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PubMed2003

The detection of small simulated field defects using multifocal VEPs.

INTRODUCTION: The multifocal visual-evoked potential (mfVEP) has been widely investigated in the study of diseases of the visual system. However, the sensitivity of the mfVEP in objective detection of field defects has not been determined. This study investigates the variation of the mfVEP responses whilst simulating field defects by using different sizes of mask on the stimulus pattern. METHODS: Simulated field defects of four different sizes (2, 3, 5, and 7 degrees) at two different eccentricities (10 and 16 degrees) were generated on a standard mfVEP dartboard stimulus using opaque masks. These masks were placed at the centre of each dartboard sector and the modified stimuli were used to elicit mfVEPs from 10 normal subjects. The response densities and latencies of N1, P1 of the mfVEP were compared, without and with small simulated field defects. RESULTS: The minimum size of simulated field defect causing significant response density reduction in P1 and N1 was 5 degrees at both retinal eccentricities. N1 showed similar reduction in response density at both retinal eccentricities, but P1 showed larger reduction at the 10-degree location than at the 16-degree location. There was no change in latencies with simulated field defect at either location. CONCLUSIONS: The mfVEP is only sensitive to a simulated field defect equal to or larger than 5 degrees in diameter, and mfVEP has greater sensitivity at 10-degree eccentricity than at 16-degree eccentricity.

Adult↗
PubMed2005

The detection of small relative simulated field defects using multifocal VEPs.

INTRODUCTION: The multifocal visual-evoked potential (mfVEP) has been widely used in the study of diseases of the visual system. However, the sensitivity of the mfVEP in the objective detection of relative field defects has not been determined. This study investigates variations in mfVEP responses while simulating relative field defects by using different luminous transmission masks [neutral density (ND) filters] on the stimulus pattern. METHODS: Simulated relative field defects with four different luminous transmissions were obtained by using 0.2, 0.4, 0.6, and 0.8 ND filters, 5 degrees in size, at two different retinal eccentricities (10 and 16 degrees) on a standard mfVEP dartboard stimulus. Eleven normal subjects were recruited for mfVEP measurements. The response amplitudes and latencies of the N1 and P1 of the mfVEP, with and without small simulated relative field defects, were compared. RESULTS: The mfVEP amplitudes of N1 and P1 decreased substantially when 0.6 and 0.8 ND filters were introduced. The effects were similar at both the 10- and 16-degree eccentricities but there was no change in latency with simulated field defects at either location. CONCLUSIONS: The mfVEP can detect a simulated relative field defect 5 degrees in size starting with 0.6 log unit reduction in luminance at both 10-degree and 16-degree eccentricities. This illustrates that the sensitivity of the mfVEP measurement is nearly comparable with that of the Humphrey Visual Field Analyser.

Adult↗
PubMed2005

Biosonar behaviour of free-ranging porpoises.

Detecting objects in their paths is a fundamental perceptional function of moving organisms. Potential risks and rewards, such as prey, predators, conspecifics or non-biological obstacles, must be detected so that an animal can modify its behaviour accordingly. However, to date few studies have considered how animals in the wild focus their attention. Dolphins and porpoises are known to actively use sonar or echolocation. A newly developed miniature data logger attached to a porpoise allows for individual recording of acoustical search efforts and inspection distance based on echolocation. In this study, we analysed the biosonar behaviour of eight free-ranging finless porpoises (Neophocaena phocaenoides) and demonstrated that these animals inspect the area ahead of them before swimming silently into it. The porpoises inspected distances up to 77 m, whereas their swimming distance without using sonar was less than 20 m. The inspection distance was long enough to ensure a wide safety margin before facing real risks or rewards. Once a potential prey item was detected, porpoises adjusted their inspection distance from the remote target throughout their approach.

Animals↗
PubMedDate not supplied

[The characteristics of detecting the tick-borne encephalitis virus antigen in the ELISA and indirect hemagglutination reaction by means of scanning electron microscopy].

