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PubMed1997

Accuracy of ultrasonography in assessing spleen and liver size in patients with Gaucher disease: comparison to computed tomographic measurements.

A comparison was made between volume measurements of spleen and liver by ultrasonography and by computed tomography, the two most common modes of assessment of organ size in patients with Gaucher disease, who require frequent follow-up measurements. The two measurements showed a high degree of correlation within a broad range for both spleen and liver volumes. An algorithm for conversion of one measurement to the other was derived for both spleen and liver.

Adolescent↗
PubMed1994

Dosimetry of large, irregularly shaped fields by the circle method. A feasibility study.

The Circle Method is an algorithm for dose calculation in an irregularly shaped field. The algorithm is based on measurements of circle fields at the therapy machine in use. A separation into primary and scattered radiation components is not necessary. Clarkson's sector-integration method and an off-axis correction are embodied. Experimental and calculated dose values agree within +/- 2.8% in the treatment field and under block shieldings.

Algorithms↗
PubMed2026

Linking cortical structure and delirium in the elderly: insights from cohort study and shared genetic risk analysis.

BACKGROUND: This study aimed to assess the association between regional cortical changes measured via baseline magnetic resonance imaging (MRI) and the incidence of delirium. METHODS: Observational associations were assessed using a prospective cohort from the UK Biobank and an independent clinical cohort. The population-based study included participants aged 60 years or older who had undergone structural brain MRI since 2014. Regional cortical volume, mean thickness, and surface area were extracted based on the Desikan-Killiany cortical atlas. Delirium was defined using ICD-10 diagnostic codes. Additionally, preoperative brain MRI images from participants in another cohort were collected and automatically segmented using deep learning algorithms to obtain cortical measurements. Logistic analysis was performed to investigate the associations between cerebral cortical structure and delirium risk. Lastly, genome-wide association study data derived from the ENIGMA Consortium and FinnGen Biobank were utilized to conduct conditional/conjunctional false discovery rate (cond/conjFDR) analyses to identify shared genetic loci associated with cortical structures and delirium. RESULTS: This observational analysis included 31,890 participants from the UK Biobank and 152 participants from an independent cohort. In the UK Biobank cohort, decreased cortical thickness in the 17 regions was associated with a significantly increased risk of delirium. Similarly, a preoperative reduction in cortical volume in 7 regions was associated with an increased risk of delirium in the independent cohort. Besides, 100 single-nucleotide polymorphisms (SNPs) were identified as significantly associated with cortical structures when conditioned on delirium. Finally, colocalization analysis demonstrated that these pleiotropic risk loci modulated the expression of NT5C2, RGP1, CCDC25, TPM2, EEF1AKMT2, IQANK1 and LHPP in blood and brain tissues. CONCLUSION: Regional cortical atrophy is associated with an increased risk of delirium in the elderly. Brain MRI examinations may be beneficial for preoperative delirium risk assessment in elderly individuals undergoing elective surgery.

Humans↗
PubMed1995

Discriminant analysis algorithm based on a distance function and on a Bayesian decision.

We propose a new algorithm for the allocation of an individual to one of several possible groups or populations. The algorithm enables us to define a finite partition over the sample space, based on distance function. This partition is used, jointly with the application of a standard Bayesian decision rule, to allocate individuals to the populations. The algorithm also provides a measure of the allocation confidence for each individual, in a similar manner to that of logistic regression. The error rates for classification are also computed using the leave-one-out method. Results are compared with those obtained with other discriminant analysis techniques previously reported: Fisher's linear discriminant function, the quadratic discriminant function, logistic discrimination, and others.

Adolescent↗
PubMed1991

Optimal a posteriori time domain filter for average evoked potentials.

