Real-time curvilinear and improved rectilinear volumetric imaging
Current real time volumetric scanners use a two-dimensional array to scan a pyramidal volume comprised of many sector scans stacked in the elevation direction. This scan format is primarily useful for cardiac imaging to avoid interference from the ribs. However, a real time curvilinear or rectilinear volumetric scan with a wider field of view close to the transducer could prove more useful for abdominal, breast, or vascular imaging. In previous work, computer simulations of very sparse array transducer designs in a rectilinear volumetric scanner demonstrated that a Mills cross array showed the best overall performance given current system constraints. Consequently, a 94×94 Mills cross array including 372 active channels operating at 5 MHz has been developed on a flexible circuit interconnect. In addition, the beam former delay software and scan converter display software of the Duke volumetric scanner was modified to achieve real-time rectilinear volumetric scanning consisting of a 30 mm × 8 mm × 60 mm scan at a rate of 47 volumes/sec. Real-time rectilinear volumetric images were obtained of tissue mimicking phantoms showing spatial resolution of 1-2 mm. Images of carotid arteries in normal subjects demonstrated tissue penetration to 6 cm. In addition, a Mills cross curvilinear array was built with a radius of curvature of 40 mm having a 44° × 11° curvilinear scan. Lastly, a new rectilinear periodic array containing over 65,000 elements was designed and built to increase the field of view to 30 mm × 30 mm × 60 mm.
