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PubMedDate not supplied

Somatosensory amplification and its relationship to heartbeat detection ability.

OBJECTIVE: Somatosensory amplification has been defined as the tendency to experience normal bodily sensations as intense, noxious, and disturbing. The present experiment investigated whether this tendency is due to heightened physiological sensitivity to bodily sensations. METHODS: The relationship between Somatosensory Amplification Scale (SSAS) scores and objective measures of the ability to detect bodily (ie, heartbeat) sensations derived from the Method of Constant Stimuli procedure was assessed. Although somatosensory amplification characterizes hypochondriacs, the relationship between somatosensory amplification and sensitivity to bodily sensations was examined in nonhypochondriacal, nonpatient participants in an effort to dissociate somatosensory amplification from other variables associated with hypochondriasis and/or patient status. RESULTS: Heartbeat detectors were found to exhibit significantly lower SSAS scores than nondetectors. CONCLUSION: This finding suggests that somatosensory amplification is not due to heightened sensitivity to bodily sensations.

Adolescent↗
PubMed1996

The use of pooled red cells and column techniques for routine red cell antibody detection.

The object of antibody screening is to detect all clinically relevant antibodies. In order to do this effectively red cells are selected with an appropriate antigen profile. The introduction of column techniques for antibody screening by indirect antiglobulin testing (IAT) and two-stage enzyme testing (ETC) is perceived to lead to an increased sensitivity and an ability to detect red cell antibodies more easily than by traditional tube techniques because reactions in columns are more easily read and are stable. We evaluated the use of a column technology with pooled red cells for routine antenatal screening. The pooled cells used contained at least one cell with homozygous antigen expression for the majority of clinically significant antibodies known to be present, except for Kell. Pooled cell results were not as easy to read in gel columns when compared with single cell results due to weaker reactions which were often diffused throughout the gel in the column. We concluded that the use of pooled cells led to a decreased sensitivity which proved problematic for the interpretation of results. We used a two-cell and a three-cell pool and found that detection of known antibodies was reduced in IAT and ETC methods.

Antibodies↗
PubMed1996

An experimental investigation of the effect of light-box luminance on the detection of low contrast objects in mammography.

It has been hypothesized that light-box luminance is an important factor in the detection of objects on radiographs. In this work, existing psychophysical data relating to the measurement of visual thresholds at various scene luminance levels are applied to the problem of the observation of radiographs on a light-box. These data suggest that for a given stimulus size, the threshold contrast varies little over several orders of magnitude of scene luminance. In a series of contrast detail experiments performed over a wide range of light-box luminances it has been demonstrated that the detection of low contrast objects on mammographic film is dominated by external noise, that is noise on the film, rather than the internal visual noise of the observer. It is therefore suggested that in mammography it is inappropriate to base recommendations for optimal values of light-box luminance on psychophysical studies of visual noise. It has been shown that commonly used light-box luminances are suitable for viewing mammograms at the higher average optical densities now being recommended, provided that precautions are taken to avoid glare and reflection.

Contrast Sensitivity↗
PubMed1999

Four-gated transcranial Doppler ultrasound in the detection of circulating microemboli.

OBJECTIVE: Embolus detection by transcranial Doppler ultrasound is very time consuming and semi-automated detection is mandatory. The device studied, a TC4040, Nicolet-EME, uses the four-gate technique and allows for audiovisual off-line verification of the recorded events. METHODS: Twenty controls, 10 patients with mechanical prosthetic heart valves and 12 patients with occlusive carotid artery disease were investigated by transcranial colour-coded duplex sonography and, subsequently, underwent a 1-h unilateral embolus detection from the middle cerebral artery using four-gate TCD. We investigated the Doppler spectrum background, microembolic signals (MES) and artefacts produced. A detection threshold of 5 dB or more was defined taking into account natural fluctuations of the Doppler spectrum. RESULTS: Sensitivity of the software was 91.9% and observer-software agreement on MES was 7.8% in the valve patients, and 77.7% and 7.5% in the carotid artery disease patients, respectively. Weaker MES were more likely not to be detected in all four channels. The artefact signal rejection rate was 62%. MES produced either positive or zero time delays in adjacent channels. Artefact signals produced either no delay, or a positive or a negative time delay. Duration of MES ranged from 1-88 ms. CONCLUSIONS: Besides refined recognition of MES using the time delay, four gates give faint MES no less than four opportunities to overcome the detection threshold. With this device's satisfying sensitivity, regions of interest in a 1-h recording can audiovisually be evaluated off-line in a few minutes by an investigator.

