Electromagnetic Waves Excitation by Thin Impedance Vibrators and Narrow Slots in Electrodynamic Volumes

Linear vibrator and slot radiators, i.e., radiators of electric and magnetic type, respectively, are widely used as separate receiver and transmitter structures, elements of antenna systems, and antenna-feeder devices, including combined vibrator-slot structures. Widespread occurrence of such radiators is an objective prerequisite for theoretical analysis of their electrodynamic characteristics. During the last decades, researchers have published results which make it possible to create a modern theory of thin vibrator and narrow slot radiators. This theory combines the fundamental asymptotic methods for determining the single radiator characteristics, the hybrid analytic-numerical approaches, and the direct numerical techniques for electrodynamic analysis of such radiators. However, the electrodynamics of single linear electric and magnetic radiators is far from been completed. It may be explained by further development of modern antenna techniques and antenna-feeder devices, which can be characterized by such features as multielement structures, integration, and modification of structural units to minimize their mass and dimensions and to ensure electromagnetic compatibility of radio aids, application of metamaterials, formation of required spatial-energy, and spatial-polarization distributions of electromagnetic fields in various nondissipative and dissipative media. To solve these tasks, electric and magnetic radiators, based on various impedance structures with irregular geometric or electrophysical parameters and on combined vibrator-slot structures, should be created. This chapter presents the methodological basis for application of the generalized method of induced EMMF for the analysis of electrodynamic characteristics of the combined vibrator-slot structures. Characteristic feature of the generalization to a new class of approximating functions consists in using them as a function of the current distributions along the impedance vibrator and slot elements; these distributions are derived as the asymptotic solution of integral equations for the current (key problems) by the method of averaging. It should be noted that for simple structures similar to that considered in the model problem, the proposed approach yields an analytic solution of the electrodynamic problem. For more complex structures, the method may be used to design effective numerical-analytical algorithms for their analyses. The demonstrative simulation (the comparative analysis of all electrodynamic characteristics in the operating frequencies range) has confirmed the validity of the proposed generalized method of induced EMMF for analysis of vibrator-slot systems with rather arbitrary structure (within accepted assumptions). Here, as examples, some fragments of this comparative analysis were presented. This method retains all benefits of analytical methods as compared with direct numerical methods and allows to expand significantly the boundaries of numerical and analytical studies of practically important problems, concerning the application of single impedance vibrator, including irregular vibrator, the systems of such vibrators, and narrow slots

The role of ultrasound in the differential diagnosis of liver tumors

Background. Liver lesions are increasingly found in a huge number of patients. Ultrasound (US) is the method of choice in liver lesion characterization. The limitations of traditional US techniques are well known. Multiparametric ultrasound (MPUS) includes multiple facets of the US examination, and their combination can significantly improve the diagnostic capabilities of the method.Objective. To evaluate the capabilities of MPUS in the differential diagnosis of liver tumors.Material and Methods. A retrospective analysis included 172 patients with morphologically confirmed liver tumors. All patients underwent an MPUS examination.Results. Traditional US techniques have a rather low specificity in the differential diagnosis of liver neoplasms: the sign of “contour clarity” was typical for hemangiomas, hepatocellular adenomas (HCA), liver metastases and was recorded in 82, 100, 96% cases, respectively; heterogeneous echostructure was noted in all nosological entities, groups of hepatocellular carcinomas (HCC), liver metastases and HCA were characterized by foci of various types of echogenicity. Specific symptoms were discovered in patients with liver metastases (32%) and focal nodular hyperplasia (FNH) (96%). Intratumoral blood flow was recorded in 34 (19.7%) cases. The study of spectral characteristics was possible only in 11 (6.4%) patients. Statistically significant differences in contrast-enhanced US parameters “contrasting onset in focus” were found between the groups “FNH & hemangioma” (р < 0.000046), “FNH & HCA” (р < 0.006293), “MTS & FNH” (р < 0.028125), “FNH & HCC” (р < 0.024933), “maximum fill-in time” – “FNH & hemangioma” (р < 0.012590), “FNH & HCC” (р < 0.007983), “MTS & HCC” (р < 0.000243). Statistically significant differences in the wash-out time were obtained in “MTS & HCC” and “MTS & HCA” groups.Conclusion. Conventional US should be used as basic screening, follow-up and navigation in the neoplastic biopsy. Contrast-enhanced US within MPUS is currently a well-established technique which allows a more precise and confident diagnosis of liver tumors

