Sander De Bock

Feasibility of a priori numerical assessment of plaque scaffolding after carotid artery stenting in clinical routine: proof of concept.

Purpose Carotid artery stenting (CAS) is an alternative procedure for the treatment of severely stenosed carotid artery lesions in high-risk patients. Appropriate patient selection and stent design are paramount to achieve a low stroke and death rate in these complex high-risk procedures. This study introduces and evaluates a novel virtual, patient-specific, pre-operative environment to quantify scaffolding parameters based on routine imaging techniques. Methods Two patients who underwent CAS with two different sizes of the Acculink stent (Abbott Vascular, Santa Clara, CA, USA) were studied. Pre-operative data were used to build the numerical models for the virtual procedure. Numerical results were validated with post-operative angiography. Using novel virtual geometrical tools, incomplete stent apposition, free cell area and largest fitting sphere in the stent cell were evaluated in situ as quantitative measures of successful stent placement and to assess potential risk factors for CAS complications. Results A quantitative validation of the numerical outcome with post-operative images noted differences in lumen diameter of 5.31 ± 8.05% and 4.12 ± 9.84%, demonstrating the reliability of the proposed methodology. The quantitative measurements of the scaffolding parameters on the virtually deployed stent geometry highlight the variability of the device behavior in relation to the target lesion. The free cell area depends on the target diameter and oversizing, while the largest fitting spheres and apposition values are influenced by the local concavity and convexity of the vessel. Conclusions The proposed virtual environment may be an additional tool for endovascular specialists especially in complex anatomical cases where stent design and positioning may have a higher impact on procedural success and outcome.

Supersonic shear wave imaging to assess arterial anisotropy: Ex-vivo testing of the horse aorta

Supersonic shear wave imaging (SSI) has recently emerged as a reliable technique for soft tissue characterization in bulk tissues (e.g. in the context of breast and liver cancer diagnostics). Another promising application of SSI is arterial stiffness assessment, though challenged by complex shear wave (SW) propagation phenomena in this thin-walled setting such as guided waves, dispersion, reflection and refraction on the arterial walls. Therefore, we investigated the sensitivity of SSI to (i) stretch-induced stiffening and (ii) the arterial fiber organization in a simpler ex-vivo arterial setup based on equine aortic tissue, where the SW propagation is deprived of dispersion and guided-wave effects. For this purpose, we conducted simultaneous dynamic mechanical testing of the tissue along with SSI measurements. The probe was rotated around its axis relative to the tissue to investigate whether SSI is able to determine the dominant collagen fiber direction in the tissue. The cyclic behavior of the SW velocities as a response to the dynamic mechanical testing demonstrated the ability of SSI to detect stretch-induced stiffening, though mainly in the circumferential direction. Furthermore, SW velocities were lower when the probe was positioned away from the circumferential direction of the tissue, which could be explained due to the uni-axial testing, the arterial anisotropy and the progressive recruitment of collagen fibers in the circumferential direction. The elasticity modulus assessed from the SSI measurements and the mechanical testing demonstrated the feasibility of SSI to detect the increase in E-modulus as expected from the measured stress-strain curve (factor 2.1 versus 2.3 increase for SSI and mechanical testing respectively). Future work will include performing histology on the investigated tissue to confirm these findings and clarify the link between SSI measurements and the actual fiber orientation.