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PubMed2001

Interactive navigation system for shock wave applications.

The latest generation of shock wave lithotripters, with therapy heads mounted on articulated arms, have found widespread application in the treatment of orthopedic diseases. Currently, integration of an ultrasound probe in the therapy head is the dominant modality for positioning the shock wave focus on the treatment area. For orthopedic applications, however, X-ray imaging is often preferred. This article describes a new method to locate the therapy head of a lithotripter. In the first step, the surgeon positions the tissue to be treated at the isocenter of a C-arc. This is achieved using AP and 30-degree lateral projections, with corresponding horizontal and vertical movements of the patient under fluoroscopic guidance. These movements register the anatomic location in the coordinate system of the C-arc. In the second step, the therapy head is navigated to align the shock wave focus with the isocenter. Position data are reported from an optical tracker mounted on the X-ray system, which tracks an array of infrared LEDs on the therapy head. The accuracy of the tracking system was determined on a test bench, and was calculated to be 1.55 mm (RMS) for an angular movement of +/-15 degrees around a calibrated position. Free-hand navigation and precise alignment are performed with a single virtual reality display. The display is calculated by a computer system in real time, and uses graphical symbols to represent the shock wave path and isocenter. In an interactive process, the physician observes the display while navigating the therapy head towards the isocenter. Precise alignment is achieved by displaying an enlarged view of the intersecting graphical symbols. Results from the first tests on 100 patients demonstrate the feasibility of this approach in a clinical environment.

Computer Simulation↗
PubMed1988

[Assessment of motivation for achievement in connection with rehabilitation measures].

Reported are the results obtained in assessing young brain-injured patients of a rehabilitation hospital (N = 39, male subjects). "Vocational therapists" had evaluated the patients relative to achievement and achievement motivation variables, and results of routine performance testing had also been available. The KEMB (Konstanzer Erfolgs-Misserfolgs-Batterie--Constancy success-failure battery) was administered in addition. Vocational therapists' ratings and KEMB findings permit the conclusion that the less severely disabled patients tend to hold unrealistically high objectives. Whereas results were found to be consistent in this patient group even across the different methods used for evaluating achievement motivation variables, this did not apply to the more severely disabled subjects. For this latter group, the KEMB achievement motivation findings show hardly any relation with the achievement motivation ratings given, but, rather, with specific performance tests used in organic brain damage and with duration of the condition. It seems that achievement motivation can in the less severely disabled subjects be understood in its usual sense; those with more severe disability on the other hand seem to strongly orientate their motivation on the specific deficits associated with the organic brain damage, thus arriving at possibly more reality-adjusted objectives. KEMB and progress in general performance within the rehabilitation programme--especially in the more severely disabled patients--are found to correlate much closer then is the case for the various performance tests administered routinely for outcome prediction.

Achievement↗
PubMed2005

Cyber visual training as a new method for the mastery of endoscopic surgery.

BACKGROUND: We devised a new method incorporating cyber visual training whereby novices in endoscopic surgery are instructed via repetition of a video-recorded procedure. We then conducted a study designed to investigate the impact of this cyber visual training on the mastery of intracorporeal knot-tying as an endoscopic technique. METHODS: For the cyber visual training a 10-min video of the same procedure was replayed at normal, slow, and rapid speeds or presented in a series of still images. The training was undertaken by 36 medical students and 1st year trainee doctors who had had no experience of endoscopic surgery. They were divided into three groups, each of all received the same introductory lecture. Group A was only given training with the instructor for 15 min. Group B trained with the instructor for 15 min and was allowed self-training for 10 min. Group C viewed the cyber video beforehand and then underwent training with the instructor for 15 min. For all participants, the time required to complete a knot-tying task was measured and the level of endoscopic skill before and after the training was assessed using a virtual reality system the minimally Invasive Surgical Trainer-Virtual Reality (MIST-VR), in terms of the following three parameters: time, errors, and efficiency of hand movements. The Steel-Dwass test was used to evaluate the differences among the three groups in task performance. RESULTS: Group C completed the knot-tying task faster than group A (p = 0.0375), but there were significant differences between groups A and B and groups B and C. There were no significant differences in the parameters assessed using the MIST-VR. CONCLUSIONS: Our new concept of cyber visual training is effective for mastering the knot-tying technique. This type of training should be widely applicable to other procedures, such as dissection, clipping, and hemostasis.

Adult↗
PubMed2005

Molecularly targeted therapies for breast cancer.

BACKGROUND: The management of patients with localized and advanced breast cancer continues to evolve. Chemotherapy, endocrine therapy, and trastuzumab are effective therapies but leave considerable room for improvement. As the cellular aberrations inherent to cancer cells in general and breast cancer cells specifically are better understood, therapies to target specific cellular pathways continue to be developed with the goal of expanding available effective therapy through better patient selection. METHODS: We conducted a computerized search of the medical literature as well as a manual search of selected meeting abstracts. RESULTS: Several targeted therapies are in phase III clinical trials testing their promise in the treatment of breast cancer. Many other agents are completing phase I and II testing. An overview of the most promising agents in clinical development is discussed herein. CONCLUSIONS: Targeted therapy for breast cancer is a reality at this time, and several new agents hold promise for expanding and refining the pool of patients likely to further benefit from this approach in the near future.

