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At least 397 records · Page 22Linked to original sources
PubMed2000

Dose efficiency and low-contrast detectability of an amorphous silicon x-ray detector for digital radiography.

The effect of dose reduction on low-contrast detectability is investigated theoretically and experimentally for a production grade amorphous silicon (a-Si) x-ray detector and compared with a standard thoracic screen-film combination. A non-prewhitening matched filter observer model modified to include a spatial response function and internal noise for the human visual system (HVS) is used to calculate a signal-to-noise ratio (SNR) related to object detectability. Other inputs to the SNR calculation are the detective quantum efficiency (DQE) and the modulation transfer function (MTF) of the imaging system. Besides threshold detectability, the model predicts the equivalent perception dose ratio (EPDR), which is the fraction of the screen film exposure for which the digital detector provides equal detectability. Images of a contrast-detail phantom are obtained with the digital detector at dose levels corresponding to 27%, 41%, 63% and 100% of the dose used for screen-film. The images are used in a four-alternative forced choice (4-AFC) observer perception study in order to measure threshold detectability. A statistically significant improvement in contrast detectability is measured with the digital detector at 100% and 63% of the screen-film dose. There is no statistical difference between screen-film and digital at 41% of the dose. On average, the experimental EPDR is 44%, which agrees well with the model prediction of 40%.

Equipment Design↗
PubMed2002

"Clockness" in the detection of dementia: a semantic-conceptual effect.

We studied aspects of clock cognition that might underlie the sensitivity of the CDT in screening for dementia of the Alzheimer type (DAT). Two groups, 15 patients with mild-moderate DAT and 15 controls, were assessed with the CDT and specially designed tests of clock-related cognition. Patients were impaired on the CDT, but they did not differ from controls in copying a clock face or selecting the correct representation of a given time. Patients were worse than controls at distinguishing between clock and nonclock objects, detecting anomalies in clocks, and in setting time irrespective of response format. These findings suggest that semantic-conceptual aspects of clock-related cognition are important in discriminating between patients with DAT and controls.

Aged↗
PubMed1998

Serial fiberoptic endoscopic swallowing evaluations in the management of patients with dysphagia.

OBJECTIVE: To determine whether serial fiberoptic endoscopic evaluation of swallowing (FEES) can be used successfully and efficiently in deciding to change a patient's feeding status from nonoral (NPO) to oral (PO) with no adverse health outcome. DESIGN: A prospective, consecutive, cohort study. SETTING: Inpatient population of a tertiary-care university teaching hospital. SUBJECTS: Thirty-two adults were recruited from a cohort of 400 consecutive subjects who participated in a previous dysphagia study. INTERVENTION: Serial FEES was performed 3 to 6 times in each subject to detect objectively pharyngeal phase dysphagia, aspiration, and aspiration risk and to provide information for recommendations regarding oral feeding status and therapeutic intervention. The number of FEES was based on the subject's medical status, evidence of dysphagia, and clinical judgement. MAIN OUTCOME MEASURES: Identification of pharyngeal phase dysphagia, aspiration, and aspiration risk, and recommendations for initial feeding status, when to resume oral feeding, and what bolus consistencies to use for optimal swallowing success. RESULTS: In all subjects, serial FEES detected pharyngeal phase dysphagia, aspiration, and aspiration risk and enabled determination of initial feeding status (NPO or PO), when to resume successful oral feeding, and what bolus consistencies to use for optimal swallowing success. Specifically, 15 of 32 (47%) subjects received FEES 3 to 5 times within only 6 to 22 days. Timely serial FEES allowed 22 of 32 (69%) subjects to resume an oral diet as early and safely as possible. CONCLUSIONS: No subject who resumed an oral diet based on results of FEES developed an aspiration pneumonia. Serial FEES, therefore, enabled feeding status to be successful and efficiently changed from NPO to PO with no adverse health outcome. FEES was an efficient procedure with regard to appointment scheduling, transportation, patient issues, and personnel requirements.

