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PubMed2006

Aging and the detection of observer and moving object collisions.

The authors examined age-related differences in the detection of collision events. Older and younger observers were presented with displays simulating approaching objects that would either collide or pass by the observer. In 4 experiments, the authors found that older observers, as compared with younger observers, had less sensitivity in detecting collisions with an increase in speed, at shorter display durations, and with longer time-to-contact conditions. Older observers also had greater difficulty when the scenario simulated observer motion, suggesting that older observers have difficulty discriminating object motion expansion from background expansion from observer motion. The results of these studies support the expansion sensitivity hypothesis-that age-related decrements in detecting collision events involving moving objects are the result of a decreased sensitivity to recover expansion information.

Accidents, Traffic↗
PubMed1996

Unified measurement of observer performance in detecting and localizing target objects on images.

In this paper methods used to measure observer performance are reviewed, and a simple general model for finding and reporting target objects in gray-scale image backgrounds is presented. That model provides the basis for a combined measurement of detection and localization performance in various image-interpretation tasks, whether by human observers or by realized computer algorithms. The model assumes that (1) an observer's detection response and first choice of target location both depend on the "maximally suspicious" finding on an image, (2) a correct (first-choice) localization of the actual target occurs if and only if its location is selected as the most suspicious, and (3) a target's presence does not alter the degree of suspicion engendered by any other (normal) image findings. Formalization of these assumptions relates the ROC curve, which measures the ability to discriminate between images containing targets and images without targets, to the "Localization Response" (LROC) curve, which measures the conjoint ability to detect and correctly localize the actual targets in those images. A maximum-likelihood statistical procedure, developed for a two-parameter "binormal" version of this model, concurrently fits both the ROC and LROC curves from an observer's image ratings and target localizations for a set of image interpretations. The model's application is illustrated (and compared to standard ROC analysis) using sets of rating and localization data from radiologists asked to search chest films for pulmonary nodules. This model is then extended to multiple-report ("free-response") interpretations of multiple-target images, under the stringent requirement that an observer's detection capability and criterion for reporting possible targets both remain stationary across images and across the successive reports made on a given image. That extended model yields formulations and predictions for the so-called "Free-Response" (FROC) curve, and for a recently proposed "Alternative FROC" (AFROC) curve. Tests of that model's "stationarity" assumptions are illustrated using radiologists' free-search interpretations of chest films for pulmonary nodules, and they suggest that human observers may often violate those assumptions when making multiple-report interpretations of images.

Algorithms↗
PubMed2006

Fluorescence quencher improves SCANSYSTEM for rapid bacterial detection.

BACKGROUND AND OBJECTIVES: The optimized scansystem could detect contaminated platelet products within 24 h. However, the system's sensitivity was reduced by a high fluorescence background even in sterile samples, which led to the necessity of a well-trained staff for confirmation of microscope results. MATERIALS AND METHODS: A new protocol of the optimized scansystem with the addition of a fluorescence quencher was evaluated. Pool platelet concentrates contaminated with five transfusion-relevant bacterial strains were tested in a blind study. RESULTS: In conjunction with new analysis software, the new quenching dye was able to reduce significantly unspecific background fluorescence. Sensitivity was best for Bacillus cereus and Escherichia coli (3 CFU/ml). DISCUSSION: The application of a fluorescence quencher enables automated discrimination of positive and negative test results in 60% of all analysed samples.

Bacteriological Techniques↗
PubMed2004

An object-based approach for detecting small brain lesions: application to Virchow-Robin spaces.

This paper is concerned with the detection of multiple small brain lesions from magnetic resonance imaging (MRI) data. A model based on the marked point process framework is designed to detect Virchow-Robin spaces (VRSs). These tubular shaped spaces are due to retraction of the brain parenchyma from its supplying arteries. VRS are described by simple geometrical objects that are introduced as small tubular structures. Their radiometric properties are embedded in a data term. A prior model includes interactions describing the clustering property of VRS. A Reversible Jump Markov Chain Monte Carlo algorithm (RJMCMC) optimizes the proposed model, obtained by multiplying the prior and the data model. Example results are shown on T1-weighted MRI datasets of elderly subjects.

Algorithms↗
PubMed2003

Detection of endometrial intraepithelial neoplasia (EIN) in postmenopausal endometrium.

