Power Drive Circuits for Diagnostic Medical Ultrasound

Ultrasound imaging is widely used as a medical diagnostic tool by providing both anatomical and physiological information. In cardiology, the heart´s shape and motion are visualized in addition to the blood´s flow pattern. In radiology, various tumors, inflammatory diseases and other malignancies can be detected. Ultrasound is the best-suited diagnostic modality to visualize homodynamics in organs and the vascular system. An ultrasound image is acquired by launching acoustic waves and receiving echoes that are reflected from cell boundaries. The role of power electronics in medical ultrasound arises from the specific requirements of launching the acoustic waves. The waves are generated with transducers made of ferroelectric material. The transducer is electrically excited and the ferroelectric material creates a vibration that couples as a wave into the human body. Generating this electrical waveform poses a substantial challenge. The electrical load impedance is typically highly capacitive and drive signals of several hundred volts are required to generate the necessary acoustic pressure. Further, the introduction of 2D arrays requires that several thousand parallel drive circuits be placed in a space of only a few cubic centimeters. An efficient implementation of the drive circuitry is essential to the progress of ultrasound imaging. Depending on the application either signal switches, bior tri-level pulse generation circuits or high voltage linear drivers are required. This talk derives the need for more advanced and higher integrated power electronics to transmit the ultrasound waves. It further focuses on the pulser´s particular requirements stemming from the ultrasound application