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At least 1,531 records · Page 85Linked to original sources
PubMed1998

Comparative prognostic value of automatic quantitative analysis versus semiquantitative visual analysis of exercise myocardial perfusion single-photon emission computed tomography.

OBJECTIVES: The purpose of this study was to determine the prognostic value of automatic quantitative analysis in exercise dual-isotope myocardial perfusion single-photon emission computed tomography (SPECT) and to compare the prognostic value of quantitative analysis to semiquantitative visual SPECT analysis. BACKGROUND: Extent, severity and reversibility of exercise myocardial perfusion defects have been shown to correlate with prognosis. However, most studies examining the prognostic value of SPECT in chronic coronary artery disease (CAD) have been based on visual analysis by experts. METHODS: We studied 1,043 consecutive patients with known or suspected CAD who underwent rest Tl-201/exercise Tc-99m sestamibi dual-isotope myocardial perfusion SPECT and were followed up for at least 1 year (mean 20.0+/-3.7 months). After censoring 59 patients with early coronary artery bypass grafting or percutaneous transluminal coronary angioplasty, <60 days after nuclear testing, the final population consisted of 984 patients (36% women, mean age 63+/-12 years). RESULTS: During the follow-up period, 28 hard events (14 cardiac deaths, 14 nonfatal myocardial infarctions) occurred. Patients with higher defect extent (>10%), severity (>150) and reversibility (>5%) by quantitative SPECT defect analysis, as well as those with an abnormal scan (>2 abnormal segments, summed stress score >4 and summed difference score >2) by semiquantitative visual SPECT analysis, had a significantly higher hard event rate compared to patients with a normal scan (p < 0.001). With both visual and quantitative analyses, hard event rates of approximately 1% with normal scans and 5% with abnormal scans (p > 0.05) were observed over the 20-month follow-up period. A Cox proportional hazards regression model showed that chi-square increased similarly with the addition of quantitative defect extent and visual summed stress score variables after considering both clinical and exercise variables (improvement chi-square = 11 for both, p < 0.0007). There were no significant differences in the areas under receiver operating characteristic curves between quantitative and visual analysis (p > 0.70). Linear regression analysis also indicated that quantitative assessments correlated well with visual semiquantitative assessments. CONCLUSIONS: The findings of this study indicate that automatic quantitative analysis of exercise stress myocardial perfusion SPECT is similar to semiquantitative expert visual analysis for prognostic stratification. These findings may be of particular clinical importance in laboratories with less experienced visual interpreters.

Aged↗
PubMedDate not supplied

Automatic and strategic processing in obsessive-compulsive disorder: attentional bias, cognitive avoidance or more complex phenomena?

Slowed color naming of threat-related words on the modified Stroop task has been interpreted as indicative of selective processing biases, although alternative models have been proposed to explain inconsistent findings. The present study compared the performance of participants with obsessive-compulsive disorder (OCD) and normal controls on a computerized version of the modified Stroop, and investigated the relationship of Stroop effects to avoidant cognitive strategies. Contrary to predictions, control and OCD groups were notably faster at color naming OCD threat, general threat, and positive words compared to neutral words at the strategic level of awareness. This was not the case for OCD threat words at the automatic level of awareness where faster color naming was observed, although the expected differences between groups were not found. A thought replacement measure was generally predictive of OCD participants' automatic pattern of interference for negatively valenced words. Results indicate the complexity of the Stroop effect and the need for its ongoing review.

Adult↗
PubMed1994

A two-month study of the effects of oral irrigation and automatic toothbrush use in an adult orthodontic population with fixed appliances.