Adult↗
PubMed2001

[The significance of nucleotide repeat sequences in FVIII gene for detecting hemophilia A carriers].

OBJECTIVE: To detect the carriers in hemophilia A(HA) families by haplotype analysis of the microsatellite polymorphisms at intron 13 [13(CA)n] and 22[22(GT)n(AG)n] in the factor VIII (FVIII) gene. METHOD: Multi-PCR amplification of 13(CA)n and 22(GT)n(AG)n combined with silver staining were used. RESULTS: In 35 HA families, 11 had HA history. There were 21 female members in the 11 HA families and all of them were subjected to molecular study. Fourteen of the 21 females were confirmed to be carriers and approximately 72.7%(8 of 11) of these families were informative. CONCLUSIONS: Besides the reliable detection of HA carriers, multi-PCR combined with silver staining in HA analysis has the advantages of time saving, simplicity for performing and no radiation contamination.

Alleles↗
PubMed2003

[Detection of P2z/P2x7 receptors].

OBJECTIVE: To detect the P2z/P2x7 receptors of human leukocytes. METHODS: Re-suspending different kinds of leukemic cells, including CEM, THP-1, HL-60, NB4, Dami/Damin and Raji cells in buffer; adjusting their concentration to 2 x 10(7)/ml, and then detecting the P2z/P2x7 receptors respectively. RESULTS: (1) It was found that 0.4 mmol/L ATP enhanced obviously the fluorenscence strength of THP-1, NB4 and HL-60 cells, the activity rates were 54.91%, 39.45% and 30.46%, respectively. But for CEM, Dam and Raji cells, the activity rates were as low as 10.43%, 13.21% and 2.67%, respectively. KN-62 inhibited obviously the fluorescence strength of THP-1 cells, the inhibition rate reached 88.74%, but for NB4 and HL-60 cells the inhibition rates were only 15.81% and 12.50% respectively, and Raji cells were not affected by KN-62. (2) All the leukemic cells detected with polyclonal antibody were found with positive result. CONCLUSION: THP-1 cells have P2z/P2x7 receptors. The receptors in NB4 and HL-60 belong to P2 receptor family, but they are not P2z/P2x7 receptors. The polyclonal antibody used in immunohistochemical ABC method is not specific to P2z/P2x7 receptors.

Adenosine Triphosphate↗
PubMed1996

Using multiple objective memory procedures to detect simulated malingering.

The present study evaluated five objective assessment procedures used to detect malingered memory deficits. Twenty students and 20 psychiatric subjects completed the procedures under instructions to malinger and/or try their best. These groups were compared to 20 memory-impaired subjects who completed the procedures under instructions to try their best. While each test was able to correctly classify all of the subjects performing their best and the actual memory-impaired patients, the correct classification rates for experimental-malingerers varied from 5%-85% on the 10 scores derived from the five tests. Combining all of the cutting scores, and using deficient performance on one procedure as the criteria for classification, resulted in a 92.5% hit rate for subjects who were instructed to malinger and a 100% hit rate for the control and memory-impaired subjects who were instructed to try their best.

Adult↗
PubMed1978

Effect of CT noise on detectability of test objects.

Three types of test objects were superimposed on noisy backgrounds and observed by 58 subjects: large low-contrast disks to simulate tumors, small disks to simulate calcifications, and bars to simulate blood vessels. Three types of noise were used: random noise, CT noise (reconstructed random noise), and an actual water scan taken with an EMI CT1010 scanner. In addition, each image was smoothed by a factor of two, giving six test patterns altogether. Photographic images were presented to 25 lay observers, while 25 other lay observers and eight radiologists used a viewing console. The photographs produced a slightly lower true positive rate than the console, although the degree of confidence in the identifications was slightly greater. The anticorrelation property of CT noise gives it a "lumpy" structure, which aided the identification of bars but impeded the identification of small disks. Smoothing did not significantly affect the detectability with random noise, but with CT noise, smoothing improved the detectability of bars and large disks.

Humans↗
PubMed2005

An evaluation of automated neonatal seizure detection methods.

