A synthetic aperture ultrasonic imaging method: experiment

An ultrasonic imaging method based on a synthetic aperture approach and holography was evaluated experimentally. Object data were recorded using a 3.5-MHz multielement phased array with a fairly wide-angle beam. Images were reconstructed numerically in a microcomputer using the spatial frequency domain which allows an efficient use of FFT algorithms. The reconstruction algorithm can be made fast enough for a real-time scanner. The spatial resolution was defined by imaging thin wires in a water bath. The lateral (-6-dB) resolution was about 1 mm in the depth range of 23-95 mm. The dynamic range and resolution were studied by imaging a standard tissue phantom. The study shows that if a compromise is made between the spatial resolution (beamwidth) and the dynamic range, the detectability of cysts, for example, is greatly improved