[Current problems of medical physics in the radionuclide diagnosis]. / Aktual'nye problemy meditsinskoi fiziki v radionuklidnoi diagnostiki.

The most important problems of medical physics in clinical radionuclide diagnosis are considered on the basis of the data available in the literature. The matter and trends in the development of investigations, into radiopharmaceutical, hard- and software, methodological, and algorithmic supports of radionuclide diagnosis, as well as those into its quality insurance and provision of radiation safety of patients and the personnel are also analyzed.

[Identification of radiopharmaceutical transport models in functional radionuclide diagnosis]. / Identifikatsiia modelei transporta RFP v funktsional'noi radionuklidnoi diagnostike.

The paper is devoted to the problems of assessment of structural identification of parameters of compartmental models, employed for processing of the results of radionuclide investigations of function of various physiological systems. Methods for assessment of structural identifiability and a regularized algorithm for the identification of parameters of linear and nonlinear compartmental models of almost any structure were proposed. The algorithm possesses a high rate of convergence of the iteration searching process and a low sensitivity to errors of measurements. It was implemented as a software package in Pascal language and utilized on a RDR 11/34 computer for processing the results of radionuclide diagnosis (using 99mTc-COREN) of function of the reticuloendothelial system.

[Mathematical model of radioactive colloid transport in the evaluation of the functional state of the reticuloendothelial system]. / Issledovanie matematicheskoi modeli transporta radioaktivnogo kolloida dlia otsenki funktsional'nogo sostoianiia retikuloéndotelial'noi sistemy.

The authors assess the functional potentialities of a mathematical model of transport of labeled colloids in the body. Some additions to and modifications of the model were analyzed. They made it possible to get 4 diagnostically important indices: the rate of colloid excretion from the vascular bed, the rate phagocytosis, RES volume, and the rate of RP accumulation by the liver. Besides, the authors presented the results of a computerized experiment for the determination of maintenance characteristics of a program developed for computer. The iteration algorithm for parameter identification based on a method of linearization of minimized function, was used in the program. They also formulated recommendations for a choice of arbitrary components of a calculation procedure and the use of a method of barrier functions, developed as a result of prolonged maintenance of the program.

[Combination radiodiagnosis of the functional state of the urinary tract in cancer of the kidney]. / Kompleksnaia luchevaia diagnostika funktsional'nogo sostoianiia mochevydelitel'noi sistemy pri rake pochki.

The results of combined radiodiagnosis of the urinary system in patients with renal tumors before and after nephrectomy were analyzed. Investigations included excretory urography and renography with the processing of the results of measurements by a common algorithm and on the basis of 3 mathematical models of RP body transport. The results were correlated with the findings of biochemical blood and urine tests and pathoanatomical investigation of the removed kidney. Ample potentialities of renography for the detection of latent renal insufficiency in the preoperative period and for accurate and exhaustive assessment of function of the urinary system were shown.

[Radionuclide diagnosis of vasculogenic impotence]. / Radionuklidnaia diagnostika vaskulogennoi impotentsii.

Pathogenesis of vasculogenic impotence is most adequately revealed by modern methods of the investigation of the hemodynamic mechanisms of erection with the enhancement of arterial perfusion of corpora cavernosa by artificial sexual stimulation. Radionuclide diagnostic methods effectively differ from the methods of radiocontrast phalloangiography by the simplicity of investigation and the absence of traumatism for a patient. The authors have proposed a mathematical model of a process of filling in the functioning volume of the penile vascular bed with a radiopharmaceutical preparation against the background of erection induced by intracavernous administration of papaverine hydrochloride solution. Parameters of the model determine the ratio of blood flow volumetric rates in the penis at rest and when erect.

[Choice of method for determining the individual clearance of the kidneys]. / Vybor metoda opredeleniia razdel'nogo klirensa pochek.

Some criteria for assessment of the adequacy of various radionuclide methods of determination of the separate renal clearance were proposed. Some methods were analyzed according to these criteria: one of them was proposed by S. U. Schlegel et al. and used in the paper by M. E. Karaev and R. N. Samedov, and the other one was proposed by V. Kh. Frenkel' and V. B. Shushkovskii. Both methods were shown to be insufficiently substantiated from physiological and mathematical view-points. A method of assessment of the separate renal clearance in the form of a circulation model was proposed. It was based on the minimal possible number of simplifying allowances and made it possible to define the state of secretory-excretory (or filtration) function and the state of hemodynamics of each kidney as a result of single administration of a transit nephrotropic radiopharmaceutical.

[Method of determining separate kidney clearance]. / Metod opredeleniia razdel'nogo klirensa pochek.

The task was to develop a simple and effective method of radionuclide determination of separate clearance of the kidneys (SCK), i.e. separate assessment of secretory-excretory function of each kidney. The other earlier known methods of SCK determination were either methodologically incorrect or very difficult. A method of SCK determination intended both for gamma-chambers and standard radiographic units based on common renographic methods, was proposed. An algorithm for processing of measurement results was based on the generalization of the mathematical apparatus of circulation models usually employed for a study of the central and organ hemodynamics, and on its development for transitory nephrotropic radiopharmaceuticals (RP). An investigation of 21 healthy persons and 51 patients with renal tumors using 131I-hippuran showed that the proposed method possessed sufficient sensitivity for its clinical use. Advantages and shortcomings of the method were analysed. All the allowances were justifiable.

