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At least 793 records · Page 44Linked to original sources
PubMed1999

Electrical defibrillation: new technologies.

Two-thirds of deaths from coronary disease occur in the pre-hospital phase and are caused by ventricular fibrillation or pulseless ventricular tachycardia, for which electrical defibrillation is the only effective treatment. The time delay between the onset of ventricular fibrillation and the administration of the first defibrillatory shock is the most important determinant for survival. To achieve the earliest defibrillation possible, rescuers others than physicians need to be able to initiate this treatment. The international scientific community strongly supports the concept of early defibrillation in the setting of a strong chain of survival. New technological developments of automated external defibrillators (AEDs) allowed the implementation of defibrillation by the first responding professional rescuer. As a consequence of the technological evolution in implantable defibrillators, much research has also been done on new defibrillation waveforms and alternative energy levels in external defibrillators. After initial animal research, human clinical investigation has shown that initial low energy (150J) nonprogressive (150J-150J-150J) impedance-adjusted biphasic waveform defibrillatory shocks for patients in out-of-hospital ventricular fibrillation are safe, acceptable and clinically effective. Reporting on outcome from cardiac arrest must be as uniform as possible to allow conclusions on performance of emergency medical service systems. The 'Utstein Style' nomenclature is a glossary of terms and a reporting guideline for uniform description of cardiac arrest, resuscitation, the emergency medical service (EMS) system and the outcome. Reports on experiences with AED programmes by traditional and non-traditional professional rescuers support the view that AEDs should not be implemented in EMS systems as an isolated intervention, but that efforts are equally needed to strengthen the other links of the chain of survival. The international scientific community (American Heart Association, International Liaison Committee on Resuscitation and European Resuscitation Council) have issued guidelines for the use of AEDs by EMS providers and first responders, and a universal treatment algorithm is proposed.

Journal Article↗
PubMed2000

Fast iterative algorithm for metal artifact reduction in X-ray CT.

RATIONALE AND OBJECTIVES: The reduction of metal artifacts in x-ray computed tomography (CT) has important clinical applications. An iterative method adapted from the expectation maximization (EM) formula for emission CT was shown to be effective for metal artifact reduction, but its computational speed is slow. The goal of this project was to accelerate that iterative method for metal artifact reduction. MATERIALS AND METHODS: Using the row-action/ordered-subset (EM) formula for emission CT as a basis, the authors developed a fast iterative algorithm for metal artifact reduction. In each iteration of this algorithm, both reprojection from an intermediate image and backprojection from discrepancy data are performed. RESULTS: The feasibility of the fast iterative algorithm was demonstrated in numerical and phantom experiments. In comparison with the nonaccelerated iterative algorithm, the speed of iterative metal artifact reduction is improved by an order of magnitude given image quality in terms of visual inspection, I-divergence in the projection domain, and the euclidean distance in the image domain. CONCLUSION: The fast iterative algorithm corrects intermediate reconstruction according to subsets of projections and produces satisfactory image quality at a much faster speed than the previously published iterative algorithm. This algorithm has important potential in clinical applications, such as orthopedic, oncologic, and dental imaging.

Algorithms↗
PubMed2001

Validation of exposure estimation for benzene in the Australian petroleum industry.

A nested case-control study was undertaken to investigate whether an excess of lympho-haematopoietic cancers in the Australian petroleum industry was associated with benzene exposure. The benzene exposures of the cases and controls were estimated using a quantitative algorithm based largely on exposures measured in the Australian petroleum industry. The algorithm was used to estimate, for each subject, the benzene exposure in parts per million (ppm) for each job held in the industry, and the cumulative exposure in ppm years. Because of the critical importance of the exposure assessment in this design of epidemiological study, particular attention was paid to the reliability of the inputs to the algorithm. The inputs [base estimates (BEs) of exposure and technology-specific exposure modifiers (EMs)] were compared to data from other sources including the occupational hygiene literature. Where such comparison data were available, they were generally found to confirm the values used in the algorithm, although four input values were changed as a result of the validation exercise. The integrity of the task-based algorithm was validated by employing it to calculate the exposures of the tanker drivers in the study and comparing these with measured daily exposure for tanker drivers in the Australian petroleum industry and exposure values found in the occupational hygiene literature. After adjustment for the mix of products carried by the Australian tanker drivers, the estimates from the algorithm were found to be comparable to the measured and literature values. This exercise provided evidence that the exposure assessment for the epidemiological study was reliable and that the results of the study can be used as the basis for evaluating the relationship between exposure to benzene and the risk of lympho-haematopoietic cancer.

Algorithms↗
PubMed2004

Modified polytopic vector analysis to identify and quantify a dioxin dechlorination signature in sediments. 2. Application to the Passaic River.

