Fractional anisotropy (FA) estimated using diffusion tensor magnetic resonance imaging (dMRI) is considered as a promising biomarker in ischemic stroke (IS). The basis of this study is the assumption that the assessment of FA indices for different white matter tracts will be able to predict the main aspects of the rehabilitation potential even without determining the structural and functional bases of these influences.Objective: to study the diagnostic significance of changes in FA indices to assess various aspects of the rehabilitation potential in acute IS.Patients and methods. Examinations were made in 100 patients with IS and in 10 individuals without stroke and cognitive impairment. All the patients underwent dMRI and assessments of rehabilitation potential indicators on days 3 and 10 of the disease and at discharge.Results and discussion. The indices of FA of the ipsilateral upper longitudinal and cingulum bundles, FA and the size of an infarct focus, asymmetry of FA of the cingulum bundle (rFA), corticospinal tract (at the level of the knee of the internal capsule and bridge) and the anterior limb of the internal capsule, as well as the FA of the splenium and knee of the internal capsule of the intact hemisphere are of the most value for the functional outcome of acute IS. The microstructure of these zones determines the state of most rehabilitation domains. With respect to global outcome, the integrity of the associative tracts of the affected hemisphere is more valuable than the microstructure of the intact hemisphere and rFA. The tracts of the intact hemisphere are of particular importance for the restoration of complex rehabilitation spheres, such as cognitive status and daily living and social skills, which is necessary to ensure patient independence.Conclusion. The FA indices of the tracts under study seem to be a clinically acceptable biomarker of various aspects of the rehabilitation potential in acute IS.
Studies of the biomarkers of atrial cardiopathy seem to be promising for identifying patients with cryptogenic stroke (CS), in which an intensive search for atrial fibrillation is indicated. Nevertheless, the diagnostic value of these markers and their threshold values require clarification.Objective: to present the characteristics of echocardiographic markers for atrial cardiopathy and the serum concentration of N-terminal pro-Btype natriuretic peptide (NT-proBNP) in embolic CS versus cardioembolic stroke (CES) and non-cardioembolic stroke (non-CES) to determine the threshold values of parameters with the highest sensitivity and specificity in differentiating CES and non-CES.Patients and methods. A total of 259 patients with ischemic stroke were examined. The standard examination additionally involved calculation of the parameters that reflected left atrial LA) function (LAF): LA emptying fraction (LAEF), and LA functional index (LAFI). The serum NT-proBNP concentration was also determined in 75 patients.Results and discussion. The patients with CES versus those with CS and non-CES were characterized by a considerable increase in LA diameter (4.3 [3.5; 4.5] cm vs 3.7 [3.4; 4.0] cm vs 3.7 [3.4; 3.9] cm; p=0.005 and p=0.009, respectively), LAVI (35.7 [30.5; 39.9] ml/m2 vs 28.5 [25.6; 34.6] ml/m2 vs 27.1 [24.5; 31.2] ml/m2 ; p< 0.001) and NT-proBNP level (559 [409; 1144] pg/ml vs 164 [65; 308] pg/ml vs 191 [63; 446] pg/ml; p=0.002 and p=0.019, respectively), as well as by a lower LAEF value [50.3 [48.5; 51.1]% vs 54.7 [51.6; 56.6]% vs 54.9 [52.5; 56.8]%; p< 0.001). The only parameter that showed significant differences between all the three groups (CES, CS, and nonCES) was LAFI (0.24 [0.2; 0.32] units vs 0.37 [0.3; 0.47] units vs 0.40 [0.34; 0.47] units; p<0.00 1), while maintaining the differences in the values for the two groups (CS and non-CES) (p=0.004). The following threshold values of biomarkers were obtained for CES and nonCES; these were a LA diameter of 41.5 mm (p< 0.001), a LAVI of 36.3 ml/m2 (p< 0.001), a LAEF of 51.8% (p< 0.001), a LAFI of 0.28 units (p< 0.001), and an NT-proBNP of 316 pg/ml (p< 0.001). Analysis of the ROC curves and the area under the curve (AUC) revealed that the most informative criteria for sensitivity and specificity were LAEF (79 and 88%, AUC 0.89), NT-proBNP (67 and 91%, AUC 0.89) and LAFI (93 and 72%, AUC 0.81).Conclusion. The CS group and non-CES one are comparable in the echocardiographic manifestations of atrial cardiopathy and in serum NTproBNP values. LAEF and NT-proBNP concentrations are promising biomarkers to classify CS patients into potential arterio- and cardioembolic types.
