An experimental characterization of elastographic spatial resolution: analysis of the trade-offs between spatial resolution and contrast-to-noise ratio

An experimental study of the spatial resolution in elastography was conducted. Models that involved two cylindrical inclusions arranged as a wedge were used to characterize the axial and lateral resolution of the axial strain elastograms. A study of the dependence of the spatial resolution on several factors such as the algorithmic parameters, the applied strain and the modulus contrast was performed. The axial resolution was found to show a linear dependence with respect to the algorithmic parameters, namely the window length and the window shift used for strain estimation. The lateral resolution showed a weak dependence on the algorithmic parameters. A weak dependence of the spatial resolution on factors such as the modulus contrast and the applied strain was found. The trade-offs between the spatial resolution and the elastographic contrast-to-noise ratio (CNR(e)) were then analyzed. A nonlinear trade-off between the CNR(e) and the axial and lateral resolution was shown for conventional strain estimation techniques, with the CNR(e) improving at a more than linear rate with respect to a linear degradation in the resolution. This study provided an experimental framework for characterizing the spatial resolution in elastography and facilitating a comparison of the CNR(e) with spatial resolution.