McGee, O. M. | Search bioRxiv

bioRxiv2021

An Investigation into Patient-Specific 3D Printed Titanium Stents and the use of Etching to Overcome Selective Laser Melting Design Constraints.

There is currently a clear clinical need in the area of stenting for paediatric patients, whereby currently commercially available adult stents are often required to be used off-label for paediatric patients resulting in less than optimal outcomes. The increasingly widespread use of CT and/or MR imaging for pre-surgical assessment, and the emergence of additive manufacturing processes such as 3D printing, could enable bespoke devices to be produced efficiently and cost-effectively. However, 3D printed metallic stents need to be self-supporting leading to limitations in the design of stents available through additive manufacturing. In this study we investigate the use of etching to overcome these design constraints and improve stent surface finish. Furthermore, using a combination of experimental bench testing and finite element methods we investigate how etching influences stent performance and using an inverse finite element approach the material properties of the printed and etched stents were calibrated and compared. Finally, using patient-specific finite element models the stent performance was tested to assess patient outcomes. Within this study, etching is confirmed as a means to create open-cell stent designs whilst conforming to additive manufacturing rules and concomitantly improving stent surface finish. Additionally, the feasibility of using an in-vivo imaging to product development pipeline is demonstrated that enables patient-specific stents to be produced for varying anatomies to achieve optimum device performance. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/434132v1_fig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@1aafa72org.highwire.dtl.DTLVardef@205339org.highwire.dtl.DTLVardef@37c33forg.highwire.dtl.DTLVardef@f3832a_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO Graphical abstract. C_FIG

bioengineering↗

bioRxiv2021

A Patient-Specific Model of Transcatheter Valve Replacement in aBicuspid Heart Valve

Bicuspid Aortic Valves (BAVs) are a common congenital heart disease where two cusps of the aortic heart valve become fused together, this leads to two unequally sized leaflets compared to the normal trileaflet valve. Transcatheter Aortic Valves are currently used in off-label treatmet of stenosed BAVs, however, due to the abnormal valve anatomy, debate surrounds the sizing of transcatheter valves. In this study, finite element models were developed to simulate the deployment of two different valves sizes (a 25 mm and a 27 mm) of the Lotus valve into the patient-specific aortic root geometry of a clinical stenosed BAV case. These models were used to investigate and compare the eccentricity, stress and mal-apposition of the two valve sizes. The results demonstrated that the 25 mm valve was the most suitable in terms of eccentricity and stress reduction. It was also shown that the smaller 25 mm valve size did not increase the likelihood of mal-apposition. As the 25 mm valve was deemed suitable based on current sizing algorithms, on the basis of these results traditional annulus measurement and device sizing may be suitable in the case of the Lotus valve.

bioengineering↗