Ultrasonic imaging apparatus

Abstract

In an ultrasonic contrast imaging method in which signals specific to a contrast agent are extracted to form an image, imaging is performed with the following three well-balanced properties: frame rate, spatial resolution, and contrast-agent selectivity. A first chirp signal whose frequency increases with time and a second chirp signal obtained by inverting the first chirp signal about the time axis are used, and they are individually transmitted and received. A decoder having decode filters each adapted for a coded sequence, which is obtained when the chirp signal is decomposed into a pulse signal and a coded sequence, is provided. The decode filters are adapted for echo signals received in response to two chirp signals, respectively, and outputs of the two decode filters are input to a subtractor, whereby the difference therebetween is determined. Thus, contrast-agent selectivity is balanced with spatial resolution.