An Integrated System for Superharmonic Contrast Enhanced Ultrasound Imaging: Design and Intravascular Phantom Imaging Study
Objective: Superharmonic contrast enhanced ultrasound imaging, also called acoustic angiography, has previously been used for the imaging of microvasculature. This approach excites microbubble contrast agents near their resonance frequency and receives echoes at nonoverlapping superharmonic bandwidths. No integrated system currently exists could fully support this application. To fulfill this need, an integrated dual channel transmit/receive system for superharmonic imaging was designed, built, and characterized experimentally. Method: The system was uniquely designed for superharmonic imaging and high resolution B mode imaging. A complete ultrasound system including a pulse generator, a data acquisition unit, and a signal processing unit were integrated into a single package. The system was controlled by a field programmable gate array, on which multiple user defined modes were implemented. A 6 35 MHz dual frequency dual element intravascular ultrasound transducer was designed and used for imaging. Result: The system successfully obtained high resolution B mode images of coronary artery ex vivo with 45 dB dynamic range. The system was capable of acquiring in vitro superharmonic images of a vasa vasorum mimicking phantom with 30 dB contrast. It could detect a contrast agent filled tissue mimicking tube of 200 mm diameter. Conclusion: For the first time, high resolution B mode images and superharmonic images were obtained in an intravascular phantom, made possible by the dedicated integrated system proposed. The system greatly reduced the cost and complexity of the superharmonic imaging intended for preclinical study. Significant: The system showed promise for high contrast intravascular microvascular imaging, which may have significant importance in assessment of the vasa vasorum associated with atherosclerotic plaques.
IEEE Transactions on Biomedical Engineering