Effect of Radial Displacement of Lens on Response of Focused Ultrasonic Transducer

Abstract

A lens-focused single-element transducer designed for high-resolution medical imaging requires a high ratio of radius of curvature to source radius. Therefore, classical models neglecting the radial contribution may not be accurate. The objective of this study is to evaluate the contribution of radial displacement to the pressure response of the transducer, both in terms of focal spot and pulse response characteristics. To achieve this objective, two finite element method calculations (FEM) were performed (commercial atila® software), namely those for free and clamped radial displacements. A propagation code adapted to an axisymmetric transducer geometry was implemented to compare the radiated fields, and FEM results for the transducer surface were used as inputs to obtain the radiated fields. Subsequently, the differences between the results of the two calculations results were determined. However, it was demonstrated that the radial displacements slightly affect the propagated field and can therefore be neglected in realistic transducer designs. Moreover, the effects of lens acoustic properties were studied for realistic configurations in terms of resolution and sensitivity to obtain an optimal ultrasound image quality.