Adult↗
PubMedDate not supplied

Strategies for automated fetal cell screening.

Studies to date have demonstrated fetal sex determination and aneuploidy detection from maternal blood, but a clinical screening technique has not yet emerged. A key limiting factor is the small number of fetal cells, which makes detection specificity and reliability critical. Visual inspection of unsorted or sorted fetal cells is laborious, and cells can be easily missed. Moreover, it is impractical to examine manually all the separated cells. It is highly likely that automation may increase the number of cells inspected, resulting in higher detection sensitivities. Flow and image cytometry are two feasible approaches for automated detection of cells. This review details computerized microscopy (image cytometry) techniques for the automatic detection of fetal cells. Microscopy-based approaches used to identify fetal origin include: (i) immunocytochemical identification of fetal haemoglobin-specific cells (light or fluorescence microscopy); (ii) identification of sex chromosomes and/or aneuploidy using fluorescence in-situ hybridization; and (iii) morphological identification of nucleated red blood cells using light microscopy. The relevant instrumentation, including motorized stages and filters, cameras and digitizer boards are discussed, and software algorithms, including image enhancement, autofocusing, object detection and relocation, and features for operator review and data analysis, are outlined.

Autoanalysis↗
PubMedDate not supplied

Variability in memory performance in aged healthy individuals: an fMRI study.

Episodic memory performance varies in older subjects but underlying biological correlates remain as yet ambiguous. We investigated episodic memory in healthy older individuals (n=24; mean age: 64.4+/-6.7 years) without subjective memory complaints or objective cognitive impairment. Episodic memory was assessed with repetitive learning and recall of abstract geometric patterns during fMRI. Group analysis of brain activity during initial learning and maximum recall revealed hippocampal activation. Correlation analysis of brain activation and task performance demonstrated significant hippocampal activity during initial learning and maximum recall in a success-dependent manner. Neither age nor gray matter densities correlated with hippocampal activation. Functional imaging of episodic memory thus permits to detect objectively variability in hippocampal recruitment in healthy aged individuals without subjective memory complaints. Correlation analysis of brain activation and performance during an episodic memory task may be used to determine and follow-up hippocampal malfunction in a very sensitive manner.

Aged↗
PubMed1997

Unusual vestibular and visual input in human dynamic balance as a motion sickness susceptibility test.

BACKGROUND: Motion sickness (MS) is commonly thought to arise from a sensory conflict. However, few quantitative methods based on this theory are available to detect MS susceptibility. HYPOTHESIS: It was asked whether the standardized unusual stimulation of a single sensory channel under quantified dynamic balance conditions in man could elicit a sensory conflict and therefore trigger motion sickness (MS) METHODS: Vestibular and visual channels were stimulated by galvanic current and rotating prismatic glasses, respectively. The moving platform used to create the requirements for dynamic balance conditions was chosen not only to worsen the malaise but also to obtain an objective measurement of the balance consequences of the stimulations. RESULTS: Both vestibular and visual stimulation, applied separately, elicited MS-like symptoms (in 56% and 73% of subjects, respectively) and stereotyped balance reactions. A relationship was found between subjective MS-like symptoms and objective measurements of dynamic balance performance. Subjects sensitive to unusual vestibular messages differed from the others by a greater increase in the parameters indicating a difficulty of balance whereas subjects sensitive to unusual visual messages were recognized by the strategy they used to balance themselves. CONCLUSIONS: These results demonstrated that a sensory conflict can trigger MS-like symptoms. We conclude that the measured parameters of a global somatomotor activity, such as the dynamic balance task proposed here, could be useful for objectively detecting subjects predisposed to MS, for training them and testing the efficiency of anti-MS drugs.

Adult↗
PubMed2006

Predicting outcomes of HLA-identical allogeneic stem cell transplants from variable number of tandem repeat disparity between donors and recipients.