Antibodies, Monoclonal↗
PubMed2006

Alteration of postural responses to visual field motion in mild traumatic brain injury.

OBJECTIVE: Balance deficits in individuals experiencing mild traumatic brain injury have been documented in numerous recent studies. However, long-lasting balance deficits and specific mechanisms causing these deficits have not been systematically examined. This article aimed to present empirical evidence showing destabilizing effects of visual field motion in concussed individuals up to 30 days postinjury. METHODS: Sixty student athletes participated in the pilot (n = 12) and major experiments (n = 48) before injury. Eight of these 48 subjects who experienced mild traumatic brain injury in athletic events were tested again on Days 3, 10, and 30 after the incident. Postural responses to visual field motion were recorded using a virtual reality environment in conjunction with balance (AMTI force plate) and motion tracking (Flock of Birds) technologies. RESULTS: The area of the center of pressure during upright stance did not change from Day 3 to 30 postinjury with respect to pre-injury status (P > .05). However, balance deficits induced by visual field motion were present up to 30 days postinjury. Destabilizing effect of visual field motion was observed via significant increase of the center of pressure data (P < .05) and reduced coherence value. CONCLUSION: Our data suggest the presence of residual sensory integration dysfunction in concussed individuals at least 30 days postinjury and may indicate a lower threshold for brain reinjury.

Adult↗
PubMed2006

Assessment of individual and combined toxicities of four non-essential metals (As, Cd, Hg and Pb) in the microtox assay.

Although most researches with non-essential metals (NEMs) have been done with single or individual metals, in reality, organisms are often exposed to multiple contaminants at the same time through the air, food and water. In this study, we tested the toxicity of four NEMs, As, Cd, Pb, and Hg, individually and as a composite mixture using the microtox bioassay. This assay uses the reduction of bioluminescence of the bacterium Vibrio fischeri as a measure of toxicity. The concentrations of each chemical in the mixture were based on multiples of their maximum contaminant levels (MCLs) set by the U.S. EPA. The highest concentration of exposure was 20 times the MCL, which translated into 200, 100, 40 and 300 ppb for As, Cd, Hg and Pb, respectively. The ratio for the mixture from these concentrations was 10:5:2:15 for As, Cd, Hg and Pb, respectively. Among the individual metals tested, the ranking of toxicity was Hg>Pb>Cd>As based on the EC50 values of 109, 455, 508 and 768 ppb for Hg, Pb, Cd and As, respectively. The EC50 for the composite mixture was 495% MCL which translated into nominal concentrations of 49, 25, 10 and 74 ppb for As, Cd, Hg, and Pb, respectively. Overall, the EC50 value of each NEM within the mixture was lower than the EC50 of the individual chemical; an evidence of synergism for the mixture. The individual toxic units (TU) were 0.06, 0.05, 0.09, and 0.16 for As, Cd Hg, and Pb, respectively and the summed toxic unit (TU) was 0.37 (less than 1). This study provides needed scientific data necessary for carrying out complete risk assessment of As, Cd, Hg, and Pb mixtures of some priority compounds.

Aliivibrio fischeri↗
PubMed2004

Medical packaging: towards global harmony.

The goal of one uniform set of rules that can be interpreted and applied to all medical device packages, wherever they are produced or utilised, is closer to becoming reality. Just a few more operational steps are required for completion. The shape of the future as well as current and future test methods are outlined.

Equipment Contamination↗
PubMed1990

Importance of a neurologic evaluation in women with lower urinary tract dysfunction.

The normal coordinated functions of the bladder and urethra are controlled by a set of central and peripheral reflex mechanisms. Disruptions of these neuronal reflexes may produce abnormalities in the storage and expulsion of urine. Electrophysiologic testing can be employed to complement other urodynamic tests used in the evaluation of these patients and also to document that abnormalities previously thought to be anatomic in origin in reality may be secondary to neurologic dysfunction.

Electroencephalography↗
PubMed1982

Wear-screening and joint simulation studies vs. materials selection and prosthesis design.

Satisfactory friction and wear performance of orthomedic biomaterials is an essential criterion for both hemiarthroplasty and total joint replacements. This report will chart the clinical historical experience of candidate biomaterials with their wear resistance and compare/contrast these data to experimental test predictions. The latter review will encompass publications dealing with both joint simulators and the more basic friction and wear screening devices. Special consideration will be given to the adequacy of the test protocol, the design of the experimental machines, and the accuracy of the measurement techniques. The discussion will then center on clinical reality vs. experimental adequacy and summarize current developments.

Bone and Bones↗
PubMed2001

[Beta risk: an unrecognized risk of statistical error].

