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At least 1,333 records · Page 74Linked to original sources

PubMed2005

Evaluation of computer-aided detection (CAD) prompting techniques for mammography.

Computer-aided detection (CAD) systems, in which abnormalities are automatically detected and their locations presented to the radiologist as prompts, are increasingly being used to improve reader performance. The performance of CAD systems can be evaluated in two ways: by measuring the performance of the algorithms, or by monitoring the performance of readers using the system. All aspects of evaluation need careful consideration to avoid potential bias. This paper examines a variety of different approaches to evaluation and discusses their relative strengths and weaknesses.

Algorithms↗

PubMed2002

Convergence rates for iterative vector space projection methods for control of two deformable mirrors for compensation of both amplitude and phase fluctuations.

The control of two deformable mirrors for compensation of time-varying fluctuations in the complex field that results from wave propagation through a turbulent medium is considered. Iterative vector space projection methods are utilized to determine the control commands to be applied to the two deformable mirrors. Convergence of the iterative algorithm is accelerated when the algorithm is initialized, at each measurement period, with the values for the phase commands obtained from the previous measurement period. Furthermore, it is found that, if the sample frequency is sufficiently greater than the Greenwood frequency, then only a single iterative step at each measurement period is required to obtain good compensation of both amplitude and phase fluctuations.

Journal Article↗

PubMed2004

Interferometric ellipsometer with wavelength-modulated laser diode source.

An interferometric ellipsometer, with no moving parts and an inexpensive laser diode source, is demonstrated. Temporal fringes are produced by a small modulation of the laser diode bias current and unbalanced arms in the interferometer. Fringe analysis algorithms are developed, and accurate measurements of the optical properties of a number of samples are made. Temperature tuning the laser diode center wavelength allows the frequency dependence of the optical properties to be determined over a wavelength range of approximately 1 nm.

Journal Article↗

PubMed2005

Evidence for wavelength dependence of the scattering phase function and its implication for modeling radiance transfer in shelf seas.

More than 90% of stations from the Irish and Celtic Seas are found to have significantly higher back-scattering ratios in the blue (470 nm) than in the red (676 nm) wave band. Attempts to obtain optical closure by use of radiance transfer modeling were least successful for stations at which backscattering ratios are most strongly wavelength dependent. Significantly improved radiance transfer simulation results were obtained with a modified scattering correction algorithm for AC-9 absorption measurements that took wavelength dependency in the scattering phase function into account.

Journal Article↗

PubMed2005

Fringe projection profilometry with nonparallel illumination: a least-squares approach.

Under a nonparallel illumination condition, fringe patterns projected on an object have unequal fringe spacing that would introduce a nonlinear carrier phase component. This Letter describes a nonlinear carrier removal technique based on a least-squares approach. In contrast with conventional methods, the proposed algorithm would not magnify phase measurement uncertainty, nor does it require direct estimation of system geometrical parameters. The theoretical expression of the carrier phase function on the reference is derived and expanded in a power series. The unknown coefficients in the series are determined by a least-squares method. By subtracting the calculated carrier phase function from the unwrapped phase map, the phase distribution of the object profile is obtained.

Journal Article↗

PubMed2004

Longitudinal mapping of cortical thickness and brain growth in normal children.

Recent advances in magnetic resonance imaging (MRI) technology now allow the tracing of developmental changes in the brains of children. We applied computer-matching algorithms and new techniques for measuring cortical thickness (in millimeters) to the structural MRI images of 45 children scanned twice (2 yr apart) between the ages 5 and 11. Changes in brain size were also assessed, showing local brain growth progressing at a rate of approximately 0.4-1.5 mm per year, most prominently in frontal and occipital regions. Estimated cortical thickness ranged from 1.5 mm in occipital regions to 5.5 mm in dorsomedial frontal cortex. Gray matter thinning coupled with cortical expansion was highly significant in right frontal and bilateral parieto-occipital regions. Significant thickening was restricted to left inferior frontal (Broca's area) and bilateral posterior perisylvian (Wernicke's area on the left) regions. In the left hemisphere, gray matter thickness was correlated with changing cognitive abilities. For the first time, developmental changes in gray matter thickness, brain size, and structure-function relationships have been traced within the same individuals studied longitudinally during a time of rapid cognitive development.

Adult↗

PubMed2005

Transition from stochastic to deterministic behavior in calcium oscillations.

Simulation and modeling is becoming more and more important when studying complex biochemical systems. Most often, ordinary differential equations are employed for this purpose. However, these are only applicable when the numbers of participating molecules in the biochemical systems are large enough to be treated as concentrations. For smaller systems, stochastic simulations on discrete particle basis are more accurate. Unfortunately, there are no general rules for determining which method should be employed for exactly which problem to get the most realistic result. Therefore, we study the transition from stochastic to deterministic behavior in a widely studied system, namely the signal transduction via calcium, especially calcium oscillations. We observe that the transition occurs within a range of particle numbers, which roughly corresponds to the number of receptors and channels in the cell, and depends heavily on the attractive properties of the phase space of the respective systems dynamics. We conclude that the attractive properties of a system, expressed, e.g., by the divergence of the system, are a good measure for determining which simulation algorithm is appropriate in terms of speed and realism.

