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PubMed2005

VSOne, a virtual reality simulator for laparoscopic surgery.

The introduction of computer-based training systems for laparoscopic surgery has increased the training quality and made the learning effect measurable with objective criteria. This paper introduces VSOne as a fully-featured virtual reality training system for laparoscopic surgery. VSOne utilizes the state-of-the-art in virtual reality techniques, soft tissue simulation and haptic device control and guarantees realistic training possibilities for various laparoscopic procedures. An authoring software helps to create individual simulation models easily within the shortest time based on real patient data using standardized data formats. We have developed several Basic Task Training (BTT) modules to improve dexterity and complex Surgical Procedure Task (SPT) modules for full training of laparoscopic procedures such as cholecystectomy, tubal sterilization and myomectomy. VSOne has been evaluated in a comparative study with classic training methods and has shown the typical learning curves for inexperienced trainees and the transferability of the learning effect to the real-world situation.

Journal Article↗

PubMedDate not supplied

Simultaneous pancreas kidney transplantation: initial experience of the Emory University transplant service.

The successful replacement of islet tissue by pancreas transplantation appears to be beneficial in the early course of those uremic diabetic recipients who receive a simultaneous renal transplant. The long-term advantages of SKP transplantation remain to be determined, however, current improvement in patient and graft survival following SPK and the difficulties thus far reported in islet cell transplantation have renewed clinical interests in SPK, PAK and PA transplantation. In our experience, pancreas transplantation has been a challenging technical, immunological and physiological endeavor which was well received by our patients despite the initial problems and complications we and they encountered. Notwithstanding extensive preparation, our team experienced a "learning curve" and we present many of the lessons we learned. This knowledge has aided our transplant team in the successful management and avoidance of these complications and other inherent problems associated with SKP transplantation in subsequent patients.

Anastomosis, Surgical↗

PubMed2006

[Influence of intracerebroventricular infusion of beta-amyloid peptide on learning dynamics in Wistar and non-linear rats].

Effect of intracerebroventricular infusion of beta-amyloid peptide fragment Abeta(25-35) on light-dark discrimination in a Y-maze with positive food reinforcement, assessed as a decrease in the number of errors, was investigated in Wistar rats and non-linear rats. We proposed to use exponential mathematical model for the learning curve that represents the transfer function for the first order system together with regression analysis. Dynamics of learning in Wistar and non-linear rats coincided with the model. Injection ofbeta-amyloid into the right lateral ventricle of the brain led to a disruption in performance between the first and the second session without total cessation of the learning process. This disappearance of the curve may be the first sign of the initial effect of beta-amyloid because Student's t-test did not reveal any significant difference between control and amyloid-treated Wistar rats. Beta-amyloid in non-linear rats only decreased the velocity of learning though kept being similar to the mathematical model. These results suggest that the non-linear rats possess some genetically specified defense mechanism against damaging action of beta-amyloid.

Alzheimer Disease↗

PubMed2005

Clinical evaluation of USCOM ultrasonic cardiac output monitor in cardiac surgical patients in intensive care unit.

BACKGROUND: The USCOM ultrasonic cardiac output monitor (USCOM Pty Ltd, Coffs Harbour, NSW, Australia) is a non-invasive device that determines cardiac output by continuous-wave Doppler ultrasound. The aim of this study was to evaluate the accuracy of the USCOM device compared with the thermodilution technique in intensive care patients who had just undergone cardiac surgery. METHODS: We conducted a prospective study in the 18-bed intensive care unit of a 600-bed tertiary referral hospital. Twenty-four mechanically ventilated patients were studied immediately following cardiac surgery. We evaluated the USCOM monitor by comparing its output with paired measurements obtained by the standard thermodilution technique using a pulmonary artery catheter. RESULTS: Forty paired measurements were obtained in 22 patients. We were unable to obtain an acceptable signal in the remaining two patients. Comparison of the two techniques showed a bias of 0.18 and limits of agreement of -1.43 to 1.78. The agreement may not be as good between techniques at higher cardiac output values. CONCLUSIONS: The USCOM monitor has a place in intensive care monitoring. It is accurate, rapid, safe, well-tolerated, non-invasive and cost-effective. The learning curve for skill acquisition is very short. However, during the learning phase the USCOM monitor measurements are rather 'operator dependent'. Its suitability for use in high and low cardiac output states requires further validation.

Adult↗

PubMed2001

Nuances in acoustic neuroma surgery.

This article describes surgical methods developed during my resection of 600 acoustic neuromas, 599 of which were total removals. This series began in 1965, with the introduction of the surgical microscope and the development of microsurgical technique. In the 1960s, there was no established technology for the microsurgery of acoustic neuromas. Much of the work of the great early neurosurgeons--Cushing, Dandy, Olivecrona, and other remarkable pioneers--did not really apply. New approaches, solutions, and tools were introduced at that time, and there was a long, steep learning curve. I hope that some of the discussion herein makes learning easier for the new generation of neurosurgeons as they develop their own operative nuances.

