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PubMed1999

Automatic detection of left ventricular contours from cardiac cine magnetic resonance imaging using fuzzy logic.

RATIONALE AND OBJECTIVES: Gated cardiac cine magnetic resonance imaging provides accurate dynamic data of the left ventricular function. However, the manual extraction of important physiologic parameters such as myocardium wall thickness and left ventricular volumes is invariably time consuming and subjective. To reduce the variability and time constraints inherent in observer contour tracing, the authors developed an automatic left ventricle contour-detection method. METHODS: The purpose was to apply fuzzy logic-based automatic contour detection to identification of endocardial and epicardial borders in short-axis magnetic resonance images. The automatic contouring was compared with manual tracing using the calculated ejection fraction as the comparison criterion. RESULTS: A good correlation was found between the two approaches (r2 = 0.98). CONCLUSIONS: The ejection fraction can be obtained using this automatic contouring method.

Adult↗
PubMed1996

Automatic Oxford-Medilog 9200 sleep staging scoring: comparison with visual analysis.

We report the results of a comparison study between automatic sleep staging using the ambulatory Oxford-Medilog 9200 system and visual analysis in a group of 30 subjects. Sleep analysis was performed during the second nighttime period of each 48-h polygraphic monitoring. The automatic analysis determined a significant underestimation of total sleep time and stage 2 non-rapid eye movement (NREM) sleep and an overestimation of stage 1. No significant differences were found between the two analyses regarding slow-wave sleep and REM sleep. The differences between automatic and visual analysis of stage 2 were correlated positively with the amplitude and duration of K-complexes and negatively with the amplitude and frequency of spindles. Differences in electroencephalographic characteristics of these sleep figures were correlated negatively with age. Our results showed that (a) the Oxford-Medilog 9200 sleep staging system did not improve the scoring of stages 1 and 2 NREM sleep and (b) the degree of differences between visual and automatic analysis are related to the amplitude and frequency of sleep figures, i.e., spindles and K-complexes, used in the scoring of stage 2.

Adolescent↗
PubMed2002

Automatic detection of coronary artery disease in myocardial perfusion SPECT using image registration and voxel to voxel statistical comparisons.

The purpose of this study was to compare the performance of automatic detection of coronary artery disease (CAD) with that of expert observers. A male and female normal image template was constructed from normal stress technetium-99m single photon emission computed tomography (SPECT) studies. Mean and standard deviation images for each sex were created by registering normal studies to a standard shape and position. The test group consisted of 104 patients who had been routinely referred for SPECT and angiography. The gold standard for CAD was defined by angiography. The test group studies were registered to the respective templates and the Z-score was calculated for each voxel. Voxels with a Z-score greater than 5 indicated the presence of CAD. The performance of this method and that of three observers were compared by continuous receiver operating characteristic (CROC) analysis. The overall sensitivity and specificity for automatic detection were 73% and 92%, respectively. The area (Az) under the CROC curve (+/-1 SE) for automatic detection of CAD was 0.88+/-0.06. There was no statistically significant difference between the performances of the three observers in terms of Az and that of automatic detection (P> or =0.25, univariate Z-score test). The use of this automated statistical mapping approach shows a performance comparable with experienced observers, but avoids inter-observer and intra-observer variability.

Algorithms↗
PubMed2002

Improved automatic analysis of ambulatory blood pressure data based on precise detection of individual night-time from diurnal profile of heart rate.

BACKGROUND: Software programs sold with ambulatory blood pressure monitoring (ABPM) devices are designed to use some set 'typical' night-time (e.g. 2300-0700) to estimate daytime/night-time blood pressure (BP) with limited accuracy. Alternative use of individual periods of sleep/wakefulness from patient diaries is time consuming and subjective. We developed a simple mathematical algorithm for the detection of the 'night-time' as a period of low values in diurnal profiles of heart rate (HR) allowing accurate automatic analysis of daytime/night-time blood pressure. To test this technique we designed a software application allowing automatic analysis of ABPM data based on the different night-time definitions, including the developed algorithm and compared reproducibility of the degree of BP dipping produced by the different methods across two days of 48-h ABPM. METHODS: A 48-h ABPM study was performed in 33 patients with uncomplicated stage II hypertension. Means and standard deviations (SD) of the differences in the degree of BP dipping between two 24-h periods of 48-h ABPM were obtained separately for three methods of night-time definition: automatic detection from individual HR profiles, fixed 2300-0700 h interval and sleep time from patient diaries. RESULTS: Reproducibility of the BP dip estimation across 2 days of BP monitoring was significantly better for night-time detected from individual HR profiles than for the fixed 2300-0700 h interval or sleep time from diary. The SD of the differences was 6.7/8.2 compared with 13.5/18.3 and 13.0/14.8 respectively (systolic BP/diastolic BP, mmHg). CONCLUSIONS: Implementation of the developed method of night-time definition may significantly improve automatic analysis of ABPM data.

