Modeling geometric artefacts in intravascular ultrasound imaging

A model has been developed for estimating the geometric distortions in intr avascular ultrasound (NUS) imaging caused by the position of the ultrasound catheter within the artery. Geometric distortion causes degradation on cro ss-sectional images of the vessel wall where, for characteristic positionin g of the transducer within the vessel, a circular artery is seen on IVUS im ages as a noncircular vessel represented by more or less complex shapes, Ar tefacts, therefore, have a clinical impact on the accuracy of qualitative a nd quantitative intravascular analyses. The main distortions are due to the inclination and the off-centered position of the transducer within the ves sel. These effects are increased by two factors: first, the point of origin of the ultrasound beam does not coincide with the rotation axis of the cat heter; second, in the case of a mechanical rotating transducer, the ultraso und beam is not perpendicular to the long axis of the catheter, but has an inclination such that the transducer looks forward from the emitting point. All these parameters are taken into account in the three-dimensional (3-D) geometric model developed in this paper. The model was formulated to predi ct the geometric deformation for artery contour of various shapes and can m odel artefacts during stent implantation (Finet et al, 1998), Simulations w ere made for various geometric configurations and compared to in vitro and in vivo IVUS images. The model results are consistent with the experimental results. Finally, the model was used for estimating the values of the geom etric parameters that cause distortions on ultrasonic images. (C) 1999 Worl d Federation for Ultrasound in Medicine & Biology.