Humans↗

PubMed2001

[Intraoperative ultrasonography in laparoscopic cholecystectomy].

BACKGROUND: Laparoscopic ultrasonography has been increasingly used over the last several years as a new imaging modality. This study assessed the effectiveness of laparoscopic ultrasonography in detecting main biliary duct stones during laparoscopic cholecystectomy. MATERIAL AND METHODS: During the eight-year period 1991-98, 441 patients treated by laparoscopic cholecystectomy were at the same time included in laparoscopic ultrasonography. After port placement and dissection of the gallbladder, laparoscopic ultrasonography of the extrahepatic common bile duct was performed in the longitudinal plane. RESULTS: Laparoscopic ultrasonography failed to recognise the intrapancreatic part of the common bile duct in 64 cases (14%). The time used for sonography was approximately eight minutes. In this study, common bile duct stones were found in 29 cases (7%). One false negative result was recognised. INTERPRETATION: Laparoscopic ultrasonography is a safe, repeatable, noninvasive and cost-effective procedure, but a considerable learning curve is necessary in order to optimise its efficacy. Once learned, however, the method can be used as a primary screening procedure for bile duct calculi.

Adolescent↗

PubMed1992

Nursing care of a child following an arterial switch procedure for transposition of the great arteries.

The restoration of the left ventricle as the systemic pump and the lack of sinus node dysfunction (assessment with the Senning or Mustard procedure) have been suggested as the major advantages of the arterial switch procedure. Although the results are encouraging, children will require follow up to assess: long-term left ventricular function; coronary ostial growth; aortic and pulmonic anastomosis growth; long-term aortic valve (anatomical pulmonary valve) dysfunction. A learning curve is inherent to a new surgical procedure. During this learning period, both surgical technique and patient selection criteria improve, resulting in reduced morbidity and mortality. The arterial switch procedure for TGA is certainly not an exception. Expert nursing assessment and intervention during the postoperative period is imperative and may reflect on the long-term outcome of these children.

Cardiac Surgical Procedures↗

PubMed2005

Three-Dimensional (3D) Vision: Does It Improve Laparoscopic Skills? An Assessment of a 3D Head-Mounted Visualization System.

Laparoscopic urologic procedures have become increasingly popular, but their widespread use has been limited by training issues. The use of 3-dimensional (3D) vision might aid in training and performance of laparoscopic tasks. The purpose of this study was to evaluate a 3D visual system used by novice laparoscopists. In this prospective, randomized study, 24 novice laparos-copists were evaluated on a validated and standardized laparoscopic task using both 2-dimensional (2D) and 3D visualization systems. The task was performed more rapidly with 3D visualization (108 vs. 127 seconds, P < .05). On subjective evaluations, participants believed the task was easier with the 3D system, and participants preferred the 3D system to the 2D system by a 2:1 margin. 3D visualization improves the learning curve for laparoscopic surgery. Surgeons should consider 3D systems when learning complex laparoscopic surgeries. Further evaluation of operative times and complications is needed in clinical studies.

Journal Article↗

PubMed2000

Vital dye and radiolabelled colloids--complement or alternative?

Several different protocols for retrieval of the sentinel node (SN) have been described: gamma probe (GP) and/or dye guided biopsy, preceded by lymphoscintigraphy or not. Especially in American studies, predominantly executed by surgeons, dye or GP guidance only is used with good results. The disadvantages of applying dye only are: an extensive learning curve, lower retrieval rate of the SN and, especially in the learning phase, a higher rate of false negative biopsies. If only GP guidance is applied, the technique seems more simple to master. A recent multicentre study, however, revealed an unacceptably high false negative rate. It must be considered that most published studies were executed by highly experienced surgeons. In most European studies, scintigraphy is a standard part of the procedure. Lymphoscintigraphy provides the surgeon with a "road map", revealing the number and approximate location of the SNs in the lymphatic basin(s). Scintigraphy proves useful especially if an SN is situated close to the injection site (breast cancer), or if SNs are situated at unexpected locations (head-and-neck or trunk melanoma). A combination of all three available steps results in the highest number of successful procedures with the lowest false negative rate. This may prove to be especially important for general hospitals where the number of biopsy procedures is often smaller compared to specialized centres.

Axilla↗

PubMed1985

Short term changes of event related potentials during concept learning.

In a concept learning task, the time course of P3 amplitudes following the stimuli to be categorized was investigated. That time course did not coincide with the learning curve: it was not until the 4th to 6th trial after learning that P3 amplitudes grew larger. Some implications of this effect are discussed.