MULTIPARAMETRIC ULTRASOUND IN THE DIAGNOSIS OF LIVER TUMORS

Liver neoplasms represent a group of tumors of benign and malignant nature, and their differential diagnosis is rather challenging. At present, it becomes necessary to select a non-invasive, highly informative and sufficient research method for solving diagnostic problems, staging and treating focal liver lesions. Ultrasound examination using modern technologies has advantages in the diagnosis of focal liver disease. The review highlights ultrasound differential and diagnostic signs of focal liver tumors when using various methods of ultrasound diagnostics

Clinical case for diagnosis of textiloma in gastrointestinal tract

In the described clinical case we presented features of a clinical presentation, difficulties of textiloma diagnosis which resulted in acute intestinal obstruction in several years after surgery. The high diagnostic value of an ultrasonic method in diagnostics of foreign bodies was shown

Analysis of ultrasonography and cytology potential in differential diagnosis of major salivary gland neoplasms

Background: Salivary gland tumors account for up to 5% of all head and neck neoplasms. Ultrasonography is one of the main diagnostic modalities for the salivary gland pathology; however, its diagnostic potential is under scrutiny. Fine needle aspiration cytology is considered the main diagnostic method, although its role in the differential diagnosis is disputable.Objective: To identify, based on morphology results, the effectiveness of the main ultrasonographic signs indicating major salivary gland neoplasms in the differential diagnosis and study these signs, to evaluate the effectiveness of fine needle aspiration in the diagnosis of benign and malignant major salivary gland neoplasms.Materials and methods: This retrospective study evaluated a group of 220 patients. We calculated sensitivity, specificity, and accuracy of qualitative ultrasonographic signs of salivary gland neoplasms, analyzed the fine needle aspiration effectiveness, and compared results accuracy by calculating Pearson’s empirical χ-square.Results: Common ultrasonographic signs of benign salivary gland neoplasms included a clear contour (97.5%) and decreased echogenicity (72.7%). Malignant tumors frequently presented with a clear contour (76.7%), uneven contour (72.1%), and decreased echogenicity (69.8%). Fine needle aspiration sensitivity and specificity in the diagnosis of benign neoplasms were 75.5% and 53.6%, respectively. Fine needle aspiration sensitivity and specificity in respect of malignant tumors were 50% and 94%, respectively. Pearson’s χ-square value for the clear contour had significant differences in favor of benign neoplasms.Discussion: Benign and malignant salivary gland neoplasms often have a similar ultrasonographic pattern. A significant diagnostic sign of malignant tumors is the uneven contour. We compared the effectiveness of cytological differentiation between benign and malignant neoplasms and found high rates of specificity and accuracy for malignant tumor diagnosis.Conclusions: Clear contour and decreased echogenicity are significant ultrasonographic signs in the differentiation of benign neoplasms. Uneven contour is a significant differentiating factor for malignant neoplasms. Cytology can be used for initial morphology in diagnosing major salivary gland neoplasms, but in half of the cases it fails to identify the nature and type of the tumor

Value of radiology techniques for diagnosis of obstructive jaundice in admission department

Obstructive jaundice may be caused by many different diseases associated with bile duct obstruction leading to severely impaired liver function as well as injuries of other organs and systems. Early identification of the causes and nature of hyperbilirubinemia is of paramount importance in patient management and decreases the incidence of serious complications and fatalities. Radiology techniques are extremely helpful for the differential diagnosis of obstructive jaundice. High awareness of these methods’ possibilities and their rational use allow one to choose the most appropriate treatment strategy and determine disease outcome. The study describes the feasibility and proper order of various diagnostic methods employed to examine patients with suspected obstructive jaundice

Entropic Tightening of Vibrated Chains

We investigate experimentally the distribution of configurations of a ring with an elementary topological constraint, a ``figure-8'' twist. Using vibrated granular chains, which permit controlled preparation and direct observation of such a constraint, we show that configurations where one of the loops is tight and the second is large are strongly preferred. This agrees with recent predictions for equilibrium properties of topologically-constrained polymers. However, the dynamics of the tightening process weakly violate detailed balance, a signature of the nonequilibrium nature of this system.Comment: 4 pages, 4 figure