Forty-seven adult orthodontic patients with fixed orthodontic appliances were divided into three study groups: (1) oral irrigation with automatic toothbrush, (n = 16); (2) oral irrigation with manual toothbrushing, (n = 16); (3) control group with continued normal toothbrushing only, (n = 15). Gingival and plaque indices, bleeding after probing, and gingival sulcus depths were assessed at baseline, 1-month, and 2-month periods. Marked and significant gingival and plaque improvements from baseline were measured in all three study groups. After 1 to 2 months use of the automatic toothbrush and/or the oral irrigation device, there was a significant reduction in plaque when compared with the control group who used only the manual toothbrush (p = 0.026). Also, there was a significant reduction in gingival inflammation (p = 0.045) and evidence for reducing bleeding after probing (p = 0.037). No significant differences were found in probe depths among the three study groups, however, use of both devices reduced the pocket depth significantly from baseline by 0.5 mm (p < 0.0002). For this population of orthodontic patients, significant reductions in plaque, gingival inflammation, and a tendency for reduced bleeding after probing occurred in both groups with the power device. These improvements were most attributable to the effect of the oral irrigation device.

Adult↗
PubMed1997

The Transition from Automatic to Controlled Processing.

The transition from automatic (unconscious) to controlled (conscious) processing is described in terms of a neural network model of classical conditioning ([Schmajuk et al., 1996]). In the framework of the network, an environmental stimulus is processed in controlled or conscious mode when Novelty and attention to the stimulus are large, and in automatic or unconscious mode otherwise. In the model, indirect dopamine (DA) agonists, such as amphetamine or nicotine, enhance the DA representation of Novelty, thereby increasing attention and engaging conscious processing of environmental stimuli. By contrast, DA receptor antagonists, such as haloperidol, reduce the DA representation of Novelty, thereby decreasing attention, and engaging unconscious processing of the stimuli.

Journal Article↗
PubMedDate not supplied

A method for the automatic characterization of bone architecture in 3D mice microtomographic images.

We developed an automatic method to characterize mice bone architecture from three-dimensional (3D) microtomographic images. The distal metaphyses of the femur of mice were imaged using 3D synchrotron radiation microtomography at the European Synchrotron Radiation Facility (ID19) with a voxel size of 6.65 mum. Within each reconstructed volume, a region of interest was defined and trabecular and cortical bones were automatically separated. Then, 3D morphologic and topologic model-independent parameters quantifying the 3D bone architecture were computed in both regions. The technique was applied to study the response of the C57BL/6J@Ico strain of mice submitted to a model of bone loss by hind limb unloading produced by tail-suspension.

Animals↗
PubMedDate not supplied

Automatic detection of left ventricular borders on electron beam CT sequential cardiac images using an adaptive algorithm.

Detection of myocardial borders on sequences of electron beam CT images is carried out using an adaptive segmentation algorithm developed to enhance dynamic analysis of cardiac function. Adaptivity is based on description of the myocardial borders from the mean and standard deviation of the grey level and gradient distributions on each image of the sequence. Comparison of segmentations from five experimentators with automatically determined borders on a set of 416 endocardial and epicardial contours indicated differences between automatic and manual tracing very close to differences due to inter-observer reproducibility.

Algorithms↗
PubMedDate not supplied

A pyramidal approach for automatic segmentation of multiple sclerosis lesions in brain MRI.

Quantitative assessment of Magnetic Resonance Imaging (MRI) lesion load of patients with multiple sclerosis (MS) is the most objective approach for a better understanding of the history of the pathology, either natural or modified by therapies. To achieve an accurate and reproducible quantification of MS lesions in conventional brain MRI, an automatic segmentation algorithm based on a multiresolution approach using pyramidal data structures is proposed. The systematic pyramidal decomposition in the frequency domain provides a robust and flexible low level tool for MR image analysis. Context-dependent rules regarding MRI findings in MS are used as high level considerations for automatic lesion detection.

Algorithms↗
PubMed1999

Failures of automatic and strategic processing in schizophrenia: comparisons of event-related brain potential and startle blink modification.

