An integrated circuit is fabricated by micromachining a hexagonal array of cMUT elements on top of a substrate comprising a hexagonal array of CMOS cells. Each cMUT element overlies a respective CMOS cell in one-to-one correspondence. During layout of the mask for micromachining the cMUT layer, either the hexagonal pattern or the alignment key is rotated until an axis of symmetry of the hexagonal pattern is aligned with an axis of the alignment key. Later, when the mask is superimposed on the CMOS substrate, the alignment key on the mask is aligned with an alignment key on the substrate. This ensures that the cMUT elements formed by optical lithography will be matched to the CMOS cells.

A DRA with preferentially controlled grading lobes is described. The DRA comprises a plurality of elements, collectively defining a main lobe nearest the DRA boresight and a set of grating lobes near the main lobe, wherein each of the grating lobes in the set of grating lobes is angularly displaced from the main lobe by a grating lobe angle that varies asymmetrically about that main lobe. In one embodiment, the plurality of elements comprises a first row of elements extending in a first direction that is tilted relative to the Northerly direction by an angle .psi., and a second row of elements, parallel to the first row of elements, the second row of elements offset from the first row of elements in the first direction by a stagger distance S.

An ultrasonic imaging method and apparatus are described for imaging the coronary arteries of the heart. The vascular system is infused with an ultrasonic contrast agent. A volumetric region of the heart wall including a coronary artery is three dimensionally scanned. A projection image of the volumetric region is produced from the scanning, providing a two dimensional contrast image of the coronary artery with the appearance of an angiogram. Preferably the coronary artery signals are segmented from contrast signals emanating from the myocardium and the heart blood pool so that the coronary arteries are clearly highlighted and distinct in the ultrasonic angiogram.

An ultrasound transducer array includes a multiplicity of subelements interconnected by a multiplicity of microelectronic switches, each subelement comprising a respective multiplicity of micromachined ultrasound transducer (MUT) cells. The MUT cells within a particular subelement are hard-wired together. The switches are used to configure the subelements to form multiple concentric annular elements. This design dramatically reduces complexity while enabling focusing in the elevation direction during ultrasonic image data acquisition.