Subharmonic contrast intravascular ultrasound for vasa vasorum imaging.

The feasibility of subharmonic contrast intravascular ultrasound (IVUS) imaging was investigated using a prototype nonlinear IVUS system and the commercial contrast agent Definity . The system employed a mechanically scanned commercial catheter with a custom transducer element fabricated to have sensitivity at both 15 and 30 MHz. Experiments were conducted at a fundamental frequency of 30 MHz (F30; 25% bandwidth), with on-axis pressures ranging from 0.