Combining micro computed tomography and three-dimensional registration to evaluate local strains in shape memory scaffolds.

Appropriate mechanical stimulation of bony tissue enhances osseointegration of load-bearing implants. Uniaxial compression of porous implants locally results in tensile and compressive strains. Their experimental determination is the objective of this study. Selective laser melting is applied to produce open-porous NiTi scaffolds of cubic units. To measure displacement and strain fields within the compressed scaffold, the authors took advantage of synchrotron radiation-based micro computed tomography during temperature increase and non-rigid three-dimensional data registration. Uniaxial scaffold compression of 6% led to local compressive and tensile strains of up to 15%. The experiments validate modeling by means of the finite element method. Increasing the temperature during the tomography experiment from 15 to 37°C at a rate of 4 K h(-1), one can locally identify the phase transition from martensite to austenite. It starts at ≈ 24°C on the scaffolds bottom, proceeds up towards the top and terminates at ≈ 34°C on the periphery of the scaffold. The results allow not only design optimization of the scaffold architecture, but also estimation of maximal displacements before cracks are initiated and of optimized mechanical stimuli around porous metallic load-bearing implants within the physiological temperature range.

Rapid vessel prototyping: vascular modeling using 3t magnetic resonance angiography and rapid prototyping technology.

OBJECT: Conversion of thoracic aortic vasculature as measured by Magnetic Resonance Imaging into a real physical replica. MATERIALS AND METHODS: Several procedural steps including data acquisition with contrast enhanced MR Angiography at 3T, data visualization and 3D computer model generation, as well as rapid prototyping were used to construct an in-vitro model of the vessel geometry. RESULTS: A rapid vessel prototyping process was implemented and used to convert complex vascular geometry of the entire thoracic aorta and major branching arteries into a real physical replica with large anatomical coverage and high spatial resolution. CONCLUSION: Rapid vessel prototyping permits the creation of a concrete solid replica of a patient's vascular anatomy.