OBJECTIVES: To detect the presence of endometrial intraepithelial neoplasia (EIN) in the endometrium of postmenopausal patients. PATIENTS AND METHODS: Sixty-three postmenopausal patients with endometrial polyps (n=48), hyperplasia (n=12) and endometrioid carcinoma (n=3) were enrolled for this study. The diagnosis of EIN was made by using morphological criteria and immunohistochemical methods for detection of PTEN and bcl-2. RESULTS: EIN lesions were found in cases of endometrial polyp (n=1), atrophic endometrium (n=1) and in hyperplasia (n=1). The glands were packed, showed cytological atypia and were negative for both PTEN and bcl-2. Three patients with endometrial hyperplasia had isolated PTEN-negative glands but they were still bcl-2 positive. CONCLUSIONS: The use of immunohistochemical methods helps detect the presence of EIN in the postmenopausal endometrium but does not substitute the morphological criteria for this diagnosis.

Adult↗
PubMed2004

Flat colorectal lesions: colonoscopic detection without dye spray or magnification and clinical significance.

OBJECTIVE: The detection of flat colorectal lesions with possible malignant potential has been described by Japanese endoscopists. This study looks at the detection of flat lesions using standard colonoscopic techniques and examines the clinical significance of these lesions. METHODS: The records of patients who underwent complete colonoscopy by a single colorectal surgeon in an outpatient setting over a 4-year period were reviewed. The site and number of flat lesions and their histology were noted. Patients with incomplete intubation of the colon were excluded. RESULTS: A total of 491 patients underwent 593 colonoscopic examinations. There were 236 flat lesions identified in 91 patients: 24% (56/236) were adenomas showing mild or moderate dysplasia, and 63% (148/236) were hyperplastic. CONCLUSIONS: Flat colorectal lesions are common and can be detected without the aid of dye spray and magnification. One-quarter of these lesions are adenomatous and we recommend routine hot biopsy or polypectomy of these lesions.

Adenoma↗
PubMed2006

Voxel-based detection of white matter abnormalities in mild Alzheimer disease.

OBJECTIVE: To detect white matter abnormalities in patients with mild Alzheimer disease (AD) by diffusion tensor imaging and to determine their topographic relationship with gray matter atrophy. METHODS: Thirteen patients with mild AD and 16 normal age-matched volunteers underwent diffusion tensor imaging and three-dimensional spoiled gradient-recalled sequence scanning. Voxel-based morphometry was conducted to detect regions of gray matter atrophy in the AD group relative to the control group. Fractional anisotropy (FA) maps were processed using SPM2 to make voxel-wise comparison of anisotropy in whole brain between the two groups. The relationship between locations of abnormalities in the white and gray matter was examined. RESULTS: Significant reductions in anisotropy were found in the white matter of both medial temporal lobes, bilateral temporal stems, bilateral superior longitudinal fasciculi, bilateral internal capsules, and cerebral peduncles, as well as the white matter of left middle temporal gyrus and right superior parietal lobule, the body and genu of the corpus callosum, and the right lateral capsule in patients with AD. Although the decrease in FA was consistent with cortical volumetric reduction in both temporal lobes, the widespread involvement of bilateral superior longitudinal fasciculi was dominant in these white matter findings. CONCLUSIONS: Voxel-wise comparison of whole-brain anisotropy revealed widely distributed disintegration of white matter in mild Alzheimer disease (AD). The white matter shows a different pattern of degeneration from gray matter and may be an independent factor in the progress of AD.

Aged↗
PubMed2003

Detection of novel chlamydiae in cats with ocular disease.

OBJECTIVE: To detect and characterize the full range of chlamydial infections in cats with ocular disease by use of polymerase chain reaction (PCR) assays, cytologic examination, immunohistochemical analysis, and evaluation of clinical information including status for feline herpesvirus-1 (FeHV-1). SAMPLE POPULATION: DNA extracted from 226 conjunctival samples obtained from cats with clinically diagnosed keratitis or conjunctivitis and 30 conjunctival samples from healthy cats. PROCEDURE: PCR assays for the 16S rRNA gene specific for the order Chlamydiales and a new Chlamydophila felis (formerly Chlamydia psittaci) species-specific 23S rRNA gene were performed. Seventy-four conjunctival samples were prepared with Romanowsky-type stain, grouped on the basis of inflammatory pattern, and screened for chlamydial inclusions by use of immunohistochemical analysis. Clinical information and FeHV-1 status were recorded. RESULTS: 26 (12%) specimens had positive results for the only known feline chlamydial pathogen, C felis. Surprisingly, an additional 88 (39%) were positive for non-C felis chlamydial DNA. Identification of non-C felis chlamydial DNA by direct sequencing revealed 16S rRNA gene sequences that were 99% homologous to the sequence for Neochlamydia hartmannellae, an amebic endosymbiont. Chlamydial prevalence was significantly higher in cats with ocular disease. CONCLUSIONS AND CLINICAL RELEVANCE: Application of a broad-range detection method resulted in identification of a new agent associated with ocular disease in cats. Finding chlamydia-like agents such as N hartmannellae in coinfections with their obligate amebic host, Hartmannella vermiformis, raises questions about the potential role of these microorganisms in causation or exacerbation of ocular disease in cats.