Data collected in a medical study should, from a methodological point of view, be considered as a sample taken from a larger population. The purpose of the statistical analysis is to check whether the differences in the experimental results observed in different subgroups are related to chance or not. The risks of error must be known to assess the validity of the conclusions. The first order risk, also called the alpha risk, is the risk of announcing a wrongly positive conclusion, that is to conclude that there is a significant difference that in reality does not exist. By convention, an alpha risk of 5 p. 100 is generally accepted. This means that it is acceptable to announce a statistically positive test when no difference exists in at most 5 p. 100 of the cases. After recording and processing the data, the statistical analysis produces a value called p that is the exact value of the first order risk in the given situation. If p is less than or equal to the alpha risk accepted before the study, it can be concluded that the observed difference is statistically significant at the chosen alpha level and that the p value represents the risk of first order risk in the given situation. If p is greater than the initially accepted alpha, the observed difference is not considered to be significant at the alpha level. But the assertion that two samples are equivalent, also involves a second order risk, also called the beta risk, that must be known. The beta risk is the risk of announcing wrongly negative results, that is to conclude that two samples are equivalent while in reality they are different. The number of elements in each sample necessary to demonstrate a difference becomes greater as the size of the difference becomes smaller. The beta risk increases as the alpha risk decreases, the number of cases becomes smaller, and the difference to detect becomes smaller. If a difference is not statistically significant at the chosen alpha level, the beta risk of an erroneous conclusion of equivalence is generally less than or equal to 20 p. 100. In most cases, the beta risk is not determined before the study but after, being calculated from the alpha risk, the sample size, and the non-significant difference observed. If the beta risk is found to be greater than 20 p. 100, no conclusion can be drawn and the study data are useless. It is therefore preferable to define both the alpha and beta risk and the smallest clinically pertinent difference, and to calculate the necessary sample size, before initiating the study. Let us take a numerical example where two different treatments, A and B, are given to two groups of 100 patients each. Treatment A produced success in 70 cases and treatment B in 80 cases. The chi-squared test yields a p value of 0.10. The observed difference is thus not statistically significant at an alpha level of 5 p. 100. In this case, the calculated beta risk is 54 p. 100. With 200 patients and a beta risk of 20 p. 100, a difference of 20 p. 100 in the success rates between the two groups cannot be detected. If it is accepted that a difference of 10 p. 100 between the success rates is clinically pertinent, to have an acceptable beta risk of 20 p. 100 and detect the difference, the study would have to include 500 patients instead of 200. In conclusion, when a comparative study concludes that there is no significant difference between two groups, one cannot deduct that these two groups are identical unless the beta risk is less than 20 p. 100. If the beta risk is greater than 20 p. 100, or if it is not mentioned, one cannot conclude that the two groups are equivalent.

Bias↗
PubMed2002

Performance of a Brazilian population sample in the Boston Diagnostic Aphasia Examination: a pilot study.

Brazilian researchers and health professionals often face the challenge of having to use tests developed in foreign languages and standardized for populations of other countries, especially in the fields of Neuropsychology and Neurolinguistics. This fact promotes a feeling that some scoring systems may be inadequate for our sociocultural reality. In the present study, we describe the performance of a Brazilian population sample submitted to a translated and adapted version of the Boston Diagnostic Aphasia Examination (BDAE). Sixty normal volunteers (21 men and 39 women), all Portuguese native speakers, ranging in age from 15 to 78 years (average 43.7) and with an educational level of 2 to 16 years (average 9.9), were tested using a translated and adapted Portuguese version of the BDAE. Cut-off scores are suggested for our population and the performance of the Brazilian sample is compared to that of American and Colombian samples, with the results being closely similar in all tasks. We also performed a correlation analysis between age, gender and educational level and the influence of these variables on the performance of the subjects. We found no statistically significant differences between genders. Educational level correlated positively with performance, especially in the subtests involving reading and writing. There was a negative correlation between age and performance in two subtests (Visual Confrontation Naming and Sentences to Dictation), but a coexisting effect of educational level could not be ruled out.

Achievement↗
PubMed1993

Simulation study of methods to detect periodontal associations when they are inconsistent among subjects.

Most statistical methods used to evaluate associations between indices of clinical periodontal diseases and purported prognostic markers test for effects across subjects. If associations exist within only a subset of subjects, however, associations may be masked, particularly in small studies. This issue was explored by using simulation to study four methods for detecting periodontal associations. Built into the simulations was the possible biological reality that a non-zero association between the two variables of interest (squared correlation coefficients, rho 2, ranged from 0.1 to 0.9 depending on simulation), measured at 16 sites per subject, did not exist in all of 10 hypothetical subjects. The four methods for testing the null hypothesis that rho = 0, or a related hypothesis; were: (1) Sites, analysis based on 160 sites incorrectly considered independent observations; (2) Subjects, analysis based on one score for each of 10 subjects; (3) Each subject, separate analyses based on sites within each of 10 subjects, family-wise type I (alpha) error corrected for multiplicity, and (4) the Each Subject method where P-levels were estimated using permutation procedures rather than t-distributions. Each Subject methods were found to have greater relative power (although there are differences in null hypotheses) under conditions of heterogeneity in rho and are considered to be particularly relevant in exploratory periodontal research when the primary interest is establishing the existence of a relationship, even if in only a subset of subjects.

Biomarkers↗