Dual-frequency transducer for nonlinear contrast agent imaging

A new transducer for superharmonic and subharmonic contrast imaging was designed. This transducer was constituted of two elements: the outer low frequency (LF) element was centered at 4 MHz while a high frequency element (HF) was centered at 14 MHz. The center element was pad printed using InSensorTM TF2100 PZT paste. The outer element was mould with FerropermTM Pz26 and a curved porous FerropermTM Pz37 was used as backing. Each piezoelectric element was characterized to deduce electromechanical performance with thickness coupling factor around 45%. After the assembly of the transducer, pulse echo and hydrophone measurements were performed showing a large bandwidth (70% at -3dB) of the HF element. Finally, experiments with BR14^® microbubbles were performed. Both superharmonic and subharmonic components were successfully observed from microbubble responses. The wide bandwidth of HF allows the detection of five harmonics with a good sensitivity.