Description: We developed computer simulation method and software to investigate the effect of radiofrequency field (RF) on MRI signal intensity at ultra-high field strength, RF coil design and RF safety. The outcome clarified the mechanism of both RF field non-uniformity and MR signal inhomogeneity and enabled us to characterize phase and magnitude of the transmit field and receive sensitivity. These solutions have been used to evaluate patient safety from absorbed RF energy and improve the design of RF coils at high field. The method with the computer simulation greatly reduced the cost for advancement of MRI hardware and evaluation of RF safety. These studies demonstrated my ability to apply computer simulation to solve the problems and difficulties presented by MRI techniques and applications.