The surface of polystyrene plates was studied at different stages of the enzyme immunoassay (EIA) and the passive hemagglutination (PHA) test by the method of scanning electron microscopy in the detection of tick-borne encephalitis (TBE) virus antigen. The study revealed that in the process of EIA larger antigens were washed away from the plate surface. The objects detected on the polystyrene surface were identified as conglomerations of the virions of TBE virus, but whole virions were shown to play no decisive role in EIA. The conclusion was made that, due to some specific features of this method, EIA was more sensitive in reaction with small antigens (individual glycoproteids, their small complexes). And, respectively, the PHA test was more sensitive in reaction with large antigenic complexes (whole virions, their conglomerations, immune complexes).

Antigens, Viral↗
PubMed1991

Automated image-based cytometry with fluorescence-stained specimens.

The combination of digitized microscopy, algorithms for object recognition and fluorescent labeling is a promising approach for reliable, quick, automated and cost-effective screening of clinical specimens. We describe two conceptually different algorithms for detecting objects in fluorescence microscopic images. One, which is partially automated, compares a mask that represents a typical object with every position in the image; the other, which is fully automated, calculates threshold intensities to segment the image into regions of objects and background. Applications of the algorithms in conjunction with a prototype image-based cytometer are demonstrated for determining the DNA ploidy distribution of cultured human endometrial cells and determining the DNA ploidy distribution and the fraction of cells expressing the E6 antigen of human papilloma virus serotypes 16 and 18 in a PAP smear. The encouraging results from this study suggest that automated image-based cytometry utilizing fluorescent stains will be a valuable asset for clinical screening.

Algorithms↗
PubMed2005

Value of different follow-up strategies to assess the efficacy of circumferential pulmonary vein ablation for the curative treatment of atrial fibrillation.

BACKGROUND: The objective of this study was to compare transtelephonic ECG every 2 days and serial 7-day Holter as two methods of follow-up after atrial fibrillation (AF) catheter ablation for the judgment of ablation success. Patients with highly symptomatic AF are increasingly treated with catheter ablation. Several methods of follow-up have been described, and judgment on ablation success often relies on patients' symptoms. However, the optimal follow-up strategy objectively detecting most of the AF recurrences is yet unclear. METHODS: Thirty patients with highly symptomatic AF were selected for circumferential pulmonary vein ablation. During follow-up, a transtelephonic ECG was transmitted once every 2 days for half a year. Additionally, a 7-day Holter was recorded preablation, after ablation, after 3 and 6 months, respectively. With both, procedures symptoms and actual rhythm were correlated thoroughly. RESULTS: A total of 2,600 transtelephonic ECGs were collected with 216 of them showing AF. 25% of those episodes were asymptomatic. On a Kaplan-Meier analysis 45% of the patients with paroxysmal AF were still in continuous SR after 6 months. Simulating a follow-up based on symptomatic recurrences only, that number would have increased to 70%. Using serial 7-day ECG, 113 Holter with over 18,900 hours of ECG recording were acquired. After 6 months the percentage of patients classified as free from AF was 50%. Of the patients with recurrences, 30-40% were completely asymptomatic. The percentage of asymptomatic AF episodes stepwise increased from 11% prior ablation to 53% 6 months after. CONCLUSIONS: The success rate in terms of freedom from AF was 70% on a symptom-only-based follow-up; using serial 7-day Holter it decreased to 50% and on transtelephonic monitoring to 45%, respectively. Transtelephonic ECG and serial 7-day Holter were equally effective to objectively determine long-term success and to detect asymptomatic patients.

Atrial Fibrillation↗
PubMed2005

Caries risk assessment: methods available to clinicians for caries detection.

