Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “object detection”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed2003

Comparison of quantitative 99mTc-HMPAO and 67Ga citrate lung scans in patients with active diffuse infiltrative lung disease.

Diffuse infiltrative lung disease (ILD) is a heterogeneous group of disorders that predominantly affect the lung parenchyma and spare the airway. To objectively assess the degree of pulmonary vascular endothelium damage in active ILD, lung/liver uptake ratios (L/L ratios) on 99mTc hexamethylpropylene amine oxime (99mTc-HMPAO) lung scans were determined in 21 patients with active ILD. Meanwhile, the 67Ga citrate uptake index (GUI) on 67Ga lung scans was measured in order to evaluate the severity of lung inflammation in active ILD. The results show there were statistically significant differences between normal controls and patients with active ILD, as shown in the L/L ratio and GUI. However, when the patients were divided into two groups: (1) eight patients with normal chest X-ray findings, and (2) 13 patients with abnormal X-ray findings, there was no significant difference between groups 1 and 2 for the results of L/L ratio and GUI. In addition, no correlation between the degree of damage to the pulmonary vascular endothelium and the severity of lung inflammation was found. In conclusion, L/L ratios on 99mTc-HMPAO lung scans and GUI on 67Ga lung scans are different to the findings of chest X-rays and have the potential to objectively detect the degree of damage to the pulmonary vascular endothelium and the severity of lung inflammation in active IDL. However, the relationship between L/L ratio and GUI in active ILD is not significant.

Acute Disease↗
PubMed1997

Performance and cost-effectiveness of selective screening criteria for Chlamydia trachomatis infection in women. Implications for a national Chlamydia control strategy.

BACKGROUND AND OBJECTIVES: Detection of subclinical Chlamydia trachomatis infection in women is a high but costly public health priority. GOALS: To develop and test simple selective screening criteria for chlamydia in women, to assess the contribution of cervicitis to screening criteria, and to evaluate cost-effectiveness of selective versus universal screening. STUDY DESIGN: Cross-sectional study and cost-effectiveness analysis of 11,141 family planning (FP) and 19,884 sexually transmitted diseases (STD) female clients in Washington, Oregon, Alaska, and Idaho who were universally tested for chlamydia using cell culture, direct fluorescent antibody, enzyme immunoassay, or DNA probe. RESULTS: Prevalence of cervical chlamydial infection was 6.6%. Age younger than 20 years, signs of cervicitis, and report of new sex partner, two or more partners, or symptomatic partner were independent predictors of infection. Selective screening criteria consisting of age 20 years or younger or any partner-related risk detected 74% of infections in FP clients and 94% in STD clients, and required testing 53% of FP and 77% of STD clients. Including cervicitis in the screening criteria did not substantially improve their performance. Universal screening was more cost-effective than selective screening at chlamydia prevalences greater than 3.1% in FP clients and greater than 7% in STD clients. CONCLUSIONS: Age and behavioral history are as sensitive in predicting chlamydial infection as criteria that include cervicitis. Cost-effectiveness of selective screening is strongly influenced by the criteria's sensitivity in predicting infection, which was significantly higher in STD clients. At the chlamydia prevalences in the populations studied, it would be cost saving to screen universally in FP clinics and selectively in STD clinics, the reverse of current practice in many locales.

Adolescent↗
PubMed2000

Release of platelet activation markers during coronary angioplasty.

