Measuring the curvature and radiation distribution of spherically focused ultrasound transducers using the electric continuity and the emitted pressure

Focused ultrasound has been used in clinic for the treatment of different diseases, but predominantly in oncology. The main characteristic of this technique is the production of a strongly focused acoustic field composed by a near-field and far-field zones, separated by a well-defined focus. Usually, due to the complexity of the vibration of real transducers, this acoustic field is assumed to be produced by a uniform vibrating curved radiator, with a characteristic but unreal acoustic field. If the radiation of the transducer is not uniform, the acoustic field changes importantly. In this paper, we are proposing a technique to characterize the shape of the focused transducers and to measure the radiation distribution very close to the transducer radiating curved surface. The technique uses the electric continuity to detect the position of the transducer surface at each point using a 3D automated positioner (6.4 μm of step resolution). The position is saved, and another measurement is carried out using a hydrophone to measure the pressure at each same point, and obtain the radiating profile. The technique has shown to be appropriate for determining the transducer's shape, with a resolution limited by the positioning system. The pressure radiating profile shown a ring-type behaviors as expected.