C-scan imaging by radiation force stimulated acoustic emission method

A novel C-scan imaging method is presented. This method utilizes the radiation force to stimulate an acoustic emission by the object at low frequencies. The radiation force, which is highly localized, is produced employing two intersecting focused ultrasound beams driven by two CW sources at slightly different frequencies. The acoustic emission is generated at the difference, or the beat, frequency. This field is nondirective and is detected by a hydrophone. It is shown that the amplitude of the acoustic field is linearly proportional to the peak instantaneous ultrasound power. This has been verified experimentally using a pinhead object and two identical transducers in a water tank. C-scan images are obtained by displaying the amplitude of the acoustic field versus beam position while the object is raster scanned.