It is hypothesized that occlusal lesions are initiated on the fissure walls and can therefore be obscured by sound superficial tissue. Additionally, there is evidence that one effect of regular use of fluorides is greater opacity of enamel, which may obscure underlying lesions in dentin, the so-called 'hidden lesions'. Dental radiographs are inadequate for detecting decay in the occlusal surfaces until the lesion is well advanced through the enamel and into the dentin. The clinician relies on visual observation of texture and discoloration, clinical judgment based upon experience, and on tactile sense by probing with an explorer. An objective detection method to complement the traditional visual assessment is used by the clinician for arriving at clinical decisions on the management of the carious lesion: whether invasive therapy or a more conservative, noninvasive approach. Objective and reliable longitudinal monitoring of the lesion's response to preventive measures allow the selection of an appropriate therapy before the lesion progresses to the stage where invasive treatment is required. This paper discusses the problem of the lack of appropriate clinical methods for the detection and quantification of carious lesions. A few commercially available methods are described (the quantitative light-induced fluorescence method, the DIAGNOdent device, and electrical caries monitor) and some new techniques mentioned.

Dental Caries↗
PubMed1998

Detection of moving objects in pulsed-x-ray fluoroscopy.

We investigated the detectability of moving, low-contrast objects in white-noise image sequences. The computer-generated, cylindrical phantoms mimicked arteries, catheters, and guide wires in medical, x-ray fluoroscopy image sequences at 16 acquisitions/s (pulsed-16) or 32 acquisitions/s (pulsed-32). We measured detectability by using a reference-test, adaptive forced-choice method whereby reference and test presentations were alternated during an experimental session to minimize effects of subject attention and accuracy criteria. In the case of the largest cylinder (diameter 0.48 deg), the highest speed (5.86 deg/s) increased absolute detectability by approximately 42% compared with that in the stationary case. With the smallest cylinder (diameter 0.023 deg), this motion decreased detectability by approximately 51%. The dose savings of pulsed-16 was approximately 18% of that for pulsed-32, with relatively little effect of velocity or object size. In general, subjects took slightly longer to respond in the case of low-acquisition fluoroscopy. Detectability data were modeled with a nonprewhitening matched filter that included a physiological, spatiotemporal contrast sensitivity function and a suboptimal, spatiotemporal signal template with time-limited memory.

Fluoroscopy↗
PubMed2002

Fluorescence-assisted image analysis of freshwater microalgae.

We exploit a property of microalgae-that of their ability to autofluoresce when exposed to epifluorescence illumination-to tackle the problem of detecting and analysing microalgae in sediment samples containing complex scenes. We have added fluorescence excitation to the hardware portion of our microalgae image processing system. We quantitatively measured 120 characteristics of each object detected through fluorescence excitation, and used an optimized subset of these characteristics for later automated analysis and species classification. All specimens used for training and testing our system came from natural populations found in Lake Biwa, Japan. Without the use of fluorescence excitation, automated analysis of images containing algae specimens in sediment is near impossible. We also used fluorescence imaging to target microalgae in water samples containing large numbers of obtrusive nontargeted objects, which would otherwise slow processing speed and decrease species analysis and classification accuracy. Object drift problems associated with the necessity to use both a fluorescence and greyscale image of each microscope scene were solved using techniques such as template matching and a novel form of automated seeded region growing (SRG). Our system proved to be not only user-friendly, but also highly accurate in classifying two major genera of microalgae found in Lake Biwa-the cyanobacteria Anabaena spp. and Microcystis spp. Classification accuracy was measured to be over 97%.

Anabaena↗
PubMed2000

The role of antennal hair plates in object-guided tactile orientation of the cockroach (Periplaneta americana).

The searching behavior of blinded cockroaches was examined under unrestrained conditions, in an arena, and on a treadmill. When cockroaches searching in a circular arena touched a stationary object (metal pole) with their antennae, they frequently approached the object more closely, and then climbed up it. Similar orientation behavior was observed in tethered animals in open loop conditions, walking on a Styrofoam ball. In these restrained cockroaches, a single antenna sufficed to distinguish the angular positions of an object, in the horizontal plane (0 degrees, 45 degrees, and 90 degrees). A group of mechanosensitive hairs on the basal segment of the antenna (scapal hair plate) appears to play a major role in antennal object detection in the horizontal plane, as gauged by shaving off these scapal hair plates. In unrestrained cockroaches, shaving the scapal hair plate increased the time needed to approach an object. Under tethered conditions, the ability to turn towards and to establish antennal contact with a test object was significantly impaired.

