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The aim of this work is to present methods for classifying images and locating extraneous objects within images. Our methods make use of higher order statistics, transforms of data into the frequency domain, and characteristics of the resulting clusters.
The performances of eight currently available computerized pulse-detection algorithms were compared on signal-free noise and physiological luteinizing hormone (LH) time series. Signal-free noise was made to vary from 4 to 36% for Gaussian and empirical distributions. Physiological LH data were obtained by immunoassay of blood samples withdrawn every 5 min for 24 h in 8 healthy men, so that the data sets could be emended to simulate varying sampling intensities. Whenever possible, programs were tested at a presumptive 1% false-positive rate. In relation to signal-free noise, the Santen and Bardin program and its modification manifested elevated false-positive rates when the intraseries coefficients of variation increased. The Regional Dual-Threshold program yielded a 1% false-positive rate except on simulated series with high variance. The Cluster and Detect programs both approximated a 1% false-positive rate and the Ultra program approximated a 2.3% false-positive rate throughout the entire range of variance tested. In regard to physiological LH data, all algorithms disclosed a significant impact of sampling intensity on estimates of LH pulse frequency. Sampling-intensity dependent estimates of LH peak frequency by three of the eight programs (Ultra, Cluster, and Detect) were statistically indistinguishable from each other but distinct from the five other programs tested. Furthermore, when judged in relation to their ability to identify individual peaks, the three congruent programs were minimally distinguishable (McNemar's test). Rather, these programs identified the same particular peaks (as defined by concordance of peak maxima) at least 72% of the time.
High-end graphics workstations (GWS) have been used for surgical simulators utilizing Computer Graphics (CG) and Virtual Reality (VR) technologies. This is because the simulators need lots of computing power, mainly for collision detection among objects modeled as a set of polygons. In this paper, we propose to use mathematical functions to model objects for collision detection. However, for graphic display we continue to use polygonal representation. Using the new model, we have developed a PC based ocular surgery simulator, which creates realistic surgery image in real-time. The computation time was found to be much lower than that in the conventional method.
According to investigations in veterinary medicine, published in 1983, it is possible to differentiate between real and pretended slaughtered pigs: by isoelectric focusing of muscular tissue the occurrence of a narrow band at the isoelectric point pH 6.3 was observed. The intention of the actual study was to prove, whether these results could be transmitted to human medicine to determine duration of agony or manner of death. The band appeared in 40 of 47 cases in variable intensity. A connection to duration of agony, manner of death or time of death could not be realized.
Spontaneous frequencies of the total mitotic segregation (ms) and mitotic crossing over (mco) in two strains of Saccharomyces cerevisiae, T1(RAD RAD) and T2(rad2 rad2) have been studied. 90 independent experiments were conducted for T1 and 75 for T2. We observed the following frequencies: 0.17 +/- 0.19% ms, T1; 0.30 +/- 0.034% ms, T2: 0.23 +/- 0.0055% mco, T1; 0.043 +/- 0.0142% mco, T2. The following experimental design is proposed for mutagen screening: at least three independent experiments for control and treatment, with 1000 or more colonies checked in every experiment. If the results of control as well as experimental sets are homogenous, then the Kastenbaum - Bowman test can be applied to evaluate the difference between control and treated groups.
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The upward shift in basal body temperature (BBT) observed in women of child-bearing age is often used as an indicator that ovulation has occurred and that a period of infertility has begun. In natural family planning programmes it is important to detect the BBT shift reliably and with a minimum of user uncertainty, against a background of physiologically induced temperature variations. The cumulative sum (CUSUM) test is adapted to the problem of detecting BBT shift and applied to 137 BBT charts obtained from 21 women using natural family planning. Results show successful detection of the shift in all cases. Shifts occurred at gynaecologically appropriate times in the menstrual cycle.
The paper deals with the development of devices for visualization on intravascular formations by using multifiber optical catheters, describes a scheme for a pilot testing unit based on periodical pulse-acting Nd:YAG laser that operates at the second harmonics (lambda = 532 nm). Analyzes errors while processing the return signal received by intravascular objects, proposes a statistical model which describes the received signal, which permits the development a of block diagram for an optimized device for initial processing of signals.
Research strategy in the auditory system has tended to parallel that in the visual system, where neurons have been shown to respond selectively to specific stimulus parameters. Auditory neurons have been shown to be sensitive to changes in acoustic parameters, but only rarely have neurons been reported that respond exclusively to only one biologically significant sound. Even at higher levels of the auditory system very few cells have been found that could be described as "vocalization detectors." In addition, variability in responses to artificial sounds have been reported for auditory cortical neurons similar to the response variability that has been reported in the visual system. Recent evidence indicates that the responses of auditory cortical neurons to species-specific vocalizations can also be labile, varying in both strength and selectivity. This is especially true of the secondary auditory cortex. This variability, coupled with the lack of extreme specificity in the secondary auditory cortex, suggests that secondary cortical neurons are not well suited for the role of "vocalization detectors."
