A review on the association of thrombus composition with mechanical and radiological imaging characteristics in acute ischemic stroke.

Thrombus composition and mechanical properties significantly impact the ease and outcomes of thrombectomy procedures in patients with acute ischemic stroke. A wide variation exists in the composition of thrombi between patients. If a relationship can be determined between the composition of a thrombus and its mechanical behaviour, as well as between the composition of a thrombus and its radiological imaging characteristics, then there is the potential to personalise thrombectomy treatment based on each individual thrombus. This review aims to give an overview of the current literature addressing this issue. Here, we present a scoping review detailing associations between thrombus composition, mechanical behaviour and radiological imaging characteristics. We conducted two searches 1) on the association between thrombus composition and the mechanical behaviour of the tissue and 2) on the association between radiological imaging characteristics and thrombus composition in the acute stroke setting. The review suggests that higher fibrin and lower red blood cell (RBC) content contribute to stiffer thrombi independent of the loading mode. Further, platelet-contracted thrombi are stiffer than non-contracted compositional counterparts. Fibrin content contributes to the elastic portion of viscoelastic behaviour while RBC content contributes to the viscous portion. It is possible to identify fibrin-rich or RBC-rich thrombi with computed tomography and magnetic resonance imaging vessel signs. Standardisation is required to quantify the association between thrombus density on non-contrast computed tomography and the RBC content. The characterisation of the thrombus fibrin network has not been addressed so far in radiological imaging but may be essential for the prediction of device-tissue interactions and distal thrombus embolization. The association between platelet-driven clot contraction and radiological imaging characteristics has not been explicitly investigated. However, evidence suggests that perviousness may be a marker of clot contraction.

Development of a Soft Tissue Elastography Robotic Arm (STiERA).

High fidelity surgical simulations must rely upon accurate soft tissue models to ensure realism of the simulations. Simulating multi-layer tissue becomes increasingly complex due to the specific mechanical properties of each individual layer. We have developed a Soft Tissue Elastography Robotic Arm (STiERA) system capable of identifying layer specific properties of multi-layer constructs while maintaining the integrity of each layer. The system was validated using tissue mimicking agar gel phantoms and showed great promise by identifying the layer specific properties with accuracy of greater than 80% when compared to known ground truth values from a commercial material testing system.