PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Mathematical Computing”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources
PubMed1989

Computer system and software of POSITOLOGICA II: a whole body positron emission tomograph.

Since a whole body PET-scanner POSITOLOGICA II was installed at the National Institute of Radiological Sciences (NIRS) in 1982, improvements of the computer system and developments of new software have been continuously made to correspond to clinical requirements. As the result, POSITOLOGICA II possesses one of the most powerful systems and sophisticated software in Japan. This report describes the present status of the computer system and software of POSITOLOGICA II. It also discusses problems which still exist and proposes a future computer system for the PET study.

Brain↗
PubMed1989

Reliability of the Cobb angle index derived by traditional and computer assisted methods.

The reliability of the traditional Cobb angle index, which at present exhibits a wide range of reported values, was determined in this study and amounted to a within subject error of +/-4.3 degrees and a between subject error of +/-4.9 degrees. An attempt to pinpoint the source of this variability by investigating the influence of choice of end vertebrae proved inconclusive. The reliability of a computer assisted Cobb angle index, developed to improve measurement accuracy, was also examined and an estimated within subject error of +/-1.5 degrees and a between subject error of +/-1.6 degrees obtained. A comparison of the traditional and computer assisted methods indicates a high correlation between the Cobb angle derived using the two methods when measuring like curves and an improved reliability obtained by the computer method. Such an improvement is worth implementing clinically but of course the availability of a computer and digitizer and a little extra time for an operator to input the X-ray coordinates may be a barrier to its general use.

Diagnostic Errors↗
PubMed1996

Grading and prognosis of infiltrating ductal breast carcinoma by mean nuclear volume estimates.

OBJECTIVE: Quantitative evaluation of nuclear size in breast cancer is performed with the aim of investigating whether the data obtained are related to subjective grading and prognosis. STUDY DESIGN: Unbiased stereologic estimates of the volume-weighted mean nuclear volume (nuclear vv) in paraffin-embedded tissue from 44 specimens of infiltrating ductal breast carcinoma were obtained by the point-sampled intercepts method. RESULTS: Histologically graded cases showed an overlap in nuclear vv estimates, but significant differences were demonstrated in which averaged values increased from grade 1 to 3 breast carcinomas. Nuclear vv estimates in grade 3 breast carcinoma (mean, 495.4 microns 3; SD, 101.7 microns 3) were significantly larger than those in grades 1 (mean, 327.8 microns 3; SD, 90.9 microns 3) and 2 (mean, 409.9 microns 3; SD, 72.6 microns 3) (P < .01). Minor statistically significant differences (P < .05) were found between grades 1 and 2. Estimates of nuclear vv based on systematic sampling within the specimen showed high efficiency, with > 80% of the total observed variance contributing to biologic differences between individual specimens. Univariate prognostic study showed that clinical stage, and not histologic grade, was of prognostic value in the cases studied. Similarly, nuclear vv estimates were associated with disease recurrence and survival, with a cutoff point of 425 microns 3. CONCLUSION: Based on the cases investigated, shape-independent nuclear vv estimates may be an adjuvant tool in the grading and prognostic evaluation of infiltrating ductal breast carcinoma.

Breast Neoplasms↗
PubMed1996

Quantification of nuclear pleomorphism using an asymptotic fractal model.

OBJECTIVE: Nuclear pleomorphism (nuclear membrane irregularity) was investigated using transmission electron microscope (TEM) micrographs of 1,419 nuclei (32 oral carcinomas and normal cells from surgical margins). STUDY DESIGN: Nuclear profiles (1,400 x) were digitized (1 pixel = 35 nm) and fractal dimension estimated using the "yardstick" method. RESULTS: Log-log plots of yardstick length vs. perimeter showed a significant effect on length measurement typical of fractals at low resolutions (large yardsticks), but this effect disappeared at higher resolution (small yardsticks); that is compatible with Rigaut's asymptotic fractal model. Analysis of the asymptotic fractal parameters c, L and Bm showed that c was higher in normal nuclei, but log(L) and Bm were higher in malignant nuclei. A linear discriminant analysis using c, log(L) and Bm reclassified correctly 78.8% of the nuclei (normal 88.0%, tumor 70.2%). CONCLUSION: Asymptotic fractal analysis of nuclear profiles appears to show great potential for quantitative discrimination of oral cancer cell features.

Carcinoma, Squamous Cell↗
PubMed1997

Autowave tunneling through a non-excitable area of active media.

The mechanisms of autowaves propagation through local non-homogeneities in active media relevant to diverse class of physiological systems were studied by means of a computer simulation. The model proposed by Zel'dovich and Frank-Kamenetsky and that of FitzHugh-Nagumo were used for studying autowave tunneling, which in a broad sense implies underbarrier passing. It was shown that for every fixed parameter value corresponding to the degree of non-excitability of local area a critical value for non-excitable zone latitude exists. An autowave overcomes the barrier and continues to propagate when the value of zone latitude is less than critical. Critical conditions for origination of a source of periodical sequence of impulses in excitable medium were found. The source properties, as shown, can be modified by regulation of size of a non-excitable zone and a zone of higher excitability. In particular, the conditions when spatial irregularity behaves as a source of unidirectional and/or asynchronous sequence of impulses were explored.

Animals↗
PubMed1982

Fluid dynamics of the mitral valve: physiological aspects of a mathematical model.

This paper presents a computational method that can be used to study the fluid computational method that can be used to study the fluid dynamics of the natural or prosthetic mitral valve in a computer test chamber with contractile muscular walls that model the left side of the heart. Having solved the equations of motion and predicted the performance of the valve, the computer presents the results in terms of flow patterns (streamlines), pressure-contour plots, and graphs of velocity, pressure, flow, tension, and distance as functions of time. Predicted echocardiograms and phonocardiograms are also generated by the computer. These predictions are compared with the results of animal experiments, and the method is used to study the diastolic role of the chordae tendineae, the pathophysiology of mitral valve prolapse syndrome, and the fluid dynamics of pivoting disc valves. Our results support the hypothesis that the chordae have a functional role during diastole. The results also establish a computer model of mitral prolapse, which should be useful in functional studies of that condition, and show that the position of the pivot point and the curvature of the occluder can have a profound effect on the angle of opening of pivoting disc valves. These studies illustrate the applications of the method in physiology, pathophysiology, and prosthetic valve design.

Animals↗
PubMed1991

A mathematical model for the computation of carboxyhaemoglobin in human blood as a function of exposure time.

A mathematical model is developed for the carbon monoxide (CO) uptake by the blood by taking into account the molecular diffusion, convection, facilitated diffusion and the non-equilibrium kinetics of CO with haemoglobin. The overall rate for the combination of CO with haemoglobin is derived by including the dissociation of CO from carboxyhaemoglobin (COHb). The resulting coupled system of nonlinear partial differential equation with physiologically relevant initial, entrance and boundary conditions is solved numerically. A fixed point iterative technique is used to deal with nonlinearities. The concentration of COHb in the blood is computed as a function of exposure time and ambient CO concentration. The COHb levels computed from our model are in good agreement with those measured experimentally. Also, results computed from our model give better approximation to the experimental values compared with the results from other models. The time taken by the blood COHb to attain 95% of its equilibrium value is computed. The COHb concentration in the blood increases with the increase in ventilation rate, association rate coefficient of CO with haemoglobin and total haemoglobin content in the blood, and with the decrease in dissociation rate coefficient of CO with haemoglobin and mean capillary blood PO2. It is found that the COHb level in the blood is not affected significantly because of endogenous production of CO in the body under normal condition. However, the effect may be significant in the patients with haemolytic anaemia.

Capillaries↗