Ultrasonic imaging device
View Patent ↗This invention provides an ultrasonic imaging system that implements imaging by distinguishing sharply and definitely the echo components generated by scattering in a microbubble contrast medium, from the tissue harmonic components generated by nonlinear propagation of a transmitted pulse. This ultrasonic imaging system, constructed to transmit/receive ultrasonic pulses to/from a living body and form a contrast image of the inside of the living body by using the contrast-imaging microbubbles, repeats the transmitting/receiving operations four times in all, under the same transmitting/receiving focus conditions at different phase angles [(a)=0°, (b)=120°, (c)=−120°, (d)=180°] of the carrier of a transmitted pulse wave including a common envelope signal, sums up three time-series receive echo signals associated with (a), (b), (c), forms the contrast image, sums up two time-series receive echo signals associated with (a), (d), forms an image of the living body having a nonlinear pulse propagation property, and makes a superimposed display of the two kinds of images.
1. An ultrasonic imaging device for transmitting/receiving ultrasonic pulse to/from a living body in which microbubbles for contrast are introduced, and forming a contrast image of the inside of the living body, comprising:
a transmit beamformer for generating a transmit pulse, said transmit beamformer including a D/A converter and a non-linear amplifier;
a receive beamformer for generating a time-series reception echo signal with adding receive signals, to each of which a delay time is given for generating receiving sensitivity having directivity;
an adder for summing the time-series reception echo signals; and
a transmit/receive sequence controller for controlling the transmit beamformer and the receive beamformer;
wherein in a first sequence, the transmit/receive sequence controller controls the transmit beamformer and the receive beamformer to perform transmitting/receiving operations N times (N=an integer of three or greater) by controlling a sampling frequency of the transmit pulse being an integer-multiple of 3 with respect to a central frequency of frequency components of the transmit pulse, and N pieces of transmission pulse waves having a common envelope signal and different waveforms under a transmission/reception wave focus condition, and controlling carrier waves of the transmission pulse waves so as to vary in phase by 360° /N from one wave to a next wave, and receiving returned ultrasonic waves as N pieces of the time-series reception echo signals; and
wherein said adder sums the N pieces of the time-series reception echo signals so as to output an output signal as a signal indicative of a spatial distribution of the microbubbles.
2. The system ultrasonic imaging device according to claim 1 , wherein a sampling frequency of an output signal of the D/A converter is an integer-multiple of 3 with respect to the central frequency of frequency components of the transmit pulse.
3. The ultrasonic imaging device according to claim 1 , wherein the transmit pulse wave has a waveform formed by summing a fundamental wave and the second-order harmonics associated with the fundamental wave.
4. The ultrasonic imaging device according to claim 1 , wherein the transmit/receive sequence controller controls imaging with selectively changing the first sequence and the second sequence of performing transmitting/receiving operations twice by controlling transmission pulse waves having a common envelope signal under a transmission/reception wave focus condition, and controlling carrier waves of the transmission pulse waves different in phase by 180 degree from each other, and receiving returned ultrasonic waves as two of the time-series reception echo signals, and said adder sums two of the time-series reception echo signals so as to output an output signal as a signal indicative of a spatial distribution of the microbubbles.
5. The ultrasonic imaging system according to claim 4 , wherein
the transmission amplitude in the first sequence is different from the transmission amplitude in the second sequence.
6. The ultrasonic imaging system according to claim 5 , wherein
the transmission amplitude in the first sequence is larger than the transmission amplitude in the second sequence.
7. The ultrasonic imaging system according to claim 5 , wherein
both of the output signals obtained in the first sequence and the second sequence are output together.