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At least 577 records · Page 32Linked to original sources
PubMed1998

[Loss of heterozygosity microsatellite DNA on chromosome loci 3, 5, 7, 9 and 18 in human pancreatic cancer].

OBJECTIVE: Detecting the loss of heterozygosity in paraffin-embedded pancreatic cancer tissues. METHODS: Analysing loss of heterzygosity (LOH) of microsatellite DNA on chromosome loci 3,5,7,9 and 18 with PCR-SSLP-silver stain method in pancreatic cancer. RESULTS: In 45 sporadic pancreatic cancer samples and their paired control tissue, LOH was detected on site for D18S46( 18q21.1,31.0%), D18S474 (18q21.1, 20.0%), D9S176 (9q22-31,20.0%), D3S1234 (3p14.2,17.5%),D 3S1289 (3p21.1, 15.7%), D3S1481 (3p14.2,4.9%), D7S486 (7q22,3.6%), D5S365 (5q32, 3.2%) and D3S587 (3p24-26, 2.6%). CONCLUSION: Different percentages of loss of heterzygosity on specific chromosomal regions were found, and the meaning of the results was discussed. Some key genes may play a role in the pathogenesis of pancreatic cancer.

Adult↗
PubMed2007

Design and implementation of gradient vector flow snake to detect a reference object in pelvic x-rays for preoperative total hip arthroplasty planning application.

The main interest of this research project is to promote automation in performing preoperative planning for hip joint replacement surgery using a special medical image viewing software, ViewPro. Preoperative planning is performed to carefully prepare the surgery and to accurately select the hip implants. The first step of preoperative planning is to calibrate the x-ray image to adjust the magnification factor. A femoral head implant is used as magnification factor reference. Automation is introduced by developing an algorithm to automatically detect this reference object in the image. The algorithm used for performing the automatic detection of the reference object is gradient vector flow (GVF) snake. A study has been performed to compare the newly developed semiautomatic algorithm to the old manual calibration algorithm. The results show a close relation between the two algorithms (less than 1% of average relative difference). It is concluded that the developed semiautomated algorithm can be used as an alternative for performing the manual calibration.

Algorithms↗
PubMed1980

Some effects of pretectum lesions on the frogs' detection of stationary objects.

Frogs with bilateral aspiration lesions of the caudal thalamus were unable to avoid collision with a vertically striped barrier that partly surrounded the animal. This striking deficit co-existed with normal visual guidance of feeding and avoidance of threat. In addition, all lesioned animals were unable to turn towards an aperture within black or white enclosures in order to escape noxious stimulation. Some residual detection of stationary edges remains, however, since most lesioned animals were able to avoid a small barrier placed before them. It is concluded that pretectal visual neurons play a key role in the detection of stationary objects in contrast to the motion detection functions of the frogs optic tectum.

Animals↗
PubMed2003

Validity of the Hewlett-Packard actograph in detecting fetal movements.

OBJECTIVE: To detect fetal movements during non-stressed cardiotocography to evaluate the validity of the Hewlett-Packard Doppler ultrasound actograph in detecting fetal movements. METHODS: This was a prospective, observational study. Thirty healthy pregnant women were divided into two gestational age groups (Group I, 31 + 0 to 34 + 0 weeks, n = 15; Group II, 37 + 0 to 40 + 0 weeks, n = 15). A Hewlett-Packard M-1350-A actocardiograph was used to make recordings of 45 min for each woman. Fetal movements were also detected sonographically by an observer and they were recorded independently by the pregnant woman. Ninety consecutive 30-s periods were analyzed to study agreement between the three techniques. RESULTS: The mean total agreement for fetal activity plus quiescence between ultrasound and the actograph was 63.7% for Group I, and 72.2% for Group II. In cases of fetal activity only, these values were 45.8% and 47.6%, respectively. Total agreements between ultrasound and the pregnant woman were 74.0% and 79.0%, respectively, for Groups I and II. Cohen's kappa values for total agreement between ultrasound and actograph were 0.31 (95% CI, 0.27-0.36), indicating 'fair' agreement in Group I, and 0.43 (95% CI, 0.38-0.47), indicating 'moderate' agreement in Group II. CONCLUSIONS: Use of the Hewlett-Packard actograph may offer some additional information during routine cardiotocography. However, our results were disappointing; the technique appears not to be suitable for detailed recordings of fetal behavior, and may even be misleading when difficult cardiotocographic patterns have to be interpreted.

