Influence of catheter position on estimated strain in intravascular elastography

In elastography, an erroneous strain estimate is obtained when the radial s train and the probing ultrasound beam are not properly aligned: the "strain projection artifact". In practice, an angle between the strain and the ult rasound beam will be present in most of the cases due to inhomogeneities or nonuniform compression. In this study, a theoretical function describing t he strain projection artifact is derived as a function of the angle between the radial strain and the ultrasound beam. Two main factors for an angle b etween strain and ultrasound beam in intravascular elastographic experiment s are eccentricity and tilt of the transducer. The theoretical functions de scribing these errors are corroborated with strain estimates from an experi ment with a circular, homogeneous gel-based vessel phantom. Comparison betw een the theoretical functions and the experimental results reveals that the strain projection artifact is well described by the theoretical findings. As a result, the experimental data can be corrected for this artifact. The corrected elastograms reveal that correct strain estimates are obtained whe n the eccentricity of the intravascular catheter is less than 63%. An "off- the-wall" device may be required to advance intravascular elastography to i n vivo implementation.