheter-based techniques (>300 percutaneous cases), including carotid angioplasty and stenting (CAS); the remaining 16 participants were interventional novices (<5 percutaneous cases). The Procedicus VIST simulator, composed of real-time vascular imaging simulation software and a tactile interface coupled to angiographic catheters and guide wires, was used. After didactic instruction regarding CAS and use of the simulator, each participant performed a simulated CAS procedure. The participant's performance was supervised and evaluated by an expert interventionalist on the basis of 50 specific procedural steps with a maximal score of 100. Specific techniques of guide wire and catheter manipulation were subjectively assessed on a scale of 0 to 5 points based on ability. After evaluation of the initial simulated CAS procedure, each participant received a minimum of 2 hours of individualized training by the expert interventionalist, with the VIST simulator. Each participant then performed a second simulated CAS procedure, which was graded with the same scale. After completion, participants assessed the training program and its utility via survey questionnaire. RESULTS: The average simulated score for novice participants after the training program improved significantly from 17.8 +/- 15.6 to 69.8 +/- 9.8 (P < .01), time to complete simulation decreased from 44 +/- 10 minutes to 30 +/- 8 minutes (P < .01), and fluoroscopy time decreased from 31 +/- 7 minutes to 23 +/- 7 minutes ( P < .01). No statistically significant difference in score, total time, or fluoroscopy time was noted for experienced interventionalists. Improvement was noted in guide wire and catheter manipulation skills in novices. Analysis of survey data from experienced interventionalists indicated that the simulated clinical scenarios were realistic and that the simulator could be a valuable tool if clinical and tactile feedback were improved. Novices also thought the simulated training was a valuable experience, and desired further training time. CONCLUSIONS: An endovascular training program using the Procedicus VIST haptic simulator resulted in significant improvement in trainee facility with catheter-based techniques in a simulated clinical setting. Novice participants derived the greatest benefit from simulator training in a mentored program, whereas experienced interventionalists did not seem to derive significant benefit.

Blood Vessel Prosthesis Implantation↗

Bias in error estimation when using cross-validation for model selection.

BACKGROUND: Cross-validation (CV) is an effective method for estimating the prediction error of a classifier. Some recent articles have proposed methods for optimizing classifiers by choosing classifier parameter values that minimize the CV error estimate. We have evaluated the validity of using the CV error estimate of the optimized classifier as an estimate of the true error expected on independent data. RESULTS: We used CV to optimize the classification parameters for two kinds of classifiers; Shrunken Centroids and Support Vector Machines (SVM). Random training datasets were created, with no difference in the distribution of the features between the two classes. Using these "null" datasets, we selected classifier parameter values that minimized the CV error estimate. 10-fold CV was used for Shrunken Centroids while Leave-One-Out-CV (LOOCV) was used for the SVM. Independent test data was created to estimate the true error. With "null" and "non null" (with differential expression between the classes) data, we also tested a nested CV procedure, where an inner CV loop is used to perform the tuning of the parameters while an outer CV is used to compute an estimate of the error. The CV error estimate for the classifier with the optimal parameters was found to be a substantially biased estimate of the true error that the classifier would incur on independent data. Even though there is no real difference between the two classes for the "null" datasets, the CV error estimate for the Shrunken Centroid with the optimal parameters was less than 30% on 18.5% of simulated training data-sets. For SVM with optimal parameters the estimated error rate was less than 30% on 38% of "null" data-sets. Performance of the optimized classifiers on the independent test set was no better than chance. The nested CV procedure reduces the bias considerably and gives an estimate of the error that is very close to that obtained on the independent testing set for both Shrunken Centroids and SVM classifiers for "null" and "non-null" data distributions. CONCLUSION: We show that using CV to compute an error estimate for a classifier that has itself been tuned using CV gives a significantly biased estimate of the true error. Proper use of CV for estimating true error of a classifier developed using a well defined algorithm requires that all steps of the algorithm, including classifier parameter tuning, be repeated in each CV loop. A nested CV procedure provides an almost unbiased estimate of the true error.

Algorithms↗

Medical students' attitudes toward the use of an endoscopic sinus surgery simulator as a training tool.

