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PubMed2006

Brain imaging tools in neurosciences.

In this chapter brain imaging tools in neurosciences are presented. These include a brief overview on single-photon emission tomography (SPET) and a detailed focus on positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). In addition, a critical discussion on the advantages and disadvantages of the three diagnostic systems is added. Furthermore, this article describes the image analysis tools from visual analysis over region-of-interest technique up to statistical parametric mapping, co-registration methods, and network analysis. It also compares the newly developed combined PET/CT scanner approach with established image fusion software approaches. There is rapid change: Better scanner qualities, new software packages and scanner concepts are on the road paved for an amply bright future in neurosciences.

Animals↗
PubMed2003

Perceptual organization of local elements into global shapes in the human visual cortex.

The question of how local image features on the retina are integrated into perceived global shapes is central to our understanding of human visual perception. Psychophysical investigations have suggested that the emergence of a coherent visual percept, or a "good-Gestalt", is mediated by the perceptual organization of local features based on their similarity. However, the neural mechanisms that mediate unified shape perception in the human brain remain largely unknown. Using human fMRI, we demonstrate that not only higher occipitotemporal but also early retinotopic areas are involved in the perceptual organization and detection of global shapes. Specifically, these areas showed stronger fMRI responses to global contours consisting of collinear elements than to patterns of randomly oriented local elements. More importantly, decreased detection performance and fMRI activations were observed when misalignment of the contour elements disturbed the perceptual coherence of the contours. However, grouping of the misaligned contour elements by disparity resulted in increased performance and fMRI activations, suggesting that similar neural mechanisms may underlie grouping of local elements to global shapes by different visual features (orientation or disparity). Thus, these findings provide novel evidence for the role of both early feature integration processes and higher stages of visual analysis in coherent visual perception.

Humans↗
PubMed1996

Sleep stage scoring using the neural network model: comparison between visual and automatic analysis in normal subjects and patients.

In this paper, we compare and analyze the results from automatic analysis and visual scoring of nocturnal sleep recordings. The validation is based on a sleep recording set of 60 subjects (33 males and 27 females), consisting of three groups: 20 normal controls subjects, 20 depressed patients and 20 insomniac patients treated with a benzodiazepine. The inter-expert variability estimated from these 60 recordings (61,949 epochs) indicated an average agreement rate of 87.5% between two experts on the basis of 30-second epochs. The automatic scoring system, compared in the same way with one expert, achieved an average agreement rate of 82.3%, without expert supervision. By adding expert supervision for ambiguous and unknown epochs, detected by computation of an uncertainty index and unknown rejection, the automatic/expert agreement grew from 82.3% to 90%, with supervision over only 20% of the night. Bearing in mind the composition and the size of the test sample, the automated sleep staging system achieved a satisfactory performance level and may be considered a useful alternative to visual sleep stage scoring for large-scale investigations of human sleep.

Adult↗
PubMed1990

Detection of mild coronary stenoses using the Dynamic Spatial Reconstructor.

The accuracy of the Dynamic Spatial Reconstructor (DSR) in the detection of moderate coronary artery stenoses was examined in 20 closed-chest dogs. Twenty-eight hollow plastic cylinders were embolized into the left coronary arteries and produced 25% to 56% reductions in arterial lumina diameter. For each dog, one three-dimensional (3-D) image of the heart was reconstructed from each DSR scan recorded during injection of contrast into the aortic root. Analysis involved blinded visual analysis by four independent observers of multiview projection images computed from the single 3-D image. Postmortem coronary angiograms of the isolated heart were considered definitive for location of the stenoses. Overall sensitivity of detection by DSR was 89% and specificity 81%. Sensitivity of detecting stenoses greater than or equal to 50% was 98%. Receiver operating characteristics (ROC) analysis showed that detection of stenoses in the left coronary arteries is of equal sensitivity and specificity.

Animals↗
PubMed1992

Postictal switch in blood flow distribution and temporal lobe seizures.

