JPH0312140A - Acoustic velocity adaptive ultrasonic image pickup device - Google Patents

Abstract

PURPOSE:To automatically improve the deviation of focusing by correcting delay time so as to decrease phase difference for the ultrasonic echo signals of two sound rays to be obtained based on a delay map which is set by fixing acoustic velocity. CONSTITUTION:A CPU 7, which controls respective elements through a bus 8, sets the delay time, for which the acoustic velocity is fixed, to the delay map of a real time controller 4 at first. Next, a dual beam former 3 is controlled and an observing point is focused. Then, ultrasonic echo signals A and B are obtained and phase frequency detection is executed to these signals by frequency detectors 5a and 5b respectively. Afterwards, the signals are inputted to color mapping processors 6a and 6b and data are mutually exchanged. Then, mutual correlation arithmetic is executed, phase difference between acoustic rays is obtained and delay time difference is obtained. When the delay time difference is the advanced phase, the delay time is corrected to be long so that the phase can be delayed. When the delay time difference is the delayed phase, the delay time is corrected to be short so that the phase can be advanced. Then, the deviation of focusing is automatically corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a sound velocity adaptive ultrasound imaging device, and is particularly useful for improving the image quality of an ultrasound diagnostic imaging device.

[Prior Art] In an ultrasonic imaging apparatus, force synchronization is performed by electronically controlling the drive and reception timing for each transducer in a transducer array using a delay line.

That is, a certain observation point is focused by increasing the delay time for a transducer that is close to a certain observation point, and decreasing the delay time for a transducer that is far from the certain observation point.

The delay time given to each vibrator is stored as a delay map.

The conventional delay map uses an oscillator e as shown in Figure 2.
When focusing on the observation point P with the l-em array, the delay time Ti has a distribution as shown in FIG. 3, for example.

The distribution of this delay time Ti is calculated assuming that the speed of sound in a living body is constant.

[Problems to be Solved by the Invention] However, in reality, the speed of sound differs slightly in different parts of the body, such as muscles, fat, and bones.

As a result, when using a conventional delay map in which the speed of sound is set as constant, there is a problem in that a slight shift in focus occurs and sufficient resolution cannot be obtained.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a sound speed adaptive ultrasonic imaging device that automatically corrects focus deviations caused by differences in sound speed in various parts of a living body to perform optimal focusing. be.

[Means for Solving the Problems] The sound speed adaptive ultrasound imaging device of the present invention performs ultrasound transmission and reception to obtain ultrasound echo signals from a predetermined observation point using two different sound lines based on a delay map in which the sound speed is set as constant. a phase difference calculating means for calculating a phase difference between the two sound rays; and a delay map correcting means for correcting the delay time of the delay map so that the phase difference is reduced. It is something to do.

In the above configuration, the ultrasonic transmitting/receiving means may use two different transducers to obtain two-tone ultrasonic echo signals, or may use two different apertures (sub-arrays) to obtain two-tone ultrasonic echo signals. It may also be one that obtains a sonic echo signal.

Further, the ultrasonic echo signals of two sound rays may be obtained simultaneously or may be obtained in a time-division manner.

Furthermore, in the above configuration, the phase difference calculation means may utilize a color flow mapping processor (CFMP) that has been conventionally included in ultrasonic image diagnostic apparatuses.

[Operation] The two-tone ultrasonic echo signals obtained based on the delay map in which the sound speed is set as constant actually have a phase shift when there is a difference in sound speed.

That is, the difference in sound speed in each part of the living body is detected as a phase difference.

Therefore, if the delay time is modified to reduce this phase difference, the focus shift can be improved.

[Example] Hereinafter, the present invention will be explained in more detail based on the example shown in the drawings. Note that this invention is not limited to this.

FIG. 1 shows an ultrasonic blood flow imaging apparatus 1 including a sound velocity adaptive ultrasonic imaging apparatus according to an embodiment of the present invention.

This ultrasonic blood flow imaging apparatus 1 is capable of simultaneously receiving two sound rays using the probe 2 and the dual beam former 3.

Focusing is performed during transmission (TX) and reception (RX) based on a delay map included in the real-time controller 4.

The ultrasonic echo signal A of one of the two sound rays is phase-detected by a detector 5a, and subjected to autocorrelation calculation by a color flow mapping processor 6a to calculate average velocity dispersion and power.

