JPS6337665B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a medical ultrasound diagnostic apparatus.

Current ultrasonic diagnostic equipment applies electrical high-frequency pulses of about 1 to 10 MHz at regular intervals to an ultrasonic probe consisting of an ultrasonic transducer such as a piezoelectric element, and radiates the ultrasonic pulses into the living body. Ultrasonic echo signals that are partially reflected and returned at places where there is a difference in acoustic impedance (product of density and sound speed) inside the body are received by the same ultrasound probe, converted into electrical signals, and then amplified and detected. The mainstream method is one that uses a processing method (pulse reflection method). However, such an ultrasonic diagnostic apparatus has a problem of adverse effects caused by side lobes in the azimuth direction. This problem will be explained in detail with reference to FIG.

For example, in FIG.
When a BM is emitted and hits an obliquely placed reflector T, in addition to the echo signal (main lobe) from the intersection point d between the ultrasound beam BM (main beam) and the reflector T, there are also echo signals from the surroundings. Echo signals (side lobes) will be received. Among these sidelobes, the sidelobe from point b, where the beam input perpendicularly to the reflector T is reflected, becomes stronger,
As shown in Figure 1B, the side lobe from point b is as if the main beam BM is located at a distance of ab = ac.
It will be received as if it were an echo signal (main lobe) from point c above. This has resulted in the inconvenience of artifacts occurring on the display screen. Furthermore, since echoes are continuously generated within a living body, there is a problem in that phase differences and interference occur, resulting in irregularities in images depending on frequency and the like.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an ultrasonic diagnostic apparatus that can reduce artifacts due to side lobes and improve the above drawbacks.

The present invention will be specifically explained below using Examples.

FIG. 2 is a waveform diagram for explaining the principle of the present invention, particularly the principle of sidelobe reduction. The present invention first radiates an ultrasonic beam in a desired direction and position in a normal sound field, thereby creating a main rope Ml at point c and a strong side lobe Sl at point b, as shown in Fig. 2A. transmits and receives signals, then creates a specific sound field,
In this sound field, an ultrasonic beam is emitted without changing the position and direction of the main beam, and the main lobe Ml is at point c, as shown in figure B, and the side lobe Sl is generated at a position other than point b. By transmitting and receiving signals that appear to be It is something.

An embodiment of an ultrasonic diagnostic apparatus for realizing the above principle will be described with reference to FIG. In the figure, 1 is a linear electronic scan probe in which n oscillators are arranged in a row, and 2 is a pulsar group including pulsars for exciting each of the n oscillators via n lines. 3 is a transmission delay line (transmission DL) group for delay driving each of the pulsers, and 5 is a group of n preamplifiers for respectively amplifying the echo signals received by the n oscillators. 6 is a receiving delay line (receiving DL) group that delays and outputs the output signal from each preamplifier, and 7 is an addition line that adds and outputs each output signal from the receiving DL group 6. It is a vessel. 4 is a transmission timing signal So, signals S ₁ and S 2 for controlling the pulser group 2, transmission and reception DL groups 3 and 6, preamplifier group ₅ , and adder 7, and a switching signal S for a switch 8, which will be described later. In particular, the control signals S ₁ and _{S 2 are} output alternately, and the switching signal S ₃ is outputted every time the control signals S ₁ and S ₂ are output. This signal is used to switch the N taps of the switch 8 at synchronized timing. 9 is a set of two line memories 1a, 1b, 2a, 2b... into N sets (Na,
This is a line memory group having up to Nb), and is adapted to store each line of data from the adder 7 which is switch-connected to the N taps of the switch 8 mentioned above. Reference numeral 10 denotes an arithmetic unit which, for example, multiplies the data of each pair of line memories and sequentially outputs the result. 11 is a calculation unit 10
The output from the main amplifier 11 (which is converted into an analog signal by a processing circuit not shown) is supplied to the display section 12 to display an image.

Here, the relationship between the control signals S ₁ and S ₂ from the controller 4 will be explained in detail with reference to FIG. 4. The control signals S ₁ and S ₂ are signals used to change the state of the sound field in which ultrasonic waves are transmitted and received, and Fig. 4 shows the focus of the ultrasonic beam as a method of creating different sound fields. An example of changing the position is shown. For example, Figure 4a
First, among the oscillators NO1 to NOn in the linear electronic scan probe 1, eight oscillators NO2 to NO9 are driven by the first control signal _S1 , and then NO1 is driven by the second control signal _S2 . The first transmission/reception scan is completed by driving the 10 vibrators of ~NO10, and then again by the first control signal _S1 .
After driving the 8 vibrators NO3 to NO10, the second
The _second scanning is completed by driving the 10 vibrators NO2 to NO11 using the control signal _{S2 of}
This shows the case where the third and fourth scans are performed while sequentially shifting the set of transducers one by one. In this case, the delay state by the transmission DL group 3 and the reception DL group 6 is made to be particularly different between the control signals S ₁ and S ₂ depending on the focus. When such a transducer driving method is used, as _{shown in FIG} . The ultrasonic beam BM ₂ (indicated by the broken line in the figure) generated by
It only changes from P ₁ (distance l ₁ ) to P ₂ (distance l ₂ ). Therefore, the ultrasonic waves transmitted and received based on each beam BM ₁ and BM ₂ are understood as waves in different sound fields.