Animals↗
PubMed2000

Detection of gene amplification in archival breast cancer specimens by laser-assisted microdissection and quantitative real-time polymerase chain reaction.

Gene amplification is one of the most important mechanisms leading to deregulated gene expression in cancer. The exact quantitative detection of this frequent genomic alteration in solid tumors is often hampered by an admixture of nonneoplastic bystander and stroma cells. To overcome this obstacle and to develop an objective quantitative method we have combined laser-assisted microdissection of tumor cells with the novel 5'-exonuclease-based real-time polymerase chain reaction (PCR) assay. The latter method enables the highly reproducible exact quantification of minute amounts of nucleic acids. As a model system amplification of c-erbB2/Her-2/neu gene and the adjacent topoisomerase IIalpha gene was determined in paraffin-embedded breast cancer specimens (n = 23) after immunohistochemical labeling and laser-based microdissection of tumor cells. The high sensitivity of real-time PCR enabled the reliable and objective detection of low-level amplifications in as few as 50 cells from archival tissue sections. Low-level amplifications were shown to escape from detection unless tumor cells were isolated by microdissection. In selected cases intratumor heterogeneity was demonstrated using areas of approximately 50 to 100 cells. This novel approach combining immunohistochemistry, laser microdissection, and quantitative kinetic PCR allows morphology-guided studies in archival tissue specimens and will enable the exact quantification of gene copy numbers in even small and precancerous lesions.

Antigens, Neoplasm↗
PubMed1994

Subjective evaluations of mammographic accreditation phantom images by three observer groups.

RATIONALE AND OBJECTIVES: Mammography providers are under increasing pressure to become certified by the American College of Radiology (ACR). Successful accreditation is contingent on passing a phantom image quality test. This study was undertaken to evaluate viewer performance with the phantom image evaluation process and to determine any observer group differences. METHODS: A series of standard phantom images were viewed by 30 medical physicists, 30 diagnostic radiologists, and 30 inexperienced observers. From the responses, object detection rates and passing rates according to the ACR criteria were established. These responses were analyzed with standard nonparametric tests to assess the degree of variability, correlation, and agreement among different observer groups. RESULTS: Median passing scores were similar for the radiologists and untrained readers, but the medical physicists appear to differ from the other two groups. There was not sufficient evidence to indicate that special training among physicists made a significant difference in median passing scores or mass detection rates. However, such training appeared to significantly affect the detection of microcalcification and fibril test patterns among the physicists' subgroups. Agreement among observer groups was high for all groups, but tended to be lower for overall passing rates than for any of the individual test objects. Agreement among physicists was affected by their subspecialty, presumably caused by their levels of specific training for these visual tasks. CONCLUSIONS: The authors conclude that choosing medical physicists to evaluate mammographic phantom films appears to be a good choice among potential observer groups, and that special training for reading these images affects their detection abilities and consistency. However, because passing rates did not appear to be affected by special training and given the current rapid degree of change in this area, more testing of medical physicists is desirable to examine these effects over time, and to study the effect of developing standards for training.

Accreditation↗
PubMedDate not supplied

A self-learning segmentation framework--the Taguchi approach.

The detection of object boundary is an interesting and challenging task in computer vision and medical image processing. The active contour model (snake model) has attracted much attention for object boundary detection in the past decade. However, due to the lack of understanding on the effect of different energy terms to the behavior of related objective functions for an image, the assignment of weights for different energy terms in this model is usually fulfilled empirically. Few discussions have been brought out specifically for assigning these weights automatically. In this paper, a novel self-learning segmentation framework, based on the snake model is proposed and applied to the detection of cardiac boundaries from ultrasonic images. The framework consists of a learning section and a detection section, and provides a training mechanism to obtain the weights from a desired object contour given manually. This mechanism first employs Taguchi's method to determine the weight ratios among distinct energy terms, followed by a weight refinement step with a genetic algorithm. The refined weights can be treated as the a priori knowledge embedded in the manually defined contour and be used for subsequent contour detection. Experiments with both synthetic and real echocardiac images were conducted with satisfactory outcomes. Results also show that the present method can be used to analyze successive images of the same object with only one training contour. Finally, the validity of the weight determining process was verified by the analysis of variance method (ANOVA).

