Automatic virtual transducer locating system to assist in interpreting ultrasound imaging.

Bodymarkers are used to label the location and orientation of the transducer during ultrasound examination. We attempt to evaluate the usefulness of a new system that indicates transducer location over that of the conventional bodymarker. The proposed system uses an electromagnetic tracking device to track the three-dimensional (3-D) position and orientation of a small electromagnetic receiver attached to the ultrasound transducer relative to a transmitter placed under the bed. The new bodymarker is displayed as a 3-D graphic model. The physique of the examinee is calibrated by representing five locations on the body on the original bodymarker. To evaluate the accuracy of the system visually, we compared the transducer position indicated in the new bodymarker and the actual transducer position in four abdominal sections. Actual and displayed position and orientation closely agreed in all cases, and the transducer position indicator in the bodymarker display moved smoothly. Automatic transducer locator on the virtual 3-D bodymarker accurately indicated its position and orientation. This system is useful and convenient in clinical examinations.