Biomedical subjects
Publications and source records attributed to A Savina.
A study of the 23 MRI sites functioning in France at the end of 1987 provides an overall view of the organizational and economic aspects of these sites as well as an initial assessment of their activity in terms of the types of equipment used and the institutions, private or public, within which they have been set up.
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The over-estimate of plasma volume noted at the time of the substitution of iodine 131 labeled human serum albumin by indium 113m transferrin, probably results from a defective fastening of the radionucleide on the binding protein and not at all from a particular behavior of this last one as it has often been admitted.
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The results of a radioisotopic exploration are not independant of the physical characteristics of the tracer used. Thus in the measurement of cardiac output index by external detection, the substitution of 131I fastened on the human serum albumine by 99mTc fastened on red cells introduces a systematic average error of +20% whose origin is double. Because of the plasma or red cell kind of the tracer, the average error done on the volume is, in 130 measurements, 26% whereas that which results from the difference of photon energy is -6%. Only this last error affects the measurement of the cardiac output and, by that time, it is demonstrated that a direct determination of the cardiac output index by STEWART-HAMILTON'S relation is impossible.
The fixation of iodine 131 on thyroid is often disturbed by iodine overdose. In order to detect such conditions, the authors propose a method of estimation of urinary iodide based on the use of a selective crystalline membrane electrode.
The method for measuring coronary blood flow, which is described here, is based on the estimate, by external detection, of the quantity of 86Rb fastened on the cardiac muscle about ten minutes after the injection. The discussion which follows after this report, shows that the use of such a late time for the measurements does not contradict the fondamental hypothesis but allows to work in perfect technical conditions. The results obtained,widely superposable to those which have been published until to-day, prove a posteriori the availability of the method.
The short life tracers permit the use of high activities and so allow to follow with a good statistic accuracy fast phenomenons such as the different phases of cardiac revolution. However, this advantage may be quickly limited by the dead-time of the detection unit used. It results from this, in high activities, a non linear response which introduces non negligible errors which we have calculated and verifies thanks to experience in the measurement of right ventricular volumes.