BACKGROUND AND OBJECTIVES: Detecting differences in the variable number of tandem repeats (VNTR) between a recipient and a donor has already been used to monitor the degree of chimerism after allogeneic stem cell transplantation (SCT). Alongside major histocompatibility complex disparity, the disparity of various polymorphous proteins encoded by several genes may play a critical role in the pathogenesis of graft-versus-host disease (GVHD) in allogenic SCT. However, the biological effect of VNTR disparity has scarcely been studied. BACKGROUND AND OBJECTIVES: Eighty-four patients receiving an SCT from an HLA-identical sibling (n=68) or an unrelated donor (n=16) were analyzed. The patients were transplanted because of acute myeloid leukemia (ns=48), acute lymphoblastic leukemia (n=8), chronic myeloid leukemia (n=15), non-Hodgkin's lymphoma (n=18) and myelodysplastic syndrome (n=3). Polymerase chain reaction analysis was performed to amplify three VNTR regions (D1S80, D1S111, and D17S5). These regions were classified as fully matched, partially matched, or mismatched between donors recipients. RESULTS: A strong correlation was observed between D1S80 matching status and transplant outcomes in terms of overall survival (p=0.0179) and non-relapse mortality (p=0.0305), but not for the D1S111 or D17S5 disparity. The fully matched D1S80 pairs showed a better overall survival (72% vs 38%) and lower non-relapse mortality (17% vs 50%) compared to the partially matched or mismatched pairs. In multivariate analyses, a fully matched D1S80 pair was found to be an independent favorable prognostic factor for overall survival (p=0.03) and non-relapse mortality (p=0.05). In addition, D1S80 disparity was significantly associated with the occurrence of gut chronic GVHD (p=0.05). INTERPRETATION AND CONCLUSIONS: The present data suggest that disparities in D1S80--located in chromosome 1--are associated with an increased incidence of gut chronic GVHD and non-relapse mortality.

Adolescent↗
PubMedDate not supplied

[Aortic debris in cerebrovascular ischemic disease].

BACKGROUND: The aortic atherosclerotic debris is considered a high risk embolic source, being an independent predictor for cerebrovascular ischemia. The incidence is higher in the elderly and in patients with coronary artery disease. Transesophageal echocardiogram (TEE) is an important diagnostic tool that allows its detection. OBJECTIVE: To describe characteristics of patients with ischemic stroke and echocardiographic diagnosis of aortic debris. PATIENTS AND METHODS: We analyzed the group of patients with debris diagnosis in 209 TEE performed between 01/01/99 and 31/05/02, in 835 consecutive ischemic events. The information was collected from the Stroke Database of the Neurology Department of Policlinica Bancaria. RESULTS: TEE was accomplished in 25% of all assisted events. The mean age was 66.56 years (SD 11.22). In 30 studies (14%) aortic debris was detected. In this group of patients, 26 men and 4 women, was also found: plaques grade IV 60%, left atrial dilatation 40% and spontaneous echo contrast 20%. The most frequent risk factors were hypertension, dislipemia and smoking, with no significative difference compared to the group without debris. 40% had a prior cerebrovascular event. They presented with clinical subtype LACI 53%, PACI 27%, POCI 17%. 63% of patients had lacunar infarct (53% anterior and 10% posterior). CONCLUSION: The contribution of TTE for detection of embolic sources is relevant. A high percentage of the population with echocardiographic diagnosis of aortic debris, had a lacunar infarct, defined radiologically and by clinical features.

Adult↗
PubMed1989

Image cytometry in automated cervical screening.