Adenosine Triphosphate↗

PubMed2001

[Enzymes and muscle diseases]

Skeletal muscle disorders may result in release of muscle enzymes into the circulation and give increased serum enzyme activity. A variety of enzymes routinely determined in the clinical laboratory may be elevated, but creatine kinase is the enzyme present in the highest concentration in muscle, and in every variety of muscle disease is the serum enzyme which shows the greatest incidence and degree of elevation. Aspartate aminotransferase is the enzyme associated most significantly with inflammation. A diagnostic algorithm based on the combined measurement of creatine kinase, aspartate aminotransferase and aldolase has been found to discriminate muscular dystrophies from polymyositis and other myopathies. This combination of laboratory tests has diagnostic application and thus allows the clinician to better select patients who need to have a skeletal muscle biopsy as a diagnostic procedure.

Journal Article↗

PubMed1994

Monitoring alcoholic liver injury.

Evidence for the economic, social, and health benefits of a more aggressive policy towards alcoholism is beginning to overcome nihilistic attitudes. Psychological, clinical, and laboratory measures are integrated in an algorithm for management.

Humans↗

PubMed2000

Comparison of radiometric and histometric features of bone samples from ribs.

OBJECTIVE: To correlate quantitative data gathered from conventional radiograms as well as from quantitative computed tomography (QCT) images of bone samples with histometric coefficients of the same specimens. STUDY DESIGN: Bone samples were obtained from standardized sites of ribs during autopsy of 40 males aged 15-84 years. In the bone samples the following assessments were performed: densitometry of bone using QCT, estimation of radiostructural quantitative coefficients (coefficient of trabecular arrangement anisotropy, trabecular thickness coefficient); histometry (area of bone matrix, trabecular thickness coefficient); relative weights of dry, decalcified bone and bone in ash form; and concentration of calcium in ash. Radiometry and histometry were performed using image analysis methods with IBAS for Windows (Kontron, Eching b. München, Germany) equipment. Radiostructure of bone was evaluated with the use of our own algorithm; concentration of calcium was measured spectrophotometrically. Analysis of variance, cross correlation, regression analysis and others were the statistical tools applied. RESULTS: From the variables analyzed, the following indicates a significant correlation with the histometric area of bone matrix: radiologic trabecular anisotropy, QCT densitometry (especially of cancellous bone) and the ratio of weight of dry sample to fresh sample. The coefficient of radiologic trabecular thickness appeared not to be a valuable feature for estimation of bone histology. CONCLUSION: Quantitative estimation of radiostructure of bone carried out on conventional radiograms may be helpful in the detection of histologic properties of bone, an important factor in assessment of the fragility of bone.

Adolescent↗

PubMed2000

[Thoraco-abdominal wound in peaceful time].

The results of treatment of 63 injured persons with thoracicoabdominal trauma were analyzed. Injured persons with severe trauma and pronounced infringements of hemodynamic (41.25%); with severe injury of inferior organs and stable hemodynamical indexes (47.62%), light injury (11.12%) were detailed. Algorithm of curative-diagnostical measures for every group was elaborated. Among the injured persons 11 (17.46%) died.

Abdominal Injuries↗

PubMed2003

Automatic sleep-wake and nap analysis with a new wrist worn online activity monitoring device vivago WristCare.

STUDY OBJECTIVE: Vivago WristCare is a new activity monitoring device, which allows long-term online monitoring of the activity of the user. This study evaluates the ability of the device to discriminate sleep/wake patterns during nighttime and during napping. DESIGN: Participants spent one night in the sleep laboratory where signals from polysomnography, actigraphy and WristCare were acquired. In addition, actigraphy and WristCare were used for 3-6 days for nap-analysis. SETTING: NA. PATIENTS OR PARTICIPANTS: Participants were 32 adults aged 26-89 years. The participants were studied in three study groups: all subjects, senior subjects (age > 65 years) and middle-aged subjects (age < 65 years). INTERVENTIONS: NA. RESULTS: Sleep/wake patterns were extracted from polysomnography, actigraphy and WristCare for the night slept in sleep laboratory. The agreement percents between the scorings of polysomnography and actigraphy, and between polysomnography and WristCare were about 80 % for all study groups. As total sleep time was estimated and the algorithm was optimized for this measure, the performance of the WristCare and actigraphy were similar. Both actigraphy and WristCare overestimated appreciably total sleep time (TST). Also in nap-analysis, actigraphy and WristCare performed similarly as the number of naps and the length of the naps were compared. CONCLUSIONS: The performance of the WristCare can be assumed to be well comparable to actigraphy in sleep/wake studies. The study suggests that the device may be used in long-term monitoring of sleep/wake patterns with similar performance to actigraphy.

