JPH0282952A - Transmitter/receiver of ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To reduce the number of delay elements while keeping the quality of a tomographic image by a method wherein a delay circuit is constituted only of delay elements used at the same time and the number of the ultrasonic vibrators connected to said delay elements are made different corresponding to different focal positions. CONSTITUTION:The delay element 31 at a focal position 1F is set so that the number and value thereof are used with respect to other focal positions as they are and, by changing the number of the ultrasonic vibrators 71 connected to one delay element 31, the qualities of image data due to all of focal positions are matched with that of the focal position 1F. By this constitution, image quality becomes almost same to that in the case of the focal position 1F but a lowering of image quality as a whole is not generated. Further, by using the same delay elements 31 at all of the focal positions of four places, it is necessary to prepare 77 delay elements 31 having different delay values conventionally but the number of the delay elements may be 14 in this apparatus and the number of necessary delay elements can be reduced without lowering the image quality of a tomographic image as a whole.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention converges and scans ultrasonic waves by electrically controlling them, and utilizes the reflection of the ultrasonic waves inside the human body as a subject. The present invention relates to a transmitting/receiving device of an ultrasonic diagnostic apparatus for performing medical diagnosis by visualizing a tomographic plane of a subject.

[Conventional technology]

Ultrasonic diagnostic equipment emits ultrasonic waves into the human body being examined and receives the ultrasonic waves reflected from the interfaces of organs within the body, which is repeated by changing the position, and then transmitting the received signals. A tomographic image of a human body is obtained by performing arithmetic processing using a computer.

In order to obtain two-dimensional tomographic images, ultrasound diagnostic equipment emits ultrasound that focuses at several different positions in the depth direction of the human body, and obtains image data in the depth direction for each focus. One image data in the depth direction is obtained by appropriately combining the data for each. Furthermore, one tomographic image can be obtained by scanning the surface direction of the human body perpendicular to the depth direction at predetermined intervals to obtain two-dimensional image data. Creation of such a tomographic image 1
By performing this several tens of times per second and displaying it on a television monitor as a display device, images can be obtained that are synchronized with changes inside the human body and movements of an ultrasound probe as an ultrasound transmitter/receiver by an operator.

In order to obtain such a tomographic image, high-speed processing is required, so all processing is performed using electronic circuits.

FIG. 3 is a conceptual diagram for explaining the operation of a conventional transmitting/receiving device of an ultrasonic diagnostic apparatus. In this figure, a transmission circuit l generates a transmission signal that is a high-frequency pulse of a predetermined frequency, and this transmission signal is converted into a plurality of transmission signals having different delay times by a delay circuit 30 composed of a plurality of delay elements 31. Then, these transmission signals are selected by the delay element selection circuit 4 according to the number and combination of ultrasonic transducers 71 of the ultrasonic probe 7 for each delay element 31 in accordance with the focal position, and the ultrasonic transducers The selection circuit 60 selects the ultrasonic transducers 71 that should emit ultrasonic waves corresponding to the scanning position, and the selected ultrasonic transducers 71 each emit ultrasonic waves. These ultrasonic waves are focused at the focal position set by the delay element selection circuit 4 on the scanning line set by the ultrasonic transducer selection circuit 60.The transmission/reception selection circuit 5 only allows signals to pass through during transmission. .

The ultrasonic waves emitted into the subject are reflected at interfaces such as the surfaces of organs within the subject, and the reflected ultrasonic waves are received by the ultrasonic transducer 71.

The reflected ultrasound is received by the ultrasound probe 7, converted into a reception signal as an electric signal, and traced in the opposite direction to the transmission time to reach the reception circuit 2. The process is as follows. All the ultrasonic transducers 71 constituting the ultrasonic probe 7 receive reflected ultrasonic waves and output received signals converted into electrical signals.
Since the ultrasound transducer selection circuit 60 is maintained in the same state as when transmitting, only the reception signal received by the ultrasound probe 7 that emitted the ultrasound during transmission is output to the transmission/reception selection circuit 5. At the beginning of reception, the transmission/reception selection circuit 5 outputs only the reception signal corresponding to the ultrasonic transducer 71 that emitted the transmission signal with a large delay time, and the others are blocked by the transmission/reception selection circuit 5, and as time elapses. As it receives reflected ultrasound from a deeper position, it is also controlled to output a reception signal corresponding to the ultrasound transducer 71 that emitted the transmission signal with a smaller delay time. The output signal of the transmission/reception selection circuit 5 is inputted to the delay element selection circuit 4 and is passed through the same delay element 3 as used during transmission.
1 to the receiving circuit 2, each input signal of the delay circuit 3 is inputted to the delay circuit 3 because the distance between the reflection position and the position of the ultrasonic transducer 71 differs depending on the position of the ultrasonic transducer 71. The phases of the respective received signals differ by the difference, but this phase difference is corrected by the delay circuit 3, and the respective received signals are added and emphasized to become the input signal of the receiving device 2. Become.