Severe restrictions with regard to false negative rates have played a major role in the development of the LEYden Television Analysis System (LEYTAS). The present paper describes a test with a continuous series of 1500 cervical samples illustrating the accuracy of LEYTAS in a fully automated screening procedure using cell selection transformations and artefact rejection procedures. Specimen classification with a cut-off at greater than 0.3% alarms (= percentage of automatically selected objects per epithelial cells) and greater than 10 alarms, results in a false negative rate (FNR) of 0.3% (1 case out of 321 cases with severe dysplasia or more serious lesions), a false positive rate (FPR) of 13% (663 negative cases) and a rejection rate of 2.7%. Besides a machine classification, LEYTAS offers a second, machine-interaction classification of those preparations which have been declared positive by the machine. Machine-interaction involves visual evaluation of the stored images of the detected objects (alarms) and reduces the FPR from 13 to 8%. Statistical tests further demonstrate the significance of the screening results. Presently the main drawback for routine use of automated screening with LEYTAS seems to be the time consuming preparation procedure, since instrumentation has now been updated to a new, fast and user-friendly version of LEYTAS.

Acriflavine↗
PubMed2005

A three-dimensional active shape model for the detection of anatomical landmarks on the back surface.

In this study relations between anatomical landmarks on the dorsal surface of the human torso corresponding to underlying skeletal structures are established. By examining the statistics of the positions of the landmarks in a training set of subjects a point distribution model is derived. Rotations of the pelvis are simulated in order to show that the main mode shapes of variation are consistent with rotations of the pelvis relative to the trunk. The parameters of these mode shapes can therefore be used as independent measures of clinical parameters such as pelvic inclination, pelvic tilt, etc. The point distribution model is further applied to improve reliability and robustness for an automatic and objective detection of the anatomical landmarks on the back surface (active shape model). The results show that it is possible to replace radiographs by surface measurements in order to measure position and orientation of the pelvis, which is particularly valuable in the case of functional examinations that normally involve a large number of radiographs (e.g. to measure the position of the pelvis in a scoliosis).

Adolescent↗
PubMed1984

Detection of transient ischemic episodes by ambulatory ECG recordings.

In summary, ambulatory ECG monitoring detects episodes of S-T segment shifts with and without chest pain in patients with coronary heart disease. These most likely represent ischemic episodes. There is limited information available as yet for use of ambulatory monitoring as a screening test applied to totally asymptomatic individuals, particularly from populations in which the frequency of coronary artery disease is low. Equipment used for ambulatory ECG monitoring and methods of quantifying the ischemic episode require further evaluation. At present, ambulatory ECG monitoring can be used to objectively detect silent and symptomatic ischemic episodes and monitor effectiveness of therapy designed to prevent ischemia in individuals with ischemic heart disease.

Ambulatory Care↗
PubMed2007

Selection and fusion of color models for image feature detection.

The choice of a color model is of great importance for many computer vision algorithms (e.g., feature detection, object recognition, and tracking) as the chosen color model induces the equivalence classes to the actual algorithms. As there are many color models available, the inherent difficulty is how to automatically select a single color model or, alternatively, a weighted subset of color models producing the best result for a particular task. The subsequent hurdle is how to obtain a proper fusion scheme for the algorithms so that the results are combined in an optimal setting. To achieve proper color model selection and fusion of feature detection algorithms, in this paper, we propose a method that exploits nonperfect correlation between color models or feature detection algorithms derived from the principles of diversification. As a consequence, a proper balance is obtained between repeatability and distinctiveness. The result is a weighting scheme which yields maximal feature discrimination. The method is verified experimentally for three different image feature detectors. The experimental results show that the fusion method provides feature detection results having a higher discriminative power than the standard weighting scheme. Further, it is experimentally shown that the color model selection scheme provides a proper balance between color invariance (repeatability) and discriminative power (distinctiveness).

Algorithms↗
PubMed1982

Back complaints and findings in transport workers performing physically heavy work.

