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PubMed1994

Visualization and analysis of co-occurrence and cross-tabulation data in medical research.

Analyzing raw data can be prohibitively time consuming. A variety of graphical techniques have been developed to address this problem. Although graphical analysis can provide a simple yet comprehensive overview of a large dataset, often these techniques fail to capture the essence of data trends. In addition, the ability to easily query any component of the data subset frequently remains burdensome. In this paper, we present a general method to address these issues for cross-tabulation tables and provide examples of their use in medical research.

Computer Graphics↗
PubMed1997

Nonlinear analysis of visual evoked potentials elicited by color stimulation.

The relationship between chromatically modulated stimuli and visual evoked potentials (VEPs) was considered. VEPs of normal subjects elicited by chromatically modulated stimuli were measured under several color adaptations, and their binary kernels were estimated. Up to the second-order, binary kernels obtained from VEPs were so characteristic that the VEP-chromatic modulation system showed second-order nonlinearity. First-order binary kernels depended on the color of the stimulus and adaptation, whereas second-order kernels showed almost no difference. This result indicates that the waveforms of first-order binary kernels reflect perceived color (hue). This supports the suggestion that kernels of VEPs include color responses, and could be used as a probe with which to examine the color visual system.

Adaptation, Ocular↗
PubMed1999

18F-FDG PET studies in patients with extratemporal and temporal epilepsy: evaluation of an observer-independent analysis.

UNLABELLED: The aim of this study was to evaluate an observer-independent analysis of 18F-fluorodeoxyglucose (FDG) PET studies in patients with temporal or extratemporal epilepsy. METHODS: Twenty-seven patients with temporal epilepsy and 22 patients with extratemporal epilepsy were included in the study. All patients with temporal epilepsy and 7 patients with extratemporal epilepsy underwent surgical treatment. In patients who showed significant postoperative improvement (temporal, n = 23; extratemporal, n = 6), the epileptogenic focus was assumed to be located in the area of surgical resection. In extratemporal epilepsy patients who did not undergo surgery, the focus localization was determined using a combination of semiology, ictal and interictal electroencephalography, [99mTc]ethyl cysteinate dimer SPECT, MRI and [11C]flumazenil PET. Visual analysis was performed by two experienced and two less experienced blinded observers using sagittal, axial and coronal images. In the automated analysis after anatomic standardization and generation of three-dimensional stereotactic surface projections (SSPs), a pixelwise comparison of 18F-FDG uptake with an age-matched reference database (n = 20) was performed, resulting in z score images. Pixels with the maximum deviation were detected, summarized and attached to one of 20 predefined surface regions of interest. For comparison with 18F-FDG PET and MR images, three-dimensional overlay images were generated. RESULTS: In patients with temporal epilepsy, the sensitivity was comparable for visual and observer-independent analysis (three-dimensional SSP 86%, experienced observers 86%-90%, less experienced observers 77%-86%). In patients with extratemporal epilepsy, three-dimensional SSP showed a significantly higher sensitivity in detecting the epileptogenic focus (67%) than did visual analysis (experienced 33%-38%, each less experienced 19%). In temporal lobe epilepsy, there was moderate to good agreement between the localization found with three-dimensional SSP and the different observers. In patients with extratemporal epilepsy, there was a high interobserver variability and only a weak agreement between the localization found with three-dimensional SSP and the different observers. Although three-dimensional SSP detected multiple lesions more often than visual analysis, the determination of the highest deviation from the reference database allowed the identification of the epileptogenic focus with a higher accuracy than subjective criteria, especially in extratemporal epilepsy. CONCLUSION: Three-dimensional SSP increases sensitivity and reduces observer variability of the analysis of 18F-FDG PET images in patients with extratemporal epilepsy and is, therefore, a useful tool in the evaluation of this patient group. The benefit of this analytical approach in patients with temporal epilepsy is less apparent.

Adolescent↗
PubMed1991

Computerized fetal heart rate analysis in labor.

Observer variation in visual analysis of fetal heart rate (FHR) records is reportedly high, but can be avoided by computerized numerical analysis. The FHRs of 394 women in labor at 37 or more weeks' gestation were recorded on-line and analyzed to examine how different patterns related to outcome, as judged by umbilical arterial base deficit or Apgar score on delivery. The range of normality and the diversity of patterns of those delivered without acidemia were great. Late decelerations were of poor prognostic value. There was an increase in FHR variation during labor averaging 40%. In this preliminary study, conventional attributes of the FHR, alone or in combination, did not predict metabolic acidemia. Epidural analgesia in 240 women was identified as a confounding variable that significantly affected FHR patterns without influencing the condition of the infant at birth. It was associated with a higher FHR, less FHR variation and fewer decelerations, primiparity, longer labors, more operative deliveries, and a threefold greater cesarean rate. The rise in basal FHR, perhaps due to a rise in maternal temperature, may partly explain the high intervention rate in those without fetal acidemia.

