Multi-Push (MP) ARF assessment of viscoelastic properties in a tissue mimicking phantom effect of time separation

We present a new approach to differentiating the viscoelastic properties of tissue, Multi-Push Acoustic Radiation Force (MP ARF) ultrasound, in which displacements achieved by successive ARF excitations are compared to qualitatively assess viscoelastic tissue parameters. We evaluate the MP ARF measures of marginal peak displacement (MPD) in four tissue-mimicking phantoms using different time separations between successive excitations. A time separation of 0.4 ms between excitations yielded the best contrast when differentiating between a phantom with low stiff, low viscosity and a phantom with high stiffness, low viscosity. Similarly, 0.4 ms between excitations gave the best MPD contrast between a phantom with low stiffness, low viscosity and a phantom with low stiffness, high viscosity. A time separation of 1.2 ms gave the optimal separation when differentiating between a phantom with high stiffness, low viscosity and a phantom with high stiffness, high viscosity. MPD was also shown to be is less depth-dependent than first peak displacement.