JPH03286747A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To prevent the generation of a shift and a distortion of an image by providing a controlling for controlling a focus or a deflection by adjusting the delay quantity of each element so as to form an image by allowing other each receiving signal to coincide with a receiving in which an echo from the same point appears at the latest. CONSTITUTION:The device is provided with an ultrasonic probe 7 having many ultrasonic vibration elements, and to each of its elements, a transmitting delay line 8 and receiving delay lines 9, 10 are connected. Transmitting driving pulses pass through this transmitting delay line 8 and are delayed, respectively, and thereafter, a given to each element, and receiving signals from each element pass through the receiving delay line 9 or 10 and are delayed, respectively, and thereafter, synthesized, and sent to an image display circuit. The reason why two sets of receiving delay lines 9, 10 are provided is because they are used alternately at the time of receiving dynamic focus. As for these delay lines 8, 9 and 10, each delay quantity thereof is controlled by control data.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an ultrasonic diagnostic apparatus for performing medical diagnosis using ultrasonic waves. [Conventional technology]

In an ultrasonic diagnostic apparatus, electronic focusing and deflection control are usually performed for transmitting and receiving ultrasonic waves. In other words, an ultrasonic probe consists of a large number of ultrasonic transducer elements, and one delayed drive pulse is given to each element, and the transmitted ultrasonic pulse is focused on one point by controlling the amount of delay. Alternatively, by delaying the received signals from each element and controlling the amount of delay, a certain point is set as the receiving focus. Furthermore, by making the amount of delay asymmetrical, the focal position is tilted and deflected.

[Problem to be solved by the invention]

However, when performing such electronic control of ultrasound waves, there is a problem in that image shifts and distortions occur. In particular, when performing so-called dynamic focusing, in which the receiving focus is switched when a single echo is received, if there is a large change in the aperture plane (the number of elements driven simultaneously) at each focus stage, a shift in the distance direction will occur on the image. An accurate image cannot be obtained. SUMMARY OF THE INVENTION An object of the present invention is to provide an improved ultrasonic diagnostic apparatus that prevents image shift and distortion from occurring.

[Means to solve the problem]

In order to achieve the above object, the ultrasonic diagnostic apparatus according to the present invention includes a probe having a large number of ultrasonic transducer elements, a delay device that delays transmitted and received signals for each element, and a probe that simultaneously receives signals. By adjusting the amount of delay of each element, the delay amount of each element is adjusted so that the received signal whose echo from the same point appears the latest among the received signals from each element is focused with the other received signals. Alternatively, a control device that controls deflection, an image display circuit to which the delayed reception signals from each element are combined and sent, and a clock signal of this image display circuit that is delayed in accordance with the above imaging time. It is characterized by being equipped with a delay circuit that allows

[For production]

The amount of delay for each of the multiple elements that simultaneously transmit or receive waves is determined by the focal length, deflection angle, or aperture surface. The imaging time is also determined according to this amount of delay. Corresponding to this imaging time, the clock signal of the image display circuit to which the delayed reception signals from each element are combined and sent is delayed. Since the time axis of the screen is then changed in accordance with the imaging time, the effect of the difference in imaging time does not appear on the screen at all.