In addition, FIG. 4b shows that each control signal S ₁ and S ₂ correspond to the same group of oscillators (for example, 8 oscillators NO1 to NO8).
In this example, the delay state of the transmitting and receiving DL groups 3 and 6 is determined between the control signals _S1 and _S2 .
It is changed separately into the first (DL ₁ ) and second (DL ₂ ). In this case as well, since the focus point is changed without changing the position and direction of the main beam, each sound field will be different.

Next, the operation of the apparatus having the above configuration will be explained. The transmission timing signal So from the controller 4 is given a predetermined delay by the transmission DL group 3 and is sent to the pulsar group 2. At this time, transmission DL group 3 and pulsar group 2
A predetermined delay line and pulser are selected by the control signal _S1 , and the transducer in the probe 1 is thereby selectively driven to emit an ultrasonic wave (for example, as shown in Fig. 5). solid line BM ₁ condition). The echo signal from the reflector T is received by the same transducer and taken into the adder 7 via the pre-wap group 5 and the receiving DL group 6. At this time, the switch switching signal _S3 from the controller 4 is output and the switch 8
is connected to the first tap, so 1 of adder 7
Addition data for a line is stored in the first line memory 1a in the line memory group 9. Next, the second control signal _S2 is output from the controller 4 and transmitted.
The selection status of DL group 3 and pulsar group 2 changes,
A predetermined vibrator is selected according to the signal from the pulser 2 at this time, and ultrasonic waves are emitted (for example, the state indicated by the broken line _BM2 in FIG. 5). At this time, the echo signal obtained from the reflector T is taken into the adder 7 via the preamplifier group 5 and the reception DL group 6. At the same time, the switch 8 is switched to the second tap by the switch changeover signal _S3 from the controller 4, so that one line of added data from the adder 7 is stored in the first pair of taps in the line memory group 9. 2
It is stored in the line memory 1b. Here, as mentioned above, since the ultrasonic sound field created by the first control signal _S1 and the sound field created by the second control signal _S2 are different, the received signal also has a main lobe. Although the position and direction of the side lobe remain the same, two types of signals (for example, A and B in FIG. 2) with different side lobe generation positions and levels are obtained. Thereafter, two types of signals obtained from the same position and direction are similarly stored in each set of line memories.

The calculation unit 10 multiplies the signals of each group in the line memory group 9 to obtain a signal (for example, C in FIG. 2).
are generated and sent out sequentially to the main amplifier 11. An image is displayed on the display section 12 based on the output of the main amplifier 11 as described above.

As is clear from the above explanation, since the output signal from the calculation unit 10 becomes a signal as shown in FIG. 2C with reduced side lobes, no artifacts occur in the image.

The present invention is not limited to the embodiments described above, and various modifications can be made. For example, in the embodiment described above, two different types of sound fields were created at the same position and direction to achieve the objective, but three or more types of sound fields were created to further increase the sidelobe reduction rate. It's okay. Furthermore, methods for creating different sound fields are not limited to the above embodiments, and may include methods such as changing the frequency of the generated ultrasonic waves multiple times, replacing different acoustic lenses multiple times, and using different apertures multiple times. It's okay.

Further, in the above embodiment, a linear electronic scan probe was used as the probe, but the probe is not limited to this. For example, as shown in FIG. It is also possible to create a different sound field by rotating it in the θ direction, or by using a diamond-shaped matrix probe 1' with transducer chips arranged radially as shown in Figure 7, it can be rotated in the X and Y directions. Different sound fields may be created by selectively driving the vibrators.
Furthermore, for example, in the case of four different sound fields, the X direction, Y direction, (+x/2, +y/2), (-x/2,
-y/2) Different sound fields may be created using four types of directions.

[Brief explanation of the drawing]

FIGS. 1A and 1B are diagrams for explaining the cause of sidelobe generation, and FIGS. 2A to 2C are waveform diagrams for explaining the principle of sidelobe reduction according to the present invention.
FIG. 3 is a block diagram of an embodiment of the device of the present invention, and FIG.
Figures a and b are schematic diagrams for explaining the control method by the device of the present invention, Figure 5 is an explanatory diagram of the state in which different sound fields are created by the device of the present invention, and Figures 6 and 7.
The figure is a schematic diagram of a probe used in another embodiment of the invention. 1...Probe, 2...Pulser group, 3...Transmission DL group, 4...Controller, 5...Preamplifier, 6
... Reception DL group, 7 ... Adder, 8 ... Switch,
9...Line memory group, 10...Calculation section, 11...
...Main amplifier, 12...Display section.

Claims (1)

[Claims] 1. An ultrasonic probe, a driving means connected to the ultrasonic probe and transmitting an ultrasound beam multiple times in a sound field in which the position and direction of the main beam are aligned and the side lobe generation positions are different from each other; 1. An ultrasonic diagnostic apparatus comprising a calculation means for calculating a plurality of ultrasound echo signals obtained by transmitting a sound wave beam to reduce side lobes.