Adolescent↗

PubMed1999

Early experience with laparoscopic pelvic lymphadenectomy in women with gynecologic malignancy.

STUDY OBJECTIVES: To compare the results of laparoscopic pelvic lymphadenectomy with those of open lymphadenectomy; to assess differences in lymph node yield, operating time, and rate of positive nodes based on experience (early and late); and to evaluate the clinical course of laparoscopic lymphadenectomy. DESIGN: Retrospective case review (Canadian Task Force classification II-2). SETTING: University-affiliated hospital. PATIENTS: Sixty-one women with cervical cancer, one with vaginal cancer, and one with endometrial cancer. INTERVENTIONS: Laparoscopic lymphadenectomy followed by laparotomy or radical vaginal hysterectomy was performed in 19 women between 1994 and 1995, and radical abdominal hysterectomy with pelvic lymphadenectomy was performed in 44 women between 1993 and 1995. MEASUREMENTS AND MAIN RESULTS. Mean lymph node yields at laparoscopic pelvic lymphadenectomy were significantly increased in the group operated during the last 6 months compared with the first 6 months (16.2 +/- 6.8 vs 33.2 +/- 10. 5, p <0.05). After 6 months' experience, lymph node yields were 23.9 +/- 10.3 for laparoscopic lymphadenectomy followed by laparotomy and 23.2 +/- 10.2 for laparoscopic lymphadenectomy followed by radical vaginal hysterectomy (NS). The rate of positive lymph nodes was not significantly different between procedures, 16% and 14%, respectively. Operating time for laparoscopic lymphadenectomy was significantly shorter in the last 6 months (143 +/- 34 vs 78 +/- 18 min, p <0.05). Major complications of the procedure were injury to aberrant obturator and iliac veins in two cases in the early period. Average blood loss was 150 to 350 ml. Two women died due to disease recurrence at minimum of 2.5 years' follow-up; the others were alive without recurrence. CONCLUSION: Laparoscopic pelvic lymphadenectomy was feasible and safe, and did not compromise short-term survival. A learning curve was associated with the procedure, but after a period of learning, pelvic lymphadenectomy can be performed as effectively by laparoscopy as by laparotomy. (J Am Assoc Gynecol Laparosc 6(1):59-63, 1999)

Adult↗

PubMed1979

Age effect hearing levels for a white nonindustrial noise exposed population (ninep) and their use in evaluating industrial hearing conservation programs.

A nonindustrial noise exposed population (NINEP) describing age effects for white males and females has been established that can be used as a reference in evaluating an industrial noise exposed population (INEP) data base. In making this comparison, it is desirable to match the two populations properly with respect to sex, race and age characteristics. Since there presently does not exist an equivalent black NINEP, it is necessary to first isolate the data representing the black population from the industrial sample. A definite learning curve exists in industrial audiometric data bases, with the degree of learning dependent upon the effectiveness of the hearing conservation program. Therefore, this variation must be considered when attempting to compare the industrial audiometric test data with the white NINEP data base presented herein.

Adolescent↗

PubMed2004

Asymptotic properties of the Fisher kernel.

This letter analyzes the Fisher kernel from a statistical point of view. The Fisher kernel is a particularly interesting method for constructing a model of the posterior probability that makes intelligent use of unlabeled data (i.e., of the underlying data density). It is important to analyze and ultimately understand the statistical properties of the Fisher kernel. To this end, we first establish sufficient conditions that the constructed posterior model is realizable (i.e., it contains the true distribution). Realizability immediately leads to consistency results. Subsequently, we focus on an asymptotic analysis of the generalization error, which elucidates the learning curves of the Fisher kernel and how unlabeled data contribute to learning. We also point out that the squared or log loss is theoretically preferable-because both yield consistent estimators-to other losses such as the exponential loss, when a linear classifier is used together with the Fisher kernel. Therefore, this letter underlines that the Fisher kernel should be viewed not as a heuristics but as a powerful statistical tool with well-controlled statistical properties.

Algorithms↗

PubMed2007

Evaluation of an intelligent tutoring system in pathology: effects of external representation on performance gains, metacognition, and acceptance.