Опыт применения контраст-усиленного ультразвукового исследования при наиболее часто встречающихся злокачественных новообразованиях печени

Aim. To study the features of contrast enhancement of malignant neoplasms of the liver in patients with and without cirrhosis (LC), to study the differences in the dynamics of contrast enhancement of liver are metastatic lesions (MTS) and hepatocellular carcinoma (HCC).Material and methods. A retrospective analysis results 58 patients with HCC (group 1) and 51 patients with liver metastases (group 2) was carried out based on morphological data. According to the criterion for the presence of LC, group 1 was divided into two subgroups. The main method of radiological diagnostics was contrast enhancement ultrasound (CEUS).Results. The indicators of the dynamics of the Wash-in of an ultrasound contrast agent into the HCC node and the dynamics of the drug WASH-OUT from the focus in patients with LC did not significantly differ from those in patients without cirrhosis. HCC is characterized by the onset of leaching of the ultrasound contrast agent after 62 seconds from the beginning of the study, which significantly differs from MTS (p <0.05). The parameters in predicting the G3 stage of the tumor were as follows: the parameter “onset of WASH-OUT” of the from the focus <79 sec, the parameter “time of maximum WASH-OUT” of the ultrasound contrast agent <270 seconds. In our opinion, certain difficulties are presented by the diagnosis of highly differentiated carcinomas due to the absence of the WASH-OUT phenomenon in 50% of patients. Differential diagnosis of metastases should be based on a combination of a number of signs, the most important of which, in our opinion, are: early onset of elution of ultrasound contrast agent, “black hole” symptom, peripheral ring-shaped enhancement in arterial phase.Conclusion. The data obtained with the help of CEUS confirm the effect of “arterialization of hepatic blood flow” in patients with LC. Differences in the parameters of contrasting HCC nodes in subgroups of patients with and without LC are not statistically significant. The polymorphism of the signs detected in MTS in the liver is due to the morphology of the primary tumor and the size of the neoplasms. Differential diagnosis should be based on a combination of signs of the dynamics of ultrasound contrast agents.Цель исследования: изучение особенностей контрастирования злокачественных новообразований печени у пациентов с циррозом печени (ЦП) и без, изучение отличий динамики контрастирования метастазов печени (МТС) и гепатоцеллюлярной карциномы (ГЦК).Материал и методы. На основании морфологических данных проведен ретроспективный анализ обследования 58 пациентов с ГЦК (группа 1) и 51 пациента с МТС печени (группа 2). По критерию наличия ЦП группа 1 была разделена на две подгруппы. Основным методом лучевой диагностики в обеих группах было контраст-усиленное ультразвуковое исследование (КУУЗИ).Результаты. Показатели динамики поступления ультразвукового контрастного препарата (УЗКП) в узел ГЦК и динамики вымывания препарата из очага у пациентов с ЦП достоверно не отличались от показателей у пациентов без цирроза. Для ГЦК характерно начало вымывания УЗКП после 62-й секунды от начала исследования, чем она достоверно отличается от МТС (р < 0,05). Параметры в прогнозировании G3 стадии опухоли были следующими: параметр “начало вымывания” УЗКП из очага <79 с, параметр “время максимального вымывания” УЗКП < 270 с. На наш взгляд, определенные сложности представляет диагностика высокодифференцированных карцином ввиду отсутствия феномена WASH-OUT у 50% пациентов. Дифференциальная диагностика метастазов должна строиться на комбинации ряда признаков, наиболее важными из них, на наш взгляд, являются: раннее начало вымывания УЗКП, симптом “черной дыры”, периферическое кольцевидное усиление в артериальную фазу.Выводы. Полученные при помощи КУУЗИ данные подтверждают эффект “артериализации печеночного кровотока” у больных с ЦП. Различия показателей параметров контрастирования узлов ГЦК в подгруппах пациентов с ЦП и без статистически недостоверны. Для очаговых поражений характерны различные рисунки контрастирования, которые являются основой определения их злокачественности. Полиморфизм признаков, выявляемых при МТС в печени, обусловлен морфологией первичной опухоли и размерами новообразований. Дифференциальная диагностика должна строиться на комбинации признаков динамики УЗКП