JP3062222B2 - Ultrasound imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to ultrasonic imaging for correcting a phase error in order to prevent a deterioration in image quality due to a phase error generated when transmitting and receiving wave energy and performing imaging using a reflected wave. Related to the device.

(Prior Art) Ultrasonic waves are considered in a wave energy transmitting / receiving device. The ultrasonic imaging device irradiates an ultrasonic signal into the subject from the ultrasonic probe, receives a signal reflected from a tissue or a lesion in the subject with the ultrasonic probe,
This is a device that displays a tomographic image formed by the reflection signal on a CRT and uses it for diagnosis.

(Problems to be Solved by the Invention) By the way, in an ultrasonic signal that propagates inside the subject, is reflected by the reflector, propagates again in the body, and is received by the ultrasonic probe, the ultrasonic signal that is a medium Since each tissue is not homogeneous, a phase difference occurs in the ultrasonic waves arriving at the stage of being received by the ultrasonic probe, and a phenomenon called a phase canceling effect occurs in which the phase of the received ultrasonic waves is distorted. . Due to this effect, the delay distribution of the reflected wave in the aperture plane of the ultrasonic probe does not conform to the theory. For this reason, even if the aperture is enlarged, the resolution is improved, and the image quality is improved, it is not as good as expected.

For this reason, a phase error correction process for correcting the phase error caused by the phase canceling effect and focusing on the image to improve the image quality is performed. In order to perform the phase error correction processing, first, it is necessary to know the distribution of the phase shift from the ideal state. However, in the conventional method, since the echo of the soft tissue is used as the reference signal, this operation becomes difficult if the S / N ratio of the input echo for one element of the element array is deteriorated. One of the causes is that data for phase correction is to be obtained with the echo itself in the target area.

The present invention has been made in view of the above points, and an object of the present invention is to provide an ultrasonic imaging apparatus which solves the problem that phase error correction becomes difficult when the SN ratio of an echo is small.

(Means for Solving the Problems) The present invention for solving the above problems transmits and receives wave energy to and from a target located in a region that has passed through a region where the velocity distribution is non-uniform. In the phase error correction method for performing good imaging by correcting the generated phase error, a strong echo having a strong reflection intensity exists at a short distance from the target in a path through which a transmission / reception wave to the target passes. Transmitting and receiving to and from the source to determine the amount of phase error due to non-uniform velocity distribution; and correcting the phase error of the received signal contained in the echo from the target using the obtained amount of phase error. It is characterized by the following.

(Operation) An echo signal from a strong echo source in the path to the target is received, and a phase error included in the echo signal is obtained.
The phase error included in the echo signal from the target is corrected.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of a phase error correction performed by the ultrasonic imaging apparatus of the present invention. In the figure, reference numeral 1 denotes a probe having an element array 2 composed of a plurality of elements for transmitting and receiving ultrasonic waves, and performs transmission and reception while being in close contact with a body surface 3. Reference numeral 4 denotes a region near the body surface 3 where the speed of sound is uneven, and 5 denotes a region where the speed of sound is uniform such as a real organ such as a liver or a fetus in amniotic fluid. 6 is the region of interest (FOI) 7
The target object 8 to be observed in the B-mode image designates a strong echo source existing on or near the path where the sound ray of the ultrasonic wave transmitted from the element array 2 irradiates the target object 6. It is a marker to do. E ₁ , E ₂ ,…
E ₇ shows an example of a strong echo source in front of the FOI7.

Next, the phase error correction in the above embodiment will be described. Ultrasonic waves are transmitted and received from the element array 2 of the probe 1 and the FOI 7 or the target 6 is observed. Since the echo from the FOI 7 is weak and the S / N ratio is poor, it is difficult to converge even if the phase error is corrected. Alternatively, the averaging time is long in the correction calculation. Here, the marker 8 is moved on the B-mode image and placed on a strong echo source (E _{6 in the} figure) in front of the FOI 7. This strong echo source is, for example, E ₁ ~
Is a boundary or the like of the organs indicated by E _7. In the time zone in which the echo of the sound ray at the center of the marker 8 returns, the deviation of the phase distribution of the received signal on the element array 2 from the ideal state is detected, and based on the detection result of the deviation of the phase distribution, The phase error of the echo signal from the FOI 7 or the target 6 is corrected. For the method of phase error correction, a method described in Japanese Patent Application Laid-Open No. 1-135333 may be used,
Here, the method is not the subject, so the description is omitted.

The effect of the method thus performed will be described with reference to FIG. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals. In the figure, E _i is that generally illustrates the echo source in the region where the sound ray of the FOI7 as exemplified by a strong echo sources E ₁ to E ₇ shown in FIG. 1 passes.
Here to match the marker 8 to E _i, performs transmission and reception of ultrasonic waves in the direction of the marker 8, and measuring the phase shift by the echo from E _i, the target product 6 in the phase error correction is echo source in FOI7 is performed, in this case, since it is generally without any serious errors phase error correction also receive sound ray in the vicinity incidentally, the phase error correction reception sector regions 9 of the small section indicated by the dashed line that follows the rear part of the echo source E _i Can be done. As a result, the focused reception can be performed in the sector area 9 regardless of the disturbance on the sound side in the non-uniform sound velocity area 4 shown in FIG.

Further, an important feature of this method is that even if an attempt is made to perform phase error correction using the signal in FOI7, the echo is weak, the S / N ratio is poor, and convergence is difficult, or averaging takes a long time. Even if there is such a defect, as shown in the example, if the attenuation before the FOI 7 is not received, or if the echo of the surface of the tissue with a large reflection intensity as the echo source is used, the SN ratio is good, so that Accurately and quickly converging, six images of the target in the FOI 7 can be obtained as in-focus images on the image.

The above method is applicable to radar, sonar, optics, and the like. Also, E _i need not be the echo source, and the system need not be a pulse echo system. In any case, as shown in the present embodiment, the present invention can be applied by making it possible to receive a weak signal source at the rear part with a phase error corrected state by relying on a strong signal source at the front.

(Effect of the Invention) Good phase error correction can be performed even for a target having a low echo intensity and a small SN ratio, and the practical effect is large.

[Brief description of the drawings]

 FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an example of the effect of the embodiment of FIG. 1 Probe 2 Element array 4 Non-uniform sound velocity area 5 Uniform sound velocity area 6 Target 7 FOI 8 Marker

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-135333 (JP, A) JP-A-63-51846 (JP, A) W. Flax and M.S. O'Donnell, "Phase-Acronation Correction Using Signals From Point Reflectors and Diffuse Scratch Scratchers: BasicTransactionsFrontEconanceFrontTransactions. 35, No. 6, pp 758-767 (58) Field surveyed (Int. Cl. ⁷ , DB name) A61B 8/00-8/15

Claims (1)

(57) [Claims] An ultrasonic image is displayed by irradiating an ultrasonic wave to a subject and performing a phase error correction on a reflected signal to correct a phase difference of the ultrasonic wave caused by a non-homogeneous tissue in the subject. An ultrasonic imaging apparatus, wherein, for the irradiation position of the ultrasonic wave, the phase difference is obtained at a position before the region of interest in the subject, and the region of interest is determined based on the obtained phase difference. An ultrasonic imaging apparatus for performing phase error correction.