Algorithms↗
PubMed1996

Quantitation of incident spinal fractures: comparison of visual detection with quantitative morphometry.

The value of quantitative morphometry in detection of new spinal fractures was assessed in serial radiographs from 83 patients with osteoporosis. From vertebral landmarks on lateral spine radiographs, a computer program allowed calculation of vertebral heights and area. By comparing vertebral dimensions in the two sets of films, incident spinal fractures could be quantitated based either on the minimum criteria of 15% reduction in vertebral height (CM2) or a fall in height and area of 20% and 10% (CM1). The results of quantitative morphometry were compared with those of the consensus and individual readings of visual detection by three experienced investigators in the same paired sets of spinal films. For incident new fractures, the visual consensus method (V-C) showed a very good agreement with individual visual detection (kappa of 0.794 to 0.916) as well as with CM1 (kappa of 0.821). However, there was a poor agreement between the results of consensus reading and of detection by CM2 (kappa of 0.341), due to excessive number of fractures identified by CM2, but not by the visual method. For incident recurrent fractures, there was a poor agreement between V-C and individual visual detection, and between V-C and quantitative morphometry (kappa of 0.306 to 0.496). It was due to severe compression fractures at baseline, which caused further changes in vertebral dimensions difficult to measure accurately by either visual or quantitative morphometry. Thus, if the visual detection of fractures by a consensus of experienced investigators is considered as the "gold standard," quantitative morphometry, based on minimum reduction in vertebral height of 20% accompanied by a minimum decline in area of 10%, provides an objective detection of incident new spinal fractures but not of recurrent fractures.

Aged↗
PubMed1997

[Clinical expression of systemic lupus erythematosus with anti-U1-RNP and anti-Sm antibodies].

UNLABELLED: The frequency of anti-U1-RNP and anti-Sm antibodies in systemic lupus erythematosus (SLE) varies according to the technique used for their detection. OBJECTIVE: To study the clinical manifestations associated with anti-U1-RNP and anti-Sm antibodies identified by different techniques. METHODS: 112 patients diagnosed with SLE were studied. Anti-U1-RNP and anti-Sm antibodies were detected by ELISA with a mixture of recombinant antigens, antigens obtained by immunoaffinity and by immunoblotting and counterimmunoelectrophoresis (CIE) with a saline extract of rabbit thymus. RESULTS: Anti-U1-RNP antibodies were detected in 70 (62.5%), 37 (33%) and 16 (14.2%) patients, and anti-Sm antibodies in 43 (38.3%), 36 (32.1%) and 10 (8.9%) patients by ELISA, immunoblotting, and CIE, respectively. Anti-U1-RNP antibodies are associated with edema in the dorsal hand region, sclerodactylia, Raynaud phenomenon and pericarditis (CIE); arthritis, hand edema, Raynaud phenomenon and sclerodactylia (anti-70 KD-U1-RNP and anti-A-U1-RNP by immunoblotting); and a lower incidence of discoid lupus and chronic renal insufficiency by lupus renal disease (ELISA). Anti-Sm antibodies are associated with Raynaud phenomenon and renal disease (CIE); cutaneous vasculitis, Raynaud phenomenon and thrombosis (anti-BB'-Sm immunoblotting); and arthritis and lower incidence of chronic renal insufficiency (ELISA). CONCLUSIONS: Anti-U1-RNP and anti-Sm antibodies detected by ELISA do not have the same clinical significance than those detected by immunoblotting or CIE. The clinical manifestations associated with such antibodies in the same SLE population vary according to the detection technique used.

Adolescent↗
PubMed1986

The development and standardization of an antigen detection ELISA for rubella virus grown in rabbit cells.