BACKGROUND: Modern adult learning theory characterizes self-directed learning as most effective. While studying the effectiveness of an endoscopic sinus surgery simulator (ES3) as a training tool and acknowledging that its successful integration into a training program is dependent on its acceptance and self-driven use by trainees, we sought to determine our study subjects' attitudes toward the simulator. METHODS: Twenty-six medical students were enrolled and trained in our ES3 study. Each student was asked to complete a 28-item questionnaire on completion of training. This questionnaire contained 10-point Likert scale instruments, yes/no questions, and one open-ended question. RESULTS: All but four subjects responded to the questionnaire; 90.9% of the respondents rated the training benefit derived from the simulator's novice mode as 6 or greater on a 10-point scale; the mean was 7.82 (+/- 2.22). The training benefit of the intermediate mode also was scored highly, with a mean score in the 7-9 range for all but one component-heart rate response to actions performed. Trainees appreciated the simulator's ability to help them adapt to a three-dimensional space on a two-dimensional display. They also noted its strengths in elucidating intranasal anatomy. CONCLUSION: Medical students who enrolled in our study, as a group,felt that the ES3 provided them with significant training benefits. Although subjective, these attitudes, coupled with objective data indicating that there is a measurable benefit from use of the ES3, will ensure itsfull acceptance and use in otolaryngology training programs.

Adult↗

Acquisition of endovascular skills for obstetrician-gynecologists.

STUDY OBJECTIVE: To identify skills not part of the training of obstetrician-gynecologists that are needed to perform endovascular procedures, especially uterine artery embolization. DESIGN: Literature review of known skills necessary to perform endovascular procedures. RESULTS: Important areas of endovascular skills are as follows. Understanding of the modern C-arm image intensifier is basic to performing endovascular procedures safely for the patient, physician, and others in the procedure room. Many states require physicians to obtain a Fluoroscopy Supervisors Permit when doing such interventions. Arteriotomy begins every endovascular procedure. Physicians must understand catheter manipulation and selection, and the use of microcatheters. An understanding of the pelvic arterial anatomy will help the surgeon identify the uterine arteries. Once in the uterine artery, the surgeon must understand how to successfully embolize the artery. As in any surgery, prevention of complications is important as well as management of complications once they arise. CONCLUSION: Obstetrician-gynecologists should plan on devoting a year for the acquisition of skills needed to perform endovascular procedures. Methods of acquiring such skills include simulator training, animal laboratory procedures, and observation of live procedures. Didactic courses will give physicians an overview of endovascular procedures.

Balloon Occlusion↗

Trauma assessment training with a patient simulator: a prospective, randomized study.

BACKGROUND: Patient simulators are computer-controlled mannequins that may increase realism during trauma training by providing real-time changes in vital signs and physical findings during trauma scenarios. We hypothesized that trauma assessment training on a patient simulator would be as effective as training with a more traditional moulage patient/actor. METHODS: This study was conducted during a surgery intern orientation at two academic trauma centers. Interns (n = 60) attended a basic trauma course, and were then randomized to trauma assessment practice sessions with either the patient simulator (n = 30) or a moulage patient (n = 30). After practice sessions, interns were randomized a second time to an individual trauma assessment test on either the simulator or the moulage patient. Two surgeon-judges rated each intern live and on video for completion of 50 predetermined assessment objectives (total score) divided into sections (primary and secondary survey, general performance, diagnostic studies/procedures, and plan) and the identification and management of an acute neurologic deterioration in the test patient (event score). Multiple linear regression with random student effects was used to estimate the independent effects of all study variables. RESULTS: Within randomized groups, mean trauma assessment test scores for all simulator-trained interns were higher when compared with all moulage-trained interns (71 +/- 8 vs. 66 +/- 8, respectively; p = 0.02). Simulator training independently showed a small but statistically significant improvement in both the total score and the event score (+4.6 and +8.6, respectively; p < 0.05). CONCLUSION: Use of a patient simulator to introduce trauma assessment training is feasible and compares favorably to training in a moulage setting. Continued research in this area of physician education is warranted.

Educational Measurement↗

Feasibility of k-t BLAST technique for measuring "seven-dimensional" fluid flow.

PURPOSE: To investigate the feasibility of rapid MR measurement of "seven-dimensional" (three velocity components, three dimensions, and time) fluid flow using the k-t Broad-use Linear Acquisition Speed-Up Technique (BLAST). MATERIALS AND METHODS: Complete k-space data were acquired for pulsatile fluid flow in a model of a stenosed carotid bifurcation. The data was subsampled to simulate "training" and "accelerated acquisition" data for reconstruction using k-t BLAST. RESULTS: Flow waveforms estimated from k-t BLAST reconstructions were in good agreement with those measured from the full data set for overall speedup factors up to approximately four times when slice-by-slice undersampling in k(y) was used. Accuracy was better than 25 mm/second or 7% (root-mean-square error) for individual time frames under these conditions. Flow patterns in the plane of symmetry, near the bifurcation, and in the stenosis were also in good agreement with those reconstructed from the full data set. Improved performance was obtained from undersampling in both k(y) and k(z), when acceleration factors up to 12 times gave acceptable results. CONCLUSION: The k-t BLAST technique can be applied to flow quantification, and may make feasible the acquisition of time-resolved blood flow from extended arterial regions within acceptable examination times.

