Detection of harmonic ultrasound scattered from microbubbles with ultrasound transducer for harmonic imaging having double peak type frequency characteristics

摘要

Ultrasound transducer with double peak type frequency characteristics was proposed for contrast harmonic imaging. It can transmit ultrasound in a fundamental mode and receive the second harmonic signal from tissues or microbubble contrast agents. The transducer has been made by stacking a piezoelectric ceramic vibrator and a subvibrating plate on the backing block made of ferrite rubber with an acoustic absorption. Glass subvibrating plate (0.4 mm thick) was found suitable for this ultrasound transducer. The second harmonic component contained in the scattered waves from microbubbles coated with surfactant wad detected experimentally with a trial manufactured ultrasound transducer with double peak type frequency characteristics. The results confirmed that the transducer can transmit ultrasound to microbubbles, excite the second harmonic component based on the nonlinear behavior of microbubbles and detect the second harmonic component. It was also found that the second harmonic component can be detected most effectively when burst waves with cycles from 5 to 10 were applied to the ultrasound transducer.