The accurate and reliable operation of medical devices is of utmost importance, as any reduction in their quality may lead to fatal consequences or cause injury. In this context, Electromagnetic Interference (EMI) and Signal Integrity (SI) are critical factors that must be taken into consideration during the design process of medical devices. This chapter discusses the noise source in printed circuit boards (PCBs), which can adversely affect the performance of medical devices. The chapter also provides insights on how to reduce the impact of noise, including the use of a clear return path toward the ground plane and a hybrid configuration for high-frequency signals. By understanding the physical behavior of SI problems from an EM perspective, medical device designers can address these issues and ensure the reliable operation of medical devices.