Animals↗
PubMed2000

[Using multiplex PCR for the detection of virulence genes in Escherichia coli O157:H7].

OBJECTIVE: To detect and characterize the virulence genes in E. coli O157:H7 isolated from various reservoir in six areas of Jiangsu province. METHOD: The virulence genes of Shiga-like toxin (SLT(1) and SLT(2)), intimin (eaeA) and hemolysin (hlyA) were chosen as the target genes and amplified in multiplex PCR assays. RESULTS: Of the eighty-five E. coli O157:H7 strains, the overall virulence gene prevalence was found to be 56.5% (48/85). The prevalence rates virulence genes of isolates from various areas were different from 0% up to 90.5%. It seemed to exist a relationship between the virulence gene prevalence and the level of incidence. In the areas where rates of incidence were divided into high, low, sporadic or zero, the prevalence rates were 85.7% (36/42), 52.6% (10/19) and 8.3% (2/24), respectively. The prevalence rates of isolates were also different from various reservoirs, decreasing by sheep, cattle, pig and poultry. One isolate from a rabbit was positive for SLT(2), eaeA and hly genes. Of forty-eight isolates carrying virulence genes, 38 (79.2%) had SLT(2), eaeA and hly genes, taking the dominate virulence gene pattern, 8 (16.6%) had all of the four virulence genes 2 (4.2%) had both SLT(2) and hly genes respectively. In addition, SLT(1) gene showed a lower prevalence, which was different from some findings abroad. CONCLUSION: Since virulence gene pattern of E. coli O157:H7 is an important molecular epidemiological marker, it can provide an useful information for epidemiologic studies, and helpful to the design of prevention and control strategies. For virulence gene detection, multiplex PCR seems to be a simple, rapid, specific and sensitive method.

Adhesins, Bacterial↗
PubMed2003

Detection of telomerase activity in patients with mycosis fungoides.

OBJECTIVES: To detect telomerase activity in patients with mycosis fungoides (MF) and to study the role of telomerase in the tumorigenesis of MF. METHODS: The technique of PCR-ELISA was employed to detect telomerase activity in 35 patients with various stages of MF. RESULTS: 92.3% tumor stage of MF, 78.6% plaque stage of MF and 75.0% patch stage of MF had positive telomerase activity. The control samples had no telomerase activity. Telomerase activity in tumor stage of MF was significantly higher than that in plaque stage, while the latter was higher than that in patch stage. Telomerase activity was correlated with the stage of MF. CONCLUSION: High level of telomerase activity frequently occurred in patients with MF, suggesting that telomerase might play an important role in the tumorigenesis of MF and is a useful marker for the diagnosis of MF possibly.

Humans↗
PubMed2003

[Detection and significance of succinate dehydrogenase of sperm mitochondria].

OBJECTIVE: To detect succinate dehydrogenase (SDH) of sperm mitochondria by an improved method, and to evaluate the relationship between SDH and the motility and viability of sperm. METHODS: In 46 fertile and infertile men (aged from 25 to 36), the motility, viability and mitochondrial SDH of sperm were detected by computer-assisted semen analysis system, dead/live sperm molecular fluorescent probe and an improved cytochemical method. Then, the correlation between the motility and viability of sperm and the positive percentage of sperm mitochondrial SDH were analyzed. RESULTS: In the 46 fertile and infertile men, the motility and viability of sperm were (67.33 +/- 7.37)% and (79.78 +/- 7.65)%, and the positive percentage of sperm mitochondrial SDH was (74.74 +/- 8.29)%. The motility and viability of sperm and positive percentage of sperm mitochondrial SDH had significant correlation (r = 0.901, P < 0.01; r = 0.876, P < 0.01; r = 0.917, P < 0.01). CONCLUSIONS: Detection of sperm mitochondrial SDH has significance in evaluation of sperm mitochondrial function and may serve as an assisted marker of sperm viability.

Adult↗
PubMed2005

[MGB probes detect Streptococcus mutans and Streptococcus sobrinus in real time].