Timely evaluation of cardioembolic stroke (CES) caused by atrial fibrillation is critical from the point of view of the possibility of prescribing effective secondary prevention with oral anticoagulants. Insular lesion is considered as a promising neuroimaging marker of CES.Objective: to analyze the role of insular cortex lesions using magnetic resonance imaging (MRI) of the brain as a potential neuroimaging marker of the pathogenetic subtype of ischemic stroke (IS).Patients and methods. 225 patients in the acute period of IS were examined. Depending on the stroke etiology, patients were divided into three groups: cryptogenic stroke (CS; n=99), CES (n=45), and non-CES (n=81). All patients underwent an MRI of the brain to analyze the insular cortex lesions. In 57 patients, foci of cerebral infarction were additionally marked manually on axial slices of diffusion-weighted MRI using the Anatomist software. The calculated MRI characteristics of foci for CES and non-CES groups were used to construct a decision tree in the WEKA 3.6 package. Echocardiographic markers of atrial cardiopathy were assessed in all patients – the left atrium (LA) emptying fraction and LA function index; in 68 patients, the concentration of serum NT-proBNP was also assessed.Results and discussion. The insula was affected in 12% of patients: most often in CES (33%), significantly less often in CS and non-CES (6 and 7.4%, respectively), without significant differences between the latter groups. The presence of insula lesion in relation to CES has a sensitivity of 33% and a specificity of 93% (p=0.002); odds ratio 6.25; 95% confidence interval 2.22–17.63. In most patients, the posterior insular cortex was involved in the pathological process. Isolated insular infarction occurred in only one patient with CES, while the involvement of the insula and adjacent zone, and the combination of insular infarction with territorial infarction, were observed more often. The group of patients with insular lesions was distinguished by the predominance of women, greater severity of stroke at admission, less deficit at discharge, larger LA diameter, lower LA emptying fraction, and functional index. CES was four times more common in the insular lesion group, while CS was two times more common in those without insular lesions. Insula involvement identifies three out of five CES patients according to the decision tree. Further analysis of the total lesion volume can locate almost all remaining patients with CES: they are characterized by the indicator >12 sm3.Conclusion. Insular lesions allow reliable differentiation of patients with CES and non-CES and can be considered a potential marker of the cardioembolic subtype of IS, which requires further investigation.
Современные радиотехнические комплексы, электронно-вычислительная аппаратура и навигационное оборудование, размещаемые на подвижных объектах (летательных аппаратах, кораблях, автомобилях и другом), в процессе эксплуатации могут испытывать значительные импульсные и вибрационные механические воздействияудары, вибрации, линейные перегрузки, акустические шумы. Эти воздействия способны искажать параметры электрических сигналов, вносить дополнительные погрешности в показания приборов и даже приводить к разрушению элементов аппаратуры. Поэтому возникает необходимость в минимизации нежелательных движений этих устройств. Одним из эффективных способов решения проблемы является организация их пассивной виброзащиты, связанной с использованием инерционных, упругих, диссипативных и других пассивных элементов. В данной статье объектом исследования служит блок электронных устройств, закрепленный с помощью системы из четырех демпферов на несущей конструкции, которая подвергается поступательному вибрационному воздействию по трем взаимно ортогональным направлениям. Вследствие этого в демпфируемом блоке возбуждаются угловые колебания. Математическое моделирование реакции блока на внешние силовые факторы осуществляется в рамках классической теории динамики твердого тела. Выполнена серия численных экспериментов по определению отклика кинематических характеристик демпфируемого блока на внешнее периодическое воздействие при различных значениях коэффициентов жесткости и коэффициентов диссипации демпферов и разном положении центра масс системы. Показано, что отклонение центра масс от положения центра жесткости, а также изменение жесткостных и диссипативных характеристик демпферов в пределах статистического разброса их значений вызывают значительное увеличение угловых колебаний демпфируемого блока.Ключевые слова: пассивная виброзащита, математическая модель, вибрационные испытания, центр жесткости, центр масс, угловые колебания, демпферы, коэффициент жесткости, коэффициент диссипации Modern radio-TV complexes, electronic equipment and navigation systems placed on moving objects (aircrafts, ships, cars and others) are subjected to pulse and vibrational mechanical loads, which may distort the device characteristics and even destroy them. Therefore, there is a need to minimize unwanted movements of these devices. The effective way to solve this problem is the organization of passive vibration isolation of a device. This article explores the mechanical vibrations of a block of shock-sensitive electronic devices fixed on a rigid platform of a supporting structure. The block is isolated from the external structure using 4 dampers. The platform is subjected to translational vibrations in three mutually orthogonal directions. As a result, angular oscillations occur in the insulated block. Mathematical modeling of the block response to external disturbances is carried out in the framework of the classical theory of rigid body dynamics. A series of numerical experiments was performed to simulate the response of the insulated block to an external per...
К числу перспективных подходов к определению реабилитационного потенциала пациентов, перенесших ишемический инсульт (ИИ), относится оценка микроструктурной целостности вещества мозга методом диффузионно-тензорной магнитно-резонансной томографии (МРТ; Diffusion Tensor Imaging, DTI), основным показателем которой служит фракционная анизотропия (ФА). Роль интактного полушария в процессе реабилитации после ИИ остается предметом споров. Гипотеза исследования заключается в том, что создание диффузионно-перфузионной модели (ДПМ), основанной на оценке ФА в комплексе с данными о скорости мозгового кровотока (СМК) и влиянии очага, позволит прогнозировать неврологический статус пациентов к концу острого периода ИИ. Цель исследования-изучение роли диффузионно-перфузионных характеристик интактного полушария в определении реабилитационного потенциала в остром периоде ИИ и построение прогностической ДПМ.
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