Abstract: A transesophageal echocardiographic scanner includes a rotatable transducer for rotating the image plane of the scanner. The transducer is a circular shaped array of parallel oriented elements which may be operated as a phased or linear array. The transducer is mounted on a bell-shaped backing box with a conical interior surface that directs reverberations from the back of the transducer into damping material which fills the box. The transducer is located in a fluid compartment which is divided by a cover member into an ultrasonic transmission region between the emitting surface of the transducer and the cover, and an adjacent bubble trap region into which bubbles may pass and preferentially remain.