A double antibody sandwich ELISA for the detection of rubella virus antigen was developed and standardized. Commercially available antisera were chosen in order to make the assay readily available. Antigen detection gave an excellent correlation to titers obtained by examination of cytopathogenic effect (CPE, r = 0.986). Replication of rubella virus grown in rabbit cells was identified with CPE and positive ELISA appearing within a difference of +/- one day. ELISA provided an objective detection of rubella virus which is often difficult by the reading of CPE. The method was found to be both sensitive and reproducible and facilitated work in rubella virus control involving a large number of virus titrations.

Antigens, Viral↗
PubMed1998

Assessment of left ventricular dyssynergy by color kinesis.

Color kinesis is a new echocardiographic technique based on acoustic quantification. It has been developed to facilitate the ability to identify contraction abnormalities and has been incorporated into a commercially available ultrasound imaging system. The potential of this technique to improve the qualitative and quantitative assessment of wall motion abnormalities is described. Evaluation of color-encoded images allows detection of decreased amplitude of endocardial motion in abnormally contracting segments as well as a shorter time of endocardial excursion in segments with severely decreased motion. Compared with off-line quantitative studies, color kinesis has the advantage to be used on-line, without time-consuming manual tracing of endocardial boundaries. In addition, a single end-systolic color image contains the entire picture of spatial and temporal contraction and can be digitally stored and retrieved. In patients with proven coronary artery disease, color kinesis had a sensitivity of 88%, a specificity of 77%, and an overall accuracy of 86% in identifying the presence of segmental dysfunction. The practical application of color kinesis might be to improve our ability to distinguish normal from hypokinesis, something that has always been difficult in clinical echocardiography. Segmental analysis of color kinesis images allows objective detection of dobutamine-induced regional wall motion abnormalities in agreement with conventional visual interpretation of the corresponding 2-dimensional views. A method for objective assessment of wall dynamics during dobutamine stress echocardiography would be of particular clinical value, because these images are even more difficult to interpret than conventional echocardiograms. Quantitative assessment of diastolic function may allow objective evaluation of segmental relaxation abnormalities, especially under conditions of pharmacologic stress testing. Acquisition of color kinesis images during dobutamine stress echocardiography, both transthoracic and transesophageal, may facilitate the assessment of hybernating but viable myocardium and enhance the sensitivity in the detection of coronary artery disease.

Echocardiography, Doppler, Color↗
PubMed2004

Development of a novel ELISA system for detection of anti-BP180 IgG and characterization of autoantibody profile in bullous pemphigoid patients.

BACKGROUND: The NC16A immunodominant region of the bullous pemphigoid (BP) antigen BP180 has been used to develop several enzyme-linked immunosorbent assays (ELISAs) as diagnostic tools for BP autoantibody detection. OBJECTIVES: Because BP180 autoantibody reactivity is not restricted to NC16A, we have investigated the possibility of developing an ELISA based on selected epitopes additional to this immunodominant region. METHODS: Initially 78 BP sera were tested using an NC16A ELISA and IgG reactivity was detected in 64 BP sera (82%). The 14 NC16A-negative BP sera were then analysed by immunological screening against seven BP180-specific epitopes. Recombinant phages displaying BP180 epitopes were grown as plaques, blotted onto a nitrocellulose filter and incubated with BP sera. RESULTS: Three and five NC16A-negative BP sera reacted with epitopes AA 1080-1107 and AA 1331-1404 of the BP180 ectodomain, respectively. Thus, a novel ELISA with GST-1080 and GST-1331 (GST-1080/1331) was developed: 32 of 78 BP sera (41%) proved positive by this assay. The combined use of ELISAs with GST-NC16A and GST-1080/1331 detected IgG reactivity in 72 of 78 BP sera, increasing the sensitivity from 82% to 92%. In addition, autoreactivity against the three extracellular epitopes appeared to be related to the presence of both skin and mucosal involvement as assessed by Fisher's exact probability test. CONCLUSIONS: Our findings further characterize the autoimmune response in BP by identifying a subgroup of NC16A-negative patients who react with different BP180 extracellular epitopes. The developed ELISA system appears more sensitive than the ELISA based on NC16A alone and also informative about the epitope profile of BP patients.

Adult↗