Imaging of microvasculature can be valuable for the diagnosis and treatment monitoring of cancer and other diseases. Ultrasound has the potential due to its excellent spatial and temporal resolution. Super-resolution ultrasound imaging using contrast enhanced ultrasound localization microscopy is able to visualize microvasculature beyond the wave diffraction limit. The microbubble based super-resolution depends on controlling the bubble concentration, which needs to be low enough to locate isolated microbubbles. However too low a concentration will prolong the data acquisition. The aim of the thesis was to evaluate the impact of microbubble concentration on super-resolution ultrasound imaging, and to improve the signal processing in super-resolution imaging. First, various concentrations of microbubble contrast agents (6×10^3 to 1.5×10^6particles/ml) were injected into a 200 microns cross-tube flow phantom. The experimental results show that the concentration affects the resolution of the cross-tube images. When the concentration is lower than the 1.5×10^5particles/ml, two tubes in a selected region of interest near the intersection that are 370 microns apart can be separated, which is close to the expected distance (390 microns). Second, the comprehensive effects of data acquisition time and concentration on imaging resolution were studied. The preferred range of concentration was determined between 1.5×10^4 to 6×10^4particles/ml. This result can be used to better inform data acquisition in the further research. Third, a weight adaptive denoising method based on morphology was developed to remove noises which were produced in the step of microbubble detection at the preferred range of concentration. Therefore, the resolution and the accuracy of the velocity map were further improved.