The timing of the transmission of high-frequency pulses by the transmitting device, the operation of the transmitting/receiving selection circuit 5, and the image synthesis based on the received signal by the receiving device 2 are controlled by a control device (not shown), and digital scans, abbreviated as D, S, and C, are controlled by a control device (not shown). The converter performs image processing.

FIG. 4 is a diagram for explaining the principle of a method of creating a focus of ultrasonic waves at a specific point. In this figure, the arc-shaped I
D is called a delay pattern with respect to the focus position IF, and the relationship is such that the focus position 111F is the center position of the delay pattern ID.

91 is the ultrasonic transducer 7 of the ultrasonic probe 7 in FIG.
1 represents the surface of the object on which the objects are lined up, and 92 represents the scanning line pointing in the depth direction of the object.

Assume that the ultrasonic transducers 71 are arranged on the arc of the delay pattern ID so that the direction of emitting ultrasonic waves is parallel to the scanning line 92, and ultrasonic waves of the same phase are emitted. Note that it is assumed that the propagation speed of the ultrasonic waves on the paper surface is all constant. All Zhao sound wave oscillators 71 and focal positions on delay pattern ID! Since the distances to the IF are the same, all the phases of the ultrasonic waves emitted from the respective ultrasonic transducers 71 are aligned at the focal position IF, and the intensity of the ultrasonic waves increases.

By providing the ultrasonic transducer on the arc of the delay pattern ID in this way, the focus is set at the center position of this arc, but in reality, image data is taken at four focal positions. A large number of delay elements 31 shown in FIG. 3 are used in order to obtain the same result as placing an ultrasonic transducer at a position with different delay patterns for each focal position. By electrically connecting and disconnecting the delay circuit 30 to predetermined ultrasonic transducers 71, the scanning position can be changed and delay patterns corresponding to different focal positions can be formed. There is. These operations are performed by the delay element selection circuit 4 and the ultrasonic transducer selection circuit 60 shown in FIG. 3, as described above.

Each delay element 31 of the delay circuit 30 in FIG.
may consist of a coil wound with a conductor of a predetermined length, or may consist of an inductance element and a capacitor connected in series and parallel, and these may be regulated as appropriate depending on the amount of delay. Also, it is common to tap a single delay element midway to obtain a plurality of delay amounts.

In FIG. 4, the amount of delay required by the ultrasonic transducer positioned on the object surface 91 at a distance X from the intersection of the object surface 91 and the scanning line 92 exceeds the delay dimension δ in this figure. Corresponds to the time it takes for a sound wave to propagate. The delay dimension δ can be uniquely calculated if LF, which is the depth dimension of the focus position and half the length of the delay pattern ID in the scanning direction, is determined.

The number of ultrasonic transducers 71 in FIG. 3 is around 100, and the number of ultrasonic transducers 71 constituting one delay pattern ID is equal to the opening size of the arc of the delay pattern ID in FIG. To move the horizontal position of the scanning line 92 in the scanning direction, which is a direction along the 0 surface 91, which is proportional to be exposed.

Figure 5 is called the multi-stage focusing method, in which a single scanning line is divided into four areas in the depth direction, and ultrasound is transmitted to each area to achieve a different focal position to obtain image data. This is a diagram showing the case of the method in which the focal points are IF, 2F, and 3F.

The delay patterns corresponding to these focal positions are ID, 2D, 3D, and 4D. The maximum delay dimension for each delay pattern is made to be the same, and as a result, the relationship is such that the aperture size is roughly proportional to the square root of the depth of each focal position, so the focal position The larger the depth DF, the larger the aperture size, and therefore the larger the number of ultrasonic transducers that transmit ultrasonic waves, which also compensates for the fact that the deeper the position, the greater the attenuation of reflected waves.

