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At least 937 records · Page 52Linked to original sources

PubMed1990

Quantitative analysis of contribution of rate response in three different ventricular rate responsive pacemakers during out of hospital activity.

The contribution of rate response provided by three different types of rate responsive pacemaker (Sensolog, Meta, and Vitatron TX) was assessed in 25 patients during out of hospital activity. Pacemakers were optimally programmed and full disclosure 24-hour Holter ECG recordings were obtained during everyday activities. Close visual analysis of these tracings revealed that rate response is active for less than 15% of the 24-hour study period with high rate response (paced rate above 100 beats/min) for just 5% of the day showing peak activation between 1600 and 2000 hours. Low rate response (paced rate below 100 beats/min but 5 beats above base rate) was maximal between 0800 hours and midday and comprised 10% of all heart beats during the study period. Thirty percent of study patients were nonpacemaker dependent and rate response in these subjects was significantly (P less than 0.001) less active between 0800 hours and midday than in pacemaker dependent patients though it was equivalent at all other times. Nonpacemaker dependent patients achieved natural sinus response in the morning and tended to rely on pacemaker supplied rate response in the latter part of the day.

Activities of Daily Living↗

PubMed1985

Stereologic studies on mitochondrial configuration in the rat pinealocytes.

Stereologic studies were performed on rat pinealocytes. In the morphometric analysis the following parameters were taken into consideration: the volume density of the outer and inner membranes, surface areas of the outer and inner membranes, inner membrane to outer membrane surface area ratio, volumes of the outer and inner compartments, and partition coefficients of these compartments. Visual analysis demonstrated three mitochondrial configurational states. Based on the mitochondrial criteria, the existence of three pinealocyte types may be demonstrated. The authors believe that these are the cells in three different functional states.

Animals↗

PubMed2005

Prediction of neonatal state and maturational change using dimensional analysis.

Nonlinear time series analysis techniques have been used to analyze physiologic signals such as EEG and heart rate. The authors illustrate the application of dimensional analysis (DA) to assess neonatal sleep states at increasing gestational ages up to full-term age. One hundred and sixteen EEG-polygraphic recordings were performed on 55 neonatal subjects between 28 and 43 weeks gestational age from which state assignments were initially scored by visual analysis. A single channel of EEG (i.e., FP1-C3) was selected for dimensional analysis. Two-tailed t-tests were used to test for differences in the correlation dimension (CD) between active and quiet sleep states for both preterm and full-term neonates as a function of maturation. A significant difference in CD between active and quiet sleep states (P < 0.001) was noted for the full-term infant. A positive correlation between CD and increasing conceptional age was noted (P < 0.001). DA showed an increase in the complexity for both active and quiet sleep as the preterm infant matured toward a full-term corrected age. Lower dimensionality (CD), indicative of reduced complexity, was noted for the healthy preterm cohort at corrected full-term age when compared with the full-term group. Dimensional analysis demonstrated a positive correlation for both active and quiet sleep, as the infant matured toward corrected term age. Lower dimensionality was noted for the healthy preterm cohort at corrected full-term age. These findings support the concept of physiologic dysmaturity for the preterm neonate as a reflection of altered neural plasticity of the brain as a result of the conditions of prematurity.

Developmental Disabilities↗

PubMed2000

A qualitative analysis of brain SPECT for prognostication of gross motor development in children with cerebral palsy.

PURPOSE: In this report, the authors assessed the clinical significance of decreased regional cerebral blood flow (rCBF) in the thalamus or cerebellar hemispheres in relation to gross motor performance in the children with cerebral palsy. MATERIALS AND METHODS: Thirty-six children with bilateral spastic cerebral palsy (BSCP) underwent brain SPECT. Visual analysis was used for the brain SPECT interpretation. The rCBF in the thalamus or cerebellum was graded as normal, mildly decreased, or severely decreased. A marked decrease or near absence of rCBF in the thalamus or cerebellum was considered as severely decreased. RESULTS: All 36 children with BSCP had hypoperfusion in the thalamus or cerebellar hemispheres. Eight of 20 children (40%) with mildly decreased rCBF on brain SPECT had mild developmental delays. On the other hand, only 1 of 16 children (6.3%) with severe hypoperfusion in the thalamus or cerebellum had a mild developmental delay, and the remaining 15 of 16 children (93.8%) had severe developmental delays. There was good correlation between the degree of developmental delay and the severity of hypoperfusion in the thalamus or cerebellum (P = 0.023). CONCLUSION: The measurement of rCBF by Tc-99m ethyl cysteinate dimer brain SPECT appears to be valuable in prognostication of gross motor development in children with BSCP.

