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PubMed2002

Appraisal of "Mahaim" automatic tachycardia.

A series of four patients with right-sided accessory pathways with long conducting times and decremental properties is reported. All patients underwent radiofrequency catheter ablation, and target areas were guided by a discrete "Mahaim" potential recorded at the lateral aspect of the tricuspid valve. A slow automatic and irregular rhythm with a QRS morphology similar to that of a fully preexcited QRS complex occurred during radiofrequency current delivery. The occurrence of so-called "Mahaim" automatic tachycardia heralded successful elimination of the accessory pathway in a manner similar to that of junctional automatic rhythm during slow pathway ablation in patients with AV nodal reentrant tachycardia. The observation of an automatic rhythm brought about during radiofrequency current ablation of a Mahaim-like accessory pathway is electrophysiologic evidence of the accessory AV nodal behavior of this structure.

Adolescent↗
PubMed2003

[Automatic classification of liver segments according to Couinaud: development of a new algorithm and evaluation spiral CT data].

PURPOSE: To develop a software tool that analyzes the anatomy of the portal vein branches and assigns segmental and subsegmental branches according to Couinaud's classification system and to evaluate its accuracy. MATERIALS AND METHODS: The algorithm was developed in C++ on a PC. The algorithm recognizes the three major branching patterns of the portal vein. Segmental and subsegmental branches are assigned to 8 segments following Couinaud and encoded by 8 colors. The software was evaluated using CT data sets of 39 patients. After the individual segmental anatomy of each patient was determined by an experienced radiologist, automatic classification was performed and the results were compared on a branch by branch basis. RESULTS: The numbering was accurate according to Couinaud's system in 358 of 409 segmental and subsegmental branches (88 %). The assignment failed in 51 of 409 branches due to unexpected anatomy or software problems. CONCLUSION: Automatic classification of portal vein branches and their appendant parenchyma is possible. The automatic designation of liver segments enables the three-dimensional visualization of the segmental anatomy. In the future, automatic analysis might facilitate the reporting and communication of CT findings.

Algorithms↗
PubMed2004

[Manual endothelial cell enumeration for transplanted corneas in comparison to software controlled, automatic enumeration].

BACKGROUND: The evaluation of the endothelial cells is the most important criterion for assessing human donor corneas. The number, morphology and the vitality of the endothelial cells are decisive for the transparency of a cornea. The study has the following aim: to verify whether there is any difference between the manual and the automatic count of the cells by means of the NAVIS(R) system. MATERIAL AND METHODS: Both methods were performed on 57 corneas of 35 patients. A photo was taken for the manual count by a microscope at 40-fold enlargement and was printed for further analysis. A grid was applied to this photo and the number of the endothelial cells was projected by a multiplicator to one square millimeter. For the automatic evaluation a picture was made with 20-fold microscopic enlargement; the examiner chose an area to be analysed. There the count of the cells was controlled by software and directly projected to one square millimetre. This was followed by a manual correction. The measurement data were statistically evaluated. RESULTS: No statistically significant difference was found between the manual and automatic counts. CONCLUSION: The manual count of the endothelial cells can be replaced by software-controlled automatic analysis and count.

Algorithms↗
PubMed2004

[Evaluation of a new software tool for the automatic volume calculation of hepatic tumors. First results].

PURPOSE: Computed tomography has become the preferred method in detecting liver carcinomas. The introduction of spiral CT added volumetric assessment of intrahepatic tumors, which was unattainable in the clinical routine with incremental CT due to complex planimetric revisions and excessive computing time. In an ongoing clinical study, a new software tool was tested for the automatic detection of tumor volume and the time needed for this procedure. MATERIALS AND METHODS: We analyzed patients suffering from hepatocellular carcinoma (HCC). All patients underwent treatment with repeated transcatheter chemoembolization of the hepatic arteria. The volumes of the HCC lesions detected in CT were measured with the new software tool in HepaVison (MeVis, Germany). The results were compared with manual planimetric calculation of the volume performed by three independent radiologists. RESULTS: Our first results in 16 patients show a correlation between the automatically and the manually calculated volumes (up to a difference of 2 ml) of 96.8 %. While the manual method of analyzing the volume of a lesion requires 2.5 minutes on average, the automatic method merely requires about 30 seconds of user interaction time. CONCLUSION: These preliminary results show a good correlation between automatic and manual calculations of the tumor volume. The new software tool requires less time for accurate determination of the tumor volume and can be applied in the daily clinical routine.

