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Image-Based Mechanical Analysis of Stent Deformation. Concept and Exemplary Implementation for TAVI Stents

Michael Gessat, Raoul Hopf, Thomas Pollok, Christoph Russ, Thomas Frauenfelder, Simon H Sündermann, Sven Hirsch, Edoardo Mazza, Gábor Székely, and Volkmar Falk
IEEE Transactions on Biomedical Engineering
Vol. 60, No. 1, pp. 4-15, January 2014

Abstract

An approach for extracting the radial force load on an implanted stent from medical images is proposed. To exemplify the approach, a system is presented which computes radial force estimation from computer tomography images acquired from patients who underwent Transcatheter Aortic Valve Implantation (TAVI). The deformed shape of the implanted valve prosthesis' Nitinol frame is extracted from the images. A set of displacement vectors is computed that parameterizes the observed deformation. An iterative relaxation algorithm is employed to adapt the information extracted from the images to a finite element model of the stent and the radial components of the interaction forces between stent and tissue are extracted. For evaluation of the method, tests were run using clinical data from 21 patients; stent modeling and extraction of radial forces was successful in 18 cases. Synthetic test cases were generated in addition for assessing sensitivity to measurement errors. In a sensitivity analysis, the geometric error of the stent reconstruction was below 0.3, which is below image resolution. The distribution of radial forces are qualitatively and quantitatively reasonable. An uncertainty remains in the quantitative evaluation of the radial forces due to the uncertainty in defining a radial direction on the deformed stent. With our approach, the mechanical situation of TAVI stents after implantation can be studied in-vivo, which may help to understand the mechanisms that lead to complications and improve stent design.


Link to publisher's page
@Article{eth_biwi_01046,
  author = {Michael Gessat and Raoul Hopf and Thomas Pollok and Christoph Russ and Thomas Frauenfelder and Simon H S\"undermann and Sven Hirsch and Edoardo Mazza and Gábor Székely and and Volkmar Falk},
  title = {Image-Based Mechanical Analysis of Stent Deformation. Concept and Exemplary Implementation for TAVI Stents},
  journal = {IEEE Transactions on Biomedical Engineering},
  year = {2014},
  month = {January},
  pages = {4-15},
  volume = {60},
  number = {1},
  keywords = {Biomedical image processing, biomedical imaging, biomechanical simulation, finite element analysis, implants}
}