Adaptive beamforming contrast enhanced super resolution imaging for improved sensitivity and resolution in deep tissues

Ultrasound contrast enhanced super resolution imaging has recently attracted extensive attention due to its extraordinary resolution. Vessels that were detected in small animals with ultrafast plane wave imaging sequences were about ten fold smaller than the resolution predicted by a the classical diffraction limit. However the imaging depth in small animals is shallow. To translate this technology to clinical use in humans, it is necessary to detect small vessels at deeper locations. In this study, we propose an “adaptive multifocus” ultrasound imaging sequence that combines the high frame rate feature of a plane wave imaging with the increased bubble detection sensitivity of a focused beam. This sequence targets two or more foci with a single emission, hence retaining a high frame rate comparable to plane wave imaging. Numerical simulations and ex vivo experiments with microtubes embedded in porcine tissue were performed to determine the improvements in penetration and detectability. Results show that the adaptive multifocus sequence improves microbubble detection sensitivity by a factor of 8 when compared to conventional methods. This translates to improved penetration. For example it is demonstrated that a 105 μm microtube can be detected as deep as 55 mm, which would not be detectable using conventional sequences.