JP2526624B2 - Ultrasonic diagnostic equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to control of a focal position of an ultrasonic beam when acquiring blood flow information by the Doppler shift method.

[Conventional technology]

2. Description of the Related Art In a medical field such as a heart or a circulatory organ, an ultrasonic diagnostic apparatus is used to observe blood flow dynamics in a living body such as the heart. This ultrasonic diagnostic apparatus is generally provided with a probe for transmitting and receiving ultrasonic waves, a diagnostic apparatus main body having a Doppler signal detecting means, a speed calculating means, etc., to which the probe is connected, diagnostic results, etc. It is composed of a CRT or the like for displaying, transmits an ultrasonic wave from the probe into the subject, obtains a Doppler signal of an ultrasonic echo reflected from the subject, and performs a fast Fourier transform ( FFT) is used to observe the blood flow direction and flow velocity distribution.

In order to improve the azimuth resolution in such an ultrasonic diagnostic apparatus, it is necessary to reduce the ultrasonic beam diameter, that is, to perform focusing, but conventionally, an acoustic lens or the like has been used for this purpose. Also, unlike fixed focusing such as this acoustic lens, a dynamic focus system in which the focal position can be changed is also adopted.

[Problems to be Solved by the Invention]

The dynamic focus as described above is generally performed by electronic focus. That is, the probe is composed of a plurality of minute oscillators, a delay function-like delay distribution is given to each of these oscillators, and the combined wavefront is controlled to be a focused wavefront instead of a plane wave. As in the case of using an acoustic lens or the like, the beam diameter is narrowed near the focus. This is shown in FIG. In the figure, 1a to 1n are transducers forming a probe, 2a to 2n are, for example, variable delay circuits, and each of these variable delay circuits 2a to 2n has a quadratic delay distribution as described above. By giving the focus position F
The composite wavefront W which is focused at is formed.

However, the setting of the focus in the conventional dynamic focus is performed manually, and the position of the focus may not always be an effective position depending on the scanning beam. In the blood flow imaging device with blood flow measurement function using pulse Doppler, if the part where blood flow exists is not in focus, it will be affected by the surroundings and the difference in the incident angle, and the accurate There is a problem that the blood flow velocity cannot be obtained. That is, in the example shown in FIG. 3, blood flow exists in the area where the ultrasonic beam B spreads, but in general, the blood flow has a fast center and a slow blood vessel wall due to the viscosity of the blood. Therefore, as shown in the figure, various blood flow velocities exist, and the obtained spectrum spreads. Further, in the example shown in FIG. 4, since blood flow still exists in the region where the beam B spreads, the incident angles θ ₁ , θ ₂ , θ ₃ are different at the center and both ends of the beam B, and the same as above. In addition, the spectrum obtained by Doppler shift spreads, and it becomes difficult to obtain an accurate blood flow velocity.

The present invention has been made in view of the above points, and an object thereof is to obtain an ultrasonic diagnostic apparatus capable of appropriately controlling the focal position and obtaining more accurate blood flow velocity information.

[Means for solving the problem]

Here, as described above, the blood flow velocity is slow near the blood vessel wall around the blood vessel due to the viscosity of the blood, and the blood flow velocity is fast near the center. Therefore, if the position where the maximum value of the blood flow velocity is obtained is detected, that position is considered to be the center of the blood flow distribution.

The ultrasonic diagnostic apparatus according to the present invention is made by paying attention to the fact that the position where the blood flow velocity has the maximum value corresponds to the center of the blood flow distribution. In the device configured to control the focal position of the ultrasonic beam by the dynamic focus method, the maximum value of the blood flow velocity data can be obtained for each scanning line from the blood flow information obtained by receiving the reflected wave. A speed maximum value position calculating means for calculating a position in the depth direction, and a focus position control means for controlling the focus position of the ultrasonic beam at the calculated speed maximum value position for each scanning line are provided. is there.

