Systems and methods for ultrasound imaging capable of achieving spatial resolutions that can resolve objects smaller than 300 µ?? are described. Ultrasound is transmitted to and steered over a volume-of-interest that contains a microbubble contrast agent to individually excite microbubbles. Signal data is acquired in response to the transmitted ultrasound, and a plurality of images are reconstructed by beamforming the acquired signal data. The spatial resolution of the beamformed images can be further increased using techniques that determine the position of the microbubble within each image to a greater level of accuracy than the point spread function ("PSF") of the ultrasound system. The images can also be combined to produce a single high resolution image of the volume-of-interest using, for instance, a maximum pixel projection technique.
