The present status of ultrasonic imaging in medicine

The ultrasonic techniques that are used routinely in medical imaging have resulted from basic scientific discoveries, new methods of signal analysis and image processing, the development of transducer materials and fabrication techniques, and the application of digital electronics. The system designer is constrained by the ultrasonic properties of tissues, especially speed and attenuation: these properties determine the optimum choices of ultrasonic frequency, and spatial contrast and temporal resolutions. Ultrasonic Doppler techniques provide information about moving targets, including blood flow. Two-dimensional images of anatomical structure and blood flow can be combined in real-time displays. Other advances include sonoelasticity imaging, computed tomography, three-dimensional imaging, contrast agents and quality assurance. Contemporary ultrasonic diagnostic techniques seem to be safe, but the search for possible hazards is continuing with emphasis on thermal effects and cavitation.