Development of transmitters in dual-frequency transducers for interventional contrast enhanced imaging and acoustic angiography

Spatial limitation can be a challenge to interventional ultrasound transducers for dual-frequency contrast-enhanced ultrasound imaging, or acoustic angiography. A low frequency (< 3 MHz) transmission with moderate peak negative pressure (PNP) and short pulse length is not easily attainable within limited dimensions. In this paper, a new design of the low frequency transmitter of dual-frequency transducers is presented. 1-3 composites for interventional transmitter design were analyzed by the Krimholtz-Leedom-Matthaei (KLM) model and finite element analysis (FEA). The dual frequency transducer prototype with a 2 MHz 1-3 composite transmitter and a 14 MHz receiver was fabricated and characterized, followed by microbubble detection tests. The transmitter showed the peak negative pressure (PNP) of -1.5 MPa. The -6 dB pulse echo fractional bandwidth for the transmitter and receiver were 61 % and 45 %, respectively. The prototyped dual frequency transducer was used to successfully excite microbubbles and to detect super harmonic responses from microbubbles. The measured harmonic signal showed a 12 dB contrast-to-noise ratio (CNR).