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At least 955 records · Page 53Linked to original sources

PubMed1998

Application of the directed transfer function method to mesial and lateral onset temporal lobe seizures.

The directed transfer function (DTF) method is a multichannel analysis based on an autoregressive model that detects flow of seizure activity. This report extends the application of the DTF method to compare patterns of flow of seizures with different sites of origin. Analysis of a seizure originating from mesial temporal structures is compared with a seizure originating from lateral temporal neocortex; both complex partial seizures were recorded with intracranial electrodes that combine subdural grid arrays and depth electrodes. The DTF method has the potential to determine patterns of flow of activity, including periods when visual analysis of the intracranial ictal EEG may not allow for definitive source localization. The extension of the DTF analyses into integrated DTF (IDTF) formats is also illustrated. When activity of a relatively discrete frequency can be identified, the IDTF analysis facilitates display of patterns of flow of this selected activity.

Algorithms↗

PubMed2003

Correlation among retinal thickness, optic disc, and visual field in glaucoma patients and suspects: a pilot study.

OBJECTIVE: To correlate losses of retinal thickness in the perifoveal area in glaucoma as measured by the Retinal Thickness Analyzer (Talia Technology Ltd, Israel) with optic nerve and visual field changes in glaucoma patients and suspects. METHODS: Observational case series of 55 consecutive patients from the Glaucoma Service who either presented with a diagnosis of glaucoma or were referred for evaluation of suspected glaucoma. The Retinal Thickness Analyzer (Talia Technology, Ltd.) was used to obtain retinal thickness maps. Retinal thickness analysis, visual field testing, and stereophotography of the optic nerve head were performed, and a glaucoma specialist who was masked to patient status and identity data randomly graded the level of severity of each parameter. Spearman rank correlations were used to assess the relationships among the three numerical measures. RESULTS: Retinal thickness losses correlated more strongly with severity of optic nerve head cupping (r = 0.75), whereas both of these measures correlated less strongly with the severity of visual field loss (r = 0.54). CONCLUSIONS: Retinal thickness measurements at the posterior pole provide another measure of neural loss in glaucoma, and may help in the clinical assessment of optic nerve cupping. However, there are limitations of the technology that must be considered.

Adult↗

PubMed2004

Color and power Doppler sonography in the diagnosis of prostate cancer: comparison between vascular density and total vascularity.

OBJECTIVE: Advances in color flow Doppler (CFD) and power Doppler imaging (PDI) have potential for prostate cancer diagnosis. Previous reports based on qualitative assessment suggest that hypervascularity increases likelihood of prostate cancer. Our objective was to compare 2 methods of vascularity assessment using PDI: total vascularity (TV) and vascular density (VD). The goal was to determine whether quantitative Doppler vascularity correlates with the likelihood of prostate cancer. Quantitative measurements were compared with subjective visual analysis of images. METHODS: Ninety patients before biopsy had gray scale sonography, CFD, and PDI. Histologic analysis showed adenocarcinoma, prostate intraepithelial neoplasia, benign prostatic hypertrophy/prostatitis, and benign findings. The CFD and PDI images were analyzed for vascularity by (1) integrating the number of blood vessels over an imaged area (TV) and (2) integrating the number of vessels over a unit area of tissue (VD). Images were also assessed visually. VD, TV, and visual assessment were compared with one another and histologic findings. RESULTS: Mean volume was not different. In each pathologic group, vascularity extent measured by TV and VD ranged from low to high. Disease groups did not exhibit a substantial difference in vascularity by either quantitative or qualitative analyses. Regionally, central gland TV was not significantly more vascular than peripheral gland TV except in benign prostatic hypertrophy. However, peripheral gland VD was 2.5 times greater than central gland VD. Seventy-one percent of the 31 focal hypoechoic lesions were hypervascular. Only 23% were carcinoma. CONCLUSIONS: Pathologic categories were not separable by apparent vascular measurement. All pathologic categories showed low, moderate, or high vascularity; thus vascular areas by themselves did not distinguish cancer types, nor did focal hypervascular hypoechoic areas increase the likelihood of cancer. These imaging techniques provided no further resolution of tumor discrimination over multiple biopsies of the prostate.

Adenocarcinoma↗

PubMed1982

[Realization of a system which permits automatic analysis of sleep of infants (2-12 months)].