Noises elicit startle blinks that are inhibited when immediately (approximately 100 ms) preceded by non-startling prepulses, perhaps reflecting automatic sensory gating. Startle blinks are facilitated when preceded by prepulses at longer lead intervals, perhaps reflecting strategic processes. Event-related brain potentials (ERPs) and startle blinks were used to investigate the well-documented prepulse inhibition failure in schizophrenia. Blinks and ERPs were recorded from 15 schizophrenic men and 20 age-matched controls to noises alone and to noises preceded by prepulses at 120 (PP120), 500 (PP500) and 4000 ms (PP4000) lead intervals. Neither blinks nor any of the ERP components elicited by the noise alone differentiated schizophrenics from controls, although responses to noises were modified by prepulses differently in the two groups. With the N1 component of the ERP, patients showed normal inhibition but lacked facilitation, and with P2, patients lacked inhibition, but showed normal facilitation. With reflex blinks and P300, inhibition was seen in both groups, but no facilitation. These results suggest that different neural circuits are involved in blink and cortical reflections of startle modification in schizophrenics and controls, with both automatic and strategic processes being impaired in schizophrenia.

Acoustic Stimulation↗
PubMed1998

H-reflex modulations during voluntary and automatic movements following upper motor neuron damage.

OBJECTIVES: It is not known whether similar mechanisms account for the impairments of voluntary movement and automatic postural responses of individuals with spasticity secondary to damage to the sensorimotor cortex and its projections (i.e. upper motor neuron syndrome (UMN)). METHODS: The present study examined changes in soleus H-reflexes preceding and during voluntary tibialis anterior (TA) muscle contraction of standing subjects and during balance platform induced postural perturbations that elicited similar TA muscle contractions. Twenty-two subjects (12 non-disabled; 4 with spastic-type cerebral palsy; 6 with adult-onset cerebral vascular accident) participated in the study. Data were analyzed using ANOVAs and Tukey HSD post-hoc comparison tests to assess the timing and magnitude of soleus H-reflex amplitude changes relative to the onset of TA muscle activation. RESULTS: Results indicated that, regardless of the level of TA activation, soleus H-reflexes of subjects with UMN involvement did not demonstrate inhibition either. during voluntary movements or during automatic postural perturbations. CONCLUSIONS: These findings indicate that postural reflexes, as well as volitional movements, are impaired following UMN damage and that deficits in neural pathways subserving reciprocal inhibition contribute to the impairments.

Adult↗
PubMed2000

Event-related potentials during conscious and automatic memory retrieval.

The effects of study-test lags of between 0 and 32 items on conscious (C) and automatic (A) memory processes in a running word-completion task were investigated with event-related potentials (ERPs). The process dissociation procedure (PDP) can distinguish between C and A contributions to memory by comparing performance when subjects respond with either an old item (inclusion) or a new item (exclusion). C can be estimated by subtracting the probability of an intrusion of an old item during the exclusion task (due to A without C) from the probability of correctly producing an old item during the inclusion task (due to C and/or A). The behavioral results showed that C was stronger when the test item followed the studied word in the next trial or after a lag of one stimulus. The strength of A did not vary with lag. The ERP waveforms contained a broad parietal positive wave between 300 and 800 ms. This parietal wave distinguished between correctly recalled old and new words. The early portion of this old-new effect was significantly affected by lag. Subtracting waveforms to obtain a measure of C revealed an effect in the later portion of this wave, lateralized over the left hemisphere. A sustained frontal negativity occurred during all recordings and was larger during conscious retrieval. There was no consistent ERP effect related to automatic memory retrieval.

Adult↗
PubMed2001

Automatic discriminative sensitivity inside temporal window of sensory memory as a function of time.

Neural representation of preceding sound-patterns stored in the human brain, as reflected by mismatch negativity (MMN) related to the automatic discriminative process, is restricted to a duration of 160-170 ms due to the short form of auditory sensory memory termed the temporal window of integration (TWI). To examine the temporal uniformity of deviation-sensitivity inside TWI of sensory memory, magnetic MMN (MMNm) responses were measured with a dual 37-channel magnetometer for complex sounds of 170 ms duration containing an omitted (silent) segment. Frequent standard stimuli (probability of 80%) consisted of five tone segments. Deviant stimuli were different from standard stimuli in that one of four segments was occasionally (probability of 5%) omitted and replaced by a silent segment. The stimulus duration of 170 ms was intended to correspond to the postulated duration of TWI. When the silent segment occurred later in deviant stimulus, the MMNm peak amplitude was attenuated and MMNm peak latency, measured from the onset of each silent segment, was delayed. Thus, automatic deviation-detection sensitivity declines nonlinearly toward the end of TWI in auditory sensory memory. In the second experiment, two types of deviant stimuli, which differed from each other only in the period after the occurrence of the silent segment, elicited MMNm with the same peak latency but with a different peak amplitude. Thus, mismatch process is triggered at the moment of change but still lasts after the detection of deviation. In other words, both standard and deviant stimuli are treated as a unitary event within a TWI.