Persistent contaminants such as dioxins have been documented to undergo dechlorination reactions in the laboratory; however, little is known about the importance of these reactions in the field. Polytopic vector analysis (PVA) is a statistical pattern recognition technique for multivariate data traditionally used to identify fingerprints of contaminant sources. A modified PVA algorithm with uncertainty analysis was used to model dechlorination fingerprints and sources. The technique was applied to 351 sediment core-derived dioxin samples from the lower reach of the Passaic River, New Jersey. A dechlorination fingerprint was identified with a highly positive 2,3,7,8-tetraCDD component and a highly negative heptaCDD component. The most important industrial source of 2,3,7,8-tetraCDD is a fingerprint related to 2,4,5-trichlorophenoxyacetic acid production. The dechlorination contribution to the data variance is 3.00 +/- 1.00%, corresponding to an average of 1.2 microg/kg of 2,3,7,8-tetraCDD per sample at the expense of heptaCDD. The possible occurrence of dechlorination was validated by comparing the local dechlorination contribution in the results to the value of the ratio 2,3,7,8-tetraCDD/total 2,3,7,8-PCDD, which indicates dechlorination in the laboratory. Bootstrap uncertainty analysis yielded the same dechlorination EM in 40% of the realizations. The results indicated that bootstrapping is an important statistical tool to quantify uncertainties with respect to the dechlorination EM and some of the source EMs.

Algorithms↗
PubMedDate not supplied

Automated software package for icosahedral virus reconstruction.

The three-dimensional reconstruction of icosahedral viruses from electron micrograph images has become an important tool for understanding virus structure, function, and pathogenesis. We have developed an integrated suite of software programs to automate most of the operations involved in producing these reconstructions from EM images. Our package combines the analytical capabilities of preexisting algorithms together with approaches we have developed to produce an interactive working environment which enhances the efficiency and usefulness of this approach to the structural analysis of icosahedral viruses.

Algorithms↗
PubMed1994

The role of the dispatch centre in preclinical emergency medicine.

Failure to recognise the importance of the dispatch centre in emergency medical services (EMS) limits standards and procedures in prehospital emergency medicine. The dispatch centre should be identified as the point of leadership and management of the entire system. Measures for quality control and quality assurance should be an integral part of EMS administration. Minimum requirements for equipment and personnel depend on EMS structure and on geographic and epidemiological factors. Clearly defined algorithms for decision-making and computer-assisted dispatching can increase efficiency and reduce costs.

Decision Making↗
PubMedDate not supplied

[Magnetic resonance imaging in the diagnosis of different forms of endometriosis].

The present paper examines the capacities of non-invasive MRI in the diagnosis of endometriosis. A standardized study algorithm is proposed, indications and methodology for MRI in different forms of endometriosis (EM) are specified. It is shown that in the diagnosis of different types of EM there are specific changes in the MR pattern of small pelvic organs, which allow one to make a differential diagnosis of this disease with a higher sensitivity (96%) and specificity (87%) as compared with ultrasound study. MRI makes it possible to assess the degree of invasion of endometrioid heterotopies into the wall of the intestine and cervix uteri with a high degree of accuracy and to judge the degree and extent of intestinal luminal narrowing. Diagnostic errors in solving these problems (as well as those associated with the detection of extragenital foci of EM in the small pelvis) are due first of all to movement artefacts a (respiration and intestinal motility) particularly in the presence of a significant adhesive process and/or after surgical intervention. MRI does not virtually yield false-negative conclusions in the diagnosis of different forms of genital endometriosis (less than 3%), which, in the authors' opinion, rather justifies some hyperdiagnosis (about 11%) made by this method in the diagnosis of endometriosis of the rectovaginal septum. MRI is a closing, specifying stage of instrumental diagnosis of not only EM, but also other small pelvic diseases.

Adult↗
PubMed1994

Evaluation of task-oriented performance of several fully 3D PET reconstruction algorithms.

The relative performance of five fully 3D PET reconstruction algorithms is evaluated. The algorithms are a filtered backprojection (FBP) method and two variants each of the EM-ML and ART iterative methods. For each of the iterative methods, one variant makes use of voxels and the other makes use of 'blobs' (spherically symmetric functions smoothly decaying to zero at their boundaries) as basis functions in its discrete reconstruction model. The methods are evaluated from the point of view of the efficacy of the reconstructions produced by them for three typical medical tasks--estimation of the average activity inside specific regions of interest, detection of hot spots, and detection of cold spots. A free parameter is allowed in the description of each of the five algorithms; the parameters are determined by a training process during which a value of the free parameter is selected which (nearly) maximizes a technical figure of merit. Such training and the actual comparative evaluation is done by making use of randomly generated phantoms and their projection data. The methodology allows assignation of levels of statistical significance to claims of the relative superiority of one algorithm over another for a particular task. We find that using blobs as basis functions in the iterative algorithms is definitely advantageous over using voxels. This result has high statistical significance. (We also include a visual illustration of it.) Comparing FBP, EM-ML using blobs, and ART using blobs, we do not find a clear difference in the overall performance of the investigated variants of the methods. If anything, our results suggest that ART using blobs may be the most efficacious of the three.