Algorithms↗
PubMed1986

Treatment of malignant ventricular arrhythmias with endocardial resection and implantation of the automatic cardioverter-defibrillator.

Although ventricular resection guided by endocardial mapping has been a successful treatment for drug-refractory ventricular arrhythmias, 20 to 30 percent of patients still have postoperative sustained ventricular tachycardia or sudden death. To improve the outcome of the procedure, we implanted an automatic cardioverter-defibrillator in conjunction with endocardial resection in 28 patients, all of whom had had previous myocardial infarctions and between one and five cardiac arrests. There were three perioperative deaths. During follow-up of 8 to 51 months (mean, 25), 4 of the 25 survivors had recurrences of hypotensive ventricular tachycardia, which in all instances were automatically terminated by the implanted device. One patient, whose automatic cardioverter-defibrillator was not functional, died suddenly. We conclude that patients undergoing mapping-directed endocardial resection can be provided with additional protection against recurrent ventricular tachyarrhythmias or sudden death by implantation of an automatic cardioverter-defibrillator.

Adult↗
PubMed1988

Use of the automatic external defibrillator in the management of out-of-hospital cardiac arrest.

The automatic external defibrillator is a simple device that can be used by nonprofessional rescuers to treat cardiac arrest. In 1287 consecutive patients with out-of-hospital cardiac arrest, we assessed the results of initial treatment with this device by firefighters who arrived first at the scene, as compared with the results of standard defibrillation administered by paramedics who arrived slightly after the firefighters. Of 276 patients who were initially treated by firefighters using the automatic defibrillator, 84 (30 percent) survived to hospital discharge (expected rate according to a logistic model, 17 percent; P less than 0.001), as compared with 44 (19 percent) of 228 patients when fire-fighters delivered only basic cardiopulmonary resuscitation and the first defibrillation was performed after the arrival of the paramedic team. Few patients with conditions other than ventricular fibrillation survived. In a multivariate analysis of characteristics that influenced survival after ventricular fibrillation, a better survival rate was related to a witnessed collapse (odds ratio, 3.9; 95 percent confidence interval, 2.0 to 7.6), younger age (odds ratio, 1.2; 95 percent confidence interval, 1.0 to 1.4), the presence of "coarse" (higher-amplitude) fibrillation (odds ratio, 4.2; 95 percent confidence interval, 1.6 to 11.0), a shorter response time for paramedics (odds ratio, 1.4; 95 percent confidence interval, 1.0 to 2.1), and initial treatment by firefighters using an automatic external defibrillator (odds ratio, 1.8; 95 percent confidence interval, 1.1 to 2.9). These findings support the widespread use of the automatic external defibrillator as an important part of the treatment of out-of-hospital cardiac arrest, although the overall impact of the use of this device on community survival rates is still uncertain.

Aged↗
PubMed2000

Accuracy of computerized automatic identification of cephalometric landmarks.

Computerized cephalometric analysis can include both landmark identification and determination of linear or angular measurements. Although its use is time saving compared with a manual method, the accuracy of automatic landmark identification remains unclear. The purpose of this study was to evaluate the accuracy of a computerized automatic landmark identification system that used an edge-based technique. The technique divides the scanned cephalogram into 8 rectangular subimage regions. After the resolution of these subimages is reduced, the edges are detected and the landmarks are located automatically. Thirteen landmarks were selected for assessment on a set of 10 test cephalograms. The results showed that the errors between manual and computerized identification for landmarks were not significantly different (P > .05) for 5 of 13 landmarks: sella, nasion, porion, orbitale, and gnathion. These results suggest that the accuracy of computerized automatic identification is acceptable for certain landmarks only. Further studies to improve the accuracy of computerized automated landmark identification are needed.

Cephalometry↗
PubMed2003

Progressive anomia with preserved oral spelling and automatic speech.