Transport work at an airport promotes the appearance of back diseases because of the lifting carrying, pulling, and pushing of loads in limited spaces. To clarify the nature of back disorders in such a group, a standardized interview for detecting subjective previous and present back symptoms was made of 366 transport workers, and 134 were given a clinical orthopedic examination for detecting objective findings. Sixty-six percent of the interviewed workers reported current back symptoms; these symptoms correlated significantly positively with height, age, and length of transport work experience. Eighty-three percent of te workers with present back symptoms also complained of former back pain. Validity tests between the interview and the clinical examination showed a sensitivity of 86% and a specificity of 31%. The results of our study suggest (i) that according to the high sensitivity the used interview is a valuable screening method for detecting back disorders, and (ii) that selection of workers according to the criteria of our results may be expected to lower the prevalence of back complaints.

Adult↗
PubMed2000

Evaluation of the roche AMPLICOR enterovirus PCR assay in the diagnosis of enteroviral central nervous system infections.

BACKGROUND: Enteroviruses cause a substantial number of cases of aseptic meningitis annually in the USA. While culture has been useful in the detection of patients with viral meningitis it is time-consuming and lacks sensitivity. Detection of viral nucleic acid in patient specimens has been demonstrated to improve enteroviral detection. OBJECTIVES: A research use only commercial amplification assay, the Roche AMPLICOR EV test, was compared to culture for the diagnosis of enteroviral meningoencephalitis. STUDY DESIGN: Four-hundred and sixty-five consecutive CSF samples sent prospectively for suspicion of enteroviral infection were evaluated by PCR and shell-vial culture. Clinical information and CSF analysis were used to resolve PCR positive, culture negative samples. Sensitivity and specificity were calculated using resolved data. RESULTS: There were 138 samples which met the definition of a true positive. Of these culture detected 77 (sensitivity 55.8%) and PCR detected 136 (sensitivity 98.6%). PCR missed two culture positive samples. Upon repeat testing, these CSF samples were found to contain inhibitors. CONCLUSIONS: The Roche AMPLICOR EV-PCR test was statistically more sensitive than culture (P<0.001) in the detection of enteroviruses in CSF in patients suspected of having enteroviral meningitis. This assay also has the advantage of a rapid turnaround time of 5-6 h compared to 3-5 days for culture.

Adolescent↗
PubMedDate not supplied

Immediate-early gene expression in the barrel cortex.

Since their detection in the early 1980s immediate-early genes (most of them being inducible transcription factors) have been regarded as molecular keys to the orchestration of late-effector genes that ultimately would enable functional and structural adaptation of the brain to changing external and internal demands. This is called neuronal plasticity and it has been intensively studied in the somatosensory (barrel) cortex of rodents. This brain region is intimately involved in the processing and probably also the storage of tactile information, stemming from the large facial whiskers, necessary for object detection or spatial navigation in the environment. On the other hand, several of the inducible transcription factors have been found to function as neuronal activity markers providing a cellular resolution, thus, enabling the cell-type specific mapping of activated neuronal circuits. Some recent data on both topics in the rodent barrel cortex will be presented in this topical review.

Animals↗
PubMed2004

Unconscious perception: a model-based approach to method and evidence.

Unconscious perceptual effects remain controversial because it is hard to rule out alternative conscious perception explanations for them. We present a novel methodological framework, stressing the centrality of specifying the single-process conscious perception model (i.e., the null hypothesis). Various considerations, including those of SDT (Macmillan & Creelman, 1991), suggest that conscious perception functions hierarchically, in such a way that higher level effects (e.g., semantic priming) should not be possible without lower level discrimination (i.e., detection and identification). Relatedly, alternative conscious perception accounts (as well as the exhaustiveness, null sensitivity, and exclusiveness problems-Reingold & Merikle, 1988, 1990) predict positive relationships between direct and indirect measures. Contrariwise, our review suggests that negative and/or nonmonotonic relationships are found, providing strong evidence for unconscious perception and further suggesting that conscious and unconscious perceptual influences are functionally exclusive (cf. Jones, 1987), in such a way that the former typically override the latter when both are present. Consequently, unconscious perceptual effects manifest reliably only when conscious perception is completely absent, which occurs at the objective detection (but not identification) threshold.