Acid-Base Imbalance↗
PubMed1989

Detection of multivessel disease in patients with sustained myocardial infarction by thallium 201 myocardial scintigraphy: no additional value of quantitative analysis.

This study was performed to determine the value of visual and quantitative thallium 201 scintigraphy for the detection of multivessel disease in 67 patients with a sustained transmural myocardial infarction. Also the viability of the myocardial regions corresponding to pathologic Q-waves was evaluated. Of the 67 patients, 51 patients had multivessel coronary artery disease (76%). The sensitivity of the exercise test was 53%, of thallium scintigraphy 69%, when interpreted visually, and 67%, when analysed quantitatively. The specificity of these methods was 69%, 56%, and 50%, respectively. Sixty-two infarct-related flow regions were detected by visual analysis of the thallium scans, total redistribution was observed in 11/62 (18%) of patients, partial redistribution in 26/62 (42%), and no redistribution in 25/62 (40%) of patients. The infarct-related areas with total redistribution on the thallium scintigrams were more likely to be associated with normal or hypokinetic wall motion (7/11: 64%) than the areas with a persistent defect (7/25:28%) (P = 0.05), which were more related with akinetic or dyskinetic wall motion. Based on our results, it is concluded that 1) both visual and quantitative analysis of thallium exercise scintigraphy have limited value to predict the presence or absence of multivessel coronary artery disease in patients with sustained myocardial infarction, and 2) exercise-induced thallium redistribution may occur within the infarct zone, suggesting the presence of viable but jeopardized myocardium in presumed fibrotic myocardial areas.

Coronary Angiography↗
PubMed1984

Schizophrenia and spectral analysis of the visual evoked potential.

Power spectral analysis was performed on the visual evoked potentials (VEPs) recorded in response to flashes of different intensity in both unmedicated schizophrenic and normal subjects. At occipital locations (O1, O2), schizophrenics showed less power than normals in the 10-14 Hz frequency range. In the 18-22 Hz range, schizophrenics showed under-activation in the left hemisphere and over-activation in the right. At temporal locations (T3, T4), schizophrenics showed abnormal (left greater than right) hemisphere patterns of activation in 10-14 Hz and 18-22 Hz ranges. There were no group differences in relationships between power and intensity changes at vertex (Cz). The results suggest abnormal cortical-subcortical interactions during analysis of visual information in schizophrenia.

Adult↗
PubMed1995

Application of automation to the detection of radiation damage using FISH technology.

A whole chromosome painting approach was employed to highlight the damaging effects of low-to-moderate doses of ionizing radiation. A detailed tally of damage involving the painted chromosomes 1 and 2 was compiled from visual analysis and compared with the results of an automatic image processing approach, where the possible outcomes were 'normal', 'abnormal', or 'rejected'. The performance of the automatic approach was tested using a set of 9000 bicolour metaphase images harvested from whole-blood cell culture following irradiation levels of 0.0, 0.5, 1.0 and 2.0 Gy. Every metaphase image in the set was analysed visually. The automatic analysis model was based on two simple image criteria to distinguish normal from abnormal; either an increase in the number of painted objects or a large asymmetry in the area distribution of the expected number of painted objects. A result was obtained without a full karyotype analysis. In practice, automatic analysis produced a set of images for review that were enriched by a factor of 3-4 in true abnormal images. Fast visual review of these images (approximately 200/h) selected the true abnormals. A comparison of the automatic analysis with the visual analysis showed that automated analysis correctly identified 60% of normal cells, 59% of abnormal cells and 73% of rejected cells.

Adult↗
PubMed2003

Hemispheric specialization for spatial frequency processing in the analysis of natural scenes.