We have developed a system which permits automatic analysis of sleep of infants from 2 to 12 months of age. It is based on the calculation of a score on the basis of 6 parameters weighted according to their importance in determining the different phases of sleep. We use 3 EEG parameters derived from spectral analysis of the Cz-Oz derivation: total spectral energy (Hjorth activity), energy of the delta band, and energy of the beta band, and 3 polygraphic parameters: variability of muscle activity in each minute, variability of the respiratory frequency and presence or absence of rapid eye movements. The analysis provides a list of the sleep phases, minute by minute, and a traditional sleep diagram; we also calculate the successive appearances of the different sleep phases, in 10 min periods, and schematize these results in a diagram which shows the general trend of each sleep phase during the night. When compared with visual analysis, these results are satisfactory, since we observe on average 86.2% agreement in the differentiation of calm, paradoxical and transitional sleep, and 76.4% agreement in the differentiation of stages II, III and IV of calm sleep.

Electroencephalography↗

PubMed1995

Atherosclerosis in angiographically "normal" coronary artery reference segments: an intravascular ultrasound study with clinical correlations.

OBJECTIVES: This study evaluated the magnitude, patterns and clinical correlates of atherosclerosis in angiographically "normal" reference segments in patients undergoing transcatheter therapy for symptomatic coronary artery disease. BACKGROUND: Pathologic studies indicate that the extent of coronary atherosclerosis is underestimated by visual analysis of angiographically normal coronary artery segments. Intravascular ultrasound allows detailed, high quality cross-sectional imaging of the coronary arteries in vivo. METHODS: Intravascular ultrasound was used to study angiographically normal coronary artery reference segments in 884 patients evaluated for transcatheter therapy for symptomatic native coronary artery disease. The reference segment was the most visually normal intravascular ultrasound cross section within 10 mm proximal to the target lesion but distal to any major side branch. Results are presented as mean value +/- 1 SD. RESULTS: Only 60 (6.8%) of 884 angiographically normal reference segments were normal by intravascular ultrasound. Reference segment percent cross-sectional narrowing measured 51 +/- 13% and correlated poorly with the target lesion percent cross-sectional narrowing (r = 0.166, p < 0.0001). Reference segments contained less calcific and dense fibrotic plaque and proportionately more soft plaque elements. Independent predictors of reference segment percent cross-sectional narrowing were male gender, patient age, diabetes mellitus, hypercholesterolemia and presence of multivessel disease. Independent predictors of reference segment calcification were patient age and serum creatinine levels. Reference segment percent cross-sectional narrowing in 723 patients undergoing transcatheter therapy was similar to that in patients studied for diagnostic purposes; however, reference segment arc of calcium was greater in treated patients (43 +/- 81 vs. 25 +/- 57, p = 0.015). Reference segment disease was not an independent predictor of subsequent angiographic restenosis or clinical events within 12 months of follow-up. CONCLUSIONS: Atherosclerosis is ubiquitous in angiographically normal coronary artery reference segments. Reference segment disease parallels the severity of target lesion disease and is associated with many of the conventional risk factors for coronary artery disease. Because of its sensitivity in detecting atherosclerosis in angiographically normal reference segments, intravascular ultrasound should enhance the study of risk factors for atherosclerosis and the results of therapies to control disease progression.

Age Factors↗

PubMed2004

Parietal generators of low- and high-frequency MN (median nerve) SEPs: data from intracortical human recordings.

OBJECTIVE: To identify low and high-frequency median nerve (MN) somatosensory evoked potential (SEP) generators by means of chronically implanted electrodes in the parietal lobe (SI and neighbouring areas) of two epileptic patients. METHODS: Wide-pass short-latency and long-latency SEPs to electrical MN stimulation were recorded in two epileptic patients by stereotactically chronically implanted electrodes in the parietal lobe (SI and neighbouring areas). To study high-frequency responses (HFOs) an off-line digital filtering of depth short-latency SEPs was performed (500-800 Hz, 24 dB roll-off). Spectral analysis was performed by fast Fourier transform. RESULTS: In both patients we recorded a N20/P30 potential followed by a biphasic N50/P70 response. A little negative response in the 100 ms latency range was the last detectable wide-pass SEP in both patients. Two HFOs components (called iP1 and iP2) were detected by mere visual analysis and spectral analysis, and were supposed to be originated within the parietal cortex. CONCLUSIONS: This was the very first study that recorded wide bandpass and high frequency SEPs by electrodes, exploring both the lateral and the mesial part of the parietal lobe and particularly that of the post-central gyrus.

Adult↗

PubMed1998

Dynamic contact maps of protein structures.