Algorithms↗
PubMed2005

Feasibility of early emergency room notification to improve door-to-balloon times for patients with acute ST segment elevation myocardial infarction.

An algorithm to lower time from first contact in the field by EMS personnel to in-hospital mechanical reperfusion is described. ECG tracings were telemetered via cellular phone to an emergency room physician, who then activated the cardiac catheterization call team to bypass usual delays seen during ER triage. Seventy-one ECGs were sent to the ER in the time interval from October 2003 to October 2004. Five ECGs (7.0%) failed to transmit due to failure of the cellular phone to receive an adequate signal. Sixty-six patients (93.0%) had an adequate ECG transmitted to the ER and six patients with ST elevation myocardial infarction were identified. Door-to-balloon times were lowered to 44 +/- 17.4 min, a substantial decrease over historical norms that range from 120 min (25th percentile) to 289 min (75th percentile).

Angioplasty, Balloon, Coronary↗
PubMed1995

Management of immediate allergic reactions.

Allergic and pseudoallergic reactions can be associated with all drug classes used in dental practice. A thorough medical history is essential to avoid challenging a patient with an agent for which they have proven intolerance. Despite this precaution, the dentist must be prepared to manage an immediate reaction, should it occur. In all cases, management should begin with standard ABC assessment and oxygen supplementation. The administration of either diphenhydramine or epinephrine is predicated on the severity of the reaction. Suggestions regarding dosages and routes of administration are summarized in Table 4. The duration of action for epinephrine is relatively brief (10 to 30 minutes), and dosages may need to be repeated if symptoms recur. Following stabilization, patients who have experienced anaphylactoid reactions should be transported by EMS to the closest emergency room for definitive management. A treatment algorithm summarizing management of allergic reactions is presented in Figure 1.

Adrenergic Agonists↗
PubMed2006

Direct comparison of kinematic data collected using an electromagnetic tracking system versus a digital optical system.

The purpose of this study was to quantify the dynamic accuracy of kinematics measured by a digital optical motion analysis system in a gait analysis laboratory (capture volume approximately 20m(3)) compared to a standard range direct-current electromagnetic (EM) tracking device (capture volume approximately 1m(3)). This is a subset of a larger effort to establish an appropriate marker set for the optical system to quantify upperlimb kinematics simultaneously with gait, in comparison to previous studies of isolated upperlimb movements that have employed EM tracking devices. Rigid clusters of spherical reflective markers and EM sensors were attached to a mechanical articulator that mimicked three-dimensional joint rotations, similar to the elbow. As the articulator was moved through known ranges of motion (i.e. gold standard), kinematic data were collected simultaneously using both tracking systems. Both systems were tended to underestimate the range of motion; however, the application of post hoc smoothing and least-squares correction algorithms reduced these effects. When smoothing and correction algorithms were used, the magnitude of the mean difference between the gold standard and either the EM or optical system did not exceed 2 degrees for any of the compound motions performed. This level of agreement suggests that the measurements obtained from either system are clinically comparable, provided appropriate smoothing and correction algorithms are employed.

Algorithms↗
PubMed2005

Evaluation of the ordered subset convex algorithm for cone-beam CT.

Statistical methods for image reconstruction such as maximum likelihood expectation maximization (ML-EM) are more robust and flexible than analytical inversion methods and allow for accurate modelling of the photon transport and noise. Statistical reconstruction is prohibitively slow when applied to clinical x-ray cone-beam CT due to the large data sets and the high number of iterations required for reconstructing high resolution images. One way to reduce the reconstruction time is to use ordered subsets of projections during the iterations, which has been successfully applied to fan-beam x-ray CT. In this paper, we quantitatively analyse the use of ordered subsets in concert with the convex algorithm for cone-beam x-ray CT reconstruction, for the case of circular acquisition orbits. We focus on the reconstructed image accuracy of a 3D head phantom. Acceleration factors larger than 300 were obtained with errors smaller than 1%, with the preservation of signal-to-noise ratio. Pushing the acceleration factor towards 600 by using an increasing number of subsets increases the reconstruction error up to 5% and significantly increases noise. The results indicate that the use of ordered subsets can be extremely useful for cone-beam x-ray CT.

Algorithms↗
PubMed1995

String editing analysis of human visual search.

