High-frequency transducers for forward-viewing intravascular ultrasound guidance

Approximately 750k minimally invasive procedures are performed each year in the U.S. to restore blood flow to coronary and peripheral arteries. Revascularization of stenotic or occluded arteries is commonly performed under fluoroscopy guidance, which provides 2-D projection images. However, current imaging modalities are unable to visualize the anatomy in 3-D or provide imaging of physiology, including hemodynamics, during the procedure. Forward-viewing intravascular ultrasound imaging can provide both anatomical and physiological imaging throughout the procedure; however, specialized high frequency transducers are required. The design, fabrication, and operation of high frequency piezoelectric transducers for intravascular imaging will be presented. In particular, the development of a forward-viewing, 2.0-mm, 16-MHz 2-D array transducer with 136 elements will be described. 3-D imaging with this and other high frequency intravascular transducers will be presented and discussed, in addition to insights in fabrication, modeling, and image formation. Using developed fabrication methods, >90% element yield and −6 dB bandwidth >60% has been achieved with small, high-frequency 2-D arrays. These arrays have demonstrated imaging of blood flow velocity and wall shear stress, a physiological marker related to stenosis development and progression. [Work supported by R01EB031101 from the National Institutes of Health.]