The two-dimensional contact map of interresidue distances is a visual analysis technique for protein structures. We present two standalone software tools designed to be used in combination to increase the versatility of this simple yet powerful technique. First, the program Structer calculates contact maps from three-dimensional molecular structural data. The contact map matrix can then be viewed in the graphical matrix-visualization program Dotter. Instead of using a predefined distance cutoff, we exploit Dotter's dynamic rendering control, allowing interactive exploration at varying distance cutoffs after calculating the matrix once. Structer can use a number of distance measures, can incorporate multiple chains in one contact map, and allows masking of user-defined residue sets. It works either directly with PDB files, or can use the MMDB network API for reading structures.

Computer Simulation↗

PubMed1993

Quantitative colorimetric analysis of liquid crystal films (LCF) for phantom dosimetry in microwave hyperthermia.

A fully quantitative analysis of liquid crystal film (LCF) color patterns, in phantom thermal dosimetry for microwave hyperthermia, is presented. An accurate determination of absorption rate density (ARD) is achieved by color image computer processing. This work is proven to be an improvement upon the semi-quantitative or qualitative descriptions of LCF colors performed essentially by visual analysis of photographs. Temperature-induced chromatic distributions are acquired as R, G, B (red, green, blue) signals by a CCD camera connected to a PC frame grabber board. These data, stored into three 512 x 512 memory buffers, are then converted to H, S, I (hue, saturation, intensity) colorimetric system. Provided a suitable calibration of the LCF, the H quantity can be transformed to temperature using a monotonic relationship. In this way, a temperature accuracy lower than 0.2 degrees C and a spatial resolution less than 1 mm are obtained. A sequence of thermal maps can be acquired and stored on disk at a maximum rate of 1 image/2 s, and then the ARD is calculated at each pixel of the map using the least squares method.

Calibration↗

PubMed1998

Extrarenal uptake of Tc-99m-DTPA in a case of retroperitoneal abscess causing spurious data in renal function assessment.

The author reports CT of the abdomen and quantitative analysis of renal scintigraphy that was spuriously assessed due to unwanted extrarenal uptake. The patient had a retroperitoneal abscess that was related to fistula from the right kidney. Renal scintigraphy was performed to assess split renal function as a preoperative evaluation for nephrectomy. The computer generated differential function did not appear to coincide with the visual analysis. This discrepancy was believed due to extrarenal uptake from the area of the retroperitoneal abscess.

Abdominal Abscess↗

PubMed1996

Congenital visual agnosia and prosopagnosia in a child: a case report.

We present an eight years old child, L.G. with congenital agnosia and prosopagnosia. This is a special case of perceptual deficits in a child which are discrete and exist in the context of a very high verbal intelligence. L.G. was administered an extensive battery of tests of cognitive functioning. He has intact basic visual skills, although his visual analysis is sometimes slow. L.G. can read, write and do math at age level or above. Four normal eight years old boys were used as controls on a selection of the perceptual tests, administered to L.G., which did not have normative data. L.G.'s object recognition skills bear the hallmarks of adult apperceptive agnosia. His visual memory and imagery are normal. Tests of face processing skills reveal, unlike adult prosopagnosics, severe deficits in addition to the familiar face recognition problem. L.G.'s agnosia and prosopagnosia are compared to the relevant literature.

Agnosia↗

PubMedDate not supplied

Clinical impact of arrhythmias on gated SPECT cardiac myocardial perfusion and function assessment.

BACKGROUND: We reported previously that mean quantified cardiac functional parameters computed by one gated single photon emission computed tomography (SPECT) technique were not significantly altered by common gating errors. However, it is not known to what extent other gated SPECT approaches that are based on different ventricular modeling assumptions are influenced by arrhythmias, nor are the effects of gating errors on visual analyses and their subsequent clinical implications known. METHODS: Projection data for 50 patients (aged 64 +/- 12 years; 68% men; 76% with myocardial perfusion defects) undergoing technetium-99m sestamibi gated SPECT who were in sinus rhythm during data acquisition were altered to simulate common arrhythmias. To determine quantitative effects, we performed calculations for original control and altered images by Gaussian myocardial detection (Quantitative Gated SPECT [QGS] program) and by wall thickening derived from gated perfusion polar maps (Emory Cardiac Toolbox program). To evaluate visual assessment in control and simulated-arrhythmia tomograms, 2 experienced blinded observers independently interpreted perfusion from polar maps and wall motion and thickening from tomographic cines, using a 4-point scale. RESULTS: Although mean functional parameters were scarcely altered, paired t tests showed ejection fraction fluctuations to be significantly different from control values, causing patients to change between abnormal and normal ejection fraction categories (2% of patients by QGS and 14% by Emory Cardiac Toolbox). Visual examination of QGS polar perfusion and function maps showed changes for 72% of cases, although in only 4% were these considered to have potential clinical consequences. The kappa statistic for visual analysis of concordance between control and arrhythmia readings showed that agreement was "excellent" for perfusion, "good" for motion, and "marginal" for thickening. CONCLUSIONS: As with quantitative measurements, thickening is the parameter most prone to error in the presence of arrhythmias. It is important to test data for gating errors to avoid potentially erroneous measurements and visual readings.

