1. A method for imaging an image field, comprising: transmitting a plurality of laterally spaced transmit beams from a probe including an array of transducer elements, each transmit beam encompassing a plurality of laterally spaced line positions; producing, using a multiline receive beamformer, a plurality of receive lines of the image field at the plurality of laterally spaced line positions for each of the plurality of laterally spaced transmit beams; delaying r.f. receive line signals of a receive line of the plurality of receive lines with a phase characteristic which varies as a function of depth and combining a plurality of r.f. receive line signals to produce transmit refocused image data using a multiline combining circuit, wherein the plurality of r.f. receive line signals combined by the multiline combining circuit relate to a common line position produced by the multiline receive beamformer and correspond to the plurality of laterally spaced transmit beams; detecting a presence of motion in the image field; and displaying an image produced utilizing the transmit refocused image data, wherein a number of the plurality of r.f. receive line signals combined by the multiline combining circuit is a function of the detected presence of motion.