FIG. 6 is a numerical array diagram showing an example of the relationship between the delay amount of one delay element corresponding to one ultrasonic transducer for each focal position, and the numbers in the No. column are the numbers of the delay elements. be. The numerical values in the value column represent the delay amount of each delay element in nanoseconds, and the depth dimension of each focal position is 25 mm for IF, 50 mm for 2F, 80 mm for 3F.
+am, 4F is 120a+@, and the interval between the ultrasonic transducers is approximately 1ffiI11. In an actual ultrasonic probe, multiple ultrasonic transducers are combined into a block, and this block is used as a unit to transmit and receive ultrasonic waves, but here, one block is used. It is expressed as one ultrasonic transducer. By the way, in the numerical example mentioned above, three actual ultrasonic transducers are
This block is called an ultrasonic transducer.

The number of ultrasonic transducers in this figure corresponds to half the aperture size of the delay pattern, and the actual number of ultrasonic transducers is, for example, in the case of focal position NIF, the number of ultrasonic transducers in this figure is 14. However, the actual number is twice this, 28. However, as is clear from FIGS. 4 and 5, the delay pattern is symmetrical, so two mutually symmetrical ultrasonic transducers on both sides of the scanning line 92 have the same amount of delay. Therefore, the number of delay elements is as shown in this figure, and the configuration is such that one delay element branches off to emit two ultrasonic transducers.

Because the number of ultrasonic transducers is finite, the actual delay pattern does not become an arc as shown in Figures 4 and 5, but changes discontinuously in a step-like manner, and the overall delay pattern is close to an arc. It becomes a shape delay pattern.

Because the delay pattern becomes discontinuous in this way, there is a phenomenon in which regions where the intensity of the ultrasonic wave increases are created on the left and right sides of the focal position. This region is called a grating lobe, and as mentioned above, In an ultrasonic probe called an array wave probe in which ultrasonic transducers are arranged, grating lobes create a virtual image in a tomographic image, causing misdiagnosis in ultrasonic diagnosis.

The position where the grating lobe is generated is the object surface 91
The angle with respect to the scanning line 92 is approximately expressed by the following equation, with the origin being the intersection of the scanning line 92 and the scanning line 92.

θa = sin −' (Nλ/d) Where, λ; Ultrasonic wavelength N; Number of ultrasound transducers transmitting simultaneously d; Distance between ultrasound transducers. This is an equation related to grating lobes that occur when ultrasonic waves that are linearly arranged on the surface 91 and have the same phase are emitted, and is strictly different from the case where ultrasonic waves whose phase is delayed by a delay element are emitted. There is no problem in using it for qualitative understanding.

In order to prevent a virtual image due to the grating lobe from appearing in the tomographic image, it is sufficient to satisfy the condition that θ6 is greater than 90 degrees, and the smaller the angle θ6, the greater the intensity of the grating lobe, and therefore the stronger the virtual image is displayed. . As mentioned above, the number N of ultrasonic transducers is the focal position IF
is the smallest, and N increases as the depth of the focal position increases from 2F, 3F, and 4F, so that the influence of the grating lobe is the greatest at the focal position IF and is the smallest at the 4F.

[Problem to be solved by the invention]

In the conventional technology, as shown in FIG. 5, one delay element is associated with one ultrasonic transducer block, and when the focal position is different, the delay amount corresponding to one ultrasonic transducer block is Therefore, it is necessary to prepare four delay elements for the ultrasonic transducer block used at all four focal positions. In FIG. 5, some delay elements happen to have the same value, but even if this is taken into account, the total number of delay elements is 77, and there is a problem in that a large number of delay elements must be prepared.

An object of the present invention is to provide a transmitting/receiving device for an ultrasonic diagnostic apparatus that maintains the quality of tomographic images and reduces the number of delay elements.

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a plurality of focal positions are set in the depth direction of the subject, and ultrasound is transmitted for each focal position, An ultrasonic diagnostic device that receives reflection data to obtain tomographic image data in the depth direction, and electronically scans the data in a direction perpendicular to the depth direction to obtain two-dimensional tomographic image data, thereby visualizing the tomographic image. A transmitting/receiving device that both transmits and receives ultrasonic pulses, which contacts the subject and uses an electrical signal as a transmission signal as an input signal to transmit ultrasonic pulses into the subject and receive reflected waves. an ultrasonic probe comprising a plurality of ultrasonic transducers that output an electric signal as a received signal in a scanning direction; and the transmitted signal and the received signal are different for each ultrasonic transducer. a delay circuit including a plurality of delay elements that sets the focal position by delaying the focus position by a delay time; and a transducer selection circuit that changes the scanning position by switching connections between the delay element and the ultrasonic transducer. In the transmitting/receiving device of an ultrasonic diagnostic apparatus, the delay circuit is made up of only delay elements that are used simultaneously, and the number of ultrasonic transducers connected to the delay elements varies depending on different focal positions.

