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At least 37 records · Page 2Linked to original sources
PubMed1975

A widely applicable method for computing dose distributions from external megavoltage beams.

A method of computing megavoltage dose distributions using an empirical mathematical model is described. The dose at a point in a medium is calculated as the product of a central axis percentage depth dose, a crossplot factor and a wedge factor. For a given set of conditions (i.e. type of machine, source-skin distance and wedge) 16 parameters are required to calculate the values of the three factors and hence the dose at any point. These parameters can be obtained from a relatively small number of experimental measurements. Dose distributions from a variety of different treatment machines have been computed by the method, and some comparisons of the calculated and measured doses have been made using "Goodness of Fit" score values. These show that the use of the method as a basis for computer treatment planning should be clinically acceptable.

Computers↗
PubMedDate not supplied

Comparison of convolution and ray-tracing methods for computing small blood vessel images in angiography.

Two methods for computing x-ray images of small blood vessels in angiography are presently available, namely, convolution and ray tracing. The convolution method, which is simpler and more powerful than the ray-tracing method, is based on the assumption that blood vessel imaging is isoplantic, whereas ray tracing is considered to provide correct images. In this study, the approximation error (difference between two images, normalized by the maximum value) due to nonisoplanatic imaging was determined by computation of blood vessel images according to both methods. The approximation error for geometric conditions normally encountered in angiography was less than 0.01. It is concluded that an approximation error of this magnitude is negligible and that the convolution method can be applied instead of the ray-tracing method for the computation of images of small blood vessels.

Angiography↗
PubMed1975

A simple method for computing acid-base state.

Simple methods are described for computing the variables derived from the Siggaard-Andersen nomogram, where the in vitro buffer line is either established by direct measurement or calculated from measurements of pH, Pco2 and haemoglobin. Calculations are performed using the equation of the pH-log Pco2 buffer line, the Henderson-Hasselbalch equation, and the polynomials: BE=-38.402+1.8970 (SB)-0.013342 (SB)-2 m-equiv/litre; SL=-69.046+17.377 (pH40)-1.1121 (pH40)-2; SH=-123.30+31.357 (pH40)-2.0143 (pH40)-2. Then haemoglobin=7.5 (1+(S-SL)/(SH-SL)) G/100 ml, where S is the slope of the buffer line. Results are sufficiently accurate for clinical purposes.

Acid-Base Equilibrium↗
PubMed1979

"Circumferential profiles:" a new method for computer analysis of thallium-201 myocardial perfusion images.

A method for computer analysis of thallium-201 scintigrams is described, in which the left-ventricular activity is measured along radii constructed from the center of the left ventricle (LV) to each point on the LV circumference. Data are then displayed graphically as a "circumferential profile" of normalized activity against radial location. Thallium defects are identified and scored by comparison of the profile curve with empirically determined normal limits. In patients with coronary artery disease, defect scores were found to be quantitative and reproducible, and to agree generally with subjective visual analysis.

Adult↗
PubMed1979

General method for computer measurement of complex chromatograms.

Usual computerized methods for measuring peak areas and associated computations on chromatograms require relatively highly reproducible retnetion times. They are prone to mis-identification of substances in chromatography of physiological fluids. The method described was developed for amino acid analyses of physiological mouse tissues. It tolerates noisy output, drifting baselines, variable retention times and unidentified peaks.

Amino Acids↗
PubMed1978

A computer assisted method for the determination of restriction enzyme recognifion sites.

A computer program has been developed which aids in the determination of restriction enzyme recognition sequences. This is achieved by cleaving DNAs of known sequence with a restriction endonuclease and comparing the fragmentation pattern with a computer-generated set of patterns. The feasibility of this approach has been tested using fragmentation patterns of 0X174 DNA produced by enzymes of both known and unknown specificity. Recognition sequences are predicted for two restriction endonucleases (BbvI and SfaNI) using this method. In addition, recognition sequences are predicted for two other new enzymes (PvuI and MstI) using another computer-assisted method.

Base Sequence↗
PubMedDate not supplied

[Method of computing positive pressure in the human lung following space cabin decompression].

The paper presents a mathematical model and differential equations to be used in computer-aided estimations of the positive pressure in human lugs upon space cabin blast decompression. The paper gives a simplified method of computing the pressure which utilizes a special diagram of decompression of a rigid container communicating with the cabin through a hole of a constant area. The characteristic feature of the method is a simultaneous computation of the air outflowing from the lungs and their expansion during decompression. The paper illustrates the advantage of the simultaneous computation of the processes and specifies the pulmonary regions of positive pressure at given blast decompressions. The paper compares theoretical and experimental (data by foreign researchers) peak values of the positive pressure in human lungs during blast decompression, indicating good agreement of the results.

Atmospheric Pressure↗
PubMed1977

A standardized method for computed tomography of the orbits.

A standardized method for the CT exploration of the orbital region has been searched for. This method makes it possible to visualize the entire orbital region with a minimum of 4 tomographic scans, each section 6 mm thick. The reference line chosen for this exploration is parallel to the optic nerve and joins the projection of the inferior border of the orbit on the lateral view with the upper border of the ear to the scalp. After each tomographic scan the patient is moved so that the new scanning line is still parallel to the reference line but distant by 9 mm from the previous one.

Humans↗