[Mathematical modeling of oxygen diffusion and consumption in malignant tumor].

A mathematical model of oxygen diffusion and consumption in a malignant spherical tumor was developed. The model takes into account the dependence of the rate of oxygen consumption by cells on oxygen concentration. The expressions for the description of the dependence of oxygen concentration on the coordinate in the tumor are presented. Some model parameters were estimated from known experimental data. The hypoxic cells fraction (index related to tumour radioresistance) at critical and limiting tumor sizes were calculated.

[The isolation of the contribution of the parenchyma to the radionephrogram and the assessment of kidney purifying function]. / Vydelenie vklada parenkhimy v radionefrogrammu i otsenka ochistitel'noi funktsii pochek.

The authors described the principle and algorithms of the separation of a summary radionephrogram into constituents, reflecting the contribution of a radiopharmaceutical, uptaken by neutrons, and RP in the surrounding tissues. The authors proposed a correct method for estimation (using the first constituent) of the efficacy indicator of RP uptake by the kidneys (Q-parameter) and the indicator of the mean time of transit (t) in the kidneys of RP uptaken by their parenchyma. The results of testing of the proposed methods of Q and t calculation were presented. Values of these parameters were determined in health and in essential hypertension, I and II degree, pyelonephritis, chronic nephritis (latent and hypertensive types), stenosis of the renal artery, obstruction of the upper urinary tracts, and in one kidney. These results indicate the physiological adequacy of the employed mathematical models, proving the diagnostic informative value of the calculated indicators.

[Permeability of the hemato-ophthalmic barrier in uveitis]. / Pronitsaemost' gematooftal'micheskogo bar'era pri uveitakh.

The results of examining the hematoophthalmic barrier permeability by radiometry and biotests with anterior chamber and vitreous humor are analyzed. Injection of the radiopharmaceutical into the vorticose veins provides the most effective pharmacokinetics, vs. suprachoroidal and subconjunctival injections. In toxis allergic uveitis the penetration of radiopharmaceuticals into the internal media of the eye (anterior chamber humor and vitreous body) is intensified, and dexason therapy of an inflammatory process in the vascular coating reduces this penetration.

[Mathematical model of the kinetics of radiopharmaceutical preparations in the right compartments of the heart]. / Matematicheskaia model' kinetiki radiofarmatsevticheskikh preparatov v pravykh polostiakh serdtsa.

The paper is concerned with the description of a mathematical model of the kinetics of radiopharmaceutical drugs (RPD) in the right heart with due regard for its two-compartmental structure. A formula has been obtained to describe a right heart radiogram (RHRG) for any RPD entry into the heart (with any type of entry function). It has been shown that in case of an impulsed entry a RHRG curve is described by the following formula (formula; see text) which is a biexponential one. The above formula shows that the determination of phi 1 and phi 2 factor on a curve gives an opportunity to obtain exact information on the correlation of cardiac chamber volumes (the auricle and ventricle). The authors point a possibility of using a RHRG curve for the determination of cardiac output and rate. The formulas obtained are of particular value for analysis of the curves of radiocardiography with 133Xe.