Evoked potentials measured with scalp electrodes are often described as a deterministic process corrupted by unrelated noise. The common procedure to determine the signal is to average N repetitive measurements. By obtaining additional information from the N measurements, signal detection can be improved. An algorithm that estimates the signal autocorrelation from N given measurements is proposed. The estimator is consistent and unbiased, and its variance tends to 0 as o(N). Two filters that are applied to the average response are introduced. Both depend on the estimation of the signal and the noise autocorrelations. One filter is based on the assumption that the average response is a stationary process. The second filter coefficients are obtained by minimizing the mean squared error (MSE) of an optimal filter of a nonstationary process applied on a single sweep. When a small number of sweeps are averaged, the stationary assumption is adequate, and the MSE of the stationary optimal filter is two to five times less than the MSE of the average response. When a large number of measurements are considered, the error in estimating the autocorrelations decreases. In this case, applying the optimal filter for a nonstationary process leads to a significant improvement in the signal estimation.

Algorithms↗
PubMed1991

Should inhomogeneity corrections be applied during treatment planning of tangential breast irradiation?

Due to the inclusion of lung tissue in the treatment volume, some parts of the breast will get a higher dose during tangential breast irradiation because of the lower lung density. Data on the accuracy of dose calculation algorithms, investigated by phantom measurements, determinations of the geometry and density of the actual lung in the patient and the results of in vivo dose measurements, are presented. From this information it can be concluded that a lung correction varying between about 3% and 7% is needed but its magnitude is slightly overpredicted in a number of commercial treatment planning systems. Because this increase in dose is already in a high dose region, it is recommended that inhomogeneity corrections should be applied during tangential breast irradiation.

Algorithms↗
PubMedDate not supplied

Calculation of dose profiles in homogeneous phantoms for irregular, partially attenuated, photon beams.

Measured and calculated dose profiles under partial attenuators which cover only part of the radiation beam are presented. The study was performed for x-ray beams generated with a 4-MV linear accelerator at a source-surface distance of 120 cm in a water phantom for lead attenuators of arbitrary shape but constant thickness. Dose correction factors, which are used to multiply the open beam data to predict doses under partial attenuators, depend strongly on attenuator parameters, such as its thickness, lateral dimensions, and distance from phantom or patient surface, in addition to depending on depths in the phantom. The dose correction factors are calculated with Clarkson sector integration techniques, and the results, in spite of the simplifying assumptions used in the algorithm, generally agree with measured data to within 3%. The calculational method therefore may be applied to general clinical situations in which partial attenuators are used.

Humans↗
PubMed1985

Measurement of blood-retinal barrier permeability: a reproducibility study in normal eyes.

Fluorescein penetration into the posterior vitreous depends on plasma-free fluorescein concentration and blood-retinal barrier (BRB) permeability. The reproducibility of two methods of deriving BRB permeability was studied in 19 normal eyes of 14 subjects using vitreous fluorophotometry on two separate occasions. Plasma-free fluorescence was measured at intervals over 1 hr and posterior vitreous fluorescence was measured before (background scan), within 6 min (bolus) and at 60 min (measurement) after intravenous fluorescein (14 mg X kg-1). A computer algorithm subtracted background fluorescence from the measurement scan which was then corrected for signal spread by using a "spread" function derived from the bolus scan. BRB permeability coefficient and vitreous diffusion coefficients were derived by fitting a mathematical model to the plasma and corrected vitreous fluorescence data. A permeability index was also calculated by dividing the area under the vitreous fluorescence by the area under the plasma fluorescence curve. There were no significant differences in the results between right and left eyes. Mean +/- SD values on first and second occasions for all eyes were permeability coefficient: (1.91 +/- 0.94) and (2.08 +/- 0.95) X 10(-7) cm X s-1; diffusion coefficient: (1.33 +/- 0.68) and (1.19 +/- 0.54) X 10(-5) cm2 X s-1; and permeability index: (2.05 +/- 1.03) and (2.11 +/- 1.02) X 10(-7) cm X s-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

An inversion algorithm for determining area-source emissions from downwind concentration measurements.

