[OPTIMIZATION OF EARLY DIAGNOSIS OF ACUTE KIDNEY INJURY IN NEWBORNS IN CRITICAL CONDITION].

UNLABELLED: Current diagnosis of acute kidney injury (AKI) is one of the most pressing problems in the newborn in critical condition. OBJECTIVE: To determine the diagnostic value of indicators of renal blood flow as a marker of acute kidney injury in critically ill newborns. MATERIALS AND METHODS: The study included 40 infants in critical condition. A clinical assessment of severity of the condition during admission was carried out with Neonatal Multiple Organ Dysfunction Score (NEOMOD) and Neonatal Therapeutic Intervention Scoring System (NTISS). All patients underwent evaluation of clinical and instrumental parameters, including ultrasound of the renal vessels, renal vascular resistance index and speed performance. CONCLUSIONS: 1) biochemical markers used in routine clinical practice were not sufficiently informative for the diagnosis of AKI. 2) For a more accurate assessment of the risk of AKI using serum creatinine, GFR calculation and evaluation on a scale RIFLE it is should be focused on performance standards, appropriate for gestational age and birth weight. 3) Evaluation of blood flow at a particular index in the resistance of the main renal arteries had the greatest predictive value and had a relatively high sensitivity and specificity for the diagnosis of AKI.

A DERATING METHOD FOR THERAPEUTIC APPLICATIONS OF HIGH INTENSITY FOCUSED ULTRASOUND.

Current methods of determining high intensity focused ultrasound (HIFU) fields in tissue rely on extrapolation of measurements in water assuming linear wave propagation both in water and in tissue. Neglecting nonlinear propagation effects in the derating process can result in significant errors. In this work, a new method based on scaling the source amplitude is introduced to estimate focal parameters of nonlinear HIFU fields in tissue. Focal values of acoustic field parameters in absorptive tissue are obtained from a numerical solution to a KZK-type equation and are compared to those simulated for propagation in water. Focal waveforms, peak pressures, and intensities are calculated over a wide range of source outputs and linear focusing gains. Our modeling indicates, that for the high gain sources which are typically used in therapeutic medical applications, the focal field parameters derated with our method agree well with numerical simulation in tissue. The feasibility of the derating method is demonstrated experimentally in excised bovine liver tissue.

FOCUSING OF HIGH POWER ULTRASOUND BEAMS AND LIMITING VALUES OF SHOCK WAVE PARAMETERS.

In this work, the influence of nonlinear and diffraction effects on amplification factors of focused ultrasound systems is investigated. The limiting values of acoustic field parameters obtained by focusing of high power ultrasound are studied. The Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation was used for the numerical modeling. Solutions for the nonlinear acoustic field were obtained at output levels corresponding to both pre- and post- shock formation conditions in the focal area of the beam in a weakly dissipative medium. Numerical solutions were compared with experimental data as well as with known analytic predictions.