OBJECTIVE: To detect and distinguish Streptococcus mutans (S. mutans) and Streptococcus sobrinus (S. sobrinus) quickly in epidemiology and investigate the distribution of S. mutans in the oral of children with rampant caries. METHODS: Designed minor groove binder (MGB) probes according to the gtf gene of S. mutans and S. sobrinus. Detected 9 reference strains of Streptococcus mutans group by MGB probes in real time and after cultivation. Evaluated the results of these two methods. 92 dental plaques from pre-school children with rampant caries were detected in real time with MGB probes. RESULTS: The primers could amplify the target sequences specificity and distinguished S. mutans and S. sobrinus from each other using MGB probes. Though the fluorescence occurred earlier in S. mutans than in S. sobrinus, they had the same results in nature. In 92 children with rampant caries, the detective ratio of S. mutans was 96.7% and that of S. sobrinus was 32.6%. All the samples which could detect S. sobrinus were positive for S. mutans. CONCLUSION: The primers and probe designed from gtf genes of S. mutans and S. sobrinus can amplify the target sequence and distinguish them from each other in real time.

Child↗
PubMed1994

Cerebral lesions in systemic lupus erythematosus detected by magnetic resonance imaging. Relationship to anticardiolipin antibody.

OBJECTIVE: To detect cerebral lesions in neuropsychiatrically symptomatic or asymptomatic patients with systemic lupus erythematosus (SLE) and investigate the relationship of these lesions to clinical and laboratory variables. METHODS: Brain magnetic resonance imaging was performed on 31 patients with SLE under the age of 50, including 2 patients with central nervous system (CNS) lupus and 29 neuropsychiatrically asymptomatic patients. RESULTS: Abnormal high intensity spots on T2 weighted images were found in 10 patients (32%), of which 5 were neuropsychiatrically asymptomatic throughout the disease course. The high intensity spot was significantly associated with the presence of high levels of anticardiolipin antibody (aCL) of IgG isotype, livedo reticularis and CNS lupus. CONCLUSION: Our results suggest that asymptomatic cerebral lesions are not rare in patients with SLE and screening of aCL would be helpful in predicting cerebral lesions. A followup study of these asymptomatic patients is necessary to clarify the clinical significance of a high intensity spot.

Adult↗
PubMedDate not supplied

Investigation of basic imaging properties in digital radiography. 8. Detection of simulated low-contrast objects in digital subtraction angiographic images.

We investigated the effects of imaging and display conditions on the detectability of low-contrast objects in digital subtraction angiographic (DSA) images. The test images were produced by superimposition of low-contrast objects on a uniform noisy background obtained with a DSA system. We employed 18-alternative forced-choice (18-AFC) experiments and predictions based on statistical decision theory to study the dependence of the threshold contrasts of the test objects on the object size, incident x-ray exposure, display window width, and display medium. The results indicated that the threshold contrast decreased with increasing object size, and that the detectability of an object of a given size increased with increasing incident x-ray exposure and decreasing width of the display window. We found that the signal-to-noise ratio (SNR) obtained from the perceived statistical decision theory model, which includes the observer's internal noise, can accurately predict the detectability of low-contrast objects in DSA images. The threshold SNR corresponding to 50% correct detection in the 18-AFC experiments had a constant value of 3.8, in agreement with results reported previously for screen-film systems. The theoretical model will be useful for prediction of the performance of a DSA system based on its physical characteristics, and for evaluation of the tradeoff between patient exposure and diagnostic accuracy for a given DSA unit.

Angiography↗
PubMed2001

Frontal evaluation and posterior representation in target detection.

This study examined the topography of the event-related potential in visual-spatial compared to visual-object target detection. The initial index of target detection in the ERP was an inferior anterior P2a accompanied by a posterior N2b. Single unit studies in the monkey indicate that the detection of task-relevant stimuli requires interaction between prefrontal cortex and perceptual representation areas in the posterior brain. The posterior brain processes the physical features of stimuli while frontal cortex performs higher-order operations, such as evaluating the task-relevance of a stimulus. Target detection requires an interaction between feature representations and relevance representations. We hypothesize that the P2a and N2b ERP indices of target detection reflect this frontal/posterior interaction. Visual-spatial feature information is processed in the dorsal posterior brain (posterior parietal cortex) and visual-object information is processed in the ventral posterior brain (inferior occipito-temporal cortex). We observed that at the peak of the P2a the N2b was located over posterior dorsal leads in visual-spatial target detection and over posterior ventral leads in visual-object target detection. The P2a was largest over inferior prefrontal leads in both tasks. We suggest that this distribution is consistent with interaction between orbitofrontal cortical areas of salience representation and posterior cortical areas of stimulus feature representation.