Measuring emissions from nonuniform area sources, such as waste repository sites, has been a difficult problem. A simple but reliable method is not available. An objective method of inverting downwind concentration measurements, utilizing an assumed form of atmospheric dispersion to reconstruct total emission rate and distribution, is described in this study. The Gaussian dispersion model is compared to a more realistic model based on K-theory and similarity expressions. A sensitivity analysis is presented indicating the atmospheric conditions under which a successful application of the method could be anticipated. Field releases of sulfur hexafluoride (SF6) from a simulated area source in flat terrain were conducted to check the method, ability to reconstruct source distribution, and total emission rate. The sensitivity analysis and the field study confirm that a few ground-level concentration measurements and a simple determination of the atmospheric dispersion characteristics are sufficient, under neutral to stable conditions, to obtain the total emission rate accurately. Reconstruction of the spatial pattern of the source is possible by utilizing concentration information from samplers located on two separate ground-level receptor lines, if a shift in the wind direction occurs and if it can be assumed that the total emission rate is time invariant. A method of cross-checking the accuracy of the reconstruction, using a simultaneous tracer release, is presented.

Air Pollutants, Occupational↗
PubMed1990

[Method of automatic recording and analysis of leukocyte migration based on the image analysis system].

The method of automatic registration and of the analysis of neutrophils' mobility with the use of the Image Analysis System is described in this paper. The authors developed an algorithm of cells identification which makes it possible to carry out cadre-by-cadre observing the shift of each cell's centre of gravity with the time interval between cadres more than 15 seconds. This algorithm also allows to measure areas, perimeters and orientation of cells and their changes. Looking after the shifts of the cells' centres of gravity allows to describe the cells' paths in the form of the following dependences: path-by-time, shift-by-time, angle of vector of shift alteration. Observing a great number of cells at the same time allows to get true statistical picture of neutrophils' activity and distribution of cells' activity in population of neutrophils during only some minutes of registration. It is shown that each cell in the population has its own constant velocity.

Algorithms↗
PubMed1990

A computer system for the identification of the cerebrospinal compensatory model.

A computer system, based on IBM PC, was designed for the cerebrospinal compensatory model identification. The intracranial pressure (ICP) signal, registered during the lumbo-lumbar infusion test is analyzed by means of the spectral analysis algorithm in order to measure precisely the pulse wave amplitude. The amplitude and the mean ICP level, calculated repetetively within the period of about 8 seconds, are stored on the disk and form the basis for further model identification. Three different methods of identification were applied. They enable one to estimate the fundamental model parameters, such as: resistance to the cerebrospinal fluid resorption, pressure-volume index, baseline pressure, rate of formation of the cerebrospinal fluid. Statistical evaluation of the results of the infusion test analysis obtained by means of the system described in two groups of hydrocephalic patients (children and adults) is presented.

Adult↗
PubMed1991

Image data compression using a new floating-point digital signal processor.

A new dual-ported, floating-point, digital signal processor has been evaluated for compressing 512 and 1,024 digital radiographic images using a full-frame, two-dimensional, discrete cosine transform (2D-DCT). The floating point digital signal processor operates at 49.5 million floating point instructions per second (MFLOPS). The level of compression can be changed by varying four parameters in the lossy compression algorithm. Throughput times were measured for both 2D-DCT compression and decompression. For a 1,024 x 1,024 x 10-bit image with a compression ratio of 316:1, the throughput was 75.73 seconds (compression plus decompression throughput). For a digital fluorography 1,024 x 1,024 x 8-bit image and a compression ratio of 26:1, the total throughput time was 63.23 seconds. For a computed tomography image of 512 x 512 x 12 bits and a compression ratio of 10:1 the throughput time was 19.65 seconds.

Algorithms↗
PubMed1990

Comparison and evaluation of a disease activity index for use in patients with rheumatoid arthritis.

