Acoustic radiation force impulse imaging: a parametric analysis of factors affecting image quality

Acoustic radiation force impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the mechanical properties of tissue. The goal of this work was to perform a parametric analysis of the effect of system parameters and target characteristics on image quality. METHODS: FEM simulations and phantom experiments have been performed using varying system configurations and tissue properties to determine their impact on ARFI image quality. Phantom experimental results were utilized to validate the FEM models. RESULTS: Matched simulation and FEM experiments support the validity of the FEM model. Due to the dynamic nature of ARFI excitation, lesion contrast is temporally dependent. Contrast efficiencies (CE) were computed immediately after force cessation, prior to appreciable wave propagation. CE does not vary with applied force, increases with lesion stiffness, and increases as the forcing volume size decreases with respect to the size of the structure being imaged. CONCLUSIONS: The response of tissue to ARFI excitation is complex and depends upon tissue geometry, forcing function geometry, and tissue mechanical and acoustic properties. These studies indicate that improved contrast in ARFI images will be achieved as forcing volume size decreases relative to the structure being imaged. Frame rate and thermal considerations present tradeoffs with small load volume sizes for ARFI imaging.