Investigating the Relationship Between Clinical Image Characteristics and Mechanical Properties of In Vitro Thrombi in Acute Ischemic Stroke

Abstract

Stroke, currently ranked as the second leading cause of mortality and the most prevalent source of enduring disability, imposes significant societal and economic consequences. These consequences encompass the necessity for extended care, rehabilitation, and the economic burdens associated with lost productivity. In the diagnostic process, physicians typically employ imaging techniques to assess cerebral blood vessels, ruling out alternative conditions when stroke is suspected. Subsequent to di agnosis, treatments like Intravenous Thrombolysis (IVT) and Endovascular Thrombectomy (EVT) are administered to either dissolve or retrieve thrombi. However, with EVT emerging as the new standard of stroke care and an increasing body of evidence indicating the substantial impact of thrombus me chanical properties on thrombectomy success, the use of clot analogues is gaining prominence as a means of facilitating efficient mechanical testing, both in terms of time and finances. By establishing a link between mechanical properties and image characteristic parameters, medical practitioners gain a better understanding of intracranial thrombi before embarking on surgical procedures. This knowledge can serve as a theoretical foundation for optimizing surgical instruments and devising effective surgical protocols in the future. In pursuit of these objectives, this study involved 29 patients and entailed several key steps: firstly, the extraction of imaging parameters from pre-EVT CT images; secondly, the creation of thrombus analogues from the patient’s blood; thirdly, the execution of five distinct mechanical tests to derive me chanical properties, encompassing cyclic compression, compression relaxation, tensile test to failure, tensile relaxation, and fracture testing. Additionally, the hyperelastic Yeoh model was utilized to simu late the behavior observed from cyclic compression and tensile to failure test. Prony series (n=2) was fitted to stress relaxation curves. In summary, this investigation revealed noteworthy observations pertaining to mechanical proper ties. Notably, hysteresis areas demonstrated robust and statistically significant correlations with com pression high-strain stiffness, low-strain stiffness, and tensile stiffness along with the ultimate tensile stress, implying that the thrombus analogue exhibits both hyperelastic and viscoelastic characteristics. In the domain of imaging parameters, the evident interdependence among the densities of the three regions of interest within both CTA and NCCT is apparent, respectively. However, it is essential to un derscore that the relationship between CTA and NCCT was not deemed statistically significant. Lastly, a noteworthy revelation was the strong negative monotonic correlation (ρ=-0.82, P=0.011) observed between the analogue contraction ratio of the thrombus analogue and the density of the middle part of NCCT in actual thrombi. This insight suggests that, in addition to thrombus composition, microstructure plays a pivotal role as well in determining their properties.