[Action]

In the present invention, the position in the depth direction where the maximum value of the blood flow velocity data is obtained is calculated for each scanning line based on the blood flow information obtained from the received wave data, and each scan is performed at the calculated position. Since the focus position is controlled for each line, the beam is focused near the region where the blood flow exists for each scanning line, and more accurate blood flow velocity information can be obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. First
FIG. 1 is a schematic configuration diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. Here, an example in which ultrasonic diagnosis is performed by sector scanning will be described. In FIG. 1, reference numeral 1 is a probe composed of a plurality of minute vibrators 1a to 1n, and each of the vibrators 1a to 1n is connected to a delay circuit 2. The delay circuit 2 is composed of variable delay circuits 2a to 2n provided corresponding to the respective transducers 1a to 1n, as shown in FIG. 5, for example, and these variable delay circuits 2a to 2n are arranged. Are connected to the delay control circuit 3. Although not shown in the figure, scanning line position data and sample position data are input to the delay control circuit 3, and the delay time of each of the variable delay circuits 2a to 2n is controlled based on these data, and the ultrasonic wave In addition to controlling the beam emission direction, beam control is performed so that the combined wavefront becomes the focused wavefront W (see FIG. 5). Further, the delay control circuit 3 controls the delay time of each of the variable delay circuits 2a to 2n on the basis of sample position data from a maximum value position detection unit 6 which will be described later, and also controls the focus position. . In this way, the delay control circuit 3 has a function as a beam control means for controlling scanning of the ultrasonic beam and forming a focused wavefront, and a function of a focus position control means for controlling the focus position. .

The ultrasonic echo signals, which are received signals from the transducers 1a to 1n, are connected to the velocity calculation unit 4. The velocity calculation unit 4 is composed of a receiving circuit, a Doppler signal extraction means, an MTI filter, an FFT calculation circuit and the like, and blood flow velocity data can be obtained at its output. A line memory 5 is connected to the output of the speed calculation unit 4,
Blood flow velocity data at each sample point of one scanning line is stored in the line memory 5. Further, 6 is a maximum value position detection unit, and this maximum value detection unit 6 is the line memory 5
The maximum value of the data stored in is calculated and the sample point position data is sent to the delay control circuit 3.

 Next, the operation will be described.

The delay circuit 2 is controlled by the delay control circuit 3 on the basis of the scanning line position data, ultrasonic waves are emitted from each of the transducers 1a to 1n according to a constant delay distribution, and these are combined and shown in FIG. As described above, the ultrasonic beam is transmitted into the subject as an ultrasonic beam that is focused in a predetermined direction and at a predetermined position. The ultrasonic beam (echo signal) reflected at each interface and blood flow in the subject is received by each transducer 1a to 1n, and STC (Sensitivity Time Control) correction, that is, the attenuation of echo signal due to distance is corrected. After the adjustment, it is input to the speed calculator 4. The STC correction is performed by an STC circuit (not shown) provided in the preceding stage of the speed calculation unit 4, and thereafter is similarly input to the speed calculation unit 4 via an A / D conversion circuit (not shown).

In the velocity calculator 4, the Doppler shift component is extracted from the echo signal, and the Doppler signal of only the blood flow component is obtained by removing the echo signal from the living tissue such as the internal organs by passing through the MTI filter. And
Blood flow velocity data can be obtained by performing FFT calculation on this. This blood flow velocity data is obtained for each sample point of each scanning line, and the blood flow velocity data of all the sample points of one scanning line is stored in the line memory 5. When all the blood flow velocity data for one scanning line are stored, that is, when the sample position data exceeds a predetermined threshold value, these blood flow velocity data are input to the maximum value position detection unit 6,
Here, the maximum absolute value of the speed data is obtained. Then, from the maximum value position detection unit 6, the position data of the sample point for which the maximum value speed data is obtained, that is, the position data in the depth direction is sent to the delay control circuit 3.