Adult↗
PubMed1994

Magnetic resonance imaging of an experimental model of intracranial metastatic disease. A study of lesion detectability.

RATIONALE AND OBJECTIVES: The detectability of brain metastases was evaluated in a rabbit model, with attention to magnetic resonance contrast dose and timing of image acquisition after injection of contrast medium. METHODS: Five New Zealand white rabbits were studied at 1.5 T 6 to 7 days and 11 to 12 days after surgical implantation of an adenocarcinoma tumor nidus. T1- and T2-weighted spin-echo images (0.9 x 0.9 x 2 mm3 voxel size) were obtained before administration of contrast medium. T1-weighted images were repeated 5, 15, and 30 minutes after intravenous injection of 0.1 mmol/kg gadoteridol. At 40 minutes, a supplemental dose of 0.2 mmol/kg (0.3 mmol/kg cumulative dose) was administered, with T1-weighted images repeated at 5, 15, and 30 minutes after the second injection. RESULTS: Six to 7 days after tumor implantation, lesion enhancement (percent change, with normalization to baseline and equilibrium values) was 42 +/- 9% at 5 minutes, 48 +/- 9% at 15 minutes, and 42 +/- 10% at 30 minutes after administration of 0.1 mmol/kg gadoteridol. After administration of 0.3 mmol/kg gadoteridol, lesion enhancement was 111 +/- 13% at 5 minutes, 116 +/- 8% at 15 minutes, and 100% at 30 minutes. On film review, 2 of 5 lesions were not detectable at 6 to 7 days after tumor implantation with 0.1 mmol/kg gadoteridol. Administration of 0.3 mmol/kg gadoteridol provided for lesion identification in each instance. Eleven to 12 days after tumor implantation, one lesion was not detectable with 0.1 mmol/kg gadoteridol. Administration of 0.3 mmol/kg gadoteridol again provided for lesion identification in all cases. Mean lesion enhancement increased from 39 +/- 15% to 104 +/- 10%. CONCLUSIONS: The administration of 0.3 mmol/kg gadoteridol (high dose) compared with 0.1 mmol/kg gadoteridol (conventional dose) improves metastatic lesion detectability in the brain. The lesions identified only at high dose were confirmed by histopathology. Smaller lesions were not detected at a dose of 0.1 mmol/kg.

Adenocarcinoma↗
PubMed2001

[Application of dot immunogold filtration assay in antibody detection for cysticercosis].

OBJECTIVE: To detect serum antibody of cysticercosis by dot immunogold filtration assay for establishing a diagnostic kit for cysticercosis patients. METHODS: Cyst fluid of cysticercus of Taenia solium after dialysis was used as diagnostic antigen in dot immunogold filtration assay and enzyme-linked immunosorbent assay to detect the serum antibody in patients with cysticercosis. Samples to be detected included 71 sera from patients with cysticercosis, 90 sera from healthy people, 20 sera from patients with other parasitic infections or brain tumor. RESULTS: The sensitivity and specificity of dot immunogold filtration assay were 90.1%(64/71) and 95.6%(86/90), respectively. No positive reaction was recorded in cases with other diseases except one serum from a patient with brain tumor. The coincidence rate between dot immunogold filtration assay and enzyme-linked immunosorbent assay was 94.4% (152/161). CONCLUSION: Dot immunogold filtration assay showed promising result for the diagnosis of cysticercosis.