Adult↗
PubMed2004

Automatic referral to cardiac rehabilitation.

OBJECTIVES: Cardiac rehabilitation (CR) remains underused and inconsistently accessed, particularly for women and minorities. This study examined the factors associated with CR enrollment within the context of an automatic referral system through a retrospective chart review plus survey. Through the Behavioral Model of Health Services Utilization, it was postulated that enabling and perceived need factors, but not predisposing factors, would significantly predict patient enrollment. SUBJECTS: A random sample of all atherosclerotic heart disease (AHD) patients treated at a tertiary care center (Trillium Health Centre, Ontario, Canada) from April 2001 to May 2002 (n = 501) were mailed a survey using a modified Dillman method (71% response rate). MEASURES: Predisposing measures consisted of sociodemographics such as age, sex, ethnocultural background, work status, level of education, and income. Enabling factors consisted of barriers and facilitators to CR attendance, exercise benefits and barriers (EBBS), and social support (MOS). Perceived need factors consisted of illness perceptions (IPQ) and body mass index. RESULTS: Of the 272 participants, 199 (73.2%) attended a CR assessment. Lower denial/minimization, fewer logistical barriers to CR (eg, distance, cost), and lower perceptions of AHD as cyclical or episodic reliably predicted CR enrollment among cardiac patients who were automatically referred. CONCLUSION: Because none of the predisposing factors were significant in the final model, this suggests that factors associated with CR enrollment within the context of an automatic referral model relate to enabling factors and perceived need. A prospective controlled evaluation of automatic referral is warranted.

Aged↗
PubMed2005

Soft-copy reading of digital chest radiographs: effect of ambient light and automatic optimization of monitor luminance.

OBJECTIVE: We sought to evaluate whether soft-copy reading of simulated pulmonary chest lesions is influenced by ambient light and automatic optimization of cathode ray tube (CRT) monitor luminance. MATERIALS AND METHODS: Four types of simulated lesions (nodules, lines, micronodules, and patchy opacities) were superimposed over an anthropomorphic chest phantom. Lesion detection with soft-copy reading was assessed using a high-contrast grayscale 2K CRT monitor under the following conditions: (1) subdued lighting (<50 lux); (2) normal lighting conditions (450 lux) without, and (3) with a sensitivity modulation to automatically adjust the CRT luminance to the increased amount of ambient light. Reading data were analyzed according to receiver operating curve. Significance of differences was tested using an analysis of variance for repeated measures. RESULTS: Ambient room light of 450 lux did not significantly influence the detection of nodules and patchy opacities. However, bright ambient light significantly decreased detection of micronodules (0.60 vs. 0.74) and lines (0.52 vs. 0.66) relative to subdued lighting conditions. Automatic luminance adjustment could compensate the effect of ambient light for the micronodules (0.77) but not for the lines (0.53). CONCLUSION: Bright ambient light significantly decreases detection of small low-contrast structures. This may be partially but not completely compensated by an automatic luminance adaptation.

Data Display↗
PubMed1997

Development of a microcontroller-based automatic control system for the electrohydraulic total artificial heart.

An automatic physiological control system for the actively filled, alternately pumped ventricles of the volumetrically coupled, electrohydraulic total artificial heart (EHTAH) was developed for long-term use. The automatic control system must ensure that the device: 1) maintains a physiological response of cardiac output, 2) compensates for an nonphysiological condition, and 3) is stable, reliable, and operates at a high power efficiency. The developed automatic control system met these requirements both in vitro, in week-long continuous mock circulation tests, and in vivo, in acute open-chested animals (calves). Satisfactory results were also obtained in a series of chronic animal experiments, including 21 days of continuous operation of the fully automatic control mode, and 138 days of operation in a manual mode, in a 159-day calf implant.