Acoustic Stimulation↗
PubMed2001

Automatic postural response systems in individuals with congenital total blindness.

This study examined the effects of the absence of vision from birth on automatic postural responses to platform displacements during stance. Postural responses were induced by producing randomly four types of perturbations which consisted of forward and backward translations, and toe up and down rotations. Nine congenitally totally blind and nine sighted adults served as subjects. EMG signals were recorded from four muscles in the right leg, and reaction time to somatosensory stimuli generated by platform displacements was measured by pushing a hand-held button. To assess the ability to control postural balance, the root mean square (RMS) values for lateral and antero-posterior sway before, during, and after perturbations were calculated. The EMG amplitude in the gastrocnemius muscle of a blind subject was smaller than that of a sighted subject with eyes closed. No significant differences were found between blind and sighted subjects in EMG latencies of the lower extremity muscles in response to perturbations. The blind subjects had significantly faster reaction times to somatosensory stimuli triggered by platform displacements, but in toe down rotations no significant difference was found between blind and sighted subjects. The difference in the EMG latencies and reaction times between the two groups suggests that blindness from birth may not affect the spinal stretch reflex, but may affect a volitional act mediated through the motor cortex. There were also no significant differences in the RMS values for postural sway between blind and sighted subjects with eyes open or closed, although blind subjects swayed more after backward translations than did sighted subjects with eyes open. Results suggest that the ability to control postural balance during perturbations was not affected by vision loss from birth. Our findings suggest that the automatic postural response systems of humans are unaffected by the absence of vision from birth and are rather hard wired.

Adaptation, Physiological↗
PubMed1989

A simple electronic and computer system for automatic spindle detection.

The authors present a new system for the automatic detection of sleep spindles. The electronic and computer analysis are described and a comparison between automatic and visual analysis, performed by two independent readers, was carried out with the aim of evaluating the reliability of the system. Results are discussed and compared with those of different systems already described.

Electroencephalography↗
PubMed2002

A comparison of conscious and automatic memory processes for picture and word stimuli: a process dissociation analysis.

Four experiments were conducted to evaluate explanations of picture superiority effects previously found for several tasks. In a process dissociation procedure (Jacoby, 1991) with word stem completion, picture fragment completion, and category production tasks, conscious and automatic memory processes were compared for studied pictures and words with an independent retrieval model and a generate-source model. The predictions of a transfer appropriate processing account of picture superiority were tested and validated in "process pure" latent measures of conscious and unconscious, or automatic and source, memory processes. Results from both model fits verified that pictures had a conceptual (conscious/source) processing advantage over words for all tasks. The effects of perceptual (automatic/word generation) compatibility depended on task type, with pictorial tasks favoring pictures and linguistic tasks favoring words. Results show support for an explanation of the picture superiority effect that involves an interaction of encoding and retrieval processes.

Adult↗
PubMed2000

Automatic artifact identification in anaesthesia patient record keeping: a comparison of techniques.

The anaesthetic chart is an important medico-legal document, which needs to accurately record a wide range of different types of data for reference purposes. A number of computer systems have been developed to record the data directly from the monitoring equipment to produce the chart automatically. Unfortunately, systems to date record artifactual data as normal, limiting the usefulness of such systems. This paper reports a comparison of possible techniques for automatically identifying artifacts. The study used moving mean, moving median and Kalman filters as well as ARIMA time series models. Results on unseen data showed that the Kalman filter (area under the ROC curve 0.86, false positive prediction rate 0.31, positive predictive value 0.05) was the best single method. Better results were obtained by combining a Kalman filter with a seven point moving mid-centred median filter (area under the ROC curve 0.87, false positive prediction rate 0.14, positive predictive value 0.09) or an ARIMA 0-1-2 model with a seven point moving mid-centred median filter (area under the ROC curve 0.87, false positive prediction rate 0.14, positive predictive value 0.10). Only one method that could be used on real-time data outperformed the single Kalman filter which was a Kalman filter combined with a seven point moving median filter predicting the next point in the data stream (area under the ROC curve 0.86, false positive prediction rate 0.23, positive predictive value 0.06).