[Effect of detector sensitivity on the accuracy of results of radionuclide kidney studies]. / Vliianie chuvstvitel'nosti detektora na tochnost' rezul'tatov radionuklidnykh issledovanii pochek.

In the course of both kidney gammachronography with an isolated detector and kidney scintigraphy with a gamma camera the detector volume sensitivity is calculated. Mathematical model of the kidney is described as a set of superimposed linear-circular cylinders. Based on the CT examinations a cylinder radius and a thickness of soft tissues attenuating gamma radiation are derived. The detector volume sensitivity is found to change up to 34% in kidney gammachronography and up to 22% in kidney scintigraphy when using low power radionuclides.

[Radionuclide study of liver hemodynamics]. / Radionuklidnoe issledovanie gemodinamiki pecheni.

A new method for processing the results of radionuclide studies on the liver blood circulation was proposed. It permitted assessing the state of the liver vascular network by a system of indicators having a specific physiological meaning: the ratio of functioning volumes of the vascular bed of the arterial and portal systems, the general, arterial and portal liver blood circulation in cardiac output fractions. The application of the method to radionuclide studies on the liver blood circulation in 5 healthy persons and 15 patients with metastatic liver lesions showed its efficacy and clinicodiagnostic significance.

[Effect of detector sensitivity on regional indices of pulmonary function]. / Vliianie chuvstvitel'nosti detektora na regional'nye pokazateli funktsional'nogo sostoianiia legkikh.

The paper is concerned with a qualitative assessment of the assumption of independence of sensitivity function on the anatomotopographic features of the region in a functional radionuclide study of the lungs. Sensitivity function of standard collimation detectors was calculated for the radionuclides 133Xe and 99mTc. Geometrical sizes of the studied region were determined by respective CT transversal sections. An analysis of the calculation results showed that sensitivity function depended significantly on the anatomotopographic features of the studied region. The error of measurement determined by the variability of sensitivity function, easily changed from 34 to 9%.

[General evaluation of the state of the endocrine system from the results of radiodiagnostic studies in vitro]. / Obobshchennaia otsenka sostoianiia éndokrinnoi sistemy po rezul'tatam radiodiagnosticheskikh issledovanii in vitro.

The paper is concerned with a comparative analysis of 3 different decision rules to give a summary evaluation of endocrine system function. The application of the rules to the evaluation of the hormonal status of patients with gastric cancer has shown that the index of the state of the endocrine system gets deteriorated compared to the normal one, however it greatly improves in clinically effective treatment. From the view-point of the quality of classifiers for an in vitro study of the endocrine status the best of the proposed classifiers is the determination of Euclidean distance from normal in the multidimensional space of the diagnostic signs.

[Changes in the regional indices of ventilation and perfusion in lung cancer patients during treatment]. / Izmenenie regionarnykh pokazatelei ventiliatsii i perfuzii u bol'nykh rakom legkogo v khode lecheniia.

A total of 27 patients with central lung cancer and 43 patients with peripheral lung cancer of various sites were examined after surgical intervention on a multichannel unit using 133Xe. The regional distribution of alveolar ventilation and perfusion blood flow were evaluated in the preoperative period as well as at varying times after operation. Statistical analysis of the results has shown that a significant decrease in the ventilation and blood flow is observed in the zone with a focus of lesion in the preoperative period. At the same time even in the preoperative period of compensatory increase in the ventilation and blood flow occurs in the lower zone of the contralateral lung. An increase in the ventilation and blood flow in all the zones of the remaining lung is observed after pulmonectomy; lobectomy does not change pulmonary function and the operated lung does not regenerate its function. No distinctions in the regional values of the ventilation/perfusion ratio were revealed during treatment. Regional perfusion and ventilation are changed in one direction, their ratio and hence the gaseous composition of the blood remain unchanged.

[Radionuclide study of reticuloendothelial system function]. / Radionuklidnoe issledovanie funktsii retikuloéndotelial'noi sistemy.

The authors propose a new method for the interpretation of the measurement data obtained during radionuclide investigations of the function of the reticuloendothelial system (RES). This method is upon the concept of a considerable effect of the blood opsonizing factor on the transport of i.v. injected radioactive colloid in the body. A non-linear compartmental model was developed that describes the binding of colloid particles with opsonins in the vascular bed followed by absorption of the particles of the colloid-opsonin complex by RES cells. The identification of the parameters of the non-linear model by the results of dynamic scintigraphy of the heart and liver makes it possible to explain some phenomena in the measurement data and to assess the relative amount of opsonins in the blood and RES phagocytic activity as a whole and its constituents. It was shown in particular in the studies on patients with hepatocirrhosis that the amount of opsonins in the blood remains almost the same as compared to the normal one whereas the phagocytic activity of RES on the whole, hepatic stellate cells and RES extrahepatic cells decreases significantly.