An algorithm (Stoke index) has been designed to give a global measure of disease activity in rheumatoid arthritis. This algorithm has been created as an easy to use flow diagram based on two objective laboratory measures (C-reactive protein and erythrocyte sedimentation rate), one subjective and two semi-objective clinical measures (morning stiffness, synovitis score and Ritchie articular index). Results of six clinical markers and seven laboratory markers of disease activity on a cohort of 371 rheumatoid patients have been used to evaluate the algorithm and compare it with a previously described index of disease activity (Mallya-Mace index). Principal component analysis validates its ability to measure disease activity. Sensitivity is described by the distribution of patients between the two index scores. Change in index score by patients over a 6-month period indicates reversibility. The Stoke index demonstrates greater sensitivity and reversibility than the Mallya-Mace index. These findings indicate that the algorithm described provides a useful index of global disease activity for use in the assessment of rheumatoid arthritis.

Adult↗
PubMed1997

Three-dimensional imaging characteristics of the HEAD PENN-PET scanner.

UNLABELLED: A volume-imaging PET scanner, without interplane septa, for brain imaging has been designed and built to achieve high performance, specifically in spatial resolution and sensitivity. The scanner is unique in its use of a single annular crystal of Nal(Tl), which allows a field of view (FOV) of 25.6 cm in both the transverse and axial directions. Data are reconstructed into an image matrix of 128(3) with (2 mm)3 voxels, using three-dimensional image reconstruction algorithms. METHODS: Point-source measurements are performed to determine spatial resolution over the scanner FOV, and cylindrical phantom distributions are used to determine the sensitivity, scatter fraction and counting rate performance of the system. A three-dimensional brain phantom and 18F-FDG patient studies are used to evaluate image quality with three-dimensional reconstruction algorithms. RESULTS: The system spatial resolution is measured to be 3.5 mm in both the transverse and axial directions, in the center of the FOV. The true sensitivity, using the standard NEMA phantom (6 liter), is 660 kcps/microCi/ml, after subtracting a scatter fraction of 34%. Due to deadtime effects, we measure a peak true counting rate, after scatter and randoms subtraction, of 100 kcps at 0.7 mCi for a smaller brain-sized (1.1 liter) phantom, and 70 kcps for a head-sized (2.5 liter) phantom at the same activity. A typical 18F-FDG clinical brain study requires only 2 mCi to achieve high statistics (100 million true events) with a scan time of 30 min. CONCLUSION: The HEAD PENN-PET scanner is based on a cost-effective design using Nal(Tl) and has been shown to achieve high performance for brain studies and pediatric whole-body studies. As a full-time three-dimensional imaging scanner with a very large axial acceptance angle, high sensitivity is achieved. The system becomes counting-rate limited as the activity is increased, but we achieve high image quality with a small injected dose. This is a significant advantage for clinical imaging, particularly for pediatric patients.

Brain↗
PubMed1986

Count-dependent filter for smoothing bivariate FCM histograms.

A data-smoothing filter has been developed that permits the improvement in accuracy of individual elements of a bivariate flow cytometry (FCM) histogram by making use of data from adjacent elements, a knowledge of the two-dimensional measurement system point spread function (PSF), and the local count density. For FCM data, the PSF is assumed to be a set of two-dimensional Gaussian functions with a constant coefficient of variation for each axis. A set of space variant smoothing kernels are developed from the basic PSF by adjusting the orthogonal standard deviations of each Gaussian smoothing kernel according to the local count density. This adjustment in kernel size matches the degree of smoothing to the local reliability of the data. When the count density is high, a small kernel is sufficient. When the density is low, however, a broader kernel should be used. The local count density is taken from a region defined by the measurement PSF. The smoothing algorithm permits the reduction in statistical fluctuations present in bivariate FCM histograms due to the low count densities often encountered in some elements. This reduction in high-frequency spatial noise aids in the visual interpretation of the data. Additionally, by making more efficient use of smaller samples, systematic errors due to system drift may be minimized.

Cell Count↗
PubMed1994

Tomographic time-of-flight optical imaging device.

