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Time-resolved near-infrared spectroscopy in monitoring acute ischemic stroke patients - Case study

Kuls-Oszmaniec Aleksandra, Kacprzak Michał, Morawiec Magdalena, Sawosz Piotr, Fiszer Urszula, Leńska-Mieciek Marta

Biocybernetics and Biomedical Engineering

2024

Vol. 44, no. 1

149--160

Stroke is a leading cause of disability and death worldwide, with acute ischemic stroke (AIS) accounting for the majority of cases. Early and accurate diagnosis of AIS is crucial for improving patient outcomes. Non-invasive monitoring techniques, such as time domain near-infrared spectroscopy (tdNIRS), have shown potential for real-time monitoring of AIS patients at the bedside. However, there is a need for further research to evaluate the effectiveness of tdNIRS in the acute phase of stroke. In this study, we present the results of a case report using tdNIRS to monitor AIS patients without any additional stimulation. The tdNIRS technique allows for noninvasively assessing cerebral oxygenation in absolute units, enabling accurate measurement of changes in oxygenated and deoxygenated hemoglobin concentrations in the brain. Our aim was to determine the feasibility of tdNIRS in monitoring AIS patients.

Numerical simulation of non-linear loading– unloading hysteresis behavior of blood clots

Tashiro Koichiro, Shobayashi Yasuhiro, Hotta Atsushi

Biocybernetics and Biomedical Engineering

2022

Vol. 42, no. 4

1205--1217

The stress-strain characteristics of a clot during loading/unloading mechanical cycles are significant features to assess the underlying mechanisms of thrombectomy, especially when multiple thrombectomy attempts are required. We investigated a damage model to predict loading/unloading response of clots. To study the validity of the model, we tested theoretical models to reproduce the experimentally obtained mechanical characteristics of clots under various conditions. Three types of clot analogs with different red blood cell (RBC) compositions were prepared. Cylindrical clot analogs were formed for the tensile and compression tests. Loading/unloading tests at 80% of strain were conducted, where the material parameters were determined by fitting the results to a theoretical curve combining the damage model and the elasto-plastic constitutive model. Through the computation for theoretical curves, unique characteristics of clots were revealed such that the hysteresis loss rate did not change by varying RBC contents, except for the clot created with 0% RBC composition, under compressive loading. In addition, the plastic strain decreased as the RBC content decreased under tensile loading, whereas it increased as the RBC content decreased under compressive loading. A three-dimensional finite element method (FEM) was employed with the determined parameters. The FEM could accurately reproduce the experimental stress-strain curves for all types of clot analogs and for both loading types up to a strain of 80%. The results indicate that the theoretical model which incorporates and combines the damage model and the elasto-plastic constitutive model is applicable to predict the non-linear stress–strain behavior of clots under loading and unloading.