BACKGROUND: Authors of several studies have reported that activation of platelets occurs during coronary angioplasty, but consistent results have not been obtained. Levels of serotonin in coronary circulation have been found to be elevated during percutaneous transluminal coronary angioplasty but greater than normal concentrations of beta-thromboglobulin and platelet factor 4 have not been detected. OBJECTIVE: To perform a serial analysis of platelet-activation markers with simultaneous measurements of levels of serotonin, beta-thromboglobulin and platelet factor 4 in blood samples from the coronary artery and coronary sinus of patients undergoing coronary angioplasty. METHODS: Twenty patients undergoing elective coronary angioplasty were studied. Measurements of levels of beta-thromboglobulin, platelet factor 4, and serotonin in samples from the ostium of the coronary artery and the coronary sinus were performed immediately before angioplasty and after the first balloon deflation. RESULTS: Concentrations of beta-thromboglobulin and platelet factor 4 in coronary artery and coronary sinus were elevated in all patients before dilatation, whereas concentrations of serotonin were elevated in 85% of the patients. Concentrations of all markers in coronary sinus decreased after the first inflation. The coronary-sinus: coronary-artery concentration ratios before dilatation for beta-thromboglobulin, platelet factor 4, and serotonin were > 1 for the majority of patients, particularly for those with complex culprit lesions, indicating that coronary activation of platelets was occurring. Ratios remained unchanged or decreased after the first inflation, depending on initial values. CONCLUSIONS: Both systemic and coronary activation occur in patients subjected to percutaneous transluminal coronary angioplasty before the onset of intervention. After balloon deflation the greater than normal baseline coronary-sinus:coronary-artery concentration ratios of all markers (beta-thromboglobulin, platelet factor 4 and serotonin) tend to decline or remain unchanged, depending on the level of activation.

Adult↗
PubMed1989

Knowledge-based approach to sleep EEG analysis--a feasibility study.

A knowledge-based approach to automated sleep EEG (electroencephalogram) analysis is described. In this system, an object-oriented approach is followed in which specific waveforms and sleep stages ("objects") are represented in terms of frames. The latter capture the morphological and spatio-temporal information for each object. An object detection module ("frame matcher"), operating on the frames, is employed to identify what features need to be extracted from the EEG and to trigger the appropriate "specialist"--specialized signal processing modules--to obtain values for these features. This leads to an opportunistic approach to EEG interpretation with quantitative information being extracted from the signal only when needed by the reasoning processes. The system has been tested on the detection of K complexes and sleep spindles. Its performance indicates that the approach followed is feasible and can become a powerful tool for automated EEG interpretation.

Electroencephalography↗
PubMed1998

Analysis of beat-to-beat variability of frequency contents in the electrocardiogram using two-dimensional Fourier transforms.

Late potentials are very small signals (1-20 microV) in the surface ECG with high-frequency components, which are found in patients prone to sustained ventricular tachycardia. Evaluation of these signals requires either very sophisticated recording techniques for single-beat analysis or signal averaging. Signal averaging, however, might disregard information about risk stratification. Therefore, we developed the Single-Beat Spectral Variance (SBSV) based on two-dimensional (2-D) Fourier transform of 80 ms segments of 128 consecutive beats. This approach depicts the beat-to-beat variability of the frequency contents of these ECG segments. An index function enables an objective detection of late potentials. We investigated 35 patients after myocardial infarction and sustained ventricular tachycardia (Group 1), 50 patients after myocardial infarction without ventricular arrhythmias (Group 2) and ten healthy volunteers. SBSV classified 29 of 35 patients (83%) of Group 1 as pathologic, 14 of these 29 patients (48%) exclusively on the basis of marked Wenckebach-like conduction pattern. In Group 2, only five of 50 patients showed abnormal SBSV. In Group 3, we found no pathologic result. Thus, SBSV is a promising new method to investigate late potentials in patients after myocardial infarction. SBSV contains not only the results of frequency analysis after signal averaging, but also evaluates variable ECG components.

Adult↗
PubMed1998

A vision-based technique for objective assessment of burn scars.

