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Biomedical subjects

E S Gelsema

Publications and source records attributed to E S Gelsema.

18 recordsLinked to original sources
PubMed1992

A new model for diurnal blood pressure profiling. Square wave fit compared with conventional methods.

For the characterization of diurnal blood pressure variation, we developed a simple mathematical model that nevertheless does justice to the specific form characteristics of individual blood pressure registrations. Analysis was based on 24-hour continuous intra-arterial measurement of blood pressure obtained in 23 hospitalized patients with mild-to-moderate untreated essential hypertension (mean +/- SD, 112 +/- 13 mm Hg). The day-night difference for mean arterial pressure varied markedly (mean, 18.6 mm Hg; range, 6.8-36.0). Inspection of profiles suggested a model of blood pressure as two contiguous, complementary periods of constant pressure, a so-called square wave. Determination of the times of transience between both periods (segmentation) was performed individually using a least-square error criterion. Results were compared with those obtained by conventional methods, including analysis by Fourier modeling. The square wave fit accounted for a larger fraction (66%) of circadian variance of mean arterial pressure than modeling based on segmentation by visual inspection (59%, considerable observer bias) or by clock time (50%). Application of the Minnesota Cosinor Method resulted in the poorest description (47%). Segmentation based on harmonic modeling (61%) appeared to be cumbersome (10 harmonics needed), and the significance of additional information offered over the square wave fit is dubious. Observer bias makes segmentation by visual inspection unsuitable for assessment of the circadian variance of blood pressure. Even when daily activities are strictly regulated (hospital environment), circadian variance is not well modeled by clock time. As compared with harmonic analysis, square wave fitting is simple, and it appears to best model the circadian variance. The method can also be applied to data obtained from noninvasive ambulatory blood pressure monitoring.

Blood Pressure Determination↗
PubMed1992

Correspondence analysis for quantification in electron energy loss spectroscopy and imaging.

Electron energy loss spectroscopy (EELS) is a technique to investigate the physical properties of material. Using this technique it is possible to detect the presence of a specific element in a specimen. When used in combination with an electron microscope, energy filtered images may be obtained, which in principle may be used to quantify the local element concentration. This involves a process of background correction, conventionally performed assuming a specific parametric behavior of the spectral intensity as a function of electron energy loss. In this article a parameter-free method is described for background correction based on the formalism of correspondence analysis. Such a method may be used in parts of the spectrum where the functional dependence of the spectral intensity is unknown. Use of this method for element detection has been suggested before. This article reports simulation experiments suggesting its suitability for quantitative determination of element distributions and element concentrations.

Image Processing, Computer-Assisted↗
PubMed1991

Quantitative analysis of electron energy-loss spectra from ultrathin-sectioned biological material. I. Optimization of the background-fit with the use of Bio-standards.

A computer program for quantitative spectral analysis is proposed for the elemental analysis of biological material by electron energy-loss spectroscopy in a conventional transmission electron microscope, the Zeiss EM902. Bio-standards are used to test the performance of this program. The application of a simplex optimization method for curve-fitting is proposed to separate the ionization edge from the background. Making use of Ce-, Ca- and Fe-bio-standards, this method is compared with Egerton's well-known two-area method.

Calcium↗
PubMed1991

Quantitative analysis of electron energy-loss spectra from ultrathin-sectioned biological material. II. The application of bio-standards for quantitative analysis.

Electron energy-loss spectroscopy (EELS) has been used to determine elemental concentrations in biological specimens, consisting of ultrathin-sectioned cells and tissues. Chelex100-based Ca- and Fe Bio-standards are used for elemental quantification to establish iron and calcium concentrations. These Bio-standards, as well as the biological materials, are treated in a standard EM procedure such that 'known' and 'unknown' sites are located in one cross-section. Uncertainties and variabilities present in the equations for calculating the concentration in the 'unknown' site (determined by comparing simplex-fitted EEL spectra from Bio-standards with those from tissue) are outlined in two examples. Using an H+ Bio-standard, the matrix composition of such biological cell material is analysed, leading to values which approach each other closely. Quantitative EELS, using Chelex100-based Bio-standards, is advocated.

Animals↗
PubMed1991

Graphical non-linear representation of multi-dimensional laboratory measurements in their clinical context.

A polygon-based graphical representation of laboratory test results using nonlinear scaling is described. It is argued that the nonlinearity of the scale and the use of colors in the representation facilitates interpretation of the test result in its relationship to the standard reference range and critical clinical decision levels. Preliminary results suggest that this representation may be fruitfully used to enhance the efficiency of the information transfer from the clinical chemistry laboratory to clinicians. Other applications, inside as well as outside the medical field, may easily be imagined.

Chemistry, Clinical↗
PubMed1990

Detection of aberrant observations in a background of an unknown multidimensional Gaussian distribution.

An exploratory iterative technique for the detection of aberrant observations on a background of a multidimensional Gaussian distribution is described. Its development was motivated by the analysis of a set of three measurements reflecting the acid-base metabolism in the blood of 2,402 intensive care patients. This new, three-dimensional treatment of such data yields a meaningful description. A technical evaluation of the method, using artificially generated data is also presented. It is shown that the model parameters of the underlying Gaussian distributions are determined with good accuracy and that the accuracy with which the contamination is estimated increases with increasing distance of the contaminating observations from the mean.