(Function) In the configuration of the present invention, the delay elements ′ constituting the delay circuit are not made into delay element groups with different numbers and delay values for different focal positions, but only one delay element is used at the same time.
The number of ultrasonic transducers to be emitted at the same time will differ depending on the focal position of the group, but by appropriately changing the number of ultrasonic transducers connected to one delay element, the focal position can be adjusted. Different delay elements having the same number and value are used to form a delay pattern corresponding to each focal position.

〔Example〕

The present invention will be explained below based on examples. FIG. 1 is a conceptual diagram showing an embodiment of the present invention, and the same components as in FIG. 3 of the prior art are given the same reference numerals and detailed explanations will be omitted.

The difference between this figure and FIG. 3 is that the number of delay elements 31 constituting the delay circuit 3 is smaller than that of the prior art shown in FIG. 3, and there is no delay element selection circuit 4 that was in FIG. Although not clearly shown in FIG. 0, the delay pattern 31 constituting the delay circuit 3 is only one that is always used, so the delay element selection circuit 4 is not required. The ultrasonic transducer selection circuit 6 has the same basic function as the ultrasonic transducer selection circuit 60 in FIG. 3, and the selected ultrasonic transducers are also the same. Since the method of connecting the vibrator and the delay element 31 is different from the conventional method, the two are not exactly the same.

FIG. 2 is a numerical arrangement diagram showing the relationship between delay elements and ultrasonic transducers corresponding to different focal positions according to the present invention.

In this figure, the leftmost column is the number of the delay element 31,
The value is the delay value (nanoseconds) of each delay element 31, and the ultrasonic transducer 71 connected to these delay elements 31
The number is shown for each focal position. Focal position ff1
In the case of F, the number of delay elements 31 is 14, and the number of ultrasonic transducers is also 14, and the number of delay elements 3 is 14.
1 and the ultrasonic transducer 71 have a one-to-one correspondence. On the other hand, when the focal position is from 2F to 4F, the delay elements 3I are the same as those at the focal position IF, and the number of ultrasound sensors connected to each delay element 31 is appropriately increased. The number of ultrasonic sensors 71 is the same as in the case of FIG. 5, with focal positions 2F, 19.3F, 24.4F, and 307'.

The number of ultrasonic transducers 71 to be assigned to each delay element 31 is determined by numerical simulation using a computer, with the optimum condition under which the generation of grating lobes is minimized.

Such numerical simulation technology is already established as a basic method used in designing medical diagnostic equipment.

In the above-mentioned explanation of the expression for the grating lobe generation angle θ, N is the number of ultrasonic transducers, but in the prior art shown in FIG. 6, the number of ultrasonic transducers 71 and delay elements 31 is equal. Therefore, N is also the number of delay elements. If the number of ultrasonic transducers 71 and the number of delay elements 31 that are simultaneously emitted are different as shown in Fig. 2, the number of delay elements 31 that determines the error when simulating a delay pattern in a discontinuous shape is different. It is reasonable to adopt this as N. Therefore, in the case of focal positions fi2F, 3F, and 4F in FIG. 2, the number of ultrasonic transducers 71 emitted simultaneously is larger than that in the case of focal position IF, but the number of delay elements 31 is made to match the focal position IF. Therefore, the generation of grating lobes is worse than in the case of FIG.

However, it is not worse than the focal point -1a position IF.

In the multi-stage focusing method with four focus positions, the quality of the tomographic image in the conventional technology is determined by the image data created by the focus position IF, and the quality of the image data created by the other focus positions is improved to some extent. However, this does not lead to an improvement in the quality of the overall image obtained.

