Medical uses of ultrasound came about shortly after the close of World War II, derived from underwater sonar research. Initial clinical applications monitored changes in the propagation of pulses through the brain to detect intacerebral hematoma and brain tumors based on the displacement of the midline. Ultrasound rapidly progressed through the 1960s from simple "A-mode" scans to "B-mode" application and compound "B-mode" images using analog electronics. Advances in equipment design, data acquisition techniques, and data processing capabilities have led to electronic transducer arrays, digital electronics, and real time image display. This progress is changing the scope of ultrasound and its applications in diagnostic radiology and other areas of medicine, such as high resolution, real time imaging, harmonic imaging, 3D data acquisition, and power Doppler are a few of the innovations introduced into clinical practice.