Humans↗
PubMed2005

Quantitative diagnosis of stress-induced myocardial ischemia using analysis of contrast echocardiographic parametric perfusion images.

AIMS: Parametric imaging of myocardial perfusion provides useful visual information for the diagnosis of coronary artery disease (CAD). We developed a technique for automated detection of perfusion defects based on quantitative analysis of parametric perfusion images and validated it against coronary angiography. METHODS AND RESULTS: Contrast-enhanced, apical 2-, 3- and 4-chamber images were obtained at rest and with dipyridamole in 34 patients with suspected CAD. Images were analyzed to generate parametric perfusion images of the standard contrast-replenishment model parameters A, beta and A.beta. Each parametric image was divided into six segments, and mean parameter value (MPV) was calculated for each segment. Segmental MPV ratio between stress and rest was defined as a flow reserve index (FRI). Receiver operating characteristics (ROC) analysis was used in a Study group (N=17) to optimize FRI threshold and the minimal number of abnormal segments per vascular territory (LAD and non-LAD), required for automated detection of stress-induced perfusion defects. The optimized detection algorithm was then tested prospectively in the remaining 17 patients (Test group). LAD and non-LAD stenosis >70% was found in 19 and 17 patients, respectively. In the Study group, FRI threshold was: LAD=0.95 and non-LAD=0.68, minimal number of abnormal segments was four and two, correspondingly. Sensitivity, specificity and accuracy in the Test group were: 75%, 67% and 71% in the LAD, and 75%, 75% and 75% in the non-LAD territories. CONCLUSION: Automated quantitative analysis of contrast echocardiographic parametric perfusion images is feasible and may aid in the objective detection of CAD.

Aged↗
PubMed2000

Detection of IgA antibodies to cat, beta-lactoglobulin, and ovalbumin allergens in human milk.

BACKGROUND: The relationship between the development of allergy during infancy and breast-feeding remains controversial. This controversy may be due to individual variations in the composition of human milk. Antibodies to food antigens to which the mother is commonly exposed are present in the milk, but their relationship to allergy is still unknown. IgA antibodies to inhalant allergens have not been previously detected. OBJECTIVE: Our purpose was to analyze secretory IgA antibody levels to cat, beta-lactoglobulin, and ovalbumin allergens in colostrum and mature milk in relation to maternal allergy. METHODS: Colostrum and samples of mature milk were obtained after 1 and 3 months of lactation from 53 nursing mothers (17 allergic and 36 nonallergic mothers) and were analyzed for total secretory IgA levels by ELISA and secretory IgA antibodies to cat, beta-lactoglobulin, and ovalbumin by an enzyme-amplified ELISA. The specificity of the assays was confirmed by inhibition experiments. RESULTS: Secretory IgA to cat, beta-lactoglobulin, and ovalbumin allergens were detected in colostrum as well as mature milk. The levels of secretory IgA to ovalbumin were lower in colostrum from allergic mothers with P =.016, whereas the levels to beta-lactoglobulin and cat were similar in the 2 groups. IgA antibodies to ovalbumin were detected in 94% of the colostrum samples from allergic and in all samples from nonallergic mothers, in 82% and 96%, respectively at 1 month, and 53% and 65% at 3 months. Fewer samples had detectable secretory IgA antibodies to beta-lactoglobulin than to ovalbumin and cat, and only 33% and 10% of the samples from the allergic and nonallergic mothers, respectively, remained positive at 3 months. All the allergic mothers had detectable IgA to cat in colostrum, whereas 83% and 73% of the samples were positive at 1 and 3 months. The corresponding numbers were 93%, 81%, and 81% in the nonallergic mothers (not significant). CONCLUSION: Even a low level of exposure of the mucosa (eg, by inhalant allergens) can induce antibody secretion into the milk, both in allergic and nonallergic mothers.

Allergens↗