Small aperture, dual frequency ultrasound transducers for intravascular contrast imaging

Intravascular ultrasound imaging is a powerful tool in assessing cardiovascular diseases, and contrast enhanced ultrasound imaging has the ability to generate high signal to noise ratio images and can provide information such as degree of plaque vascularization and molecular function. Currently, however, contrast enhanced intravascular ultrasound (CE-IVUS) imaging has not been used clinically. Design, fabrication, and characterization of a small aperture (0.6 × 3 mm), dual frequency ultrasound transducer were performed, followed by microbubble tests for viability study of CE-IVUS imaging. Results show that more than 1.23 MPa (mechanical index: 0.48) was generated by the 6.5 MHz transmission component at the imaging area, where nonlinear response of microbubbles was detected by the 30 MHz broadband (-6dB bandwidth: 58.6%) receiving component. Nonlinear echo response from microbubbles flowing through a micro-tube with diameter of 0.2 mm was clearly detected with a signal to noise ratio higher than 12 dB. These promising results show that small aperture, dual frequency transducers are capable of detecting contrast agents using split frequency detection methods and suggest they are a reasonable platform for CE-IVUS imaging.