High Resolution Ultrasound in Interventional Radiology

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We seek to create a real-time ultrasound imaging tool for guiding interventions, with resolution that exceeds that obtained using CT but without the need for radiation or iodinated contrast agents. Advancements in medical imaging and device technology allow minimally-invasive procedures for the diagnosis and treatment of various disorders. Real-time ultrasound has become an integral aspect of many image-guided interventions. Advantages of US imaging include the low cost, lack of ionizing radiation and real-time visualization of anatomy and physiology. Our approach will be to: 1) create an extended aperture 2D transducer (512 by 16 elements) capable of imaging an extended azimuthal field of 9 cm with in-plane resolution of hundreds of microns (to provide a wide field of view at high resolution), 2) apply the 2D array to image multiple adjacent planes (to facilitate the view of biopsy needles or ablations), 3) achieve a 30 volume per second update rate by using plane wave transmissions to enhance contrast imaging modes and implement novel beam formation algorithms, 4) integrate methods for aberration correction, and 5) apply this technology in B-Mode, color Doppler, volumetric vector flow imaging and contrast imaging. The array will be realized using tiled modules that can be switched in a mode-dependent fashion to accomplish B-Mode imaging, color Doppler and contrast imaging. Over the past 4 years, Stanford and the University of Southern California have designed an adult extended-aperture abdominal-imaging system and demonstrated the improved spatial resolution, field of view and contrast that can be achieved. We exploit these tools here to develop a high-volume rate capability for monitoring liver interventions. Our aims to accomplish this are to: 1) Create and integrate tileable acoustic/electronic modules to implement signal buffering and multiplexing and create a large aperture array with elevational focusing. Utilizing newly designed Integrated Circuits (IC)’s and highly sensitive and wide-bandwidth single crystal transducer material, we will construct individual 2D array modules with co-integrated transducers and electronics. 2) Optimize the protocols for guiding biopsy and ablation in phantom and animal studies. A) Create software for imaging of small lesions and microwave ablation. We will implement singular value decomposition (SVD) based beam formation for aberration correction. B) Evaluate performance in phantoms and ex vivo tissue. C) Assess speed and accuracy of needle placements. D) Conduct contrast imaging and ablative studies in porcine liver in vivo. 3) Conduct diagnostic and interventional imaging studies as a proof of concept. A) Test the protocols to image the liver of adult volunteers and establish the signal to noise ratio in vivo as compared with phantoms. B) Assess 3D visualization of liver vasculature and lesions in patients referred for MR or CT imaging of a liver lesion. C) Compare the 3D visualization of ablated zones to contrast-enhanced CT (CECT) in patients that are referred for liver ablation.