We report a patient, Newton, with a progressive classical anomia resulting from focal degeneration of the left hemisphere. In naming tasks Newton spelt aloud picture names that he could not retrieve, indicating a dissociation between orthography and phonology. Unusually, his writing and letter-pointing performance were impaired and spelling was achieved only through alphabet recitation. A study of automatic speech tasks demonstrated strikingly preserved naming performance on automatic compared to nominative tasks. We argue that automatic tasks provide phonological cues that facilitate phonological activation. With progression of disease Newton has shown increasing difficulty reading and repeating words, which we interpret in terms of a progressive elevation in the threshold for activation of phonology. Phonological cueing of picture names has yielded superior naming than word reading and even repetition, a finding consistent with the notion that task characteristics influence likelihood of phonological activation and naming success, but contrary to the notion that there exist separate task-specific output systems. We conclude that Newton exhibits a unique pattern of deficits, which have theoretical relevance for the debate on the relationship between phonology and orthography, the role of automatic speech and the relationship between naming, reading and repetition.

Aged↗
PubMed2004

Factors affecting performance on a target monitoring task employing an automatic tracker.

The experiments in this paper examined the extent to which performance on a task employing an automatic tracker was similar to performance on tasks employing other types of automation that have been studied more extensively. Automated target tracking is being used in many sensor and navigation systems to improve performance and help the operator cope with increased data loads. With many automated systems these goals are not met. In particular, the operator often misses errors made by the automated system and may report no decrease in workload. Several hypotheses have been offered for the operator's failure to monitor an automated system adequately. These include lack of experience with the manual task, a vigilance decrement, complacency, and inappropriate level of automation. The relevance of each of these hypotheses to failure to monitor an automatic tracker adequately was examined. Performance and perceived workload on a target tracking task employing an automatic tracker, in which participants had to detect and then update the position of several targets (e.g. ships) at regular intervals, were measured as a function of number of targets, training with the manual task, experience, and time on task. The results suggested that failure to detect errors made by the automated system was due largely to the lack of visibility of the automation errors relative to other errors. However, complacency could not be ruled out entirely. Unlike some other tasks, the availability of a reliable automatic tracker did lead to a substantial reduction in perceived workload.

Adolescent↗
PubMedDate not supplied

A quantitative and qualitative evaluation of an automatic occlusion device for tracheoesophageal speech: the Provox FreeHands HME.

This study aimed to evaluate a new automatic tracheostoma valve: the Provox FreeHands HME (manufactured by Atos Medical AB, Sweden). Data from four laryngectomee participants using automatic and also manual occlusion were subjected to acoustic and perceptual analysis. The main results were a significant decrease, from the manual to automatic occlusion condition, in maximum phonation time, mean intensity of read speech and percentage pause time. There was an increase in random noise in the speech signal and a significant increase in extraneous noise caused by the device. Perceptual analysis revealed no clear functional impact of these differences. Data from a questionnaire and diary suggested the main advantage of automatic occlusion was the freedom to speak while performing manual tasks. The principal disadvantage appeared to be a decrease in base-plate seal duration. The results suggest that, for some clients, the FreeHands valve is a useful option for use alongside manual occlusion.

Adult↗
PubMedDate not supplied

Level of processing and the process-dissociation procedure: elusiveness of null effects on estimates of automatic retrieval.

We describe two experiments that used the process-dissociation procedure to investigate the effects of level of processing on estimates of controlled and automatic retrieval processes in word-stem completion tasks. Despite our best endeavours, we found the null effect of level of processing on estimates of automatic retrieval reported by Toth, Reingold, and Jacoby (1994) elusive. Estimates of automatic retrieval were not independent of level of processing but inversely related to it. In part, the reason was that, following deeper levels of processing, instructions to exclude recollected words led to floor effects. But the inverse relationship persisted even when floor effects were avoided. Only participants who were not given strict instructions in the exclusion task-and who also qualified as lax responders based on answers in a structured post-test interview-showed no effect of level of processing on estimates of automatic retrieval. This null effect apparently occurred because these participants failed to exclude words that they in fact recollected from the study list. This finding violates the critical assumption that in this task participants exclude recollected words. The results are therefore paradoxical. Successful replication of the null effect occurred only under conditions that preclude the very use of the procedure. This paradox has important implications for views on how consciousness should be conceived in relation to memory.

Adult↗
PubMed2005

Semi-automatic quantification of myocardial infarction from delayed contrast enhanced magnetic resonance imaging.