Blood Flow Velocity↗

The effects of beta motor stimulation on the interpretation of signals from muscle spindles.

A previously proposed method for the interpretation of the signals in sensory nerve fibres is extended to incorporate beta activation of muscle spindles. simulations, based on previous experimental observations, of muscles spindles subjected to ramp and hold stretches are used as input to an "interpreter", where the simulated trains of action potentials are reconverted to a length change interpretation. The interpreted signals are compared with the original length change inputs to observe the effects of beta-stimulation and stochastic variability.

Action Potentials↗

The learning curve for a colonoscopy simulator in the absence of any feedback: no feedback, no learning.

BACKGROUND: The hypothesis of this study is that working on the simulator without a structured feedback does not change performance; hence, any effects shown after structured feedback would amount to useful learning of the procedure. The aim was to investigate the learning curve for the HT Immersion Medical Colonoscopy Simulator without any structured feedback. This could then be potentially applied to validate the learning curve on the simulator when structured feedback is provided. There are no previous studies on this matter. METHODS: Candidates were asked to perform colonoscopy on the HT Immersion Medical Colonoscopy Simulator. Modules 3 and 4 were used at random. In total, each candidate was asked to perform five consecutive virtual colonoscopies on the same module. These five episodes were collectively referred to as one trial. A time result of 3,600 sec (1 h) was used to denote perforation. No guidance or feedback was given to candidates before, during, or after each procedure. A total of 26 postgraduate doctors were recruited, including nine research fellows, five preregistration house officers, six specialist registrars, and six consultants. Fourteen candidates recorded five attempts each (i.e., one trial each) on the same module of the colonoscopy simulator (14 trials over 70 episodes). Another 12 candidates recorded five attempts (i.e., one trial each) on two modules of the colonoscopy simulator (24 trials over 120 episodes). Hence, 190 episodes were recorded in total, representing 38 trials. RESULTS: There was no improvement in performance on the simulator from first attempt to the fifth in the absence of feedback. If there was any initial gain in any measurable outcome, this was lost in subsequent attempts indicating lack of learning. The outcomes measured included time taken to complete the test, percentage of the mucosa visualized, depth of the instrument inserted, and the path length used. The results were statistically significant for all outcomes. CONCLUSIONS: This study demonstrates that in the absence of feedback, it is not possible to improve performance on the HT Immersion Medical Colonoscopy Simulator. Thus, there is no learning curve for the machine. The information from this study is vital for using the simulators in training and assessment because any improvement in learning curves shown after training on simulators can be presumed to be due to learning the procedure and not the simulator.

Clinical Competence↗

Modeling the variability of firing rate of retinal ganglion cells.

Impulse trains simulating the maintained discharges of retinal ganglion cells were generated by digital realizations of the integrate-and-fire model. If the mean rate were set by a "bias" level added to "noise," the variability of firing would be related to the mean firing rate as an inverse square root law; the maintained discharges of retinal ganglion cells deviate systematically from such a relationship. A more realistic relationship can be obtained if the integrate-and-fire mechanism is "leaky"; with this refinement, the integrate-and-fire model captures the essential features of the data. However, the model shows that the distribution of intervals is insensitive to that of the underlying variability. The leakage time constant, threshold, and distribution of the noise are confounded, rendering the model unspecifiable. Another aspect of variability is presented by the variance of responses to repeated discrete stimuli. The variance of response rate increases with the mean response amplitude; the nature of that relationship depends on the duration of the periods in which the response is sampled. These results have defied explanation. But if it is assumed that variability depends on mean rate in the way observed for maintained discharges, the variability of responses to abrupt changes in lighting can be predicted from the observed mean responses. The parameters that provide the best fits for the variability of responses also provide a reasonable fit to the variability of maintained discharges.

Action Potentials↗

Ethological experiments on human orientation behavior within a three-dimensional space--in microgravity.