Arrhythmias, Cardiac↗

PubMed1999

Application of correlation dimension and pointwise dimension for non-linear topographical analysis of focal onset seizures.

For many patients who are candidates for epilepsy surgery, non-invasive evaluation fails to provide sufficient information to permit surgical treatment. Since there are also definite risks and considerable costs associated with invasive procedures, new (non-invasive) techniques are required. This study provides empirical evidence that a non-linear approach applied to ictal surface electroencephalograms (EEGs) can help to delineate the area of seizure onset and may prove useful in complementing visual analysis of the EEG. Multichannel EEGs, recorded from eight patients with different drug-resistant localisation-related epilepsies, were analysed using the concept of correlation dimension and two extensions based on the pointwise dimension. The latter also provided results in cases where assessment of the correlation dimension was not feasible. Comparative values between 2 and 6 were accepted as the result of the algorithms, mostly 3-4 for the EEG channels strongly reflecting epileptic activity, and 4-6 for the other signals. The proportion of accepted pointwise values was usually 200-800% for strong epileptic EEG activity compared to the other data. The approach permitted the characterisation of the scalp area reflecting epileptic activity. The results obtained were in perfect concordance with those obtained during pre-surgical work-up and confirmed by the post-operative outcome.

Adolescent↗

PubMed1990

Quantitative analysis of fetal rate: its application in antepartum clinical monitoring and behavioural pattern recognition.

A system based on an IBM compatible personal computer is described for the computerized analysis of the cardiotocograms. The system performs a quantification of both fetal heart rate and uterine contractions providing automatically several variables including heart rate baseline; number, duration and area of accelerations and decelerations; latency time between decelerations and uterine contractions; uterine resting tone; number, duration and area of contractions. The computerized description was compared to the visual analysis of the cardiotocogram and a good agreement was evidenced. This system was applied to the analysis of heart rate variability in order to recognize the different patterns characterizing fetal behavioral states. Up to now, however, the results obtained in this latter application are not sufficiently accurate and do not allow a reliable automatic recognition of heart rate patterns.

Cardiotocography↗

PubMed1998

Ambulatory gastrojejunal manometry in severe motility-like dyspepsia: lack of correlation between dysmotility, symptoms, and gastric emptying.

BACKGROUND: Previous studies have failed to identify manometric patterns of gastrointestinal motor activity that can distinguish dyspepsia from health. AIMS: To test the hypothesis that the combined use of prolonged, ambulatory, antrojejunal manometry and computer aided analysis in patients selected for the severity of their symptoms could reveal new insights into gastrointestinal motor activity in patients with severe motility-like dyspesia. METHODS: Twenty four hour antrojejunal ambulatory manometry was performed in 14 patients and 10 healthy volunteers. Parameters characterising digestive and fasted motility were obtained by a validated computer program and visual analysis. Scoring systems quantified the degree of dysmotility as well as the severity of symptoms. Gastric emptying times were measured in each patient. RESULTS: There was a high prevalence of antral and jejunal dysmotility both during the interdigestive period (71% of patients) and in the postprandial period (78%). During the interdigestive period there was a reduced incidence of antral and jejunal phases, a larger contribution of phase 2 during migrating motor complex cycles, and aberrant configuration of jejunal phase 3 in 29% of patients. Postprandially, the most frequent finding was antral (29% of patients) or jejunal (29%) hypomotility or hypermotility. Minute rhythm was present both during the postprandial (29% of patients) and the interdigestive period (21%). There was no positive correlation between symptom scores, gastric half emptying times, or motility scores. CONCLUSION: Even with the use of prolonged recordings and advanced computer aided analysis, it is not possible to identify a specific motor pattern which can discriminate patients with severe motility-like dyspepsia from those with other diseases or even healthy individuals. Clinical symptoms or gastric half emptying times are poor predictors of gastrointestinal dysmotility in patients with functional dyspepsia.