In this paper a method for the objective assessment of burn scars is proposed. The quantitative measures developed in this research provide an objective way to calculate elastic properties of burn scars relative to the surrounding areas. The approach combines range data and the mechanics and motion dynamics of human tissues. Active contours are employed to locate regions of interest and to find displacements of feature points using automatically established correspondences. Changes in strain distribution over time are evaluated. Given images at two time instances and their corresponding features, the finite element method is used to synthesize strain distributions of the underlying tissues. This results in a physically based framework for motion and strain analysis. Relative elasticity of the burn scar is then recovered using iterative descent search for the best nonlinear finite element model that approximates stretching behavior of the region containing the burn scar. The results from the skin elasticity experiments illustrate the ability to objectively detect differences in elasticity between normal and abnormal tissue. These estimated differences in elasticity are correlated against the subjective judgments of physicians that are presently the practice.

Algorithms↗
PubMed2005

Visually distinct patterns with matching subband statistics.

A commonly used representation of a visual pattern is a statistical distribution measured from the output of a bank of filters (Gaussian, Laplacian, Gabor, etc.). Both marginal and joint distributions of filter responses have been advocated and effectively used for a variety of vision tasks, including texture classification, texture synthesis, object detection, and image retrieval. This paper examines the ability of these representations to discriminate between an arbitrary pair of visual stimuli. Examples of patterns are derived that provably possess the same marginal and joint statistical properties, yet are "visually distinct." This is accomplished by showing sufficient conditions for matching the first k moments of the marginal distributions of a pair of images. Then, given a set of filters, we show how to match the marginal statistics of the subband images formed through convolution with the filter set. Next, joint statistics are examined and images with similar joint distributions of subband responses are shown. Finally, distinct periodic patterns are derived that possess approximately the same subband statistics for any arbitrary filter set.

Algorithms↗
PubMed2005

Differential expression of angiotensin receptors in human cutaneous wound healing.

BACKGROUND: Angiotensin AT1 and AT2 receptors are expressed in human skin. Furthermore, AT2 receptors have been reported to be upregulated during tissue repair and remodelling in various noncutaneous human tissues. OBJECTIVES: Detection of alterations in angiotensin II receptor expression during wound healing in human skin. METHODS: Three models were employed. (i) Primary human keratinocytes were razor scraped in culture flasks and alterations in the expression of angiotensin receptor mRNA determined by semiquantitative reverse transcription-polymerase chain reaction for 1-12 h thereafter. (ii) Early wound healing (48 h after cutting) was studied in punch biopsies from human skin ex vivo by means of immunohistochemical staining using polyclonal antibodies against the AT1 or AT2 receptor. (iii) In vivo wound healing was studied in sections of human cutaneous scars by immunohistochemistry to determine receptor expression early (2 days) and late (2 weeks-3 months) after surgery. RESULTS: In all experimental settings, an upregulation of both receptor subtypes was noticed after wounding. Immunohistochemically stained skin sections showed a stronger expression of AT2 than of AT1 receptors within the area of scarring. Enhanced receptor expression was detectable as early as 24 h after injury and lasted for up to 3 months. CONCLUSIONS: From these data, we conclude that angiotensin AT1 and AT2 receptors are upregulated in human cutaneous wounds, giving further support to the concept that angiotensin II plays a role even at an early stage during cutaneous wound healing.

Biopsy↗
PubMed1983

Combined flow cytometry and image cytometry of the same cytological sample.

Flow cytometry and image cytometry, two measuring techniques in the field of analytical cytology, can be used sequentially on the same cytological sample. Cells stained with a fluorochrome for the determination of for example, DNA or RNA content are first analysed in suspension by flow cytometry. The results of the fluorescence analysis of the individual cells are presented after data processing as frequency histograms of the DNA or RNA content of all the cells of the sample. In these histograms certain cell populations such as those with an increased DNA content are defined and these are then selected for further investigation. This is achieved by sorting cells of interest into centrifugation buckets by means of electrostatic deflection of the droplets containing such cells. Sorted cell populations are then centrifuged on to glass slides and stained according to the acriflavine Feulgen-SITS staining procedure, a quantitative method for DNA and protein. Image cytometry of these stained cells is performed with a computer controlled television based image analysis system (LEYTAS). With this system abnormal cells with elevated DNA content or increased chromatin contrast are automatically detected, thereby eliminating almost all artefacts and normal cells. Subsequently detected objects are stored in grey-value memories after the automated analysis for visual examination by the cytologist. The possibilities of combined flow cytometry and image cytometry are illustrated in typical examples in the field of cervical, bladder and mammary cytology.