The ictal increase of regional cerebral blood flow has yet to be fully utilised in the investigation of focal seizures. Although single photon emission tomography (SPECT) is being increasingly used in the localisation of epileptic foci, the evolution and time courses of the peri-ictal perfusion changes have yet to be clarified. We performed serial SPECT studies in the interictal, ictal and immediate postictal states in 12 patients with refractory temporal lobe epilepsy to define the patterns and duration of peri-ictal cerebral blood flow changes. Visual analysis showed a constant pattern of unilateral global increases in temporal lobe perfusion during seizures which suddenly switched to a pattern of relative mesial temporal (hippocampal) hyperperfusion and lateral temporal hypoperfusion in the immediate postictal period. Quantitative analysis confirmed the visual assessment. Lateral temporal cortex ictal/normal side to side ratios were increased by mean 35.1% (95% confidence interval 21.8% to 48.4%) more in the ictal studies than in the interictal studies and mesial temporal cortex ratios increased by mean 30.8% (22.4% to 39.2%). In the postictal state, however, lateral temporal ratios were reduced by mean 7.7% (-15.8% to 0.4%) compared with interictal values, whereas mesial temporal perfusion was maintained compared with the interictal studies. These observations provide critical information for interpreting scans which can be used in the localisation of epileptic foci. This postictal switch in blood flow patterns may reflect the underlying metabolic processes of neuronal activation and recovery and have implications for understanding the neurobiology of human epileptic seizures.

Basal Ganglia↗
PubMed1994

Effects of aging on amplitude-modulation following response.

Phase spectral analysis as developed by Fridman (1982) was used to detect amplitude-modulation following response (AMFR). The threshold of AMFR was determined with greater sensitivity and accuracy by phase spectral analysis than by visual analysis. Using this method, a modulation frequency (MF) of 80 Hz was found optimal for detecting AMFR in young children (ranging in age from 2 to 4 years) during sleep, for whom there is no advantage in recording 40-Hz steady-state responses. To determine the optimal MF for detecting AMFR during sleep in children less than 2 years of age and age limitation for using 80-Hz MAFR in objective audiometry, AMFR as a function of MF was investigated during sleep in 25 children with normal hearing ranging from 4 months to 15 years of age, and 10 normal hearing adults. The stimulus was a 1000 Hz, 50 dBnHL sinusoidally amplitude modulated tone with a modulation depth of 95%. MF was varied from 20 to 200 Hz in 20 Hz steps. Response was determined by phase spectral analysis and the S/N ratio calculated by spectral amplitude at the modulation frequency and noise level around the modulation frequency using fast Fourier transform. Phase spectral analysis showed AMFR at MF of 80 Hz to be the most stable and reliable in all children during sleep among MFs from 20 to 200 Hz. Spectral amplitude analysis demonstrated 80-Hz AMFR to have a high S/N ratio in all children.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMedDate not supplied

[Visual evoked potentials to illusory contours (Kanizsa's square)].

Visual evoked potentials (VEP) were studied in 10 subjects to presentation of illusory Kanizsa's square and control visual stimulus with similar spatial organization, which did not produce a visual illusion. The VEPs to the applied stimuli were expressed in the occipital, parietal, and inferiotemporal areas. It was shown that during presentation of the illusory configuration the amplitude of VEP variation between the N180 and P230 peaks was higher and the N300 latency lower than during presentation of stimuli with real configuration. The difference between VEPs in amplitude were observed in the left and right occipital and left inferiotemporal areas, and differences in latency were pronounced in the left occipital derivation. It is suggested that there exist two contour-encoding regions in the visual system which participate in different kinds of the visual analysis. First, associative visual fields which encode the information on single sings and their complexes and inferiotemporal fields which compare the sensory and memory codes.

Adult↗
PubMed1982

Thallium-201 myocardial scintigraphy: improved sensitivity, specificity and predictive accuracy by application of a statistical image analysis algorithm.