Adolescent↗

PubMed1992

Analysis of quantitative PCR for the diagnosis of deletion and duplication carriers in the dystrophin gene.

A direct, non-radioactive method of quantitative PCR amplification has been investigated for the diagnosis of deletion and duplication carriers in the dystrophin gene. The simultaneous amplification of two loci, or several loci using multiplex PCR, allows for the direct comparison of relative amounts of products from normal homozygous loci and potentially heterozygous deleted/duplicated loci. Sufficient cycles of PCR are performed to enable visual analysis or densitometric quantification of products on ethidium bromide stained gels. The method has been verified in blind trials performed on known genotypes and by showing that under the conditions used the assay remains within the exponential phase of amplification.

Chromosome Deletion↗

PubMed1991

Reproducibility of long-term ambulatory esophageal combined pH/manometry.

Long-term ambulatory esophageal manometry is used increasingly, but normal values and data on the reproducibility of the method are not available. Thus, studies were conducted using paired 24-hour recordings, separated by 1-4 weeks, in 24 healthy volunteers (aged 19-50). Computerized analysis of each two-channel pressure recording (5 and 15 cm above lower esophageal sphincter) determined mean contraction amplitude, duration, area under the curve, contractility and propagation velocity, and the proportion of propagated contractions during day and night periods. A combined glass pH electrode (5 cm above lower esophageal sphincter) was used to register acid reflux. Visual analysis of the 24-hour contractility patterns showed marked intraindividual reproducibility but, although most subjects showed similar meal-associated increases and sleep-associated decreases in contraction frequency and amplitude, considerable interindividual variation was observed. This was confirmed by comparing the variation between subjects in the first and second recordings with the variation between recordings in the same subject; for all pH and manometry variables, the coefficient of variation was two to three times greater between subjects than between recordings in the same subject. The recordings were highly reproducible within subjects (nighttime contraction duration, P less than 0.05; all other variables, P less than 0.01). Thus, computerized ambulatory pH manometry is reproducible and because healthy volunteers have a characteristic individual pattern of esophageal motility, the method is perfectly suitable for repeated-measure design physiological and pharmacological studies. However, generally applicable normal values are difficult to define.

Adult↗

PubMed2006

Channel surfing in the visual brain.

Vision provides us with an ever-changing neural representation of the world from which we must extract stable object categorizations. We argue that visual analysis involves a fundamental interaction between the observer's top-down categorization goals and the incoming stimulation. Specifically, we discuss the information available for categorization from an analysis of different spatial scales by a bank of flexible, interacting spatial-frequency (SF) channels. We contend that the activity of these channels is not determined simply bottom-up by the stimulus. Instead, we argue that, following perceptual learning a specification of the diagnostic, object-based, SF information dynamically influences the top-down processing of retina-based SF information by these channels. Our analysis of SF processing provides a case study that emphasizes the continuity between higher-level cognition and lower-level perception.

Brain↗

PubMed2006

Evaluation of a new expert system for fully automated detection of the Alzheimer's dementia pattern in FDG PET.

OBJECTIVE: Fluorodeoxyglucose (FDG) positron emission tomography (PET) is increasingly used to support a diagnosis of Alzheimer's disease. The aim of the present study was to evaluate a new expert system (PALZ) for the fully automated analysis of FDG PET images for diagnosis of the disease. METHODS: The PALZ tool is based on the detection of the typical disease pattern in FDG PET images. Its potential for this task was evaluated in 22 consecutive patients with suspected Alzheimer's disease who had been graded as positive for the pattern by an experienced reader (visual analysis supported by statistical parametric mapping (SPM)), and in 18 controls. Dependence on scanner performance was assessed by variation of the spatial resolution of the PET images. RESULTS: All the Alzheimer's disease subjects were classified as pattern-positive by the PALZ tool. Fifteen controls were classified as normal. Sensitivity and specificity for differentiation of the patients with suspected Alzheimer's disease from the controls were 100% and 83%, respectively. The false positive finding in three controls most likely was caused by differences in attenuation correction between the normal data base of the PALZ tool (cold transmission scan) and the local data sets (hot transmission scan). There was only mild dependence on spatial resolution. CONCLUSIONS: The results of the present study suggest that the PALZ tool provides similar performance for the detection of the typical Alzheimer's disease pattern in FDG PET images as an experienced reader supported by SPM. The PALZ tool is fully automated, easy to use, and insensitive to the spatial resolution of the PET scanner used. Therefore, it has the potential for widespread clinical use.

Aged↗