Abstract: A high sensitivity, high frequency directional hydrophone is disclosed which utilizes flexible optical waveguide wrapped about an hemispherical mandrel located at the focus of a paraboloidal acoustic reflector.

Abstract: A less expensive apparatus and associated method for Magnetic Resonance Imaging (MRI) of body tissues are disclosed. A physician uses an ultrasonic detector in combination with a weak magnetic field and pulsed, low frequency R.F. generator. The patient lies partially within the field of a magnet and receives low frequency radio pulses. As is shown below, ultrasonic waves are produced within the patient's body by the ordinary occurrence of nuclear magnetic resonance. For this reason, ultrasonic acoustic detection replaces the usual radio detection of the magnetic resonance induced spin echoes. The physician manipulates a hand-held ultrasonic detector with real time image feedback in much the same way that an ultrasonic transducer is used to provide the usual ultrasonic images. In the present case, however, no ultrasonic waves are emitted by the transducer; instead, the waves emitted by the "slice" selected by the radio frequency resonance with tissue protons are the source of the ultrasonic image produced.