Brain↗

PubMed2000

Overt and covert identification of fragmented objects inferred from performance and electrophysiological measures.

The authors investigated visual processing leading to object identification by manipulating the number of fragments and nature of the study. During the study, participants either named or drew objects in Experiment 1 and drew them all in Experiment 2. During the test, participants made an identification judgment at each of 6 different fragmentation levels for studied and new objects. Fewer fragments were needed to identify studied than unstudied objects. Reaction times were faster for studied than unstudied objects both at identification and at the preceding level. Event-related brain potentials (ERPs) to unidentified objects were characterized by a late negativity in contrast to a positivity to identified objects. ERPs to studied but not to new objects contained a smaller and later version of the identification positivity at level just prior to identification, which was not due to differential response confidence. Much covert visual analysis and even object identification may precede overt identification, depending on the nature of prior experience.

Adult↗

PubMedDate not supplied

Semiautomated ROI analysis in dynamic MR studies. Part I: Image analysis tools for automatic correction of organ displacements.

The most important problem in the analysis of time sequences is the compensation for artifactual motion. Owing to motion, medical images of the abdominal region do not represent organs with fixed configuration. Analysis of organ function with dynamic contrast medium studies using regions of interest (ROIs) is thus not readily accomplished. Images of the organ of interest need to be registered and corrected prior to a detailed local analysis. We have developed an image analysis scheme that allows the automatic detection of the organ contours, the extraction of the motion parameters per frame, and the registration of images. The complete procedure requires only minimal user interaction and results in a readjusted image sequence, where organs of interest remain fixed. Both a visual analysis of the dynamic behavior of functional properties and a quantitative statistical analysis of signal intensity versus time within local ROIs are considerably facilitated using the corrected series.

Algorithms↗

PubMed1992

Analysis of intracranial pressure.

Methods for the acqusition and analysis of intracranial pressure (ICP) signals are reviewed from clinical and technical perspectives. The clinical importance of ICP monitoring is presented, and methods for ICP transduction are briefly discussed. These methods include intraventricular catheters, subarachnoid screws, epidural techniques, and the new fiberoptic ICP measurement systems. Approaches to the visual analysis of the ICP waveform are presented, with special emphasis on the relationship between the ICP waveform and the arterial blood pressure signal. Methods of computer-based ICP analysis are also reviewed, including histogram and "systems analysis" methods. Methods to predict ICP pressure rises and to estimate intracranial compliance are also discussed. Finally, ICP monitoring is reviewed from the point of view of patient outcome. It is concluded that advanced ICP waveform analysis methods warrant further clinical evaluation to demonstrate their clinical usefulness.

Humans↗

PubMed1988

A new method for the quantitative analysis of sleep spindles during continuous overnight EEG recordings.

Sleep spindles are one of the most characteristic EEG transients of sleep. Quantitative analysis of sleep spindles may be of value in the study of involuntary movement disorders, depression, and sleep disorders, but this is difficult to perform manually. Phase-locked loop based devices have previously been used to analyse preselected periods of artefact-free non-REM sleep. We have developed a device of this type that provides reliable quantitative analysis of sleep spindles during continuous overnight EEG recordings. The number of sleep spindles detected by the device during overnight recordings correlated well with the mean of two independent human observers and measurements of the amplitude and duration of individual sleep spindles were similar to those obtained by visual analysis. The general applicability of the device was demonstrated by studying 61 patients with a range of neurological disorders.

Electroencephalography↗

PubMed1996

On the relative contributions of motion energy and transparency to the perception of moving plaids.

Stoner, Albright and Ramachandran [(1990) Nature, 344, 153-155] found that moving rectangular-wave plaid patterns that admitted a transparency interpretation appeared to segment that "slide" past one another as the plaids were translated, while the components of plaids that did not admit a transparency interpretation appeared to unify and move rigidly in the direction of translation of the plaid. In experiment I, we show that the magnitude of the effect reported by Stoner et al. is due largely to their repeated-trials experimental protocol, in which plaids moving in a particular direction, upward or downward, are repeatedly presented. This protocol leads to a direction-of-motion-specific adaptation that diminishes the effectiveness of processes that are presumably involved in the unification of the various sensory signals evoked by a moving plaid. In the second experiment, we measured frequencies of nonrigidity for a larger class of moving plaid-like patterns that moved either upwards or downwards on a pseudorandom schedule identical to that employed by Stoner et al. Some of the patterns admitted a transparency interpretation, while others did not. The overall pattern of results could not be accounted for within the context of Kim and Wilson's [(1993) Vision Research, 33, 2479-2489] model of motion integration that considers only the oriented motion energy present in a moving plaid stimulus. The results indicate that additional factors, distinct from though perhaps related to the visual analysis of transparency, must also be incorporated into models of perceived plaid motion.

