Biomedical subjects
Publications and source records attributed to V P Sidorin.
A program named KODR (dosimetric monitoring of irradiation in radiodiagnosis) was developed for the SM-4 computer to ensure regional radiation monitoring. On the basis of statistical data on the distribution of x-ray studies the program made it possible to define collective effective equivalent doses and a mean value of an effective equivalent dose for one person in a given region.
The paper is devoted to an analysis of random errors in the determination of a collective effective equivalent dose resulting from radiodiagnostic investigations. The error of a collective dose does not exceed 30% and hardly depends on dose errors in human organs and tissues. The authors have established an extent of overestimation of the risk of long-term radiation effects in patients after x-ray investigations.
The paper is concerned with the results of experimental studies on the equivalent doses of irradiation of 11 organs and tissues by which one can calculate effective equivalent doses per study. Calculation were done on an anthropomorphous phantom of "conventional" man with the help of a thermoluminescent dosimetric system based on lithium fluoride. Equivalent doses were evaluated by the mean calculated value. The tabulated results make it possible to determine equivalent doses.
Basing on experimentally measured energetic radiation spectra of the RUM-7 x-ray unit, absorbed dose distributions in the homogeneous tissue equivalent medium were calculated. An approach to the optimization of the x-ray procedure on the basis of the incident radiation spectrum was proposed. Integral absorbed doses in a pathological focus and in the healthy tissues are used as benefit-damage indicators.
According to the recommendations issued by the International Commission for Radiation Protection a solution to the problem of the appropriateness of measures aimed at reducing irradiation doses, depends upon the consideration of all the pros and cons. Approaches to a quantitative evaluation of the benefit and damage of x-ray examination are considered. Damage is regarded as a risk of developing unfavorable complications of irradiation by a patient. Proceeding from the threshold-free linear concept, an effective equivalent dose is taken for a measure of damage, the quality of x-ray image for a measure of benefit. The contrast of visualized x-ray image is used for its approximate evaluation. Effectiveness function which is equal to the ratio of the quantitative benefit-damage measures, was drawn. A mathematical model of optimization with account of the heterogeneity of the studied object and the energy spectrum of x-ray radiation was developed on the basis of the above criterion. With the help of this model optimum regimens were obtained for radiography of the stomach on the RUM-20 apparatus with ZnSl.Cds-Ag screen.
The X-ray photon spectra of a number of generally used radiotherapeutic systems have been studied by using a semiconductor Ge detector. The voltage ranges from 80 to 200 kV. The procedure of converting pulse-height distributions into photon spectra is described. The relation between the shape of the spectrum and the anode current is discussed. The data are useful for more precise calculations of the absorbed dose when planning radiotherapy.
A variation of X-ray energy spectrum has been experimentally studied in operating conditions. The filtration on the irregular sites of a destroyed target has been shown to cause a growth in effective radiant energy. A possibility to stabilize the spectrum by reducing a thickness of an additional filter is discussed. The relationship between the thickness of the equivalent aluminium filter and a value of X-ray tube ageing is given, the error of the spectrum stabilization being 5%.