Exercise and 3 hour delayed redistribution thallium-201 myocardial perfusion imaging was performed in 107 patients including 87 patients with documented coronary artery disease and 20 patients with normal coronary arteriograms. A computer algorithm for statistical analysis and redisplay of the analog scintillation data was developed to augment the visual analysis of the standard analog image. The basic algorithm identified the myocardial area (pixel) with the most absolute counts and developed an appropriate standard deviation range from a table. All pixels in the area of the myocardium containing absolute counts below three standard deviation ranges (or approximately 6 standard deviations) were deleted from the final image. The remaining pixels were redisplayed in a digitized bimodal format and the image photographed. Two experienced observers compared visual analysis of the analog image alone and the analog image in conjunction with the computer-analyzed image for sensitivity, specificity and predictive accuracy in the detection of perfusion defects in patients with coronary artery disease and in normal subjects. Sensitivity in patients with coronary artery disease and in normal subjects. Sensitivity in patients with coronary artery disease for the analog scintillation image alone was 79 percent (69 of 87) and with computer analysis 95 percent (83 of 87). Specificity in the patients with no coronary disease was 100 percent (20 of 20) for both techniques. The predictive accuracy of the test was 83 percent (89 of 107) for the analog image alone and 96 percent (103 of 107) for the two images combined. It is concluded that use of a computer statistical analysis algorithm of thallium-201 analog myocardial perfusion images improves the accuracy of detection of perfusion defects in patients with coronary artery disease.

Computers↗
PubMed2000

Comparison of frequency doubling perimetry with humphrey visual field analysis in a glaucoma practice.

PURPOSE: To determine the sensitivity and specificity of frequency doubling perimetry with Humphrey visual field testing used as the gold standard. METHODS: Frequency doubling perimetry and Humphrey visual field testing (24-2) were performed on 29 consecutive patients in a glaucoma practice. Data for the right eye were used to calculate sensitivity, specificity, and receiver operating characteristic curves. RESULTS: For the frequency doubling perimetry in screening mode, and with an abnormal glaucoma hemifield test used as the gold standard, the area under the receiver operating characteristic curve was 89.3%, 81.5%, or 75.0% for the presence of mild, moderate, or severe relative defects, respectively. Similar results were found with the use of mean deviation (P <.05) to define Humphrey visual field defects. For frequency doubling perimetry in threshold mode, the area under the receiver operating characteristic curve was 93.4% with the presence of any defect (P <.05) used as the criterion for an abnormal case, and an abnormal glaucoma hemifield test as the gold standard. In all cases, the threshold mode detected defects better than the screening mode.

Adolescent↗
PubMed2003

Quantitative motion analysis and visualization of cellular structures.

The availability of cellular markers tagged with the green fluorescent protein (GFP) has recently allowed a large number of cell biological studies to be carried out in live cells, thereby addressing the dynamic organization of cellular structures. Typically, microscopes capable of video recording are used to generate time-resolved data sets. Dynamic imaging data are complex and often difficult to interpret by pure visual inspection. Therefore, specialized image processing methods for object detection, motion estimation, visualization, and quantitation are required. In this review, we discuss concepts for automated analysis of multidimensional image data from live cell microscopy and their application to the dynamics of cell nuclear subcompartments.

Animals↗
PubMed1983

Sharp targets are detected better against a figure, and blurred targets are detected better against a background.

There is growing evidence that the performance of perceptual tasks is often facilitated by perceived "figureness." Accuracy in detection and discrimination of targets is higher when the targets are presented in figural regions than when they are presented in ground regions of an image. This "figure superiority" might be a result of a functional specialization in the visual analysis of figure; recent theories have also assumed a functional specialization in the visual analysis of ground. If so, we might expect "ground superiority" in situations where task performance requires information available primarily through analysis of ground. We manipulated the spatial frequency of a small line segment and found that when it was sharp (i.e., the high-spatial-frequency components were present), it was detected better in figural regions, but when we blurred it (only the low-to-medium spatial frequencies were present) it was detected better in ground regions. These findings support the view that figure and ground analyses involve different specialized functions.

Adolescent↗
PubMed2001

Collagen-ligand interaction in dentinal adhesion: computer visualization and analysis.