Adolescent↗
PubMed2006

Kernel fisher discriminants for outlier detection.

The problem of detecting atypical objects or outliers is one of the classical topics in (robust) statistics. Recently, it has been proposed to address this problem by means of one-class SVM classifiers. The method presented in this letter bridges the gap between kernelized one-class classification and gaussian density estimation in the induced feature space. Having established the exact relation between the two concepts, it is now possible to identify atypical objects by quantifying their deviations from the gaussian model. This model-based formalization of outliers overcomes the main conceptual shortcoming of most one-class approaches, which, in a strict sense, are unable to detect outliers, since the expected fraction of outliers has to be specified in advance. In order to overcome the inherent model selection problem of unsupervised kernel methods, a cross-validated likelihood criterion for selecting all free model parameters is applied. Experiments for detecting atypical objects in image databases effectively demonstrate the applicability of the proposed method in real-world scenarios.

Journal Article↗
PubMed2000

Object localization and border detection criteria design in edge-based image segmentation: automated learning from examples.

This paper provides methodology for fully automated model-based image segmentation. All information necessary to perform image segmentation is automatically derived from a training set that is presented in a form of segmentation examples. The training set is used to construct two models representing the objects--shape model and border appearance model. A two-step approach to image segmentation is reported. In the first step, an approximate location of the object of interest is determined. In the second step, accurate border segmentation is performed. The shape-variant Hough transform method was developed that provides robust object localization automatically. It finds objects of arbitrary shape, rotation, or scaling and can handle object variability. The border appearance model was developed to automatically design cost functions that can be used in the segmentation criteria of edge-based segmentation methods. Our method was tested in five different segmentation tasks that included 489 objects to be segmented. The final segmentation was compared to manually defined borders with good results [rms errors in pixels: 1.2 (cerebellum), 1.1 (corpus callosum), 1.5 (vertebrae), 1.4 (epicardial), and 1.6 (endocardial) borders]. Two major problems of the state-of-the-art edge-based image segmentation algorithms were addressed: strong dependency on a close-to-target initialization, and necessity for manual redesign of segmentation criteria whenever new segmentation problem is encountered.

Algorithms↗
PubMed1995

Alzheimer's disease in the National Academy of Sciences-National Research Council Registry of Aging Twin Veterans. III. Detection of cases, longitudinal results, and observations on twin concordance.

OBJECTIVES: To detect cases of Alzheimer's disease (AD) in a large population of twins living throughout the United States and to examine concordance for AD in twins as a function of age and genotype for apolipoprotein E (APOE). SETTING: Nationwide survey. DESIGN: Multistage screening and field evaluation beginning with two telephone interviews and culminating with laboratory tests, longitudinal neuropsychological measures, physician examination, and diagnostic consensus among experts. PARTICIPANTS: Membership in 1990-1991 of intact pairs in the National Academy of Sciences--National Research Council Registry of veteran twins, then aged 62 to 73 years. MAIN OUTCOME MEASURES: Completeness of case detection was examined in collateral studies. Zygosity and APOE genotypes were determined by restriction mapping. Concordance was calculated by the proband method. RESULTS: Ninety subjects who screened positively for AD were studied in person, and 60 whose differential diagnoses included AD were followed up, as were their co-twins. Sensitivity of screening was estimated at greater than 99%, but 24% of subjects refused participation after initial screening. Seven of 38 diagnoses of AD have been confirmed at autopsy, and 31 other subjects eventually met criteria for probable or possible AD (prevalence estimate, 0.42%, 95% confidence interval, 0.29% to 0.56%), with good interrater reliability (intraclass r = .86). Excluding one discordant pair with unknown zygosity, concordance rates were 21.1% (4/19) for monozygotic and 11.1% (2/18) for dizygotic probands. Concordance was 50% for twins sharing the epsilon 4/epsilon 4 genotype at APOE, but there were no affected co-twins of 15 probands with onset before age 70 years, no epsilon 4 allele, and no family history of AD. The mean (SD) period of discordance in the latter pairs was 11.3 (3.3) years. CONCLUSIONS: The multistage case-detection approach achieved reliable and valid diagnoses of AD with high apparent sensitivity but substantial attrition after initial screening. Genetic influences in AD at this age are limited, except among homozygotes for allele epsilon 4 at APOE. Subjects with early-onset AD who lack the epsilon 4 allele are not rare, and their condition appears to have little genetic influence. They should be ideal for studies on environmental cause of AD.

Aged↗