Algorithms↗
PubMed1999

Automatic 3-D segmentation of internal structures of the head in MR images using a combination of similarity and free-form transformations: Part II, validation on severely atrophied brains.

Studies aimed at quantifying neuroanatomical differences between populations require the volume measurements of individual brain structures. If the study contains a large number of images, manual segmentation is not practical. This study tests the hypothesis that a fully automatic, atlas-based segmentation method can be used to quantify atrophy indexes derived from the brain and cerebellum volumes in normal subjects and chronic alcoholics. This is accomplished by registering an atlas volume with a subject volume, first using a global transformation, and then improving the registration using a local transformation. Segmented structures in the atlas volume are then mapped to the corresponding structures in the subject volume using the combined global and local transformations. This technique has been applied to seven normal and seven alcoholic subjects. Three magnetic resonance volumes were obtained for each subject and each volume was segmented automatically, using the atlas-based method. Accuracy was assessed by manually segmenting regions and measuring the similarity between corresponding regions obtained automatically. Repeatability was determined by comparing volume measurements of segmented structures from each acquisition of the same subject. Results demonstrate that the method is accurate, that the results are repeatable, and that it can provide a method for automatic quantification of brain atrophy, even when the degree of atrophy is large.

Alcohol-Induced Disorders, Nervous System↗
PubMed2002

An accurate and efficient bayesian method for automatic segmentation of brain MRI.

Automatic three-dimensional (3-D) segmentation of the brain from magnetic resonance (MR) scans is a challenging problem that has received an enormous amount of attention lately. Of the techniques reported in the literature, very few are fully automatic. In this paper, we present an efficient and accurate, fully automatic 3-D segmentation procedure for brain MR scans. It has several salient features; namely, the following. 1) Instead of a single multiplicative bias field that affects all tissue intensities, separate parametric smooth models are used for the intensity of each class. 2) A brain atlas is used in conjunction with a robust registration procedure to find a nonrigid transformation that maps the standard brain to the specimen to be segmented. This transformation is then used to: segment the brain from nonbrain tissue; compute prior probabilities for each class at each voxel location and find an appropriate automatic initialization. 3) Finally, a novel algorithm is presented which is a variant of the expectation-maximization procedure, that incorporates a fast and accurate way to find optimal segmentations, given the intensity models along with the spatial coherence assumption. Experimental results with both synthetic and real data are included, as well as comparisons of the performance of our algorithm with that of other published methods.

Algorithms↗
PubMed2001

Teaching colleagues and the general public about automatic external defibrillators.

Every year 250,000 or more people with cardiovascular disease die within an hour of symptom onset and before they arrive at a hospital. With appropriate early defibrillation and follow-up treatment many people who might have died can now live. Nurses are key health care professionals for using automatic external defibrillators in hospitals and for teaching other first responders--inside and outside hospitals--how to use automatic external defibrillators. Features of automatic and semiautomatic external defibrillators are reviewed as well as ethical considerations for the use of automatic external defibrillators.

Automation↗
PubMed2006

When the social mirror breaks: deficits in automatic, but not voluntary, mimicry of emotional facial expressions in autism.

Humans, infants and adults alike, automatically mimic a variety of behaviors. Such mimicry facilitates social functioning, including establishment of interpersonal rapport and understanding of other minds. This fundamental social process may thus be impaired in disorders such as autism characterized by socio-emotional and communicative deficits. We examined automatic and voluntary mimicry of emotional facial expression among adolescents and adults with autistic spectrum disorders (ASD) and a typical sample matched on age, gender and verbal intelligence. Participants viewed pictures of happy and angry expressions while the activity over their cheek and brow muscle region was monitored with electromyography (EMG). ASD participants did not automatically mimic facial expressions whereas the typically developing participants did. However, both groups showed evidence of successful voluntary mimicry. The data suggest that autism is associated with an impairment of a basic automatic social-emotion process. Results have implications for understanding typical and atypical social cognition.