The objective of this study was to characterize the interactions of selected ligand molecules with collagen structure through computer visualization of the reacting molecules and the resulting complexes. Five ligand molecules were studied. They were 2-Hydroxyethyl methacrylate, Glutaraldehyde-HEMA adduct, Glyceryl dimethacrylate, Methacryloyloxyethyl maleate and Acryloyloxyethyl citraconate. These ligands were selected with oxygen as a common heteroatom for a reactive or functional site. Energy minimized 3-D structures of the molecules were generated by Sybyl molecular modeling software. The structures were subjected to a systematic conformational search, yielding conformations of the molecules with a common recognition site with both steric and electrostatic complementarity to appropriate receptor sites in a type I collagen molecular structure. The ligands were also docked to collagen receptor by autodock procedures and the receptor sites where docking occurred were evaluated. The energy of the molecules and their complexes with collagen was evaluated and compared. The computer visualization results reveal that steric complementarity between receptor sites in collagen and optimally configured ligands may be the basis of micromechanical bonding between collagen and the ligands. Typically, ligands docked on the cavities of collagen molecular surface and wrapped around the cavities which follow the helical turns of the collagen macromolecule. In addition, analysis of electrostatic potential features revealed electrostatic complementarity as an additional source of interaction. Hydrogen bonds between ligands and collagen molecule were detected in the complexes of several of the conformations of all the ligands. Thus computer simulation studies show that steric and electrostatic complementarity and consequent interactions form the potential basis of binding between dentin adhesive ligands and type I collagen.

Adhesiveness↗
PubMed2005

Comparative linkage analysis and visualization of high-density oligonucleotide SNP array data.

BACKGROUND: The identification of disease-associated genes using single nucleotide polymorphisms (SNPs) has been increasingly reported. In particular, the Affymetrix Mapping 10 K SNP microarray platform uses one PCR primer to amplify the DNA samples and determine the genotype of more than 10,000 SNPs in the human genome. This provides the opportunity for large scale, rapid and cost-effective genotyping assays for linkage analysis. However, the analysis of such datasets is nontrivial because of the large number of markers, and visualizing the linkage scores in the context of genome maps remains less automated using the current linkage analysis software packages. For example, the haplotyping results are commonly represented in the text format. RESULTS: Here we report the development of a novel software tool called CompareLinkage for automated formatting of the Affymetrix Mapping 10 K genotype data into the "Linkage" format and the subsequent analysis with multi-point linkage software programs such as Merlin and Allegro. The new software has the ability to visualize the results for all these programs in dChip in the context of genome annotations and cytoband information. In addition we implemented a variant of the Lander-Green algorithm in the dChipLinkage module of dChip software (V1.3) to perform parametric linkage analysis and haplotyping of SNP array data. These functions are integrated with the existing modules of dChip to visualize SNP genotype data together with LOD score curves. We have analyzed three families with recessive and dominant diseases using the new software programs and the comparison results are presented and discussed. CONCLUSIONS: The CompareLinkage and dChipLinkage software packages are freely available. They provide the visualization tools for high-density oligonucleotide SNP array data, as well as the automated functions for formatting SNP array data for the linkage analysis programs Merlin and Allegro and calling these programs for linkage analysis. The results can be visualized in dChip in the context of genes and cytobands. In addition, a variant of the Lander-Green algorithm is provided that allows parametric linkage analysis and haplotyping.

Family Health↗
PubMed1998

Visual gait analysis: the development of a clinical assessment and scale.