Adaptation, Ocular↗

PubMed1994

SPECT images of technetium-99m-ethyl cysteinate dimer in cerebrovascular diseases: comparison with other cerebral perfusion tracers and PET.

UNLABELLED: To assess the clinical role of 99mTc-ethyl cysteinate dimer (ECD) as a cerebral perfusion tracer, 10 patients with unilateral cerebral infarction were studied. METHODS: ECD SPECT images were compared with IMP and/or HMPAO SPECT in nine patients, seven in chronic phases and two in subacute phases. Five of these patients and one additional patient with chronic infarction received PET imaging in order to compare ECD distribution with quantitative regional cerebral blood flow (rCBF) and oxygen metabolism (rCMRO2) images. RESULTS: In patients with chronic cerebral infarction, regression analysis showed excellent correlation between ECD and IMP in the uptake ratio of lesions-to-nonaffected cortices (r = 0.91). In two cases of subacute infarction, decreased uptake of ECD was observed in the area of "luxury perfusion," which showed elevated or preserved rCBF with diminished rCMRO2. On visual analysis, ECD image contrast was less prominent compared to that of IMP, but contrast was better than that of HMPAO. CONCLUSIONS: ECD uptake showed a curvilinear relationship against rCBF, suggesting flow-limited uptake in a high flow range. ECD is a clinically useful cerebral perfusion tracer with distinct characteristics when compared with other available agents.

Adult↗

PubMed1985

Quantitative analysis of liver function in percutaneous transhepatic biliary drainage patients.

The diagnostic usefulness of Tc-99m DISIDA cholescintigraphy as a predictor of eventual catheter and hepatic function in patients who have undergone percutaneous transhepatic biliary drainage (PTBD) for extrahepatic biliary obstruction was evaluated. Twenty-nine cholescintigrams were performed in 14 patients. The examinations were divided into two groups: Group A (N = 17), in which the patient's clinical status deteriorated within two to three days post-PTBD, and Group B (N = 12), in which the patients did well clinically post-PTBD. No significant difference between the two groups was demonstrated by visual analysis of the analog images or by analysis of serum bilirubin levels. A computer program, developed by the authors, quantitates several parameters of DISIDA kinetics, reflecting hepatic function based upon compartmental analysis. A significant difference (P less than .001) was demonstrated between the mean transport constants (blood clearance constant = k1; hepatic clearance constant = k2) for the two groups. It is concluded that serum bilirubin levels and visual inspection of analog images are inadequate independent predictors of hepatic function in patients post PTBD. The transport constants k1 and k2 are quantitative parameters of hepatic function that may be of prognostic value in patients post PTBD.

Adult↗

PubMed1994

[Quantification of myocardial tomography with thallium in coronary disease. Evaluation of the Cedars-Sinai technique].

OBJECTIVE: The aim of this study is to evaluate the contribution of the Cedars-Sinai quantification tomographic method (CS) in the diagnosis and localization of ischemic areas in coronary artery disease (CAD) and to optimize the threshold values proposed by CS. PATIENTS AND METHODS: Fifty patients with clinical suspicion of CAD performed a maximal stress test by cycloergometer; thallium myocardial tomographic images were obtained; applying the CS program afterwards. The sensitivity and specificity variations obtained by changing the criteria for extent of myocardial hypoperfusion (range 1% to 100%) were used to calculate the new thresholds (CS-I), using the results of coronariographic studies as a reference. The data determined by qualitative analysis were compared with that obtained by quantitative analysis by means of CS and CS-I using coronary angiography as the standard of reference. RESULTS: The coronary angiography showed coronary disease in 37 patients. The sensitivity for the diagnosis of CAD was superior using CS (97%) at the expense of low specificity (15%) which nevertheless improved with CS-I (54%). For the location of CAD, the visual analysis was statistically significant (p < 0.05) in the left anterior descending and right coronary arteries, CS being superior in the diagnosis of 3 vessel disease. CONCLUSIONS: The quantification of tomographic studies with thallium by means of CS needs a readjustment of the thresholds. The tested values (CS-I) improved the CS results, although they require prospective validation. Quantitative study permits the confirmation of visual findings, being a complementary method that can be rapidly and easily interpreted, although it is not recommended as a single technique for the diagnosis of coronary disease.

