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 InSensor (TM) TF2100 PZT paste. The outer element was mould with Ferroperm (TM) Pz26 and a curved porous Ferroperm (TM) 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 (R) 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.