Eye movement (EM) data were recorded for human subjects performing a visual search task in a stereoscopic computer-generated three-dimensional scene. Each experimental run consisted of six presentations: three different object placements on a common background (quasi-natural scene) were used and one of the placements was repeated three additional times. Raw EM searchpath data were linearized, fixation points were defined via a fixation algorithm and, finally, strings of fixation region labels were obtained based upon a priori regionalization schemes. Use of string editing techniques allowed quantitative comparison of the similarity of various searchpaths. Analysis of the similarity of searchpaths for each subject, as well as across subjects, led us to conclude that presentation of repeated object placements caused each subject to develop a partly self-consistent, but idiosyncratic searchpath based upon a spatial model for that placement pattern.

Algorithms↗
PubMed1998

Parametric image reconstruction using spectral analysis of PET projection data.

Spectral analysis is a general modelling approach that enables calculation of parametric images from reconstructed tracer kinetic data independent of an assumed compartmental structure. We investigated the validity of applying spectral analysis directly to projection data motivated by the advantages that: (i) the number of reconstructions is reduced by an order of magnitude and (ii) iterative reconstruction becomes practical which may improve signal-to-noise ratio (SNR). A dynamic software phantom with typical 2-[11C]thymidine kinetics was used to compare projection-based and image-based methods and to assess bias-variance trade-offs using iterative expectation maximization (EM) reconstruction. We found that the two approaches are not exactly equivalent due to properties of the non-negative least-squares algorithm. However, the differences are small (< 5%) and mainly affect parameters related to early and late time points on the impulse response function (K1 and, to a lesser extent, VD). The optimal number of EM iteration was 15-30 with up to a two-fold improvement in SNR over filtered back projection. We conclude that projection-based spectral analysis with EM reconstruction yields accurate parametric images with high SNR and has potential application to a wide range of positron emission tomography ligands.

Algorithms↗
PubMed2006

Nonrigid 2-D/3-D registration for patient specific bronchoscopy simulation with statistical shape modeling: phantom validation.

This paper presents a nonrigid registration two-dimensional/three-dimensional (2-D/3-D) framework and its phantom validation for subject-specific bronchoscope simulation. The method exploits the recent development of five degrees-of-freedom miniaturized catheter tip electromagnetic trackers such that the position and orientation of the bronchoscope can be accurately determined. This allows the effective recovery of unknown camera rotation and airway deformation, which is modelled by an active shape model (ASM). ASM captures the intrinsic variability of the tracheo-bronchial tree during breathing and it is specific to the class of motion it represents. The method reduces the number of parameters that control the deformation, and thus greatly simplifies the optimisation procedure. Subsequently, pq-based registration is performed to recover both the camera pose and parameters of the ASM. Detailed assessment of the algorithm is performed on a deformable airway phantom, with the ground truth data being provided by an additional six degrees-of-freedom electromagnetic (EM) tracker to monitor the level of simulated respiratory motion.

Algorithms↗
PubMed2003

On the evaluation and optimization of protein X-ray structures for pKa calculations.

The calculation of the physical properties of a protein from its X-ray structure is of importance in virtually every aspect of modern biology. Although computational algorithms have been developed for calculating everything from the dynamics of a protein to its binding specificity, only limited information is available on the ability of these methods to give accurate results when used with a particular X-ray structure. We examine the ability of a pKa calculation algorithm to predict the proton-donating residue in the catalytic mechanism of hen egg white lysozyme. We examine the correlation between the ability of the pKa calculation method to obtain the correct result and the overall characteristics of 41 X-ray structures such as crystallization conditions, resolution, and the output of structure validation software. We furthermore examine the ability of energy minimizations (EM), molecular dynamics (MD) simulations, and structure-perturbation methods to optimize the X-ray structures such that these give correct results with the pKa calculation algorithm. We propose a set of criteria for identifying the proton donor in a catalytic mechanism, and demonstrate that the application of these criteria give highly accurate prediction results when using unmodified X-ray structures. More specifically, we are able to successfully identify the proton donor in 85% of the X-ray structures when excluding structures with crystal contacts near the active site. Neither the use of the overall characteristics of the X-ray structures nor the optimization of the structure by EM, MD, or other methods improves the results of the pKa calculation algorithm. We discuss these results and their implications for the design of structure-based energy calculation algorithms in general.

Algorithms↗
PubMed2005

The role of histological examination for prognostic evaluation and therapeutic algorithm in urinary bladder tumors.

Pathological examination plays a major role in order to determine the prognostic and therapy of patients with urinary bladder tumors after a prior transurethral resection. The prognostic factors are studied to identify the risk of recurrence and tumoral progression of patients with superficial urothelial tumors and for appreciate the metastatic potential and response to therapy for patients with invasive carcinoma.

Algorithms↗