JPS60182937A - Aperture synthetic ultrasonic imaging 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 [Technical Field of the Invention] The present invention relates to an imaging device that synthesizes ultrasound images using an aperture synthesis method.

[Technical background of the invention and its problems]

The aperture synthesis method is a technology that uses a vibrator with a small aperture surface to synthesize an equivalently large aperture surface through signal processing.This method makes it possible to improve azimuth resolution over a wide range in the depth direction. High-resolution ultrasound images can be obtained regardless of depth.

The azimuth resolution when using the aperture synthesis method increases as the ultrasound beam emitted from the transducer spreads and as the sensitivity distribution of the receiving transducer spreads. and,
In order to spread the ultrasound beam and widen the receiving sensitivity distribution, it is better to make the transducer as small as possible. Finally, in order to obtain high lateral resolution, it is better to make the vibrator as small as possible.

By the way, when the transducer is made smaller, the ultrasonic waves emitted from it become weaker, and the receiving sensitivity also becomes lower, resulting in a problem of lowering the S/N ratio.

[Purpose of the invention]

An object of the present invention is to provide an ultrasonic imaging device with high lateral resolution and a sufficient signal-to-noise ratio.

[Summary of the invention]

The present invention uses an array transducer for transmitting and receiving ultrasonic waves, uses a plurality of elements for transmitting and receiving, and controls the timing of driving each element in the case of transmitting using a delay line, and in the case of receiving. The received signal 4 from each element is measured using a delay line, etc.
The feature is that it is added after being controlled.

〔Effect of the invention〕

According to the present invention, the beam can be expanded without weakening the ultrasonic waves emitted from the transducer, and the reception sensitivity distribution can be expanded without reducing the sensitivity. subordinate
As a result, it is possible to realize an ultrasonic imaging device with high lateral resolution and a sufficiently high signal-to-noise ratio.

[Embodiments of the invention]

An embodiment in which the present invention is applied to an electronic scanning ultrasound diagnostic apparatus will be described below. FIG. 1 is a block diagram thereof.

In FIG. 1, an ultrasonic probe 1 is composed of a linear array transducer. Each vibrator of the array vibrator will be referred to as an element below.

The first ultrasonic wave is transmitted to the leftmost 11 elements. The drive timing of each element is controlled by the scan controller 10, which is performed as follows. That is, the central element among the 11 elements is driven by the balsa 2 first. Next, the two elements on both sides are driven with a delay of about a fraction of one cycle of the ultrasonic wave. Next, the two adjacent elements on the outside are driven a little later than in the case of the two elements described above. This operation is repeated until reaching the outermost element. As a result, the emitted ultrasonic beam expands as it propagates. Ultrasonic waves reflected from inside the living body are received by the 11 elements used for transmission. At this time, the signals from each element are added after having their phases controlled by a delay line in the receiver 3 as follows. In other words, the signal from the center element is that! , is input to the adder. The signals from the elements on both sides are input to the adder with a delay of about a fraction of one ultrasonic cycle compared to the signal from the central element. Then, the signals from the next neighboring elements on both sides are input to the adder with a slight delay.

In this way, the signals from each element are input to the adder with a later delay from those of the outer elements. This widens the receiving sensitivity distribution.

Such transmission and reception of ultrasonic waves is performed by moving the position of the central element one element to the right every - time until it reaches the right end. Note that the resonant frequency of the vibrator is usually 2 to 10 MHz.
It is said that

The phase detectors 4 and 5 each multiply the received signal from the receiver 3 by two sine waves with a 90° phase difference supplied from the scan controller >10, and perform phase detection by passing the results through a low-pass filter. Let's do it. The frequencies of these sine waves match the resonant frequency of the vibrator.

The output of the phase detector 4°5 contains a quadrature component, a cosine (C
X(t) as the OS) component and Y(t) as the sine (SIN) component are obtained, and each of them is connected to the next stage A/D converter 6.7 (0-ADO, 5-ADO). Ru.

0-ADO6b! Hi5-ADO7 Hasole ('shi00
Eight components X(t) and SIN component Y(t) are sampled and digitized. In this case, the sampling bitch is
It is determined by considering the duration of reflected waves from point reflectors within the body. For example, if the duration is 2μ, the appropriate sampling pitch is 400nsp, which is one-fifth of that. This sampling pitch is determined by the sampling clock sent from the scan controller 10, and sampling and digitization are performed in synchronization with this clock. In this way, 00S component X (
t) and the SIN component Y(1) are both 8-bit digital values, for example.

The digitized CO8 component and SIN component are stored in the C-manual buffer memory 8. The data is stored in the S-person buffer memory 9. Writing of data to these buffer memories 8 and 9 is performed from the scan controller 10 to 0-A.
I) This is performed in synchronization with the sampling clock that is also supplied to 06 and 0-ADO7. The digitized orthogonal components (008, SIN components) are sequentially input to the input buffer memory 8, in synchronization with the sampling clock.
9 will be written. The input buffer memories 8 and 9 have the necessary capacity to store received signals corresponding to a series of reflected waves obtained by emitting one ultrasonic pulse.