OBJECTIVES: To develop and evaluate a four-point scale visual gait assessment form, the Rivermead Visual Gait Assessment (RVGA), for clinical use with patients with neurological deficits. DESIGN: Preliminary clinical testing of reliability, validity and sensitivity to change. SETTING: Patients were recruited from the Rivermead Rehabilitation Centre (RRC), a centre specializing in rehabilitation for patients with neurological disease. PATIENTS: Ten inpatients were assessed by up to seven physiotherapists for the main reliability study, and eight different patients were also assessed by two raters one week apart. Twenty outpatients with multiple sclerosis (MS) who were receiving physiotherapy to improve their mobility and 27 inpatients with various neurological conditions were also assessed and the data used to examine validity, re iability and sensitivity to change. OUTCOME: The other comparative measures used were walking time, stride length, step length asymmetry, balance and the Rivermead Mobility Index. RESULTS: Inter-rater reliability between multiple raters was reasonable both for the global scores from the gait assessment form (Kendall's coefficient of concordance; p < 0.001), and for individual items (complete agreement occurred on 63.8% of all observations). There was a significant correlation between the global RVGA score and the various criterion measures (r = 0.53-0.79; p < 0.001) and between change in the RVGA score and change in walking time in patients who received treatment (r = 0.68; p < 0.01). CONCLUSIONS: The RVGA provides the clinician with a clinical assessment of the quality of gait which may be used in conjunction with other measures to inform and monitor the value of physiotherapy treatment for people with MS and stroke, and possibly other neurological deficits.

Central Nervous System Diseases↗
PubMed1999

Neural networks for visual field analysis: how do they compare with other algorithms?

PURPOSE: To compare the performance of a neural network in identifying visual field defects with the performance of other available algorithms. METHODS: A feed-forward neural network with a single hidden layer was trained to recognize visual field defects previously collected in a longitudinal follow-up glaucoma study, and then tested on fields taken from the same study but not used in the training. The receiver operating characteristics of the network then were compared with the previously determined performance of other algorithms on the same data set. RESULTS: At a specificity greater than 90%, the neural network was more sensitive than any of the available algorithms (although only the global indices were available for comparison, as the cluster and cross-meridional algorithms did not achieve such high specificity at their current settings). At a lower specificity (80-85%), the neural network was unable to attain the high sensitivity of the cluster or cross-meridional algorithms; in fact, the cluster algorithm from the Low-Tension Glaucoma study was significantly more sensitive. CONCLUSION: The receiver operating characteristics of a feed-forward neural network designed to detect visual field defects were explored. At a very high specificity (90-95%) a neural network performed better than the global indices. However, at a lower specificity (78%-88%), the neural network performed worse than cluster and cross-meridional algorithms.

Algorithms↗
PubMed2006

Optical analysis of visual improvement after correction of anisometropic amblyopia with a phakic intraocular lens in adult patients.

PURPOSE: To analyze possible reasons for an increase in visual acuity observed in myopic patients with anisometropic amblyopia after implantation of a phakic intraocular lens (PIOL) using a theoretical eye model. DESIGN: Retrospective case series. PARTICIPANTS: Fifty-nine eyes of 48 patients with anisometropic amblyopia implanted with an angle-supported PIOL. METHODS: Inclusion criteria were anisometropia of at least 3 diopters (D) and a best spectacle-corrected visual acuity (BSCVA) of 0.7 or less in the best eye. Follow-up was performed at 1, 3, 6, and 12 months and then annually for up to 10 years. The theoretical analysis of mechanisms to explain the visual improvement was performed using a theoretical eye, based on the Kooijman model, in which the measured values of radii and thickness of the different surfaces were substituted. The magnification and spot size were calculated by a ray tracing process. MAIN OUTCOME MEASURES: Uncorrected visual acuity, improvement in best spectacle-corrected visual acuity, and spherical equivalent. RESULTS: Mean gain in visual acuity was 3 lines (range, 0-7 lines). Fifty-four eyes (91.5%) gained at least 1 line of visual acuity, whereas no eyes lost lines of vision. The change in BSCVA did not correlate with preoperative BSCVA (Pearson coefficient, r = 0.19) or with the degree of anisometropia (Pearson coefficient, r = 0.23). The calculations using a Kooijman eye model corrected with spectacles and with a PIOL accounted for the full increase in visual acuity in terms of the magnification (increased by a factor of 1.2) and the spot size (reduced by a factor of 2). CONCLUSIONS: After implantation of a PIOL, the visual acuity of myopic patients with anisometropic amblyopia showed a significant increase. This increase was explained using a theoretical eye model not only in terms of magnification but also including changes in aberrations. An evident role of neuroprocessing in this visual improvement was not identified.

Adult↗