Breast↗
PubMed1977

Echolocation performance of the vampire bat (Desmodus rotundus).

The neotropical vampire bats (Desmodus rotundus) echolocate using ultrasonic pulses like those of the Latin American phyllostomatid bats. In this paper the orally produced echolocation sounds of Desmodus are analysed and the performance of the echolocation system is studied in two-choice training experiments on two vampire bats. Ability to detect objects is relatively limited; both animals were capable of discerning the presence of a 1 cm wide metal strip at a distance of 50 cm, but they failed with 0.5 cm wide strips. The ultrasonic pulses produced at a distance of 50 cm appear to sample an area with a diameter of 2.5 to 3.0 cm (i.e., the solid angle tested with each pulse is 3 degrees to 3 degrees 40' in extent).

Animals↗
PubMedDate not supplied

Arthroscopic treatment of osteochondritis dissecans in the canine shoulder.

Twenty-three shoulders of 21 dogs were treated arthroscopically for osteochondritis dissecans (OCD). Thirteen dogs had bilateral lesions detectable radiographically; however, only two dogs had arthroscopic surgery on both shoulders. Arthroscopic procedures included removal of the osteochondral flap, curettage of the subchondral defect, and partial synovectomy. Fourteen dogs were using the treated limb within 1 day and eight dogs within 2 days, although some lameness may have persisted for several weeks. Force plate evaluation was effective for comparison of preoperative and postoperative mean peak force/body weight (PF/BW) values. Improvement was detected objectively in 9 of the 10 dogs returned for postoperative force plate analysis. All owners were satisfied with the cosmetic results and the rapid return to function.

Animals↗
PubMed2002

Noninvasive assessment of Crohn's disease activity: a comparison of 18F-fluorodeoxyglucose positron emission tomography, hydromagnetic resonance imaging, and granulocyte scintigraphy with labeled antibodies.

OBJECTIVES: Detection of disease activity in Crohn's disease (CD) is of crucial importance for diagnosis and management of the disease. Noninvasive methods for monitoring are desirable and comprise hydromagnetic resonance imaging (hydro-MRI) and leukocyte scintigraphy. In addition, a recent case report indicated the potential of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) to assess CD activity. However, comparative prospective studies are lacking. METHODS: Between February, 1999 and August, 2000, 59 patients with CD were enrolled in a prospective study to assess disease activity by FDG-PET, hydro-MRI, and immunoscintigraphy with anti-nonspecific cross-reacting antigen 95 antigranulocyte antibodies. In 28 of these patients, colonoscopy could be performed. Twelve patients with irritable bowel syndrome and 20 tumor patients without gut inflammation served as controls. Results were compared by statistical analysis. RESULTS: FDG-PET detected 127 pathological findings (average maximum standardized uptake value = 4.4 +/- 1.1) in the terminal/neoterminal ileum (37), small bowel (24), and colon (66) of 54 patients with CD, whereas no pathological findings were seen in five patients with CD, the control patients with irritable bowel syndrome, and the tumor patients without gut inflammation. In contrast, examination with hydro-MRI or granulocyte antibodies detected less pathological findings in CD patients. Forty-five of the detected foci were accessible to endoscopic verification. The correlation of the foci with endoscopic findings showed a high specificity (>89%) of all three methods to detect inflamed areas in the terminal ileum and colon of patients with CD, although analyses by hydro-MRI and granulocyte antibody scan had strikingly lower sensitivities (40.9% and 66.7%) than FDG-PET analysis (85.4%). CONCLUSIONS: FDG-PET appears to be a reliable noninvasive tool for simultaneous detection of inflamed areas in the small and large bowel of patients with CD. FDG-PET can be used to detect disease activity in the terminal ileum and colon of CD patients with high sensitivity and specificity.