Adult↗

PubMed2005

Hemispheric specialization of human inferior temporal cortex during coarse-to-fine and fine-to-coarse analysis of natural visual scenes.

Recent models of visual recognition have suggested that perceptual analysis may start with a parallel extraction of different spatial frequencies (SF), using a preferential coarse-to-fine (low-to-high SF) sequence of processing. A rapid extraction of low spatial frequency (LSF) information may thus provide an initial and crude parsing of the visual scene, subsequently refined by slow but more detailed high spatial frequency (HSF) information. However, the sequence of SF analysis could be flexible, a high-to-low (HtL) being sometimes preferred to a low-to-high (LtH) SF sequence depending on task demands. Furthermore, it has also been suggested that the right vs. left hemisphere might be differentially specialized in LSF vs. HSF analysis, respectively. By manipulating the temporal succession of LSF and HSF stimuli, the present fMRI study investigated whether such hemispheric specialization may underlie the flexible use of different time-course in SF analysis. Participants performed a matching task between two successive images of natural scenes (LSF or HSF) that were displayed either in an LtH (LSF scene presented first and HSF scene second) or in a reverse HtL sequence. A direct inter-hemispheric comparison of the neural responses evoked by each SF sequence revealed greater activations within the right occipito-temporal cortex for the LtH sequence and within the left occipito-temporal cortex for the HtL sequence. These fMRI results suggest that the hemisphere preferentially engaged during the sequential processing of different SF might be determined by the initial SF-band appearing in this sequence, and that both a coarse-to-fine and fine-to-coarse analysis might independently take place in the two hemispheres.

Adult↗

PubMed2002

Time-efficient T2 relaxometry of the entire hippocampus is feasible in temporal lobe epilepsy.

OBJECTIVE: To test the clinical usefulness and reliability of a new dual-echo turbo-spin-echo (TSE) sequence for rapid and regional hippocampal T2 relaxometry. METHODS: Hippocampal T2 relaxation time (HRT) was determined by a TSE sequence on three to four consecutive coronal images in 16 control subjects and 12 patients with mesial temporal lobe epilepsy. HRT was related to neuropathology findings in hippocampal specimens including neuronal cell density (ND), results of visual analysis of MR images, clinical outcome after epilepsy surgery, and hippocampal volumetry. RESULTS: Rapid HRT differentiated patients from control subjects; all cases of hippocampal sclerosis (HS; n = 10) were correctly diagnosed. HRT showed a strong correlation with ND in CA1 (p < 0.02) and CA3 (p < 0.05). Diagnoses based on rapid relaxometry concurred fully with results of visual inspection. Mean HRT was prolonged ipsilaterally in all patients with excellent postoperative seizure outcome and bilaterally prolonged or normal in patients with poorer outcome. Rapid HRT was concordant with hippocampal volumetry in 10 of 12 patients. Regional HRT of control subjects revealed significantly higher values in the anterior than posterior hippocampus. In patients with unilateral HS, this gradient was absent. The gradient was also absent contralaterally to HS, although surgical outcome was excellent. CONCLUSIONS: Hippocampal dual-echo TSE-relaxometry can be regarded a reliable technique to detect and quantify HS. With a scan time of 3.31 minutes and immediate off-line analysis lasting a few minutes only, TSE-T2 relaxometry is easy to integrate in the routine diagnostic assessment of hippocampal morphology in large numbers of patients.

Adolescent↗

PubMedDate not supplied

Repeat femoral arteriography in hyperlipidemic patients. A study of progression and regression of atherosclerosis.

Femoral arteriography was performed in 62 patients with significant hyperlipidemia. Sixty were asymptomatic and two had intermittent claudication. The patients participated in a study aiming to demonstrate whether serum lipid lowering by drugs could influence the development of femoral artery atheromatous disease. Half of the patients were treated with fenofibrate and nicotinic acid and the other half served as a control group. At the first arteriography atherosclerotic lesions were found in 46 of the 62 patients (74%). Arteriography was repeated up to three times without complication. Visual analysis of angiograms revealed considerable inter-observer variation. An attempt was made to assess the angiograms by a computerized method which, however, still needs improvement and a computer designed for image analysis. Most patients had small or moderate atheromatous deposits in the femoral artery at the initial examination, in most cases showing no change during the study period of 18 months. Regression was found in five patients of the treated group, but in none of the control patients as judged by visual gradation (p less than 0.001).