Adult↗

PubMedDate not supplied

[Radiation and endoscopic diagnosis of pneumonia].

The authors analyze the results of different types of radiation and endoscopic studies of 151 patients with pneumonia with an established etiological agent. There is a correlation of X-ray semiotics and endoscopic changes with the clinical manifestation and causative agent of the disease. When the studies are combined, emphasis is laid on the role of endoscopy in verifying the diagnosis, in specifying an etiological agent, and in implementing therapeutical measures to prevent complications. An algorithm of radiation imaging techniques is proposed to examine patients with pneumonia and of their purpose-oriented use according to the task set.

Adolescent↗

PubMed2003

[Possibilities for ultrasonic diagnosis of pleura pathology in patients with pleural exudate].

The authors have analyzed results of thoracovideoscopy in 45 patients with the syndrome of pleural exudate, 17 of them had undergone the ultrasonic examination of the pleural cavity before thoracoscopy. The examination has revealed high sensibility of the ultrasonic method in the diagnosis of fragmentations of pleural exudate and pathology of the pleural leaves. The endoscopic and echographic classification of the pleural exudate is given depending on the fragmentation degree. The authors consider that echography of the pleural cavity as a noninvasive and highly informative method should be included in the first rank in making an algorithm of clinico-diagnostic measures for patients with exudative pleuritis.

Adenocarcinoma↗

PubMed2005

[Changes in D-dimer levels during pregnancy and the postpartum period: results of two studies].

In outpatients D-dimer (DD) measurement is included in most algorithms to exclude venous thromboembolism (VTE). We have recently performed two studies to evaluate the evolution of DD during pregnancy and the postpartum. During pregnancy, DD increase progressively and are of poor value to exclude VTE after 20 weeks of gestation. During labour, DD are usually very high and decrease quickly during the first 3 days post-delivery. Many weeks are necessary to obtain their normalisation and therefore their utility to rule out VTE is very limited until 4 weeks postpartum. This increase of DD values until 4 to 6 weeks after delivery correlates with the length of antithrombotic prophylaxis recommended for women at high risk of VTE.

Adult↗

PubMed2005

[The role of non-invasive diagnostics of pulmonary embolism in the optimization of treatment].

177 patients with pulmonary embolism (PE) were examined to study the information value of transthoracal echoCG in early diagnostics of the disease, the possibility of noninvasive evaluation of its severity, and possibility of determining indications for thrombolytic therapy (TLT) on basis of such evaluation. The results show that the sensitivity of such a sign as elevation of pulmonary artery pressure (PAP) by 30 mmHg, is 95%, provided that the patient does not have severe or moderate concomitant diseases cousing PAP elevation (postinfarction cardiosclerosis, chronic obstructive lung disease, valvular diseases etc.). The specificity of this sign, vs the control group, was 5%. Thus, elevation of PAP in patients with clinical manifestations of PE and without concomitant pathology, is a highly informative symptom of acute PE. The sensitivity of the parameter of right ventricular (RV) dilatation was 85%, of paradoxial ventricular septum motion--54%. In patients with PE of various degree of severity and concomitant diseases, high sensitivity of the above-listed sonographic signs of RVoverload goes together with their low specificity, which is not higher than 25%. This does not allow evaluating the degree of embolism and determining indications for TLT in these patients on basis of echoCG data. The authors of the article have developed an algorithm of diagnostic and therapeutic measures in patients with suspected PE.

Echocardiography, Doppler↗

PubMed1981

Breast cancer detection utilizing biostereometric analysis.

Twelve female patients participated in a study designed to employ computer-assisted biostereometric analysis for the detection of breast masses. All breast masses were previously documented by physical examination and followed by xeromammography, stereophotography, and histopathologic confirmation of tumor type. "Contour mammograms" were produced from the biostereometric photographs. These data were analyzed first for tumor detection and location by visual inspection. A second analysis employed a computed algorithm designed to locate and measure surface aberrations that suggest the possibility of underlying breast tumor. Visual analysis yielded the exact location of breast tumors in eight of the ten malignancies; computer analysis exactly located nine of the ten malignancies. In the computer analysis, one malignancy not exactly located by quadrant was, nevertheless, located in the correct breast. The results of the study suggest that the biostereometric process may have future use in screening or prescreening procedures for breast cancer detection. It is noninvasive, applicable to large numbers of women and with suitable refinements, and capable of being fully automated.

Aged↗

PubMed1980

[An ALGOL computer program for extensive automatic data processing and evaluation of karyometric studies].

A short survey is given upon ALGOL-computer programs which are ready for use also for a biomathematical treatment of morphometrical findings. Thereafter, the numerical and the nonnumerical steps are described following the caryometrical measurements. These steps are formulated algorithmically, constituting the main parts of a computer program for data transforming and evaluation of caryometrical studies by a data processing system.

Cell Nucleus↗