Adolescent↗
PubMed1986

Presumably innate and acquired automatic processes in children with attention and/or reading disorders.

Innate and acquired automatic information processing was compared in non-problem students and three groups of educationally troublesome children: two normal reading groups with Attention Deficit Disorder (ADD), one without and one with hyperactivity, and a non-hyperactive Reading Disabled (RD) group. All groups displayed reliable, presumably innate, automatic processing on measures of temporal and frequency sensitivity, but the two ADD groups made less precise judgements than controls. Contrasted with controls, all clinical groups exhibited delayed automatization in arithmetic computation, but the handicapped groups did not differ from controls on other measures of acquired automatization (speed of writing and naming).

Attention Deficit Disorder with Hyperactivity↗
PubMed1991

Task versus component consistency in the development of automatic processing: a psychophysiological assessment.

A study was conducted to examine the role of consistency in the development of automatic processing. Subjects performed a memory search task in which consistent and inconsistent attending and responding were factorially combined. The task was performed with memory set sizes of two and four items. Results indicated that automaticity developed with consistent attending regardless of whether responding was consistent or inconsistent. However, measures of reaction time, P300 latency, and P300 amplitude revealed costs for inconsistent responding that were attributed to both stimulus evaluation and response related processes. The results suggest that total task consistency is not necessary for the development of automatic processing. Instead, it appears that automaticity can develop for consistent task components even when stimulus-response consistency is not maintained across the entire task.

Adolescent↗
PubMed1993

An evaluation of the automaticity of sensory processing using event-related potentials and brain-stem reflexes.

Selective attention effects on reflexes and evoked potentials are reviewed with the aim of evaluating three theories regarding sensory automaticity. (a) The peripheral-gating theory, which assumes that ignored stimuli can be filtered out soon after transduction, was tentatively rejected because neither auditory-nerve nor retinal potentials are reliably affected by attention. (b) At the other extreme, the assumption that sensory analyses are obligatory and cannot benefit from attentional resources (i.e., strong-automaticity theory) was also rejected, because longer latency components were found to be modifiable by attention. (c) An intermediate theory provides the best fit to present electrophysiological data. The earliest sensory analyses are assumed to be strongly automatic and then, at forebrain levels, there is a transition from strong to weak automaticity (i.e., analyses are obligatory but modifiable by attention). This transition can begin as early as about 15 ms for audition and about 80 ms for vision.

Animals↗
PubMed1991

Evidence for involvement of catecholamines in the effect of morphine on ventricular automaticity in the rat.

1. The present study examined the effects of morphine on ectopic automaticity induced by local injury in the isolated right ventricle of the rat. 2. Morphine (10(-7)-5 x 10(-5) M) induced a significant increase of ventricular rate similar to that produced by noradrenaline. The excitatory effect of morphine was not modified by the presence of naloxone (5 x 10(-5) M). The maximal effect obtained with morphine in the presence of naloxone was 60 +/- 7%, similar to that obtained with morphine alone (67 +/- 15%). The EC50 values for morphine in the absence (0.89 x 10(-7) M) and presence of naloxone (0.87 x 10(-7) M) were also similar. Apparently this effect is not mediated by postsynaptic opioid receptors. 3. The ventricular automaticity induced in isolated right ventricle of the rat was significantly decreased by the highest concentrations of naloxone (5 x 10(-5) and 10(-7) M). 4. Morphine (10(-9)-5 x 10(-5) M) did not significantly change ventricular automaticity in the presence of propranolol (5 x 10(-8) M) or in reserpinized rats (5 mg kg-1 i.p. 24 h before the experiments). The maximal increases induced by morphine in the presence of propranolol or in reserpinized rats were 5 +/- 0.8% and 16 +/- 14.7% respectively. These results were significantly different from the maximal increase obtained without propranolol or with non-reserpinized animals. It is possible that the effects of morphine on ventricular automaticity could be mediated by an indirect effect located presynaptically at the adrenergic nerve terminals through the release of catecholamines.

Animals↗
PubMed1988

Increased pacing threshold after an automatic defibrillator shock in dogs: effects of class I and class II antiarrhythmic drugs.