In weightlessness situation the subject has to realize domestic and professional tasks comparable to those performed under normal gravity, whereas the "body tool" available to him has been placed in new conditions which require significant behavioral changes. The loss of weight, the disappearance or modification of some ideothetic and allothetic cues, notably the absence of gravity for the body's referential verticality have the most obvious effect of diversifying the astronaut's orientations. The vertical position is thus no longer the only one possible. This means that in order to efficiently accomplish his tasks, the subject has to invent new motor strategies which transform the quality of displacements and manipulations on the basis of the new orientation possibilities in a three-dimensional space. The previous ethological studies have dealt, in a global way, with the astronaut's motor behavior in microgravity, revealed according to an exhaustive quantitative description of the behavioral manifestions as a whole in terms of movement, posture and orientation. We now propose focusing more specifically on his spatial behavior in a three-dimensional space in microgravity. Such a situation is an exceptional experimental paradigm since at every moment, the relationships of the body referential to the surrounding space are infinitely variable: a man in space has to extract, process or use spatial information between the referentials of his moving body in all directions of the three-dimensional space and the fixed referentials of the physical environment of the space habitat. Furthermore, in the temporal dynamics, the previous ethological results showed that the behavioral events change according to the duration of the space mission, passing through different adaptative stages from a large behavioral diversity to complete behavioral reorganization. On the first day of his space mission the astronaut has however acquired experience of microgravity through his training, simulated on the ground and realized in parabolic flights. Some immediate adaptative processes are already present. As a result, the subject's experience of such a situation has to be emphasized from the initial moments of adaptation to microgravity. We thus postulate that the subject, through his orientation behavior in a three-dimensional space, according to his experience and over time, would elaborate a new representation of the space, as part of the whole adaptative process to this new environment. In order to verify such hypotheses, the present study will propose three levels of observation, i.e. three experiments in conditions of orbital flight, parabolic flight, visual simulation.

Adult↗

Safety implications of cultural and cognitive issues in nuclear power plant operation.

This research project was designed to investigate cultural and cognitive issues related to the work of nuclear power plant operators during their time on the job in the control room and during simulator training (emergency situations), in order to show how these issues impact on plant safety. The modeling of the operators work deals with the use of operational procedures, the constant changes in the focus of attention and the dynamics of the conflicting activities. The paper focuses on the relationships between the courses of action of the different operators and the constraints imposed by their working environment. It shows that the safety implications of the control room operators' cognitive and cultural issues go far beyond the formal organizational constructs usually implied. Our findings indicate that the competence required for the operators are concerned with developing the possibility of constructing situation awareness, managing conflicts, gaps and time problems created by ongoing task procedures, and dealing with distractions, developing skills for collaborative work.

Adult↗

Valuable safeguard or unnecessary burden? Characterization of physician consultations for oral contraceptive use in Mexico City.

CONTEXT: Given the safety and efficacy of oral contraceptives (OCs), many health professionals believe that these should be widely available over-the-counter (OTC). Opponents of OTC availability argue that without a physician's consultation, women will not be properly screened and will not use OCs correctly, thereby compromising safety and efficacy. However, little is known about the content or quality of physicians' consultations. METHODS: Trained simulated patients (SPs) attended 45 appointments with Mexico City public and private physicians to request a prescription for OCs. Immediately following each appointment, the SPs filled out a checklist regarding the information provided and examinations performed by physicians. RESULTS: Both public and private physicians asked a few questions and provided little information regarding screening, pill-taking instructions, side effect information and warning sign information. Despite the fact that all SPs were appropriate OC candidates, women were denied a prescription in seven (15.6%) appointments mostly because of their age (regarded as either too old or too young). CONCLUSION: In general, Mexican physicians are not providing women thorough information and screening in OC consultations, calling into question the assumption that a physician's appointment is necessary for or will ensure safe, proper OC use.

Contraceptives, Oral↗

The use of virtual environments for percentage view analysis.

It is recognised that Visual Impact Assessment (VIA), unlike many other aspects of Environmental Impact Assessments (EIA), relies less upon measurement than upon experience and judgement. Hence, it is necessary for a more structured and consistent approach towards VIA, reducing the amount of bias and subjectivity. For proposed developments, there are very few quantitative techniques for the evaluation of visibility, and these existing methods can be highly inaccurate and time consuming. Percentage view changes are one of the few quantitative techniques, and the use of computer technology can reduce the inaccuracy and the time spent evaluating the visibility of either existing or proposed developments. For over 10 years, research work undertaken by the authors at the University of Nottingham has employed Computer Graphics (CG) and Virtual Reality (VR) in civilian and industrial contexts for environmental planning, design visualisation, accident reconstruction, risk analysis, data visualisation and training simulators. This paper describes a method to quantitatively assess the visual impact of proposed developments on the landscape using CG techniques. This method allows the determination of accurate percentage view changes with the use of a computer-generated model of the environment and the application of specialist software that has been developed at the University of Nottingham. The principles are easy to understand and therefore planners, authorisation agencies and members of the public can use and understand the results. A case study is shown to demonstrate the application and the capabilities of the technology.

City Planning↗