In the delay control circuit 3, the maximum value position detector 6
The delay amounts (delay distributions) of the variable delay circuits 2a to 2n are controlled so that the focus is set at the sample point position sent from the. Then, in this scanning line direction, the ultrasonic beam at the set focal position is emitted several times to obtain blood flow velocity information.

Such scanning is performed for each scanning line, the focus is moved to the optimum focal position for each scanning line, and measurement is performed. For example, as shown in FIG. 2, in the ultrasonic beam B ₁ , the maximum value of the blood flow velocity data can be obtained at the sample point position M ₁ closest to the center position of the blood vessel, so that the focus is on this M ₁ point. The beam is controlled as follows, and in the beam B ₂ , the central position of the blood vessel at a position deeper than the point M ₁
Since a maximum value is obtained at M ₂ and a maximum value is obtained at beam M _{3 at} beam B ₃ , beam control is performed so that the focal points are set at points M ₂ and M _{3 in} each scanning line direction.

In this embodiment, since the focus position is controlled for each scanning line direction, the focus position is not fixed in every scanning line as in the conventional device, but is adjusted in each scanning line. The optimum focus position can be set, the spread of the spectrum finally obtained can be prevented, and highly accurate blood flow velocity information can be obtained.

In the above embodiments, sector scanning was described as an example of the ultrasonic beam scanning method. However, the present invention can be applied to other cases such as linear scanning and convex scanning, and the same effects as those of the above embodiments can be obtained. . Further, the present invention is not limited to the one in which the beam is controlled by controlling the delay time as in the above-mentioned embodiment, and can be applied to the one in which the beam is controlled by performing the switching control or the phase control, for example. Of course things.

Furthermore, in the above-mentioned embodiment, the case where the blood flow velocity information is obtained by the pulse Doppler method has been described, but the present invention can be applied to an ultrasonic diagnostic apparatus of a method in which the blood flow velocity information is obtained by another method. Has the same effect.

〔The invention's effect〕

As described above, according to the present invention, the probe is composed of a plurality of minute oscillators, and the blood flow information of the subject is obtained from the echo signal obtained by electronically or mechanically scanning the ultrasonic beam. In the ultrasonic diagnostic apparatus to be obtained, from the blood flow information, calculate the position in the depth direction where the maximum value of the blood flow velocity data is obtained for each scanning line direction, and focus the ultrasonic beam at the calculated position. Since the beam is controlled so as to come to the target, the beam can always be focused near the region where the blood flow exists for each scanning line, and there is an effect that highly accurate blood flow information can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention, FIG. 2 is a diagram for explaining a focus position control operation of this ultrasonic diagnostic apparatus, and FIGS. 3 and 4 are both FIG. 5 is a diagram for explaining the problems of the conventional apparatus, and FIG. 5 is a diagram for explaining the principle of electronic focusing in the ultrasonic diagnostic apparatus. 1 ... Probe, 1a-1n ... Micro vibrator, 2 ... Delay circuit, 2a-2n ... Variable delay circuit, 3 ... Delay control circuit (beam control means, focus position control means), 4 ... ... Speed calculation unit, 5 ... Line memory, 6 ... Maximum value position detection unit.

Claims (1)

(57) [Claims] 1. An ultrasonic beam is transmitted toward a subject,
In an ultrasonic diagnostic apparatus that receives the reflected wave and obtains blood flow information of the subject, a probe that is composed of a plurality of minute oscillators and emits the ultrasonic beam, and the ultrasonic beam Beam control means for focusing and sequentially scanning the ultrasonic beam within a predetermined range, and the maximum value of blood flow velocity data for each scanning line from blood flow information obtained by receiving the reflected wave. A speed maximum value position calculating means for calculating the obtained position in the depth direction, and a focus position controlling means for controlling the focus position of the ultrasonic beam at the calculated speed maximum value position for each scanning line are provided. An ultrasonic diagnostic apparatus characterized by the above.