After all writing is completed, the stored data is read out by the converter 11 and transferred to the image memory 12.

The image memory 12 can store data for two images. This is for storing the CO8 component t) and the SIN component Y(t) read from the C-manual buffer memory 8 and the S-manual buffer memory 9, respectively. X (t), Y (t) of the image memory 12
) are each configured as schematically shown in FIG. 3. That is, the possible values of the X and Y addresses are 0 to 511, and are associated with the scanning direction and the depth direction, respectively. Each address can store 8 bits of data.

The output buffer memory 13 is for storing the image data of the composite image regarding the in-vivo tissue obtained as a result of the calculation in the combination 11, and its configuration is shown in FIG. 3 in the same manner as the image memory 12. It looks like this. Data from the output buffer memory 13 is constantly read out in synchronization with the clock from the timing controller 14.

The reading is performed in accordance with the scanning on the television monitor J6. The timing controller 14 performs data read control and generation of a television synchronization signal for displaying the image data stored in the memory card 1J13 on the television monitor 16.

Image data from output buffer memo IJ13 is transferred to D/
The signal is converted into a digital analog image signal by the A converter 15, and mixed with the synchronization signal from the timing controller 14. The combined output video signal is then input to the television monitor 16, and a composite image is displayed.

The computer 11 has the following three functions.

(1) Control of scan controller 10 (2)
) Transfer of digitized orthogonal component data (3) Image composition processing These three functions will be explained in sequence.

That is, the combination error 11 is the scan controller 1.
For 0, an instruction to emit ultrasonic waves and a hexagonal transducer to be driven are specified. When the scan controller 10 receives an instruction to emit ultrasonic waves from the conbeater 11, it immediately controls the pulser 2 to drive the designated element group.

Note that the instruction to emit ultrasonic waves is given at the time when data reading from the C-human buffer memory 8 and the S-human buffer memory 9 is completed.

The CO8 component 1) and the SIN component Y(t) obtained by one ultrasound emission are temporarily stored in the C-manpower buffer memory 8 and the S-manpower buffer memory 9, as described above. The control 11 sequentially reads these data from the large cover memory 8.9 and stores them in the image memory 1.
The information is sequentially stored at an address determined by the position and depth of the driven vibrator in 2.

The image synthesis process starts after the ultrasound scan is completed and all orthogonal component data is stored in the image memo IJ12. This will be explained below.

The processing is carried out from left to right in the image memory shown in Figure 2.
Do this in order from shallow to deep. Therefore, the first orthogonal component data taken into the computer 11 is one line of data starting with (0,0). On the other hand, as processing based on the aperture synthesis method, a composite sum with a function K(x) expressed as K (x)=exp CjAx2] is calculated. Here, A is 2π/λ2, which is determined by the wavelength λ of the ultrasonic waves and the depth Z at which images are to be combined. The absolute value of the calculation result is further taken and stored in the output buffer memory 13. The above processing is repeated until the Y address reaches 511.

An embodiment of the ultrasonic diagnostic apparatus according to the present invention has been described above. What is shown here is just one example, and various implementation methods are possible without changing the essence.

For example, the number of elements used for transmitting and receiving ultrasonic waves was set to 11,
This number is determined by considering the allowable complexity of the device, and is not necessarily limited to this number.

Further, although a plurality of elements are used for both transmission and reception, sufficient results can be obtained depending on the required performance even if a plurality of elements are used for either transmission or reception.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a diagram for explaining the configuration of an image memory and an output cover memory in the same embodiment. 1... Ultrasonic probe, 4.5... Phase detector, 6
．． 7...A, /D converter, 819...Input buffer memo IJ, 10...Scan controller, 11...Computer, 12...Image memory, 13...Output buffer memory, 15...A /D converter, 16...TV monitor.

Claims (1)

[Claims] (]) means for transmitting sound waves to a region to be imaged; means for receiving reflected waves from the region of the sound waves transmitted by the means; and means for obtaining reception No. 4 corresponding to the reflected waves; means for sequentially changing the transmitting and receiving positions by the means for transmitting sound waves, and means for synthesizing images by an aperture synthesis method based on the receiver No. 4, and the means for transmitting the sound waves is means for driving a plurality of elements. and means for controlling the timing so as to first drive the center one of the plurality of elements and gradually delay the driving timing as the distance from the center increases, and the means for receiving the reflected wave includes a means for controlling the timing so as to drive the center one of the plurality of elements and gradually delay the driving timing as the distance from the center increases. signals from the plurality of elements are inputted to the adding means earliest, and the delay time is gradually increased as the distance from the center increases. (2) the means for receiving the reflected wave includes means for receiving by one element or means for summing signals from a plurality of elements, controlling the timing; (3) the means for transmitting the sound wave; said imaging device including means for transmitting by one or more elements;