Adult↗

PubMed1996

Urinary protein excretion of semidomesticated mink in a chronic methylmercury study.

A model using semidomesticated mink was set up to study the effects of chronic oral methylmercury exposure in piscivorous mammals. Three groups of mink were fed daily with diets containing approximately 0.1, 0.5, and 0.9 micrograms/g of total mercury. Piscivorous and non-piscivorous fish, naturally contaminated with methylmercury, were used to prepare diets. Renal injury was evaluated using total urine protein/creatinine ratio and differentiation of urinary low-molecular-weight and high-molecular-weight proteins on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The significance of the total urine protein/creatinine ratio data was assessed by comparing the results to a 95% group-based reference interval. The values for total urine protein/creatinine ratio did not reveal any significant increased excretion, and no dose-related trends were observed within the reference interval. Overall the total urine protein data did not suggest renal damage. Analysis of the SDS-PAGE electrophoretograms did not suggest the presence of any persistent glomerular damage in any group. High-molecular-weight proteins were not detected more frequently for any of the dose groups. During the adaptation phase, the B2M-like protein band was not remarked during the visual analysis of the gels. The B2M-like protein band was remarked during the gel analysis only several weeks into the exposure phase. This B2M-like protein band was more prevalent in urine samples taken from minks in the 0.5 and 0.9 micrograms/g groups than in the 0.1 microgram/group. These latter data, however, did not allow an evaluation of a quantitative dose-response excretion with time. The B2M-like data are suggestive of very minor renal injury.

Albuminuria↗

PubMed2001

Does motion analysis in postexercise gated sestamibi SPECT reflect rest left ventricular motion even in severe coronary artery disease?

PURPOSE: Evidence has suggested that postexercise gated Tc-99m sestamibi SPECT (GSPECT) provides combined information about resting wall motion and exercise perfusion. No data have been published about possible differences in wall motion analysis between postexercise and resting GSPECT. METHODS: Fifty patients underwent postexercise (symptom-limited bicycle stress) and rest GSPECT and cardiac catheterization with contrast ventriculography. In 35 patients, additional rest planar Tc-99m RBC radionuclide ventriculography (RNV) was performed. Four observers independently performed left ventricular ejection fraction (LVEF) calculations and visual analysis of regional wall motion (graded in four stages) for all studies. RESULTS: The LVEF calculations in GSPECT revealed a statistically significant difference between postexercise (45.8 +/- 15.7%) and rest (48.0 +/- 16.1%; P < 0.05) determination. Postrest GSPECT LVEF showed a better correlation with LVEF determination performed with contrast ventriculography and RNV than did postexercise GSPECT LVEF. The reduced postexercise wall motion could be shown in segments with exercise-induced ischemia and in those with normal regional perfusion but not in segments with irreversibly abnormal perfusion. CONCLUSIONS: Postexercise GSPECT provides reliable information regarding global wall motion even in severe coronary artery disease, but regional wall motion is underestimated compared with rest GSPECT, because of an imprecise surface detection algorithm in ischemic wall segments and possibly postexercise stunning in severe coronary artery disease.

Aged↗

PubMed2000

Comparison of fluorine-18 deoxyglucose and O-15 water PET in temporal lobe epilepsy.

This study reports a comparison of Fluorine-18 deoxyglucose positron emission tomography (FDG-PET) and O-15 water (H2(15)O) PET with regard to lateralization of the seizure focus in patients with complex partial epilepsy. The analysis of 35 patients who had an anterior temporal lobectomy for medically intractable seizures indicated that FDG- and H2(15)O-PET were highly correlated in demonstrating the epileptic focus. FDG- and H2(15)O-PET showed significant asymmetries in 83% and 77% of cases respectively. The lateralization with visual analysis of MRI was found to be lower than both FDG and blood flow imaging. Ictal electroencephalography (EEG) lateralizations were concordant with sites of blood flow and FDG-PET abnormalities. Thirty-three patients (94%) were seizure-free or improved significantly after surgery. In conclusion, blood flow PET yielded similar results compared to FDG-PET and can be a valuable modality in preoperative evaluation of patients with temporal lobe epilepsy.

Adolescent↗