This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book introduces an implementation effort of nonmainstream processing schemes in real-time systems. It discusses in some detail the recent developments in adaptive, high-resolution and synthetic aperture array signal processing and their advantages for real-time system applications. The book reviews the basic issues involved in the study of adaptive systems for signal processing. It analyses the system concept similarities between sonar and ultrasound systems in order to exploit the use of model-based sonar signal processing concepts in ultrasound problems. The book addresses a major issue: the implementation of advanced processing schemes in real-time systems of interest. It discusses in detail the conventional, adaptive and synthetic aperture beamformers that can be implemented in the block of the generic processing structure.