【Example】

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, a clock signal with a period of, for example, 25 ns is generated from a basic clock generation circuit 1, and this is divided by a frequency divider 12 to become a clock signal with a period of 100 ns or 200 ns. This clock signal is sent to delay line 3, for example 25n
Delayed by S units. Clock signal before being delayed and 2
A large number of delayed clock signals delayed by 5 ns are input to the multiplexer 4, and one of them is selected. This selected clock signal is sent as a clock signal to an image display circuit (not shown). Multiplexer 4 (1) is controlled by data from memory 5 which is read out under the control of counter 6 which starts counting basic clock signals in response to a trigger signal. That is, as shown in FIG. The data of Δt1, then the data of Δt2, etc. are sequentially read out from the memory 5, and a clock signal having a delay amount corresponding to the data is selected and output from the multiplexer 4.In an ultrasonic diagnostic apparatus, Usually, as shown in FIG. 2, an ultrasonic probe 7 having a large number of ultrasonic transducer elements is provided, and each of the elements includes a delay line 8 for transmitting waves, a delay line 9 for receiving waves. 10 is connected to the wave transmitting delay line 8. After the wave transmitting drive pulse is delayed through the wave transmitting delay line 8, it is applied to each element, and the wave receiving signal from each element is transmitted to the wave receiving delay line 9 or 10, and then synthesized and sent to the image display circuit.The reason why two sets of wave reception delay lines 9 and 10 are provided is to use them alternately during wave reception dynamic focusing. The amount of delay of each of the delay lines 8, 9, and 10 is controlled by control data. This control data is stored in advance in a memory such as RAM or ROM as delay data for deflection and focus. Image display The circuit includes one A/D converter and one image memory.
2 is provided, and the received wave signal synthesized through the wave reception delay line 9 or 10 is first sampled and A/'D converted by the A/D converter 11, and then is converted by the address control circuit 13 of the image memory 12. When the writing for 61 screens at the designated address is completed, the readout circuit 14 reads out the contents of the image memory 12 according to the display method of the display device 15, and displays them on the display device 15. The A/D converter 11 and address control circuit 13 of this image display circuit receive the tarock signal output from the multiplexer 4 (Fig. 1), and receive the received signal in accordance with this clock signal. Signal sampling・A,/
The timing of D conversion and the timing of changing the write address of the image memory 12 are controlled. Here, we will explain in detail how to provide a delay to each element of the probe during wave transmission and wave reception. First, consider receiving ultrasonic waves from point F1 using seven elements E arranged on a plane in a probe as shown in FIG. Assuming that this point F1 is on a normal line passing through the center of the element array, the ultrasonic waves from F1 reach the central element at the earliest time and reach the elements at the upper and lower ends latest. Therefore, a delay amount dt as shown by the arrow is given to the received signal of each element. Then, after the delay, the ultrasonic signals from point F1 will be at the same time, and the focal point at the time of wave reception will be Fl, which is the same as placing each element on a curved surface as shown by the dotted line. become. The received signal waveform is shown in FIG. 5. Figure 5 shows the sound pressure waveform when a sound wave is generated at time T.
Waveform A is the waveform of the received signal obtained from the central element, waveform B is from the elements on both sides of it, waveform C is from the elements on both sides of it, and waveform is from the elements on both ends. It is from. In this way, the sound pressure waveform is fastest at the center, which is closest in terms of distance, and lags as it moves away from the center because the distance increases. Therefore, if the sound pressure waveforms are delayed so that the time of the latest one matches, the sound pressure waveforms will overlap and form an image at the time of the latest one, and the signal sensitivity near point F will increase. In this case, the delay time dtl for the center element is the largest, and delaying by this time dtl means that the received signal is moved from the center element to the actual point F1 by a distance corresponding to the delay time dtl. This means that it is treated as being from a point Fl' which is further away than . If the delay time is determined using the center element as the origin, the image appears deeper on the screen than it actually is. Looking at point F2 which is farther away than point F1, this point F
It can be seen that the difference between the time when the ultrasonic wave from 2 reaches the central element and the time when it reaches the upper and lower end elements is smaller than that at point F1.6 In other words, the amount of delay alt2 to be given to the central element is , dtl may be used. Therefore, when this amount of delay is given, the amount of deviation from point F2 to point F2' is smaller than the amount of deviation from point F1 to point Fl'. Therefore, due to the difference in the amount of shift that occurs when changing the focal length, when performing dynamic focusing that changes the focal length while receiving one echo signal, it is necessary to This will cause a shift in the image in the vicinity. The same applies when changing the aperture surface. As shown in Figure 6, when receiving waves with 7 elements, it is necessary to give a delay time dt1 to the center element, but when receiving waves with 5 elements excluding both ends, the center It is only necessary to give a shorter delay time dt2 to the element. That is, as shown in FIG. 7, the sound pressure waveform that arrives the latest is waveform C when there are five elements, so the received signal from the central element that arrives earliest at the same time (waveform A) This is because it can be delayed. Therefore, when the aperture is large, the imaging time is later than when the aperture is small. In the case of deflection, as shown in FIG. 8, even if the focal length is the same, if the deflection angle is different, the imaging time will be different. For example, the time it takes for the sound wave from point F1 in FIG. 8 to reach the top element is longer than the time it takes for the sound wave from point F2 to reach the top element. The received signal waveform of each element is as shown in FIG. Waveforms A to G correspond to each element from the top end to the bottom end. The solid line shows the sound pressure waveform from point F1, and the dotted line shows the sound pressure waveform from point F2. Therefore, even when the received signals from each element are delayed by giving a delay time so that they match in time with the latest one, the times at which the signals are made to match are different. Also, the delay time given to the central element is also dtl, d
Unlike t2, as a result, when viewed from the central element, deviations occur from Fl to Fl' and from F2 to F2', and the amount of deviation is different, resulting in the arc being represented like an ellipse. This results in image distortion. We have explained about wave reception, but the same applies to wave transmission, so the difference in image formation time during wave reception is added to the difference in image formation time during wave transmission, resulting in deviations and distortions in the image. It becomes even bigger. When the switching of the focal length, the change of the aperture plane, and the deflection are combined, the steps and distortions of these images will overlap. Therefore, especially when obtaining a B-mode image in dynamic focus, when enlarging the screen using a probe with a high resolution such as 7.5 MHz, the step at the focus switching point becomes noticeable. Therefore, as described above, the black/yellow signals of the image display circuit are delayed by Δt (Δtl, Δt2, . . . ) to compensate for the deviation in the imaging time of the received signal. This delay time Δt is dtl in FIGS. 4 and 5.
This corresponds to the time difference between dtl and dt2 in FIGS. 6 and 7, and the time difference between imaging times in FIGS. 8 and 9. For example, when performing dynamic focusing and switching to focus F1 as the first stage focus in an area close to the element in FIG. 2, and switching to focus F2 as the second stage focus in an area adjacent to the element,
Δtl of stage focus = o, Δt2 of second stage focus
=tdl-td2, the sampling/A/D conversion timing and the write address of the image memory 12 are adjusted according to the difference in the amount of deviation in imaging time between the first stage focus and the second stage focus. Since the advance of the image can be stopped, the image formed in the memory 12 has no difference in the amount of shift in image formation time. That is, on the image, the amount of deviation from F2 to F2' in FIG. 4 is matched to the amount of deviation from Fl to Fl'. This data Δt is calculated in advance for each focus stage and written into the memory 5 composed of RAM or ROM. The calculation is done by the CP built into the ultrasound diagnostic equipment.
It is calculated as the difference between each delay amount with respect to the maximum value of the imaging time delay amount, which may be calculated as U. For example, in the case of 32-step dynamic focusing, the imaging time of the received signal for one echo is determined in 32 ways, and the imaging time delay is determined in 32 ways, so each focus is determined from the maximum value of the delay amount. By subtracting the amount of delay in the stage, the first stage,
Delay times Δt1, Δt2, . . . , Δt32 for each focus stage of the 2nd stage, . This is stored in the memory 5, and as shown in FIG. A determination is made as to whether the stage focus is on, etc., and Δt1 and Δt2 are determined accordingly.
,..., are sequentially read out from the memory 5,
A clock signal given a delay time of Δt1, Δt2, . . . for each focus stage is sequentially sent to the multiplexer 4.
obtained from. Although the delay line 3 and multiplexer 4 are used above to delay the clock signal applied to the image display circuit, a circuit that stops the clock signal by Δt may also be used.