Adult↗
PubMed2001

Spatially modulated illumination microscopy: online visualization of intensity distribution and prediction of nanometer precision of axial distance measurements by computer simulations.

During the last years, measurements considerably beyond the conventional "Abbe-Limit" of optical resolution in far field light microscopy were realized by several light microscopical approaches. Point spread function (PSF) engineering, spectral precision distance microscopy (SPDM), and related methods were used to demonstrate the feasibility of such measurements. SPDM allows the measurement of position and multiple distances between point-like fluorescent objects of different spectral signatures far below the optical resolution criterion as defined by the full width at half maximum of the PSF. Here, we report a software method to obtain online visualization of light distribution in the lateral and axial direction of any object detected in a spatially modulated illumination (SMI) microscope. This strongly facilitates routine application of SMI microscopy. The software was developed using Microsoft Visual C++ running on Windows NT. Furthermore, some aspects of the theoretical limits of the SPDM method were studied by virtual microscopy. For the case of SMI microscopy the precision of axial distance measurements was studied, taking into account photon statistics and image analysis procedures. The results indicate that even under low fluorescence intensity conditions typical for biological structure research, precise distance measurements in the nanometer range can be determined, and that axial distances in the order of 40 nm are detectable with such precision.

Computer Simulation↗
PubMed2002

Favorable noise uniformity properties of Fourier-based interpolation and reconstruction approaches in single-slice helical computed tomography.

Volumes reconstructed by standard methods from single-slice helical computed tomography (CT) data have been shown to have noise levels that are highly nonuniform relative to those in conventional CT. These noise nonuniformities can affect low-contrast object detectability and have also been identified as the cause of the zebra artifacts that plague maximum intensity projection (MIP) images of such volumes. While these spatially variant noise levels have their root in the peculiarities of the helical scan geometry, there is also a strong dependence on the interpolation and reconstruction algorithms employed. In this paper, we seek to develop image reconstruction strategies that eliminate or reduce, at its source, the nonuniformity of noise levels in helical CT relative to that in conventional CT. We pursue two approaches, independently and in concert. We argue, and verify, that Fourier-based longitudinal interpolation approaches lead to more uniform noise ratios than do the standard 360LI and 180LI approaches. We also demonstrate that a Fourier-based fan-to-parallel rebinning algorithm, used as an alternative to fanbeam filtered backprojection for slice reconstruction, also leads to more uniform noise ratios, even when making use of the 180LI and 360LI interpolation approaches.

Algorithms↗
PubMed2004

Physical performance evaluation of a 256-slice CT-scanner for four-dimensional imaging.