OBJECTIVE: Accurate and reproducible assessment of myocardial infarction is important for treatment planning in patients with ischemic heart disease. This study describes a novel method to quantify myocardial infarction by semi-automatic delineation of hyperenhanced myocardium in delayed contrast enhanced (DE) magnetic resonance (MR) images. DESIGN: The proposed method automatically detects the hyperenhanced tissue by first determining the signal intensity of non-enhanced myocardium. A fast level set algorithm was used to limit the heterogeneity of the hyperenhanced regions, and to exclude small regions that constitute noise rather than infarction. The method was evaluated in 40 patients; 20 with acute infarction and 20 with chronic healed infarction using scanners from two different manufacturers. Infarct size measured by the proposed semi-automatic method was compared with manual measurements from three experienced observers. The software used is freely available for research purposes at http://segment.heiberg.se. RESULTS: The difference in infarct size between semi-automatic quantification and the mean of the three observers was 6.1+/-6.6 ml (mean+/-SD), and the interobserver variability (SD) was 4.2 ml. CONCLUSIONS: The method presented is a highly automated method for analyzing myocardial viability from DE-MR images. The bias of the method is acceptable and the variability is in the same order of magnitude as the interobserver variability for manual delineations.

Adult↗
PubMed2003

Potential and limitations of the automatic detection of fiducial markers using an amorphous silicon flat-panel imager.

Amorphous silicon electronic portal imaging devices (a-Si EPIDs) allow fast acquisition of high resolution portal images (PI). A visualization of organ movement for adaptive image-guided radiotherapy (IGRT) can be reached by implantation and automatic detection of fiducial markers. A method of automatic detection has been developed for fiducial spherical tungsten markers on PIs, acquired with an a-Si flat-panel imager. The detection method consists of a 2D Mexican hat filter (MHF), whose parameters are tuned to the particular marker signal. The high selectivity of this filter allows a reliable and precise detection of tungsten markers down to a diameter of 1.5 mm. The presented method allows fast, automatic and unsupervised detection of markers. Inevitably, the detection is hampered by image background (bone structures, etc) and noise. A detection success rate higher than 95% was reached, analysing PIs of patients with markers fixed on their skin. Furthermore, this approach to automatic marker detection can also be generalized to elliptic MHFs for the detection of cylindrical markers. The accuracy and detection probability of this method may allow accurate and fast online localization of the considered organ.

Feasibility Studies↗
PubMed2004

Automatic extraction of gene/protein biological functions from biomedical text.

MOTIVATION: With the rapid advancement of biomedical science and the development of high-throughput analysis methods, the extraction of various types of information from biomedical text has become critical. Since automatic functional annotations of genes are quite useful for interpreting large amounts of high-throughput data efficiently, the demand for automatic extraction of information related to gene functions from text has been increasing. RESULTS: We have developed a method for automatically extracting the biological process functions of genes/protein/families based on Gene Ontology (GO) from text using a shallow parser and sentence structure analysis techniques. When the gene/protein/family names and their functions are described in ACTOR (doer of action) and OBJECT (receiver of action) relationships, the corresponding GO-IDs are assigned to the genes/proteins/families. The gene/protein/family names are recognized using the gene/protein/family name dictionaries developed by our group. To achieve wide recognition of the gene/protein/family functions, we semi-automatically gather functional terms based on GO using co-occurrence, collocation similarities and rule-based techniques. A preliminary experiment demonstrated that our method has an estimated recall of 54-64% with a precision of 91-94% for actually described functions in abstracts. When applied to the PUBMED, it extracted over 190 000 gene-GO relationships and 150 000 family-GO relationships for major eukaryotes.

Abstracting and Indexing↗
PubMed1987

Transient increase in release of adenosine during rapid cardiac pacing; transient effects on overdrive suppression of ventricular automaticity.

A study was designed to test the hypothesis that endogenous adenosine concentration may increase during episodes of rapid ventricular pacing and, by virtue of its negative chronotropic effects, contribute to the transient suppression of automaticity that follows the period of overdrive. Isolated, perfused, rat ventricular preparations were subjected to periods of 6.0 Hz overdrive stimulation while adenosine release, oxygen consumption, and subsequent suppression of automaticity were measured. At the end of a 1 min episode of overdrive oxygen consumption and adenosine release were significantly increased, and the initial beating rate after 1 min overdrive was suppressed. At the end of 10 min overdrive oxygen consumption was still increased but adenosine release had returned to control values. Suppression of automaticity after 10 min overdrive was similar to that after 1 min overdrive. The relative magnitude of suppression after 1 min overdrive was decreased by theophylline (10(-4) mol.litre-1), and increased by the adenosine deaminase inhibitor, EHNA (10(-5) mol.litre-1). Neither theophylline nor EHNA had any discernible influence on suppression after 10 min overdrive. It its therefore concluded that endogenous adenosine may contribute to the suppression of ventricular automaticity that follows a 1 min episode of overdrive, but because of the transient nature of the increase in adenosine during overdrive endogenous adenosine does not contribute to the suppression that follows prolonged overdrive.