【Effect of the invention】

According to the ultrasonic diagnostic apparatus of the present invention, deviation and distortion of a B-mode image during dynamic focusing can be eliminated. Since the received signal itself is not delayed extra, characteristic deterioration caused by the received signal passing through an extra delay line can be avoided6.

[Brief explanation of drawings]

1 and 2 are block diagrams showing respective parts of an embodiment of the present invention, FIG. 3 is a time chart for explaining the operation, and FIGS. 4, 6, and 8 are ultrasonic waves. FIG. 5, FIG. 7, and FIG. 9 are waveform diagrams showing the relationship between transmission, element arrangement, and delay time. 1... Basic clock generation circuit, 2... Frequency dividing circuit, 3
...Delay line, 4...Multiplexer, 5.
...Memory, 6...Counter, 7...Probe, 8
... Delay line for transmitting waves, 9.10... Delay line for receiving waves, 11... A/D converter, 12... Image memory, 13... Address control circuit, 14... Readout circuit, 15...Display device.

Claims (1)

[Claims] (1) A probe that has a large number of ultrasonic transducer elements, a delay device that delays the transmitted and received signals for each element, and a delay device that delays the transmitted and received signals for each element. A control device that controls the focus or deflection by adjusting the amount of delay of each element so that the received signal in which the echo appears the latest is matched with the other received signals to form an image; An ultrasonic diagnostic apparatus comprising: an image display circuit to which received signals from the elements are combined and sent; and a delay circuit to delay the clock signal of the image display circuit in accordance with the imaging time. .