We have developed a prototype 256-slice CT-scanner for four-dimensional (4D) imaging that employs continuous rotations of a cone-beam. Since a cone-beam scan along a circular orbit does not collect a complete set of data to make an exact reconstruction of a volume [three-dimensional (3D) image], it might cause disadvantages or artifacts. To examine effects of the cone-beam data collection on image quality, we have evaluated physical performance of the prototype 256-slice CT-scanner with 0.5 mm slices and compared it to that of a 16-slice CT-scanner with 0.75 mm slices. As a result, we found that image noise, uniformity, and high contrast detectability were independent of z coordinate. A Feldkamp artifact was observed in distortion measurements. Full width at half maximum (FWHM) of slice sensitivity profiles (SSP) increased with z coordinate though it seemed to be caused by other reasons than incompleteness of data. With regard to low contrast detectability, smaller objects were detected more clearly at the midplane (z = 0 mm) than at z = 40 mm, though circular-band like artifacts affected detection. The comparison between the 16-slice and the 256-slice scanners showed better performance for the 16-slice scanner regarding the SSP, low contrast detectability, and distortion. The inferiorities of the 256-slice scanner in other than distortion measurement (Feldkamp artifact) seemed to be partly caused by the prototype nature of the scanner and should be improved in the future scanner. The image noise, uniformity, and high contrast detectability were almost identical for both CTs. The 256-slice scanner was superior to the 16-slice scanner regarding the PSF, though it was caused by the smaller transverse beam width of the 256-slice scanner. In order to compare both scanners comprehensively in terms of exposure dose, noise, slice thickness, and transverse spatial resolution, K=Dsigma2ha3 was calculated, where D was exposure dose (CT dose index), sigma was magnitude of noise, h was slice thickness (FWHM of SSP), and a was transverse spatial resolution (FWHM of PSF). The results showed that the K value was 25% larger for the 16-slice scanner, and that the 256-slice scanner was 1.25 times more effective than the 16-slice scanner at the midplane. The superiority in K value for the 256-slice scanner might be partly caused by decrease of wasted exposure with a wide-angle cone-beam scan. In spite of the several problems of the 256-slice scanner, it took a volume data approximately 1.0 mm (transverse) x 1.3 mm (longitudinal) resolution for a wide field of view (approximately 100 mm long) along the zeta axis in a 1 s scan if resolution was defined by the FWHM of the PSF or the SSP, which should be very useful to take dynamic 3D (4D) images of moving organs.

Biophysical Phenomena↗
PubMed1998

An evaluation of the signal and noise characteristics of four CCD-based film digitizers.

Film digitizers are common devices in radiology departments involved with picture archive and communication systems (PACS) and teleradiology. In this paper, we studied the performance of film digitizers based on charge-coupled device detectors (CCD digitizers), and compared this with the performance of a laser digitizer (the de facto standard). Our focus was on the assessment of signal, noise and useful optical density range performance. A function (L* delta D) derived from the Rose model was used to evaluate these parameters in absolute terms, based their predicted ability to detect objects of specific size and optical density difference with respect to background. We studied CCD digitizers from four different vendors and found that none was able to reliably operate up to the maximum density of 3.0 required to digitize plain radiographs, while the laser digitizer was capable of this task. Our analysis also indicated that two of the four CCD digitizers were adequate for digitizing laser-printed cross-sectional images in certain cases. Finally, our analysis indicated that digitization of SMPTE pattern films along with visual assessment of the 5% and 95% contrast patches was not sufficient for determining the utility of film digitizers for clinical tasks. Computation of the L* delta D function provides a useful means of assessing the performance of film digitizers (e.g., for acceptance testing and quality control), and this technique may be adaptable for evaluation of other digital imaging modalities.

Biophysical Phenomena↗
PubMed1989

Gating of retinal transmission by afferent eye position and movement signals.

Vision in most vertebrates is an active process that requires the brain to combine retinal signals with information about eye movement. Eye movement information may feed forward from the motor control areas of the brain or feed back from the extrinsic eye muscles. Feedback signals elicited by passive eye movement selectively gate retinal outflow at the first relay, the dorsal lateral geniculate nucleus. The gating predominantly facilitates retinogeniculate transmission immediately after eye movement and inhibits transmission when a new steady-state eye position is achieved. These two gating effects are distributed in a complementary fashion across the dorsal lateral geniculate nucleus such that the spatiotemporal activity profile could contribute to object detection and localization.

Action Potentials↗
PubMed1991

Immunofluorescence and morphology of Giardia lamblia cysts exposed to chlorine.

Giardia cyst-like objects detected by immunofluorescence in chlorinated water samples often cannot be positively identified by their morphological appearance. To determine the effect of chlorine on cyst immunofluorescence and morphology, Giardia lamblia cysts were exposed to chlorine for 48 h. The majority of cysts exposed to chlorine concentrations of 1 to 11 mg/liter at 5 and 15 degrees C lost their internal morphological characteristics necessary for identification, but most of them were still detectable by immunofluorescence.

Animals↗