Adenine↗
PubMed1999

A method for the automatic detection of arousals during sleep.

A method for the automatic detection of arousals in digital polysomnographic recordings is described. The computer program analyzed two EEG and one EMG derivations marking variable length segments as arousals. The processing of EEG data started from the wavelet transform, which characterizes the signal in the time-frequency domain, and resulted in a set of indices used to discriminate possible arousal segments. Transient increases in muscle activity were also identified, while a multichannel and context sensitive analysis allowed arousal detection. Out of 11 overnight recordings, 3 were used as the training set and 8 as the program testing set. In the first stage of the study two EEG experts inspected the tracings independently to score arousals. They then reviewed all recordings and jointly examined each event for validation, both those scored by themselves and those scored by the computer. A reference set of definite arousals (1125 in the testing set) and a number of uncertain events (266) were thus obtained. The sensitivity of the automatic system (88.1%) was higher than that of the human experts (72.4 and 78.4%) while the selectivity was lower (74.5% for the automatic system, 83.0 and 82.0% for the experts). This suggested that automatic detection, followed by an expert's validation, may render the analysis of arousals more widely feasible as well as support the study of arousal features.

Adult↗
PubMed1993

Anesthetics and automaticity of dominant and latent pacemakers in chronically instrumented dogs. II. Effects of enflurane and isoflurane during exposure to epinephrine with and without muscarinic blockade.

BACKGROUND: Atrial dysrhythmias precede ventricular dysrhythmias during epinephrine-anesthetic sensitization, and may be caused by an altered relationship between automaticity of primary and subsidiary pacemakers. The following hypotheses were tested: (1) epinephrine-induced pacemaker shifts with enflurane or isoflurane require intact vagal reflexes and (2) these anesthetics sensitize the atrial myocardium to epinephrine-induced dysrhythmias. METHODS: Eight dogs were instrumented for chronic electrophysiologic investigation, including electrodes at the SA node, atrial appendages, right ventricle, and His bundle, and along the sulcus terminalis. After conscious-state testing, dogs were anesthetized with isoflurane or enflurane and exposed to epinephrine, with or without atropine methylnitrate. Eight-channel ECG recordings were analyzed before and during epinephrine infusions. Atrial pacemakers were assigned values 1-6 with increasing distance from the SA node, normalized and expressed as the site of earliest activation value (SEA). RESULTS: Epinephrine increased SEA values during enflurane or isoflurane anesthesia. Atropine enhanced this increase during enflurane anesthesia, but abolished the increase during isoflurane anesthesia. Enflurane increased SEA values only when combined with atropine. Isoflurane did not increase SEA values under any test conditions. CONCLUSIONS: With enflurane, epinephrine-induced atrial pacemaker shifts in chronically instrumented dogs are caused by direct depression of SA node automaticity or a relative increase of automaticity in subsidiary atrial pacemakers. With isoflurane, pacemaker shifts are caused by reflex-induced vagal suppression of SA node automaticity and escape of latent pacemakers. Enflurane sensitizes the atrial myocardium to dysrhythmias when combined with muscarinic blockade; isoflurane does not sensitize the atrium.

Anesthesia↗
PubMed1982

Automatic vs manual injections for thermodilution cardiac output determinations.

To investigate the effects of operator variability on thermodilution cardiac output determinations, a group of physicians and nurses made a series of manual indicator injections and automatic injections using a gas powered injector in a simulated clinical situation. The data show significant variability in injection time, injectate flow rate, consistency of injection, and cardiac output values obtained during manual injections. There was little variability in these parameters during automatic injections. When other variables are properly controlled, the automatic injector may improve the precision of cardiac output measurements by controlling the consistency of injection and variables introduced by different operators performing manual injections. However, despite significant variation in parameters associated with manual injection, it is interesting to note that 8 out of 10 operators obtained cardiac output values by hand injection using room temperature injectate, which did not differ significantly from those obtained by automatic injection.

Animals↗