A high energy shock delivered by an automatic defibrillator may interfere with pacemaker function. To provide insight into the changes that occur in the threshold for ventricular pacing after the shock from an automatic defibrillator, we measured the time to capture during asynchronous ventricular pacing in dogs from endocardial or epicardial sites, after a 30 joule shock was delivered via conventional automatic defibrillator (AICD) patch electrodes. After a 30 joule shock, there was a transient loss of ventricular capture. The duration of capture loss was related to current strength. During endocardial pacing at threshold current, the time to capture was 4.9 +/- 1.2 s, whereas at current values twice threshold the time to capture from endocardial pacing was 2.2 +/- 0.9 s. No difference was found between endocardial and epicardial pacing sites in the time to capture. To ascertain the mechanism of capture loss we: (1) examined the effects of converting the pacing catheter to a current sink (transiently shunting to ground); (2) altered excitability by an infusion of flecainide; (3) blocked sympathetic input (propranolol). No change in time to capture was noted by shunting the pacer to ground. After an infusion of flecainide the time to capture from endocardial pacing was significantly prolonged to 14.9 +/- 2.2 s at the threshold value (P less than .01) and 5.6 +/- 2.1 s at twice threshold (P less than .05). Conversely, intravenous propranolol had no effect on the time to capture after shock from endocardial pacing. These data indicate that there is a transient increase in pacing threshold after the shock from an automatic defibrillator.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Automatic refractory period.

Pacemakers have become more and more complex over the years, whereby technological advances were used to create more and new possibilities in existing pacemaker applications. As a result a demand has grown for more automatic functions to reduce the time to program the pacemakers and eleviate follow-up procedures. One of the parameters which can be adjusted automatically is the refractory period. We measured the pacing threshold as a function of coupling interval between the stimulus and the previous paced complex and related this to the morphology of the paced evoked T-wave. When the stimulus falls far away from the T-wave the pacing threshold is constant. When it approaches the T-wave the threshold reduces slightly (superconductivity) and at the peak of the T-wave there is a sharp increase of the pacing threshold. The refractory period coincides with the period from the stimulus until the top of the T-wave (stim-T interval). This result is used in the Rhythmyx pacemaker where the stim-T interval is used to automatically adjust the pace refractory period. Automatically adjusting the refractory period has the extra advantage of higher allowable pacing rates as the refractory period shortens with increasing heart rates. Future applications will include use antitachycardia pacing where the stim-T interval can be used to prevent pacing in the refractory period or in the vulnerable zone.

Algorithms↗
PubMed1992

A new pacemaker algorithm for continuous capture verification and automatic threshold determination: elimination of pacemaker afterpotential utilizing a triphasic charge balancing system.

A new pacemaker algorithm designed to automatically verify pacemaker capture and determine pacing threshold by detection of a stimulus evoked potential was studied in 20 patients undergoing permanent pacemaker implantation. To eliminate pacing stimulus afterpotential and detect an evoked response, a hardware feedback circuit and a software template matching algorithm were used to produce a triphasic charge-balanced pacing pulse. After charge balancing the pacing lead, a residual artifact is measured. A capture window is defined as the area integral of the first 24 msec of the evoked depolarization, and a capture threshold as one third the amplitude of the capture window. The maximum allowable residual artifact is one eighth the amplitude of the capture window. Once the stimulus afterpotential is eliminated and the evoked response detected, capture threshold is automatically and continuously determined and the algorithm adds a 0.8-V safety margin to the pacemaker output. This algorithm was run automatically and after simulated loss of capture, produced by manually decreasing pacer output below threshold, in the bipolar (13 patients) and unipolar (20 patients) pacing modes. In each patient loss of capture was immediately detected. The data were consistent (P = NS) between algorithm runs. During unipolar pacing the area integral of the first 24 msec of the evoked response was 412 +/- 137 versus 413 +/- 144 and the residual artifact 5.8 +/- 4.8 versus 8.1 +/- 7.5. The resulting ratio (signal/noise) of the two parameters was 150 +/- 141 versus 145 +/- 181. Automatically determined threshold was 0.69 +/- 0.43 V versus 0.69 +/- 0.42.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