JPS6311138A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an ultrasonic diagnostic apparatus capable of displaying a B-mode image using a dynamic focus method.

(b) Conventional technology and its problems Conventional ultrasound diagnostic equipment has a method of changing the focus of the ultrasound beam emitted from the transducer in accordance with the depth position of the subject, and transmitting the echo signals obtained by this to the depth. There is a so-called dynamic focus type ultrasonic diagnostic apparatus that is configured to perform B-mode display of the entire cross section by piecing them together in the horizontal direction. That is, in this dynamic focus system, as shown in FIG. 2(a), when obtaining information from the shallow part N of the subject,
The ultrasonic beam is transmitted and received by setting the focus Fn of the ultrasonic beam to be shallow, setting the focus Fm to the middle when obtaining information from the middle part M, and setting the focus F to deep when obtaining information from the deep part F. As a result, a diagnostic image with good resolution can be obtained from the shallow part N to the deep part F of the subject.

However, with the conventional dynamic focus method, when receiving the ultrasonic beam emitted to obtain information on the shallow part N, echoes reflected from the deep part are also received at the same time, resulting in artifacts and poor image quality. sometimes deteriorated. For example, as shown in Figure 2(b),
When setting the focus to the shallow part N and emitting an ultrasound beam at a predetermined period T, the ultrasound beam is not only reflected from the shallow part N, but also has a part with different acoustic impedance in the middle part MS and the deep part F. If so, it will be reflected from each of those parts. Therefore, when the echo from the shallow part N of the ultrasound beam emitted the second time is received, the echo from the middle part M of the ultrasound beam emitted the first time is received at the same time, and furthermore, the echo from the middle part M of the ultrasound beam emitted the first time is received. When receiving the echo of the emitted ultrasonic beam from the shallow part N, a phenomenon occurs in which the echo of the first emitted ultrasonic beam is received at the same time. In this way, when information from the shallow IN is obtained, if information from the intermediate and deep areas is mixed in, a problem arises in that a virtual image is displayed superimposed on the image that should originally be displayed.

To solve this problem, set the radiation period T of the ultrasonic beam to be long enough, and wait until there are no echoes reflected from deep inside.
The next ultrasound beam may be emitted, but in this case, the time required to form one screen of diagnostic images becomes longer, and the so-called frame rate decreases, impairing real-time performance.

The present invention was developed in view of the above circumstances, and it is an object of the present invention to reduce the influence of multiple reflections and eliminate artifacts without impairing the frame rate and to achieve good image quality when applying the dynamic focus method. The purpose is to enable diagnostic images to be obtained.

(c) Means for Solving the Problems In order to achieve the above object, the present invention utilizes a dynamic focus type ultrasound system that transmits and receives ultrasound waves by changing the focus in accordance with the depth position of the subject. The ultrasound diagnostic apparatus is characterized by being provided with a power variable means that changes the radiation power of ultrasound according to each focus.

(D) Function In the ultrasonic diagnostic apparatus of the present invention, when the focus is changed in accordance with the depth position of the subject, the power variable means changes the radiation power of the ultrasonic waves. In other words, when setting the focus of the ultrasound beam to the shallow part of the subject, the power is also set to be small.
Conversely, when the focus is set deep, the power is also set high.

Therefore, the ultrasonic beam emitted to obtain information from the shallow part is also reflected from the deep part, but the power of the emitted ultrasonic beam in this case is small, so the power of the ultrasound echo reflected from the deep part is is sufficiently attenuated and therefore does not amount to a source of artifacts.

(e) Examples Hereinafter, the present invention will be explained in detail based on examples shown in the drawings.

FIG. 1 is a block diagram of the ultrasonic diagnostic apparatus of this embodiment. In the figure, reference numeral 1 indicates the entire ultrasonic diagnostic device, 2 is a transducer that transmits and receives an ultrasonic beam, and 4 is a drive pulse that generates drive pulses that excite and drive each piezoelectric element (not shown) that constitutes the transducer 2. pulsar,
Reference numeral 6 denotes a voltage control circuit that controls the pulse voltage of the drive pulse output from the pulser 4. In this embodiment, the voltage control circuit 6 is used as a power variable means that changes the radiation power of the ultrasonic wave according to the focus.

8 is an amplifier that amplifies the echo signal output from the transducer 2 based on reception of the ultrasound echo, and 10 is an STC circuit that adjusts the gain for the echo signal in accordance with the distance in the depth direction of the ultrasound beam. That is,
In this STC circuit 10, the gain is set according to the depth position of the subject so that a uniform echo signal intensity can be obtained by eliminating the influence of absorption and attenuation of ultrasound waves within the subject.

