SYNTHETIC-APERTURE IMAGING FOR SMALL-SCALE SYSTEMS

Multi-element synthetic aperture imaging methods suitable for applicat ions with severe cost and size limitations are explored. Array apertur es are synthesized using an active multi-element receive subaperture a nd a multi-element transmit subaperture defocused to emulate a single- element spatial response with high acoustic power. Echo signals are re corded independently by individual elements of the receive subaperture . Each method uses different spatial frequencies and acquisition strat egies for imaging, and therefore different sets of active transmit/rec eive element combinations. Following acquisition, image points are rec onstructed using the complete data set with full dynamic focus on both transmit and receive. Various factors affecting image quality have be en evaluated and compared to conventional imagers through measurements with a 3.5 MHz, 128-element transducer array on different gel phantom s. Multi-element synthetic aperture methods achieve higher electronic signal to noise ratio and better contrast resolution than conventional synthetic aperture techniques, approaching conventional phased array performance.