High frequency contrast imaging

Ultrasound contrast agents enhance echoes from the microvasculature and enable the visualization of flow in smaller vessels. We optically and acoustically investigate the dynamics of a microbubble with 10 MHz ultrasound insonation. Results of a numerical evaluation of the modified Rayleigh-Plesset equation are used to predict the dynamics of a microbubble. From the optical observations of a single microbubble, nonlinear oscillation (such as subharmonic components), destruction and radiation force are observed. The maximum bubble expansion using a 20 cycle 10 MHz chirp with pressure up to 3.5 MPa has been tested with initial diameters ranging from 1.5 to 5 μm, resulting in a maximum diameter kept below 8 μm. Optical and acoustical experiments provide insight into the mechanisms of destruction, including fragmentation and acoustically-driven diffusion. High frequency pulse transmission may provide the opportunity to detect contrast echoes resulting from a single pulse, may be robust in the presence of tissue motion, and may provide the opportunity to incorporate high frequency ultrasound into destruction-replenishment techniques.