Animals↗
PubMed1999

Role of phase information and eye pursuit in the detection of moving objects in noise.

As part of an ongoing study that uses objective image quality measures to optimize medical imaging x-ray fluoroscopy, we investigated two basic features of the detection of moving cylinders that mimic arteries, catheters, and guide wires. First, we compared detection with and without a phase cue consisting of a nearby alternating light and dark square. Depending on object size and velocity, phase cuing improved detection from 1% to 15% and gave an average of 6%, an effect much smaller than the 38% predicted from a Monte Carlo simulation of the ideal observer. Evidently, humans were limited in their ability to incorporate knowledge of the phase cue. Second, we evaluated the effect of eye pursuit of a fixation point that moved with the target. In general, motion at the highest velocity degraded (74%) and enhanced (68%) detection of small and large objects, respectively. With eye pursuit, both effects were substantially reduced in a manner consistent with a reduced retinal velocity. Our data compared favorably with a human observer model that included a spatiotemporal contrast sensitivity response and smooth-pursuit eye movements with a gain of 0.8. These mechanisms of perception are thought to be present in coronary artery x-ray fluoroscopy imaging, where phase information is available from the moving heart and where motion markers are available from x-ray opaque markers incorporated in thin catheters and guide wires.

Artifacts↗
PubMed2006

Lidar detection of underwater objects using a neuro-SVM-based architecture.

This paper presents a neural network architecture using a support vector machine (SVM) as an inference engine (IE) for classification of light detection and ranging (Lidar) data. Lidar data gives a sequence of laser backscatter intensities obtained from laser shots generated from an airborne object at various altitudes above the earth surface. Lidar data is pre-filtered to remove high frequency noise. As the Lidar shots are taken from above the earth surface, it has some air backscatter information, which is of no importance for detecting underwater objects. Because of these, the air backscatter information is eliminated from the data and a segment of this data is subsequently selected to extract features for classification. This is then encoded using linear predictive coding (LPC) and polynomial approximation. The coefficients thus generated are used as inputs to the two branches of a parallel neural architecture. The decisions obtained from the two branches are vector multiplied and the result is fed to an SVM-based IE that presents the final inference. Two parallel neural architectures using multilayer perception (MLP) and hybrid radial basis function (HRBF) are considered in this paper. The proposed structure fits the Lidar data classification task well due to the inherent classification efficiency of neural networks and accurate decision-making capability of SVM. A Bayesian classifier and a quadratic classifier were considered for the Lidar data classification task but they failed to offer high prediction accuracy. Furthermore, a single-layered artificial neural network (ANN) classifier was also considered and it failed to offer good accuracy. The parallel ANN architecture proposed in this paper offers high prediction accuracy (98.9%) and is found to be the most suitable architecture for the proposed task of Lidar data classification.

Algorithms↗
PubMed2003

Automatic detection of small objects from their infrared state-of-polarization vectors.

A technique for automatic detection of targets from their infrared signature's state-of-polarization vector is described. The bounds on the Bayesian total probability of errors are estimated from the observed Stokes vector imagery and used as metrics for separating targets from background clutter. The performance of the proposed approach for objects under various geometries is studied in terms of receiver operating characteristic curves. The new results, which have been obtained from data from the U.S. Air Force's Infrared Modeling and Analysis polarimetric infrared simulation tool, indicate the usefulness of polarimetric infrared signatures for the automatic detection of small targets.

Journal Article↗
PubMed2002

No within-object advantage for detection of rotation.