12 is a logarithmic amplifier, 14 is an A/D converter, and 16 is an A/D
An image memory for storing echo signal data digitized by the converter 14, 18 a D/A converter, 20 a CRT monitor, 22 selection of the number of elements and delay amount of the transducer 2, adjustment of the voltage control circuit 6, This is a control unit that controls writing and reading of echo signal data to and from the image memory 16, respectively.

Next, the operation of the ultrasonic diagnostic apparatus 1 having the above configuration will be explained.

To set the focus of the ultrasound beam according to the depth position of the subject, first, a control signal for focus setting is given from the control unit 22 to the transducer 2, and the number of elements of each piezoelectric element and each piezoelectric The amount of delay of the drive pulse provided by the element is selected.

Next, when a control signal for pulse voltage setting is given from the control unit 22 to the voltage control circuit 6, the voltage control circuit 6 adjusts the pulse voltage of the drive pulse generated from the pulser 4 in response to this control signal. .

That is, when the focus of the ultrasound beam is set to a shallow part of the subject, the pulse voltage is set to be small, and conversely, when the focus is set to a deep part of the subject,
The pulse voltage is set to be large.

Subsequently, when a control signal for ultrasonic emission is given from the control unit 22 to the pulser 4, the pulser 4 outputs a drive pulse whose pulse voltage has been adjusted in advance as described above.
This drive pulse is applied to each previously selected piezoelectric element of transducer 2 with a predetermined amount of delay. As a result, each piezoelectric element is excited, and an ultrasound beam is emitted from the transducer 2 into the subject. The focus of this ultrasonic beam is determined by the amount of delay, and
The power becomes small when the focus is set to a shallow area, and becomes large when the focus is set to a deep area.

The ultrasonic beam emitted from the transducer 2 is reflected not only from the shallow part within the subject but also from the intermediate part M and deep part F, if there are parts with different acoustic impedances, and the echoes are reflected by the transducer. The wave is received again at 2. In this case, the shallower the focus is set, the lower the power of the emitted ultrasonic beam, so the power of the echo reflected from the deeper part is sufficiently attenuated by the time it reaches the transducer 2, thus reducing the artifact. It does not reach the cause.

When the ultrasonic echo is received, the transducer 2 outputs an echo signal corresponding to the received ultrasonic echo, and after this echo signal is amplified by the amplifier 8, the 5T
It is input to the ci adjustment circuit 10. This 5TCI rectifier IO
In this method, the gain of the echo signal strength is adjusted to compensate for the effect of absorption and attenuation of ultrasound within the subject, but in this case, when the focus is set deep, the power of the emitted ultrasound beam is Since it is originally large, the power of the ultrasonic echo reflected from the deep part is greater, and therefore, sufficient echo signal strength can be obtained without setting the gain too large.

Also, when the focus is set to a shallow area, the power of the emitted ultrasonic beam is originally small, so
The power of the echo from the deep part is sufficiently attenuated by the time it reaches the transducer 2, and the gain of the STC circuit IO is also set to be relatively small for the shallow part, so the multiple reflection echoes are small enough to be ignored. .

The echo signal that has passed through the 5TCI adjustment circuit IO is logarithmically amplified by the next-stage logarithmic amplifier I2, then digitized by the A/D converter 14 and stored in the image memory 16.

The echo signal data stored in the image memory 16 is read out in synchronization with TV scanning, converted into analog data by the D/A converter 18, and then displayed on the monitor 20. As a result, the screen of the monitor 20 displays a diagnostic image with good image quality and less influence of artifacts.

In addition, in this embodiment, the ultrasonic radiation power is changed by the pulse voltage, but the invention is not limited to this, and the ultrasonic radiation power can also be changed even if the wave failure sequence of the ultrasonic wave is changed. Be able to change it.

(f) Effect As described above, according to the present invention, since the power variable means is provided to change the radiation power of the ultrasonic wave according to the focus, when applying the dynamic focus method, it is possible to The radiation period of the image can be set short, so that the frame rate is not impaired, and diagnostic images of good quality without artifacts can be obtained. Furthermore, since unnecessary ultrasonic output is not irradiated to the subject, excellent effects such as being effective in terms of safety are exhibited.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a dynamic focus method. ■...Ultrasonic diagnostic device, 2...Transducer,
6... Voltage control circuit (power variable means).

Claims (1)

[Claims] (1) In a dynamic focus type ultrasound diagnostic device that transmits and receives ultrasound waves by changing the focus in accordance with the depth position of the subject, a power variable that changes the radiation power of the ultrasound waves in accordance with each of the above-mentioned focuses. An ultrasonic diagnostic apparatus characterized by comprising means.