OBJECTIVE: Determine effects of computer-based tutoring on diagnostic performance gains, meta-cognition, and acceptance using two different problem representations. Describe impact of tutoring on spectrum of diagnostic skills required for task performance. Identify key features of student-tutor interaction contributing to learning gains. DESIGN: Prospective, between-subjects study, controlled for participant level of training. Resident physicians in two academic pathology programs spent four hours using one of two interfaces which differed mainly in external problem representation. The case-focused representation provided an open-learning environment in which students were free to explore evidence-hypothesis relationships within a case, but could not visualize the entire diagnostic space. The knowledge-focused representation provided an interactive representation of the entire diagnostic space, which more tightly constrained student actions. MEASUREMENTS: Metrics included results of pretest, post-test and retention-test for multiple choice and case diagnosis tests, ratios of performance to student reported certainty, results of participant survey, learning curves, and interaction behaviors during tutoring. RESULTS: Students had highly significant learning gains after one tutoring session. Learning was retained at one week. There were no differences between the two interfaces in learning gains on post-test or retention test. Only students in the knowledge-focused interface exhibited significant metacognitive gains from pretest to post-test and pretest to retention test. Students rated the knowledge-focused interface significantly higher than the case-focused interface. CONCLUSIONS: Cognitive tutoring is associated with improved diagnostic performance in a complex medical domain. The effect is retained at one-week post-training. Knowledge-focused external problem representation shows an advantage over case-focused representation for metacognitive effects and user acceptance.

Attitude to Computers↗

PubMed1994

Comparing models of rule-based classification learning: a replication and extension of Shepard, Hovland, and Jenkins (1961).

We partially replicate and extend Shepard, Hovland, and Jenkins's (1961) classic study of task difficulty for learning six fundamental types of rule-based categorization problems. Our main results mirrored those of Shepard et al., with the ordering of task difficulty being the same as in the original study. A much richer data set was collected, however, which enabled the generation of block-by-block learning curves suitable for quantitative fitting. Four current computational models of classification learning were fitted to the learning data: ALCOVE (Kruschke, 1992), the rational model (Anderson, 1991), the configural-cue model (Gluck & Bower, 1988b), and an extended version of the configural-cue model with dimensionalized, adaptive learning rate mechanisms. Although all of the models captured important qualitative aspects of the learning data, ALCOVE provided the best overall quantitative fit. The results suggest the need to incorporate some form of selective attention to dimensions in category-learning models based on stimulus generalization and cue conditioning.

Adult↗

PubMed1986

Evaluation of a cochlear prosthesis using connected discourse tracking.

A multichannel cochlear prosthesis was evaluated using the method of Connected Discourse Tracking. Data were obtained from five subjects over a 10-week period. Significant learning effects were obtained both with and without the prosthesis. The method of orthogonal polynomials was used to obtain a statistically precise fit for each learning curve. The curves differed both in terms of shape and average rate of learning. The two best subjects showed substantial improvements, reaching tracking rates in excess of 90 words-per-minute. A method for representing prosthesis-based improvements, which takes learning effects into account, is developed and discussed.

Analysis of Variance↗

PubMedDate not supplied

[Neurosheet: an electronic sheet for neurosurgical intensive care].

PURPOSE: A growing number of monitoring and diagnostic instruments has considerably increased the amount of information available in the intensive care unit. A data collection system which can be useful in highlighting and processing the most relevant data for the care of head-injured patients (Neurosheet) has been set up. The purpose of this study is to describe Neurosheet and to analyse the results achieved through its use. ENVIRONMENT: Neurosurgical Intensive Care Unit. METHODS: Neurosheet consists of a data sheet which follows the course of some "key" variables in head-injured patients who undergo ICP monitoring for a period of more than 48 hours. SURVEY: Through a questionnaire distributed to the medical staff, the learning period and the opinion of the staff concerning the clinical usefulness of this instrument has been evaluated. The amount of time needed to compile Neurosheet has been measured and some criteria indicating its completeness identified. RESULTS: It has been found that Neurosheet can be learned quickly and is rather easy to use. Data resulting from the study of the learning curve and from the answers to the questionnaire, suggest that its learning period is quite short (10 to 20 minutes). Among the 28 eligible patients, Neurosheet was used for 24 (86%). The data collected show 1,912 hours of monitoring, with an average of 112.8 (+/- 55) hours per patient. Neurosheet was completed in 83% of the cases. CONCLUSIONS: The aim of Neurosheet is to provide an answer to the overload of information using computerised systems able to simplify and support the daily clinical work.

Critical Care↗

PubMedDate not supplied

Lead inhibits acquisition and retention learning in bullfrog tadpoles.

Bullfrog, Rana catesbeiana, tadpoles were exposed to 0, 500, 625, 750 or 100 micrograms Pb/L as lead nitrate, and subjected to learning and retention tests. Tadpoles used in learning acquisition tests were exposed for six days (144 hours) and tadpoles used in retention tests were exposed for five days (120 hours). All tadpoles were conditioned, using shock avoidance, to associate illumination (conditioned stimulus) with shock (unconditioned stimulus). The mean latency to respond, the number of avoidances, and the differences in learning curves of the lead-exposed and control tadpoles were compared statistically. Learning acquisition tests showed increased latencies and fewer avoidances in lead-exposed as compared to control tadpoles. Retention tests showed increased latencies and fewer avoidances in tadpoles exposed to 625, 750 and 1000 micrograms Pb/L as compared to controls.

Absorption↗