Abstract: An apparatus and method for mapping data associated with spacial polar angles into a Cartesian coordinate system is disclosed. In the described application, ultrasound returns from a rotating transducer are mapped into a memory to permit presentation on a raster scanned display. A tangent function is used to compute X and Y locations in a digital differential analyzer. The selection of data for these locations is controlled with a secant function by a second digital differential analyzer to minimize quantizing errors.

Abstract: A data acquisition head for an ultrasonic imaging system which employs a plurality of transducers is disclosed. The transducers are rotated in a liquid filled chamber at a constant rate, each about an axis perpendicular to its transmission axis. The transducers are sequentially activated as their transmission axes cross a semi-rigid membrane which is in contact with the body. The acoustic impedance of the liquid and membrane, and the thickness of the membrane, are matched to enhance transmission. In one embodiment, the membrane is one-half or a full wavelength thick and comprises a low density polyethylene and the liquid has an acoustic impedance approximately equal to that of the polyethylene.