It is known that in a detection task the type of rigid transformation to be detected (reflection vs. translation) interacts with the type of display (closed vs. open contours). The advantage for closed contours found with reflection is believed to be a general within-object advantage, whilst the advantage for open contours found with translation is an exception, described as a lock-and-key process (Acta Psychol. 95 (1997) 119). We tested rotation, using a reaction time paradigm, and found the same result as for translation. Moreover, we found that the critical factor is not the number of objects present, rather it is whether the comparison is made across a surface or across an aperture between surfaces. Post-experiment interviews did not confirm any difference for observers who reported using a conscious lock-and-key mental transformation. We speculate that seeing a translation or a rotation across a closed figure is difficult because the closure of the figure emphasises the mismatch of the contour polarities on the two sides of the figure. That is, there may be a closed object advantage for detecting a difference in polarity which interferes with the task of detecting a regularity in shape. Evidence from the analysis of foil rejection trials supports such a speculation.

Adult↗
PubMed2003

Cue gradient and cue density interact in the detection and recognition of objects defined by motion, contrast, or texture.

The human visual system is able to extract an object from its surrounding using a number of cues. These include foreground/background gradients in disparity, motion, texture, colour, and luminance. We have investigated normal subjects' ability to detect objects defined by either motion, texture, or luminance gradients. The effects of manipulating cue density and cue foreground/background gradient on both detection and recognition accuracy were also investigated. The results demonstrate a simple additive relationship between cue density and cue gradient across forms defined by motion, luminance, and texture. The results are interpreted as evidence for the notion that form parsing is achieved via a similar algorithm across anatomically distinct processing streams.

Adolescent↗
PubMed2005

Optical detection of rapidly moving objects in space.

We compare the sensitivity of photon-counting and charged-coupled-device (CCD) imagers for rapidly moving objects. Our test case involves the detection of small objects in space, seen against a diffuse zodiacal light background, as observed from a space platform. We contrast photon-counting detectors, with excellent time resolution and negligible readout noise, against CCDs with a significantly larger quantum efficiency. For fast moving objects and small fields of view, the photon-counting detectors are able to detect significantly smaller targets, with the added benefit of providing angle-angle-time metric information in addition to high-time-resolution light curves. For larger fields of view and slower moving objects, the CCDs are more sensitive. These results may motivate the further development of microchannel-plate photon-counting systems and amplified CCDs for detecting and tracking space objects.

Journal Article↗
PubMed1998

Seizure detection using a self-organizing neural network: validation and comparison with other detection strategies.

OBJECTIVE: A previously described seizure detection algorithm (CNET) (Gabor, A.J., Leach, R.R. and Dowla, F.U. Automated seizure detection using a self-organizing neural network. Electroenceph. clin. Neurophysiol., 1996, 99: 257-266) was validated with 200 records from 65 patients (4553.8 h of recording) containing 181 seizures. DESIGN AND METHODS: Performance of the algorithm was manifest by its sensitivity ((seizures detected/total seizures) x 100) and selectivity (false-positive errors/Hr-FPH). Comparisons with the Monitor detection algorithm (Version 8.0c, Stellate Systems) and audio-transformation (Oxford Medilog) were performed. RESULTS: CNET detected 92.8% of the seizures and had a mean FPH of 1.35 +/- 1.35. Monitor detected 74.4% of the seizures and had a mean FPH of 3.02 +/- 2.78. Audio-transformation detected all but 3 (98.3%) of the seizures. Selectivity for this detection strategy was not defined. CONCLUSIONS: This study not only validates the CNET algorithm, but also the notion that seizures have frequency-amplitude features that are localized in signal space and can be selectively identified as being distinct from other types of EEG patterns. The ear is a specialized frequency-amplitude detector and when the signal is transformed into audio frequency range (audio-transformation), seizures can be detected with better sensitivity as compared to the other strategies examined.

Adolescent↗
PubMed2000

A multihospital survey of radiation exposure and image quality in pediatric fluoroscopy.