In this invention, the delay element 31 at the focal position ff1lF
By using the same number and value for other focal positions, and changing the number of ultrasonic transducers 71 connected to one delay element 31, the quality of image data at all focal positions can be improved. If the delay element 31 is adjusted to that of the focal position IF, the image quality will be the same as that of the focal position IF, but the quality of the image as a whole will not deteriorate.On the other hand, if the delay element 31 is set to the same value at all four focal positions By using the delay elements shown in Fig. 6, it is necessary to prepare delay elements 31 having 77 different delay values, whereas the number of delay elements in Fig. 2 is 14. Approximately one-fifth is sufficient.

In this way, the number of required delay elements can be reduced without degrading the image quality of the entire tomographic image.

In FIG. 2, the number of delay elements is set to 14, but this number is determined separately from this invention, and the number of delay elements is not limited to 14 in this invention. The delay value and the number of ultrasonic transducers assigned to one delay element at a focal position other than the IF base are determined by numerical simulation as described above, and these values are also based on this. This is not intended to limit the invention, and furthermore, there is no necessity to make the number of delay elements and the number of ultrasonic transducers at the focal position IF one to one; for example, it is possible to leave the number of ultrasonic transducers as shown in FIG. 14,
In the case of the focus position IF, where the number of delay elements is 8, it is also possible to adopt a method in which a plurality of ultrasonic transducers are connected to one delay element, as in the case of the focus position 2F in FIG. 2. In such a case as well, the optimum number of ultrasonic transducers to be assigned to one delay element at each focal position can be determined by the numerical simulation method as described above.

〔Effect of the invention〕

As described above, the present invention consists of delay elements constituting a delay circuit consisting of only one group of delay elements that are commonly used at the same time even if the focal positions are different, and ultrasonic vibrations that are simultaneously emitted due to the different focal positions. By appropriately changing the number of ultrasonic transducers connected to one delay element in response to the difference in the number of ultrasonic transducers, the same number and value of delay elements can be used even if the focal position is different. A delay pattern corresponding to the position is formed. As a result, the quality of the tomographic image is determined by the quality of the image obtained from the image data obtained at the focal position, which has the shallowest depth and therefore the least number of ultrasound transducers simultaneously transmitted, and the quality of the image obtained from the image data obtained at other focal positions. The quality will be the same. Therefore, since the overall image quality is determined by the shallowest focus position,
It is possible to maintain the same level of image quality as that of the prior art. Furthermore, since the number of delay elements can be reduced to one-fifth or less, the delay circuit can be saved and the cost can be reduced, which has the effect of helping to downsize and reduce the cost of ultrasound diagnostic equipment. is obtained.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram showing an embodiment of the present invention, Fig. 2 is a numerical arrangement diagram as well, Fig. 3 is a conceptual diagram of the prior art, and Fig. 4 is a line showing the relationship between the ultrasonic focus and the delay pattern. 5 is a diagram showing the relationship between the ultrasonic focus and the delay pattern in the case of the multi-stage focusing method, and FIG. 6 is a numerical array diagram showing an example of the prior art. 1... Transmission circuit, 2... Receiving circuit, 3.30...
Delay circuit, 31... Delay element, 5... Transmission/reception selection circuit, 6.60... Ultrasonic transducer selection circuit, 7... Ultrasonic probe, 71... Ultrasonic transducer. Further 2 Figure 6・,-ri

Claims (1)

[Claims] 1) Set multiple focal positions in the depth direction of the subject, emit ultrasonic waves for each focal position, receive reflection data to obtain tomographic image data in the depth direction, and transfer this to the depth direction. A transmitting/receiving device for transmitting and receiving ultrasonic pulses of an ultrasound diagnostic device that visualizes tomographic images by electronically scanning in a direction perpendicular to the direction to obtain two-dimensional tomographic image data. A plurality of ultrasonic transducers are installed in the scanning direction to emit an ultrasonic pulse into the subject's body upon contact and receive an electrical signal as an input signal, and also to receive a reflected wave and output an electrical signal as a received signal. a delay circuit including a plurality of delay elements that delay the transmitted signal and the received signal by different delay times for each of the ultrasonic transducers to set the focal position; In a transmitting/receiving device of an ultrasonic diagnostic apparatus comprising a transducer selection circuit that changes the scanning position by changing the connection between a delay element and the ultrasonic transducer, the delay circuit is the only delay element used at the same time. 1. A transmitting/receiving device for an ultrasonic diagnostic apparatus, characterized in that the number of ultrasonic transducers connected to the delay element differs depending on different focal positions.