Anesthesiology↗
PubMed2002

On-line novelty detection for artefact identification in automatic anaesthesia record keeping.

We report the design of a kernel-based on-line novelty detector (ADDaM - Automatic Dynamic Data Mapper) and its use in the detection of artefacts in an automatic anaesthesia record keeper (AARK).ADDaM produces a partitioned history of any ordered data stream and constructs a probability distribution function (PDF) from that history using Gaussian kernels. Two forms of PDF are possible: a static PDF where the prior probability of each kernel is determined by the number of observations it represents and a temporal PDF where more recent observations have a higher prior probability. Testing against the current PDF assesses the novelty of the next point entering the stream. The performance of this method for artefact detection in heart rate data was compared to Kalman, ARIMA and moving mean filters using receiver operator characteristic (ROC) curves. Performance was measured using the area under the curves (AUC), and the false positive rate (FPR) and positive predictive value (PPV) calculated at the optimal cost-point on the curves. The results obtained were: ADDaM (Static PDF) AUC 0.92, FPR 0.12, PPV 0.12 and ADDaM (Temporal PDF) AUC 0.97, FPR 0.12, PPV 0.15. Both ADDaM-based methods out performed all other on-line methods tested.

Algorithms↗
PubMed1999

Procedure for the semi-automatic detection of gastro-oesophageal reflux patterns in intraluminal impedance measurements in infants.

The diagnosis of gastro-oesophageal reflux (GOR) is of great interest for paediatric gastroenterologists. pH monitoring is the commonly used procedure for GOR diagnosis but a major amount of postprandial GOR is missed due to the mostly non-acidic gastric contents in infants. The multiple intraluminal impedance technique is based on the recording of the impedance changes during bolus transport inside the oesophagus. It is the first method which allows the pH-independent, long-term registration of GOR. The use of the impedance technology in clinical practice has been limited so far by the time-consuming, visual evaluation of the impedance traces. The new approach of a semi-automatic analysis of the impedance measurements allows the automated detection of reflux patterns. It is based on event marking and an optimised feature description of the impedance traces combined with a fuzzy system for pattern recognition. The classifier is developed and tested on 50 investigations in infants. Compared to the comprehensive, multiple visual evaluation the achieved precision is 75% sensitivity and 48% positive prediction. In comparison to a single visual evaluation the analysis of the automatically proposed patterns corresponds to a 96% reduction of the evaluation time with no loss of precision. Thus the applicability of the impedance technology is enhanced significantly. A combined measurement of pH and impedance gives evidence about the occurrence of GOR, its pH and the acidic exposure of the oesophagus.

Algorithms↗
PubMedDate not supplied

Automatic forensic face recognition from digital images.

Digital image evidence is now widely available from criminal investigations and surveillance operations, often captured by security and surveillance CCTV. This has resulted in a growing demand from law enforcement agencies for automatic person-recognition based on image data. In forensic science, a fundamental requirement for such automatic face recognition is to evaluate the weight that can justifiably be attached to this recognition evidence in a scientific framework. This paper describes a pilot study carried out by the Forensic Science Service (UK) which explores the use of digital facial images in forensic investigation. For the purpose of the experiment a specific software package was chosen (Image Metrics Optasia). The paper does not describe the techniques used by the software to reach its decision of probabilistic matches to facial images, but accepts the output of the software as though it were a 'black box'. In this way, the paper lays a foundation for how face recognition systems can be compared in a forensic framework. The aim of the paper is to explore how reliably and under what conditions digital facial images can be presented in evidence.

Electronic Data Processing↗