Feasibility of estimating regional mechanical properties of cerebral aneurysms in vivo Simone Balocco a and Oscar Camara b Department of Information and Communication Technologies (DTIC), Centre for Computational Imaging and Simulation Technologies in Biomedicine (CISTIB), Universitat Pompeu Fabra, E08018 Barcelona, Spain and Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), E08018 Barcelona, Spain Elio Vivas, Teresa Sola, and Leopoldo Guimaraens Neuroangiografia Terapèutica J.J.Merland, Hospital General de Catalunya, 08195 Sant Cugat del Vallés, Barcelona, Spain Hugo A. F. Gratama van Andel and Charles B. Majoie Department of Radiology, Academic Medical Centre, Univesity of Amsterdam, P.O. Box 22660, 1100 DD, Amsterdam, The Netherlands José María Pozo c Department of Information and Communication Technologies (DTIC), Centre for Computational Imaging and Simulation Technologies in Biomedicine (CISTIB), Universitat Pompeu Fabra, E08018 Barcelona, Spain and Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), E08018 Barcelona, Spain Bart H. Bijnens d and Alejandro F. Frangi e Department of Information and Communication Technologies (DTIC), Centre for Computational Imaging and Simulation Technologies in Biomedicine (CISTIB), Universitat Pompeu Fabra, E08018 Barcelona, Spain; Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), E08018 Barcelona, Spain; and Institució Catalana de Recerca i Estudis Avançats (ICREA), E08018 Barcelona, Spain Received 10 June 2009; revised 6 February 2010; accepted for publication 8 February 2010; published 22 March 2010 Purpose: In this article, the authors studied the feasibility of estimating regional mechanical prop- erties in cerebral aneurysms, integrating information extracted from imaging and physiological data with generic computational models of the arterial wall behavior. Methods: A data assimilation framework was developed to incorporate patient-specific geometries into a given biomechanical model, whereas wall motion estimates were obtained from applying registration techniques to a pair of simulated MR images and guided the mechanical parameter estimation. A simple incompressible linear and isotropic Hookean model coupled with computa- tional fluid-dynamics was employed as a first approximation for computational purposes. Addition- ally, an automatic clustering technique was developed to reduce the number of parameters to assimilate at the optimization stage and it considerably accelerated the convergence of the simula- tions. Several in silico experiments were designed to assess the influence of aneurysm geometrical characteristics and the accuracy of wall motion estimates on the mechanical property estimates. Hence, the proposed methodology was applied to six real cerebral aneurysms and tested against a varying number of regions with different elasticity, different mesh discretization, imaging reso- lution, and registration configurations. Results: Several in silico experiments were conducted to investigate the feasibility of the proposed workflow, results found suggesting that the estimation of the mechanical properties was mainly influenced by the image spatial resolution and the chosen registration configuration. According to the in silico experiments, the minimal spatial resolution needed to extract wall pulsation measure- ments with enough accuracy to guide the proposed data assimilation framework was of 0.1 mm. Conclusions: Current routine imaging modalities do not have such a high spatial resolution and therefore the proposed data assimilation framework cannot currently be used on in vivo data to reliably estimate regional properties in cerebral aneurysms. Besides, it was observed that the incor- poration of fluid-structure interaction in a biomechanical model with linear and isotropic material properties did not have a substantial influence in the final results. © 2010 American Association of Physicists in Medicine. DOI: 10.1118/1.3355933 Key words: cerebral aneurysms, patient-specific estimation of material properties, biomechanical models, inverse problems 1689 1689 Med. Phys. 37 „4…, April 2010 0094-2405/2010/37„4…/1689/18/$30.00 © 2010 Am. Assoc. Phys. Med.