BACKGROUND: Traditionally, pediatric radiologists have been advocates of fluoroscopy systems that provide diagnostic images at the lowest possible radiation dose to the pediatric patient. Manufacturers of fluoroscopic equipment vary as to their claims of "low radiation" exposures. OBJECTIVES: To obtain comparative data on radiation exposure and image quality from four pediatric hospitals, across variants of fluoroscopic equipment (such as pulsed versus continuous fluoroscopy). MATERIALS AND METHODS: Images were acquired from phantoms that simulated the size of a 3-year-old child. Phantom results, both stationary and rotating dynamic, were evaluated for radiation exposure and for image resolution of high- and low-contrast objects. RESULTS: Radiation exposure from the four fluoro units varied widely; the lowest-dose selectable fluoro mode produced exposures varying between 34 and 590 mrads/min among the four fluoro units, and the highest-dose selectable fluoro mode produced 540-2,230 mrads/min. The lowest radiation exposures were produced by pulsed fluoro units, and the very lowest radiation exposure was produced by a fluoroscope that had been especially optimized for pediatric imaging. There was only a small variation in image quality among the hospitals for visualization of stationary objects. A wide variability was noted for detection of objects on the moving phantom. CONCLUSIONS: The variability in the number of detected objects was considerably smaller than the variability in radiation exposure. Pulsed fluoroscopy provides improved resolution for moving objects. Optimization of one hospital's fluoroscope especially for pediatric imaging produced the best ratio of image quality to radiation exposure.

Age Factors↗
PubMed2004

Oscillatory model of attention-guided object selection and novelty detection.

We develop a new oscillatory model that combines consecutive selection of objects and discrimination between new and familiar objects. The model works with visual information and fulfils the following operations: (1) separation of different objects according to their spatial connectivity; (2) consecutive selection of objects located in the visual field into the attention focus; (3) extraction of features; (4) representation of objects in working memory; (5) novelty detection of objects. The functioning of the model is based on two main principles: the synchronization of oscillators through phase-locking and resonant increase of the amplitudes of oscillators if they work in-phase with other oscillators. The results of computer simulation of the model are described for visual stimuli representing printed words.

Attention↗
PubMed1979

Detectability of spherical objects by computed tomography.

A Lucite phantom was constructed with voids cut in long cylinders, short cylinders and spheres in order to quantitate the effect of partial volume averaging on detectability. Typical scans of varying contrast revealed that the long cylinders cinsistently can be detected to a smaller size than either short cylinders or spheres of the same diameter. The authors feel that low contrast detectability must involve the influence of beam profile on partial volume contrast losses for spherical objects.

Physical Phenomena↗
PubMed2005

Objective and noninvasive detection of sub-clinical lung injury in breast cancer patients after radiotherapy.

AIMS: We employed technetium-99m hexamethylpropylene amine oxime (Tc-99m HMPAO) lung scan to detect sub-clinical lung injury after radiation therapy of 60 female patients diagnosed with right breast cancer. METHODS: The degree of pulmonary vascular endothelium damage was represented as lung/liver uptake ratios (L/L ratios) calculated on Tc-99m HMPAO lung scan. All patients underwent simple mastectomy and post-operative radiotherapy of approximately 50 Gy. We divided the patients into three groups according to the interval between radiotherapy and lung Tc-99m HMPAO lung scan: Group 1 included 20 patients who received the lung scan within 1-3 months after radiotherapy, group 2 included 20 patients were within 3-9 months after radiotherapy, and group 3 included 20 patients were more than 9 months after radiotherapy. In addition, 20 age-matched normal women were included as the control group. RESULTS: The L/L ratios were 0.32+/-0.04 for normal controls, 0.59+/-0.10 for group 1, 0.55+/-0.07 for group 2, and 0.34+/-0.04 for group 3, respectively. Based on our preliminary results, we found that sub-clinical lung injury and significantly increased L/L ratio in breast cancer patients received radiotherapy may occur within the first 6 months after radiotherapy. However, the L/L ratio is markedly decreased after 9 months. CONCLUSION: Our findings concluded that the degree of pulmonary vascular endothelium damage represented as the L/L ratio on Tc-99m HMPAO lung scan has the potential to be a sensitive, objective and noninvasive method to detect sub-clinical lung injury in breast cancer patients received radiotherapy.

Adult↗