We tested the hypothesis that polarization sensitivity enhances the detection of moving, transparent objects by examining the escape response of the red swamp crayfish (Procambarus clarkii Girard) from a visual threat. A transparent, birefringent target trans-illuminated by either partially linear polarized or unpolarized light was advanced toward individual crayfish. The optical axis of the target was aligned such that it would be conspicuous to a viewer with polarization sensitivity when trans-illuminated by polarized light. Under polarized light, significantly more crayfish retreated from the target than under unpolarized light of identical intensity (P<0.00005, Fisher's exact test). Whereas the potential for polarization sensitivity has been shown in neurophysiological and structural studies of the visual system of P. clarkii and the signal crayfish Pasifastacus leniusculus (Dana), our results provide the first behavioral evidence for polarization sensitivity among crayfish. The ecological function of this ability is unclear, but it may enhance the detection of fish with silvered scales, transparent zooplankton or macroinvertebrates. Because escape responses are generally more reliably induced than other behaviors, the method employed in this study may prove useful for examining sensory capabilities in other species.
OBJECTIVE: To determine the ability of a prototype esophageal detection device (EDD) to identify esophageal misplacement of an endotracheal (ET) tube. METHODS: A prospective, randomized, blinded study of detection of esophageal intubation was conducted using 51 elective surgical patients who met inclusion criteria. A squeeze-bulb aspirator that creates a negative pressure of -80 to -90 torr was used for detection of esophageal intubation. The bulb should reinflate rapidly if the tube is in the noncollapsible trachea, but should not reinflate if the tube is in the collapsible esophagus. Each patient was prepared for surgery in the usual manner. The anesthesiologist placed an ET tube into the trachea. An identical tube was advanced the same distance into the esophagus. The tubes were labeled "A" or "B" according to a computer-generated random number list. An evaluator, who was blinded to the placement of the tubes, assessed one tube with the EDD. For most patients, a second evaluator, who was blinded to both tube placement and the results of the first evaluator, assessed the other tube. During evaluation, the tube cuffs were deflated. After data collection, the esophageal tube was removed and surgery was completed. RESULTS: All 45 esophageal tube placements were correctly identified. Thirty-five of the 40 ET tubes were correctly identified. Of the five ET tubes mislabeled, three were found in a mainstem bronchus. All had delayed bulb re-expansion. CONCLUSION: This prototype EDD is a useful method of identifying esophageal misplacement of an ET tube in anesthetized adult surgical patients.
The visual task of mammographic interpretation is considered in terms of the detection of a signal in the presence of noise, where the noise is taken to include a structure noise contribution from those areas of the imaged breast which do not contain the signal. The structure noise in a variety of typical mammographic parenchymal patterns was quantified and related to the area under observation using a statistical analysis of digitized image samples. Images of an anthropomorphic phantom were also analysed to establish it as a suitable test background for a series of contrast detail detection experiments. These experiments were performed with and without a structured background over a wide range of film dose, but at a fixed average film optical density. The presence of structure noise was found to reduce the detectability of low contrast objects, the effect becoming progressively smaller as the object size is reduced. Where the structured background was used, even large changes in dose to the film were found to produce little change in the overall contrast detail result except at the smallest detail diameters. These results are discussed in relation to existing theories of visual perception. It is suggested that the correlation between patient dose and cancer detection rate may be poorer than previously thought, as the detection task for objects larger than approximately 1 mm in diameter is dominated by the structure noise of the background parenchymal pattern rather than quantum noise.
An indirect immunofluorescence microassay, which permits automated reading, has been employed for simple, rapid and objective detection of surface and intracellular antigens. Initially, the cells, spun in microplates, are fixed with glutaraldehyde (0.25% v/v in PBS). Following fixation, the cells can be stored at 4 degrees C for up to 2 weeks before being used in the immunofluorescence microassay. The fixed cells are then stained according to standard procedures using appropriate first and fluorescein-conjugated second antibodies. An automated and quantitative evaluation of the fluorescence intensity of the cell samples was achieved using the Titertek Fluoroskan II automatic reader. This microassay was shown to be suitable for the detection of the surface MAC1 antigen and intracellular v-myc protein in the GG2EE macrophage cell line.
Traditionally military aviators have prepared for air-to-ground bombing missions with maps and aerial photographs of their targets. Mission rehearsal systems augment these media by allowing pilots to view simulated ingress to their target, as seen from the cockpit perspective. In the present experiment we assessed the benefits of mission rehearsal with a task requiring observers to view recorded approaches to target objects and to detect the target objects as quickly as possible. Results indicated that premission simulations allowed observers to detect target objects at greater stand-off ranges than did study with maps and aerial photographs alone. Actual or potential applications of this research include the deployment of a mission rehearsal system to assist aviators' mission planning.
