1. A method for adjusting region of interest (ROI) in three-dimensional/four-dimensional (3D/4D) imaging, comprising: obtaining an E image by emitting ultrasonic waves, wherein the E image comprises a reduced data size B-mode image; adjusting, using a processor, a scan line range of the ROI through the E image in a 3D/4D imaging mode, wherein the E image has a scan line range larger than that of the ROI and smaller than or equal to that of a full frame, and wherein the scan line range comprises a distance from a beginning point to an ending point substantially along a direction of propagation of the ultrasonic wave.