Time-resolved optical imaging has been used to image phantoms, animals, and humans, and offers the potential for the production of functional images of human tissues, such as the oxygenation of brain during stroke. We had previously reported a transmission scanner, and now give an early report on conversion to a rotational tomographic scanner with a non-parallel ray geometry similar to early CAT scanners. Initial scans show that 1) spatial imaging in turbid media using time-of-flight measurements, non-recursive algorithms, and standard tomographic geometry is possible, 2) separation of absorbance and scattering as an image is attainable, a key step in performing spatially-resolved chemometric analysis, 3) imaging of multiple objects buried within scattering material is feasible, demonstrating that equations derived for homogeneous media can be applied in at least some cases to inhomogeneous media such as tissue-like phantoms, and 4) imaging of brain pathology produces recognizable images with sufficient resolution for diagnostic decisions. We conclude that optical tomography is feasible for clinical use and that conversion of the present mechanically scanning device to a clinical scanner should be possible with retention of the current processing algorithms. Such a clinical scanner should ultimately be able to generate images in a few minutes with centimeter resolution at the center of living human brain.

Algorithms↗
PubMed2026

Discovery and validation of novel plasma protein biomarkers for severe tuberculosis patients.

OBJECTIVE: Severe tuberculosis (STB) imposes a substantial disease burden, yet reliable biomarkers for distinguishing STB from mild/moderate tuberculosis (MTB) remain scarce. This study aimed to identify and independently validate plasma protein biomarkers associated with tuberculosis severity. METHODS: In this multicenter prospective study, 298 adults with confirmed pulmonary tuberculosis were enrolled into screening (n = 128) and independent validation (n = 170) cohorts. Plasma samples were analysed using data-independent acquisition proteomics. Differentially expressed proteins were screened via Limma and four machine-learning algorithms, with candidate proteins measured by enzyme-linked immunosorbent assays. Receiver operating characteristic analysis assessed individual and combined diagnostic performance. RESULTS: STB patients were older and presented with lymphopenia, hypoalbuminemia, neutrophilia, and elevated lactate dehydrogenase. Among 166 differentially expressed proteins, HSPA5, HSP90B1, EEF1D, and SULT1A1 were selected for validation. In STB patients, HSPA5, HSP90B1, and EEF1D were upregulated, whereas SULT1A1 was downregulated. The four-protein panel achieved an AUC of 0.908 (95% CI 0.864-0.952), with 87.5% sensitivity and 83.8% specificity, modestly outperforming HSPA5 alone (AUC = 0.894). Functional enrichment implicated cholesterol metabolism, immune-inflammatory pathways, and endoplasmic reticulum stress. CONCLUSIONS: The four-protein panel effectively discriminated STB from MTB; however, its marginal improvement over HSPA5 alone suggests that an HSPA5-based assay may offer a simpler, more practical, and potentially cost-effective strategy for severity stratification.

Humans↗
PubMed1994

Foetal heart rate in early pregnancy by detection of optimally estimated displacements with pulsed Doppler signals.

Foetal heart rate (FHR) in the early stage of pregnancy can be optimally estimated by a simple system combining a conventional pulsed Doppler device with a microcomputer (CPU). The input signals for FHR have been obtained as low frequency components of foetal Doppler signals. These components are less than 50 Hz and are directly transferred from the conventional pulsed Doppler device to a microcomputer as radio-frequency signals by a specially designed I/O unit. The low frequency components have been converted into displacement signals by the continuous calculation of an arc-tangent function combined with five channel recordings from the foetal cardiac area, each separated by 2 mm on the same echo line. After selecting the optimal displacement data line, the FHR is measured by the proposed algorithm of non-parametric frequency estimation and/or the conventional autocorrelation method. The algorithm draws attention to the improved frequency selectivity by multiplication with reference signals, whose frequency is automatically optimized by the standard FHR rate determined by the length of pregnancy. The FHR determined from the displacement signals by this algorithm has provided a more optimally controlled selectivity than with the presently used autocorrelation method, especially in those pregnancies of less than 8 weeks gestation. Clinical application of this system allowed a complete determination of foetal heart rate from 6 weeks of gestation by a transvaginal approach and from 7 weeks by transabdominal procedures. In some specific cases, with prominent foetal components, it was possible from 5 weeks 2 days by a vaginal, and 6 weeks by an abdominal procedure.

Algorithms↗