Acid-Base Equilibrium↗
PubMed1989

Neutrophil granulation stained with May Grunwald Giemsa or pure Azure B-eosin Y quantified by image analysis.

Neutrophil granulation was quantified after staining with May Grunwald Giemsa or with the pure dyes Azure B and eosin Y. Spinner slides of the buffy coat of 3 normal subjects and 14 persons with different grades of toxic granulation were studied. Morphometric parameters were measured using an image analysis computer (Texture Analysis System, Leitz Wetzlar, FRG). The parameters for granulation varied over a wider range in Azure B (AzB) than in May Grunwald Giemsa (MGG) stained granulocytes. This is in accordance with the visual microscopy observation, that granulation is more pronounced after staining with AzB than MGG. The predominant shade of the nucleus was similar in both stains, whereas considerable and variable differences in the shade of the cytoplasm were found.

Azure Stains↗
PubMed1988

Application of the method of multiple thresholding to white blood cell classification.

A new method of image segmentation based on the principle of multiple grey level thresholding has been applied to a data set consisting of 1149 white blood cells of 13 different, clinically important types, randomly chosen on 20 blood smears from leukemia patients. Classification of these cells on the basis of quantitative measurements in the segmented images yields an accuracy of 82.6%. Some of the erroneous classifications must be attributed to intrinsic problems in the assignment of a priori labels. Correcting for such cases, the performance of the method, as measured on the present data set, increases to 89.8%. This illustrates the practical applicability of the segmentation method in automated white blood cell and possibly other cytological and histological analysis systems.

Acute Disease↗
PubMed1986

Quantitative radio-isotope cisternography for the investigation of CSF circulation in the posterior fossa and basal cisterns--a preliminary report.

In the absence of hydrocephalus there is an inclination to overlook enlargement of CSF spaces. In theory such enlargement might be the pathological basis for unexplained diseases seemingly related to disorders in CSF dynamics. By using Indium-111-DTPA in scinti-cisternography for 66 hours an attempt was made to identify such disorders by quantification of CSF circulation in the posterior fossa. The experimental data were fitted by means of two successive least square logarithmic regression analyses in order to make possible differentiation between "known" CSF disturbances and "external hydrocephalus". Theoretically, a biexponential curve would be expected. If therefore a monoexponential "best fit" is found, disturbances of CSF circulation may be taken to be present. For a definition of the features of normality in the case of a biexponential curve, however, further data on normal volunteers are needed.

Cerebrospinal Fluid↗
PubMed1985

A model for the classification of specimens containing random proportions of abnormal cells.

The effect of abnormal cell proportion on the performance of an automated cervical prescreening system is discussed in K.R. Castleman and B.S. White, Cytometry 2:155-18. The model employed assumes fixed proportions of abnormal cells, both in the design stage and in the test stage. In the present paper, an extended model is developed that allows for random variability of this proportion. It is shown, that there is a fundamental, non-zero lower limit to the false-negative specimen error rate, which depends only on the coefficient of variation. This limit may be reached even for moderate values of the coefficient of variation, which implies that a satisfactory prescreening system may not be feasible.

Cytological Techniques↗
PubMed1979

A commercially available interactive pattern recognition system for the characterization of blood cells: description of the system, extraction and evaluation of simple geometrical parameters of normal white cells.

A programmable system, the Textur Analyse System (T.A.S.) of E. Leitz, is described for use in interactive work on pattern recognition of white blood cells. The system appears well suited for the task of finding new parameters for the characterization of normal and abnormal blood cells. Hardware advantages such as speed of operation are coupled with software flexibility. The first application of the machine has been the extraction of some of the ordinary parameters for characterization of leucocytes. The value of each parameter has been analysed with the interactive statistical pattern analysis program (ISPAHAN). A separation in the five normal classes of peripheral white blood cells can be achieved, in which the nuclear/cell area ratio and nuclear area together with the density histograms proved to be the most important parameters. The interesting feature of the system is, however, the possibility of finding new data for the recognition of normal and abnormal blood cells.

Computers↗
PubMedDate not supplied

Automated white blood cell classification revisited.

A novel approach to the problem of automated white blood cell classification is described. Whereas in most earlier attempts the segmentation of the cells has been recognized as the most difficult and most critical step in the sequence of operations resulting in the classification, the method described here eliminates the necessity of the detection of the contour of the nucleus and of the cytoplasm, and is therefore less sensitive to such disturbing factors as the presence of granules, of other cells touching the cell of interest, etc. The multiple sequential threshold method to be described here in two slightly different variants yields a correct classification rate of 94.7% for a 4 class problem (90 cells in the test set), and 91.8% for an 8 class problem (279 cells in the test set). Both experiments include immature cell types.

Densitometry↗
PubMedDate not supplied

A multi-dimensional analysis of three chemical quantities in the blood.

A three-dimensional model for the analysis of the three quantities pH, pCO2 and base excess (BE), as measured in arterial blood, is presented. Whereas the conventional analysis of these quantities relies on reference regions as established from the univariate distributions, treating the quantities as uncorrelated, the present model estimates the parameters of the three-dimensional reference region from a sample of observations, based on the assumption that the observations inside the reference region follow a multi-dimensional Gaussian distribution. For observations outside the reference region, reference directions are established, corresponding to the conventionally defined specific states of acid-base disturbances. This leads to a new classification model, the results of which are compared to those of the conventional model.

Acid-Base Equilibrium↗