The same goes for the other ultrasonic echo signal B of the two sound rays, which is phase-detected by the detector 5b, subjected to autocorrelation calculation by the color flow mapping processor 6b, and the average velocity 1 dispersion and power are calculated.

The average velocity 9 variance and power calculated by the color flow mapping processors 6a and 6b are sent to the color digital scan converter 9, where they are converted into an image and converted into a CRTI image.
displayed on O's screen.

The CPU 7 is the center that controls the operation of each of the above elements,
Each of the above elements is controlled via a bus 8.

The above are the basic functions of blood flow imaging, and the operations are the same as conventional ones.

Next, the operation of the sound speed adaptation function according to the present invention will be explained.

The CPU 7 first sets a delay time in the delay map of the real-time controller 4 when the speed of sound is constant. This results in a distribution of delay times Ti as shown in FIG.

Next, the CPU 7 controls the dual beam former 3 to focus on the observation point P as shown in FIG.
Ultrasonic echo signals are obtained with the transducers el and e2.

These ultrasonic echo signals A and B are sent to a detector 5a,
Phase detection is performed at step 5b, and input to color flow mapping processors 6a and 6b.

At this time, the color flow mapping processors 6a and 6b mutually exchange data and perform a cross-correlation calculation according to a command from the CPU 7. As a result, the phase difference ω·τ between the sound rays in the oscillators e1 and el is obtained, and since ω is the demodulation carrier angular frequency and is known, the delay time difference τ can be obtained. This delay time difference τ is stored in a memory attached to the CPU 7.

Below, oscillators e2 and e3. e3 and e4. ..., if the delay time difference τ is obtained between two adjacent oscillators in order, then the fourth
A delay time difference distribution as shown in the figure is obtained.

In order to suppress the influence of variations and noise, the CPU 7 performs the above operation for a plurality of points near the observation point P to obtain a plurality of delay time difference distributions. Then, these delay time difference distributions are averaged to obtain an averaged delay time difference distribution.

Next, the CPU 7 sets the delay time for the resonator el to the original delay time TI, and sets the delay time for the resonator e2 to the original delay time T2 plus the delay time difference τ2 (el-el). change. Therefore, if the delay time difference τ2 is positive (advanced phase), the delay time is lengthened and the phase is corrected to be delayed. Further, if the delay time difference τ2 is negative (delayed phase), the delay time is shortened and the phase is corrected to advance.

Next, regarding the resonator e3, delay time differences r2(el-el) and r3(el-e
3) and are added together.

Similarly, the delay time Ti of all the oscillators ei is
is changed.

As a result, a new delay map is obtained, but this is a delay map that takes into account the difference in sound speed, and has less focus shift than the original delay map.

The CPU 7 repeats the above operation as many times as necessary to sufficiently reduce the focus shift.

Once the delay map has been corrected, blood flow imaging is performed by operating the basic functions described above.

[Effects of the Invention] According to the sound speed adaptive ultrasonic imaging device of the present invention, the focus shift caused by the difference in sound speed in each part of the observation target is automatically corrected, and highly accurate focusing can be performed. .

Therefore, the resolution of the image can be improved.

[Brief Description of the Drawings] Fig. 1 is a block diagram of an ultrasonic blood flow imaging device including a sound velocity adaptive ultrasonic imaging device according to an embodiment of the present invention, and Fig. 2 shows the relationship between the transducer array and observation points. Conceptual diagram shown, 3rd
The figure is a conceptual diagram of a delay map when the speed of sound is constant, FIG. 4 is a distribution diagram of delay time differences between adjacent vibrators, and FIG. 5 is a conceptual diagram of a corrected delay map. (Explanation of symbols) 1... Ultrasonic blood flow imaging device 2... Probe 3... Dual beam former 4... Real time controllers 5a, 5b... Detector

Claims (1)

[Claims] 1. Ultrasonic transmitting/receiving means for obtaining ultrasonic echo signals from a predetermined observation point using two different sound rays based on a delay map in which the speed of sound is set as constant, and a phase difference calculation means for calculating the phase difference between the two sound rays. and a delay map modifying means for modifying the delay time of the delay map so that the phase difference is reduced.