Experimental data coming from visual cognitive sciences suggest that visual analysis starts with a parallel extraction of different visual attributes at different scales/frequencies. Neuropsychological and functional imagery data have suggested that each hemisphere (at the level of temporo-parietal junctions-TPJ) could play a key role in spatial frequency processing: The right TPJ should predominantly be involved in low spatial frequency (LFs) analysis and the left TPJ in high spatial frequency (HFs) analysis. Nevertheless, this functional hypothesis had been inferred from data obtained when using the hierarchical form paradigm, without any explicit spatial frequency manipulation per se. The aims of this research are (i) to investigate, in healthy subjects, the hemispheric asymmetry hypothesis with an explicit manipulation of spatial frequencies of natural scenes and (ii) to examine whether the 'precedence effect' (the relative rapidity of LFs and HFs processing) depends on the visual field of scene presentation or not. For this purpose, participants were to identify either non-filtered or LFs and HFs filtered target scene displayed either in the left, central, or right visual field. Results showed a hemispheric specialization for spatial frequency processing and different 'precedence effects' depending on the visual field of presentation.

Cognition↗
PubMed1994

Image analysis and synthesis of multimodal images in medicine.

Radiologic and clinical practice can be enhanced by improved access to multimodal image information. Analysis, visualization, method characteristic image processing and image synthesis is needed not only for the interpretation of the images but also for performing effective consultations with clinical colleagues and computer supported therapy planning and control strategies. A method is presented which enables the fast display, three-dimensional visualization and the modality oriented analysis of multimodal image information. Based on a unique image format, modality specific procedures and two- or three-dimensional processing tools of image analysis produce the input data for therapy planning programs. The easy use of this multimedia visualization tool enables radiologists and clinicians to deal with their image data. The description of methods and procedures, as well as typical examples of radiologic practice will demonstrate the efficiency of the presented system.

Algorithms↗
PubMed1995

Usefulness of 99mTc-MIBI stress myocardial SPECT bull's-eye quantification in coronary artery disease.

99mTc-methoxy-isobutyl isonitrile (MIBI) myocardial SPECT quantification performed using a Bull's-eye polar map, was evaluated and compared with visual analysis in 120 patients with proven or suspected CAD. The study series comprised 106 men and 14 women, age 37-75 years (mean 51 +/- 6), 68 of whom had had a prior myocardial infarction. Coronary angiography was taken as the gold standard: one-vessel disease was present in 24 patients, two-vessel disease in 39, and three-vessel disease in 44, whereas no significant stenosis was documented in 13 cases. Forty age-matched subjects (26 men, 14 women), with less than a 5% chance of having CAD, were enrolled to establish the normal database for males and females. ROC analysis was used to calculate the optimal thresholds for the definition of the disease extension in each vascular territory of the Bull's-eye polar map: 10% for LAD, 8% for LCX, and 20% for RCA territory. The sensitivity/specificity ratio of the scintigraphy was: 75/82% with the visual and 78/74% with the quantitative analysis for LAD; 60/90% with visual and 72/64% with visual and 70/62% with quantitative analysis for RCA territory. The sensitivity/specificity ratios for the CAD diagnosis were similar with the visual and the Bull's-eye analysis in 92/61% and 93/61% respectively. Bull's-eye analysis agreed with visual analysis in 296/360 vessels. Two and three-vessel disease were most frequently observed using the Bull's-eye approach.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2001

Contribution of multiple glaucoma medications to visual function and quality of life in patients with glaucoma.

BACKGROUND: Previous studies examining the correlation between medical treatment and overall quality of life in patients with glaucoma assessed differences between a glaucoma population and a matched group (without glaucoma) and were not aimed specifically at detecting a relation between visual acuity, visual field status and medication use, and visual function and quality of life. We performed a study to determine this relation in patients with chronic open-angle glaucoma (COAG). METHODS: The study was cross-sectional. Of 235 English-speaking patients with a diagnosis of COAG, normal-pressure glaucoma or suspected glaucoma (receiving therapy) seen in a university-based glaucoma practice between Feb. 1 and Apr. 30, 1998, 224 (95.3%) agreed to participate. All subjects completed two questionnaires: the Visual Function Assessment and the EQ-5D, assessing health status (quality of life). Visual acuity, diagnosis, age, sex, country of birth, type and number of medications for topical and for oral use, dosage, and history of laser treatment and surgery were extracted from the medical record. Pearson rank correlation and multivariate analyses were performed. RESULTS: On univariate analysis visual function was correlated with age, visual acuity, number of glaucoma medications, number of applications of eyedrops, mean deviation in better eye, mean deviation in worse eye, and lower hemifield involvement in both eyes. On multivariate analysis only visual acuity and visual field status were independently associated with visual function. Univariate analysis showed that health status was correlated with age, visual function and number of medications for oral use; however, age failed to retain statistical significance in the regression analysis. INTERPRETATION: Our results suggest that the number of glaucoma medications is not predictive of quality of life.

Adult↗