OBJECTIVE: Visual contrast detection has been reported in some studies to be normal in schizophrenia patients, but in other studies impairments have been reported. Because contrast detection in the visual processing system is mediated by dopamine, and because the pharmacotherapy of schizophrenia involves blocking dopamine postsynaptic receptor sites, the authors investigated the effects of dopamine-blocking antipsychotic drugs on visual contrast detection in schizophrenia. METHOD: Visual contrast detection thresholds were measured in healthy subjects and schizophrenia patients receiving typical and atypical antipsychotic drugs; a two-alternative, forced-choice psychophysical method was used. Also included were six patients receiving no antipsychotic treatment as well as clinically unaffected first-degree relatives of the schizophrenia patients. RESULTS: Patients receiving atypical antipsychotic drugs showed unimpaired visual contrast detection, those given typical antipsychotic drugs exhibited higher visual contrast detection thresholds, and the unmedicated schizophrenic patients showed visual contrast detection thresholds significantly below those of healthy subjects. CONCLUSIONS: Dopamine modulation via D(2) receptor blockade affects sensory processes in schizophrenia, shifting visual contrast detection from hypersensitivity in the unmedicated state to normal and even to hyposensitive levels. Thus, antipsychotic drug treatment may account for the inconsistent reports concerning visual contrast detection in schizophrenia.
This paper reports on statistical aspects relevant to the use of the phase spectrum of post-stimulus EEG, in objective detection of the auditory evoked potential. The sampling statistics of two statistical estimators are discussed: the mean phase vector magnitude, and the standard deviation of an ensemble of post-stimulus EEG phases. These two estimators are circular statistics, and subject to strong sample size bias. Their confidence intervals have been derived empirically for sample sizes routinely used in clinical audiometry. A trial example illustrates the use of the objective phase statistics developed here; it is noted that the method may also be more efficient than the visual scoring of averaged responses.
The objective of this study is to compare image quality and lesion detection for full field digital mammography (FFDM) and film-screen mammography (FSM). In 200 women we performed digital mammography of one breast and film-screen mammography of the other breast. Imaging parameters were set automatically. Image quality, visualization of calcifications and masses were rated by three readers independently. Mean glandular dose was calculated for both systems. We found no significant difference in mean glandular dose. Image quality was rated by reader A/B/C as excellent for FFDM in 153/155/167 cases and for FSM in 139/116/114 cases (p<0.03/0.001/0.001). Microcalcifications were detected by FFDM in 103/89/98 and by FSM in 76/76/76 cases (p<0.01/0.06/0.01). Detection of masses did not differ significantly. FFDM provided significantly better visibility of skin and nipple-areola region (p<0.01). FFDM demonstrated improved image quality compared with film-screen mammography. Microcalcification detection was also significantly better with the digital mammography system for two of the three readers.
OBJECTIVE: To assess the usefulness of microbubble contrast-enhanced agent detection imaging in evaluating the therapeutic response of malignant hepatic masses to treatment with interventional procedures. METHODS: Fifty-eight patients with 68 hepatocellular carcinomas and 6 metastases who were treated with interventional procedures were evaluated with SH U 508A-enhanced agent detection imaging and helical computed tomography. Helical computed tomography was also performed to help establish the outcome of therapy with unenhanced computed tomography 2 weeks after transcatheter arterial chemoembolization and with dynamic contrast-enhanced computed tomography 1 day after radio frequency ablation or percutaneous ethanol injection. The studies were reviewed separately and randomly, and the sensitivity and specificity of agent detection imaging for detection of viable tumor residue were determined by follow-up imaging performed at least 3 months later. RESULTS: Follow-up computed tomography or magnetic resonance imaging revealed complete tumor responses in 44 (59.5%) of 74 cases after the therapeutic procedures. The sensitivity of agent detection imaging was 94.7% after transcatheter arterial chemoembolization and 72.7% after radio frequency ablation and percutaneous ethanol injection. The specificity of agent detection imaging for the detection of residual tumors was 80% after transcatheter arterial chemoembolization and 79.2% after radio frequency ablation and percutaneous ethanol injection. The false-positive rate for agent detection imaging in cases of radio frequency ablation or percutaneous ethanol injection was 20.8% (5 of 24), resulting from reactive hyperemia or vascularity within the safety margin. In the assessment of the therapeutic effects, the concordance of contrast-enhanced agent detection imaging with helical computed tomography was statistically significant after transcatheter arterial chemoembolization (P < .00001) and radio frequency ablation or percutaneous ethanol injection (P < .02). CONCLUSIONS: Contrast-enhanced agent detection imaging proved useful and as effective as helical computed tomography for evaluating the therapeutic effects of interventional therapeutic procedures for malignant hepatic masses.