A hydrophone is introduced that exploits the emf signal generated in aconductor when sonicated in the presence of a uniform static magnetic field.The method uses a small metal coil or metal membrane as a hydrophonereceiver. Acoustic signals at 748 kHz are introduced in 1.5T and 4.7T fieldsand recorded both through direct electrical contact with the hydrophone andvia RF pick-up coils, allowing wireless placement of the hydrophone. Linearresponse is confirmed over four orders of magnitude in the pressureamplitude. Waveforms determined from the detected voltage are shown to be inexcellent agreement with those obtained using a calibrated polyvinylidenedifluoride film, and absolute values correlate within 20%. The methods areconceptually suitable for use in the presence of the high and uniform fieldof commercial MR scanners. The hydrophone may appear particularly useful asa quality assurance device in therapeutic and diagnostic acoustic techniquesthat use MRI.
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