Our lab develops and implements ultrasonic beamforming methods, ultrasonic imaging modalities, and ultrasonic devices for diagnostic imaging applications. Our current focus is on beamforming methods that are capable of generating high-quality images in the difficult-to-image patient population. These methods include general B-mode and Doppler imaging techniques that utilize additional information from the ultrasonic wavefields. We attempt to build these imaging methods into real-time imaging systems in order to apply them to clinical applications. In addition, our lab develops ultrasonic imaging devices, such as small, intravascular ultrasound (IVUS) arrays that are capable of generating high acoustic output. These arrays are capable of generating radiation force in order to push on tissue to elucidate the mechanical properties and structure of vascular plaques, but can be utilized for therapeutic applications of ultrasound as well.
Current projects in our lab involve the simulation of nonlinear, acoustic wave propagation under complex models of human anatomy and the impact of anatomy and acoustic parameters on the resulting images. Often, the anatomy and acoustic parameters are the source of aberration and diffuse reverberation of the wavefronts, both of which contribute to image clutter. In addition to modeling and understanding these sources of clutter, we have developed imaging methods that utilize the spatial coherence of the ultrasonic wavefields in order to mitigate the impact of ultrasonic clutter (called short-lag spatial coherence [SLSC] imaging and coherent flow power Doppler [CFPD] imaging). These methods demonstrate significant improvement in image quality and the ability to detect slow flow.
Because the SLSC and CFPD imaging techniques require the individual channel signals from transducer arrays, these methods are difficult to integrate in current ultrasonic imaging scanners, where specialized hardware is utilized to generate real-time images. We have developed a prototype imaging system capable of implementing SLSC in real time. The system is currently capable of generating 10-20 frames per second of matched B-mode (conventional) and SLSC images. We are currently developing methods and approximations to the spatial coherence functions in order to increase the real-time display. This system will be utilized in clinical studies of cardiac function and focal liver lesions to compare the performance of SLSC and B-mode imaging.
We are also currently developing IVUS and catheter-based arrays to implement radiation-force based imaging techniques, such as Acoustic Radiation Force Impulse (ARFI) imaging and Shear Wave Elastography Imaging (SWEI). IVUS and catheter-based imaging transducers are generally high-frequency transducers that are capable of generating conventional B-mode displays. However, due to their small size and high frequency, they are often incapable of generating radiation forces in order to probe the mechanical properties of these tissues. We are currently building prototype IVUS and catheter transducers and arrays for the express purpose of generating radiation forces and high acoustic outputs.