OBJECTIVE: To evaluate 3 published automated algorithms for detecting seizures in neonatal EEG. METHODS: One-minute, artifact-free EEG segments consisting of either EEG seizure activity or non-seizure EEG activity were extracted from EEG recordings of 13 neonates. Three published neonatal seizure detection algorithms were tested on each EEG recording. In an attempt to obtain improved detection rates, threshold values in each algorithm were manipulated and the actual algorithms were altered. RESULTS: We tested 43 data files containing seizure activity and 34 data files free from seizure activity. The best results for Gotman, Liu and Celka, respectively, were as follows: sensitivities of 62.5, 42.9 and 66.1% along with specificities of 64.0, 90.2 and 56.0%. CONCLUSIONS: The levels of performance achieved by the seizure detection algorithms are not high enough for use in a clinical environment. The algorithm performance figures for our data set are considerably worse than those quoted in the original algorithm source papers. The overlap of frequency characteristics of seizure and non-seizure EEG, artifacts and natural variances in the neonatal EEG cause a great problem to the seizure detection algorithms. SIGNIFICANCE: This study shows the difficulties involved in detecting seizures in neonates and the lack of a reliable detection scheme for clinical use. It is clear from this study that while each algorithm does produce some meaningful information, the information would only be usable in a reliable neonatal seizure detection process when accompanied by more complex analysis, and more advanced classifiers.

Action Potentials↗
PubMed2004

On-schedule mammography rescreening in the National Breast and Cervical Cancer Early Detection Program.

OBJECTIVE: The National Breast and Cervical Cancer Early Detection Program (NBCCEDP) provides free cancer screening to many low-income, underinsured women annually but does not routinely collect all data necessary for precise estimation of mammography rescreening rates among enrollees. MATERIALS AND METHODS: To determine the percentages rescreened and to identify factors that encourage on-schedule rescreening, telephone interview and medical record data were collected from 1685 enrollees in Maryland, New York, Ohio, and Texas at least 30 months after their 1997 index mammogram. RESULTS: Overall, 72.4% [95% confidence interval (95% CI) = 70.1-74.7] were rescreened within 18 months and 81.5% (95% CI = 79.6-83.5) within 30 months. At 30 months, the adjusted odds ratios (ORs) for rescreening were higher among Hispanics (OR = 1.95, 95% CI = 1.15-3.28), women with a history of breast cancer before the index mammogram (OR = 3.36, 95% CI = 1.07-10.53), and those who had used hormone replacement therapy before their index mammogram (OR =1.94, 95% CI = 1.30-2.91). The 30-month adjusted ORs were lower for women who reported poor health status (OR = 0.60, 95% CI = 0.42-0.85), did not have a usual source of care (OR = 0.61, 95% CI = 0.40-0.94), did not know if they could have another free mammogram (OR = 0.28, 95% CI = 0.14-0.51), described their index screen as their first mammogram ever (OR for no prior mammograms versus three or more = 0.40, 95% CI = 0.27-0.60), did not recall receiving a rescreening reminder (OR = 0.35, 95% CI = 0.25-0.48), or did not think they had been encouraged to rescreen by their provider (OR = 0.61, 95% CI = 0.44-0.86). DISCUSSION: Rescreening behavior in this sample of NBCCEDP enrollees was comparable with that observed in other populations. To facilitate routine rescreening among low-income women, ongoing efforts are needed to ensure that they receive annual reminders and encouragements from their medical providers and that they know how to obtain the services they need.

Aged↗
PubMed1996

Effect of leukocyte concentration and inoculum volume on the laboratory identification of cytomegalovirus in peripheral blood by the centrifugation culture-antigen detection methodology.

OBJECTIVE: To investigate the rate of Cytomegalovirus (CMV) detection in peripheral blood by shell vial assay-indirect immunofluorescent assay technology using two leukocyte inocula concentrations and different inoculum volumes containing equivalent cell concentrations. DESIGN: Leukocyte inocula concentrations of 2 x 10(5) and 4 x 10(5) cells per 0.2 mL were assayed for the presence of CMV by shell vial assay-indirect immunofluorescent assay. The effect of different inoculum volumes (0.2 and 0.4 mL) containing an equivalent cell concentration of 4 x 10(5) was evaluated as well. The data were compared to conventional MRC-5 tube cultures, including blind passage. PATIENTS: Ninety-five patients (101 specimens) were tested sequentially. The test population consisted primarily of patients suffering from the acquired immunodeficiency syndrome. SETTING: The diagnostic virology laboratory, acquired immunodeficiency syndrome clinics, and hospital wards. RESULTS: Among the 101 specimens tested by shell vial assay-indirect immunofluorescent assay, the rate of CMV sensitivity increased by 36% using the higher leukocyte inoculum concentration of 4 x 10(5) cells per 0.2 mL (P = .002; Cochran's Q test). No significant difference in CMV yield was identified using equivalent cell concentrations with inocula volumes of 0.2 or 0.4 mL. The CMV sensitivity rate using the higher leukocyte inoculum surpassed that obtained by conventional tube culture-blind passage. CONCLUSION: These data denote the importance of leukocyte concentration on the rate of CMV detection in peripheral blood by the shell vial assay-indirect immunofluorescent assay. The data also point out the need to establish a standardized blood preparation protocol to achieve optimal clinical relevance of this widely used laboratory test.

AIDS-Related Opportunistic Infections↗
PubMed2000

An objective method for detecting time-dependent effects in graft survival.

The proportional hazards model has become increasingly important in the analysis of censored survival data after transplantation. Neverthless, in clinical transplantation it is still undefined how the influence of covariates changes over time. The additive regression model is an alternative (or extension) to the Cox model. It results in plots (Aalen plots) that may give information on the effect of covariates over time by way of the cumulative regression function plots. A total of 386 primary cadaveric kidney transplants performed between 1984 and 1996 were included in our analysis. The follow-up period ranged from 24 to 156 months. According to Aalen, an additive regression model was used and plots for the detection of time-dependent effects of covariates were determined. Patients dying with functioning grafts were classed as graft failures. Factors potentially affecting graft outcome, such as sex, donor and recipient's age, HLA A-B match, cold ischaemia time (CIT), delayed graft function (DGF), serum creatinine at 1 month (Cr1), rejection episodes within 3 months (R3), and type of brain death (BD), were considered. The slopes of the plots by donor age, DGF, HLA A-B match, R3, Cr1 and BD appear to have a significant influence throughout the observation period, with different time-dependent effects on graft survival. Slopes for DGF, Cr1, and age of donor are positive (increased hazard), while slopes for HLA match and BD are negative (decreased hazard). Estimated regression functions for DGF, donor age and Cr1 show a prompt slope (within 3 months); the covariate R3 has a clear influence for about 5 years, and then seems to disappear; and BD appears to have a consistent effect over the entire period. The additive regression model with Aalen plots represents a useful technique in the analysis of survival data after kidney transplantation. Some covariates, such as R3, may often lose their effects on graft survival, with a relevant clinical impact. Others have a clear and additive influence over the entire period (BD), while the effects of donor age, DGF and CR1 each appear to have a prompt effect in the outcome.

Adult↗
PubMed2000

Electrical impedance imaging at multiple frequencies in phantoms.

We have recently built and tested a 32 channel, multi-frequency (1 kHz to 1 MHz) voltage mode system to investigate electrical impedance spectroscopy (EIS) imaging. We completed a series of phantom experiments to define the baseline imaging performance of our system. Our phantom consisted of a plastic circular tank (20 cm diameter) filled with 0.9% aqueous NaCl solution. Conductors and nonconductors of decreasing width (W5: 3.4 cm, W4: 2.54 cm, W3: 0.95 cm, W2: 0.64 cm and WI: 0.32 cm) were positioned at various distances from the tank edge (1 cm, 2 cm, 4 cm and 8 cm). The results suggest that the detection of objects less than 1 cm in width is limited to the first 1 to 2 cm from the tank edge for absolute images, but this depth can extend to 8 cm in difference images. Larger 3.4 cm wide objects can be detected in absolute images at depths up to 8 cm from the tank edge. Generally, conductor images were clearer than their nonconductor counterparts. Not only did electrode artefacts lessen as the frequency increased, but the system's maximum resolution was attained at the highest operating frequencies. Although the system recovered the value of the electrical conductivity at the correct order of magnitude, it tended to smooth out large property discontinuities. The calculated electrical permittivity in these phantom studies was inconclusive due to the presence of electrode artefacts.

Electric Impedance↗
PubMed2006

Solution of the inverse problem of magnetic induction tomography (MIT) with multiple objects: analysis of detectability and statistical properties with respect to the reconstructed conducting region.

Magnetic induction tomography (MIT) is a technique to image the passive electrical properties (i.e. conductivity, permittivity, permeability) of biological tissues. The inverse eddy current problem is nonlinear and ill-posed, thus a Gauss-Newton one-step method in combination with four different regularization schemes is used to obtain stable solutions. Simulations with 16 excitation coils, 32 receiving coils and different spherical perturbations inside a homogeneous cylinder were computed. In order to compare the statistical properties of the reconstructed results a Monte Carlo study with a SNR of 40 dB and 20 dB was carried out. Simulated conductivity perturbations inside a homogeneous cylinder can be localized and resolved and the results prove the feasibility of difference imaging with MIT.

Algorithms↗