JPS6140417B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ultrasonic tomography apparatus that obtains an ultrasonic tomographic image by applying an ultrasonic beam to a subject such as a human body and displaying the echoes on a display means such as a cathode ray tube. A method of driving an array-type (or array-type) ultrasonic transducer for
The present invention also relates to a tomographic image display method and apparatus using received signals from an array type ultrasonic transducer. Conventionally, for electronic deflection of ultrasound beams, a method has been used in which multiple ultrasound transducers are arranged in an array and the ultrasound beam is deflected by giving a time difference to the excitation of each transducer. . Figure 1 shows this situation. If n transducers #1 to #n arranged in a straight line are simultaneously excited, the main beam of the ultrasonic wave is perpendicular to the arrangement direction (FIG. 1a).
In addition, a delay time is set for each transducer so that the wavefront of the sound wave of each transducer becomes the same phase at a distance between the transducers # _{1 and #n corresponding to the distance from d 1} to d _o (d _{1 >} d o ). τ ₁ ~ _{τ o}
(τ _o = d _o /vv is the sound speed in the observed medium, τ ₁ >
When excited by giving τ _o ), the main beam of the ultrasonic wave becomes θ
( _Fig ^. 1b). Similarly, if d ₁ < d _o (τ ₁ < τ _o ), -θ
(FIG. 1c). As described above, deflection of the main ultrasonic beam is possible by giving an appropriate delay time to the excitation of each vibrator arranged in an array. Based on this principle, it is also easy to scan the ultrasound main beam in a fan shape. Now, in such a case, in order to receive the echoes of the ultrasonic beam, perform phase matching, and display the echoes in brightness on a cathode ray tube (hereinafter abbreviated as CRT) for human observation,
It is necessary to scan the CRT beam in a fan shape in synchronization with the excitation time of the vibrator. For this purpose, the configuration shown in FIG. 2 can be considered. The output signal of the main oscillator 1 is applied to the main counter 3 and the sawtooth wave generator 2. The momentary contents of the main counter 3 are converted into analog signals by a D/A converter 4, and then converted to an analog signal by a sine converter 5 and a cos converter 6.
becomes the input. On the other hand, the sawtooth wave generator 2 is triggered by the signal from the main oscillator 1 to create a sawtooth wave, and its output signal becomes the other input of the sine converter 5 and cos converter 6. sin converter 5
The cos converter 6 has the function of multiplying the signal from the sawtooth wave generator 2 by sin or cos by the signal from the D/A converter 4. sin converter 5 and
The output of the cos converter 6 is applied to the X and Y deflection systems of the CRT 8, respectively. On the other hand, the main counter 3 controls the delay time control device 7 according to its contents, and generates a delay time in each element of the array type vibrator 9 according to the contents of the main counter 3, synchronizing with the timing of the main oscillator. Each element #1 to #n is excited with the above delay time. The receiving unit 10 receives echoes of the ultrasonic waves emitted by the array transducer 9, and transmits the echoes.
It is assumed to be the brightness signal of CRT8. The receiving section 10 is naturally equipped with a function of adjusting the phases of the received signals from each element. With the above configuration, the ultrasound beam can be deflected into a fan shape, and at the same time, the display system can also be deflected into a fan shape in response to the ultrasound beam, and the echoes from the ultrasound beam can be modulated in brightness, allowing observation of tomographic images of the subject. can do. Generally, the array type vibrator 9 is commonly used as a receiver for the receiving section 10. However, when configured in this way, the following drawbacks arise. Generally, when performing fan-shaped scanning,
Scanning is performed sequentially from one end of the fan to the other,
The ultrasonic beams that make up this fan are both transmitted and received with directivity in their angular directions. However, this directivity usually has a considerable range, so the next time the angle is slightly deflected and the ultrasonic wave is emitted, it is necessary to provide a delay several times the observation time to avoid being affected by previous multiple echoes, etc. There is. For this reason, the method of sequentially scanning from one end of the fan to the other end cannot shorten the interval between emitting ultrasonic waves.
It takes longer to obtain a desired tomographic image. In order to shorten this tomographic image creation time, instead of the sequential scanning described above, when the observation of one ultrasonic beam that makes up the fan is completed, it is possible to The next ultrasonic beam may be emitted toward a point with no lobe, that is, a point with zero directivity, but with the configuration shown in FIG. 2, the lines of the fan cannot be created in any order. In addition, in order to do so, sine converter 5 or
A special function generating means is required in place of the cos converter 6, etc., making the circuit system complicated, and the configuration of the delay time control device 7, which is a device for generating delay time given to each vibrator element, also becomes complicated. An object of the present invention is to provide an ultrasonic tomography apparatus that can eliminate the above-mentioned drawbacks. The present invention will be explained below with reference to the drawings. FIG. 3 is a circuit diagram of one embodiment of the present invention. Third
In the figure, 11 is a storage device, and this storage device 11 stores a display position designation signal for controlling the display means for any one angle of the fan according to a scanning sequence that scans in a fan shape. , a delay amount signal given to each vibrator (this delay amount does not have to be the same, but may be equivalent) are stored in advance as a set of data. The storage device 11 is
As illustrated in FIG. 4, the data access means consisting of the main oscillator 1 and the main counter 3 is used to generate display position designation signals such as sin and cos values and delay amount signals according to the contents of the main counter 3. can be extracted in parallel and input to the multipliers 12 and 13 and the delay time control device 7. This can also be configured to be taken out serially and stored in a separate storage device. With this configuration, the order in which the deflection angles are selected can be arbitrarily determined depending on how the data is arranged in the storage device 11. The sin value of this storage device 11 is sent to a multiplier 12, and the cos value is sent to a multiplier 13.
are connected to and multiplied by the signal from the sawtooth generator 2, and the output signals of these multipliers 12 and 13 are
Each is added to the X and Y deflection systems of the CRT8.
Note that the above operation can also be realized using a digital circuit. Further, each element #1 of the array type vibrator 9 is controlled by the output signal of the delay time control device 7 which receives the delay amount signal of the storage device 11.
~#n are excited with a delay time according to the delay amount signal. With such a configuration, the conventional drawbacks can be overcome. That is, the order in which the fan shapes are created can be changed by changing the arrangement of data in the storage device 11, and the amount of delay given to each vibrator can be changed, for example, by
50 No. 135082 (see Japanese Patent Publication No. 56-42293) "Ultrasonic Vibrator Driving Method and Apparatus". According to this method, it is possible to control not only the directivity of transmitted waves but also the directionality of received waves. As an example of the delay time control method,
50 No. 135082 (see Japanese Patent Publication No. 56-42293), how the delay time control device 7 and the array type vibrator 9 can be controlled depending on the contents of the storage device 11. How it is driven will be briefly explained with reference to FIG. In FIG. 5, the counter 3 sequentially counts the signals from the main oscillator 1,
At each count, an address in the storage device 11 is selected and an output M〓(i) (i is 1 to n, where n is the total number of transducers in the array) are output in parallel. This M〓(i) is previously determined and stored for all deflection angles θ. This M〓(i) is a quantity determined by normalizing the required delay time by a certain value and determining whether or not this normalized quantity has a difference between adjacent elements. Now, the parallel output M(i) becomes the preset input of the shift register 20, and becomes the serial input.
By the action of RI, LI and clock pulse CP1,
Via the gate 21, it is input to the counters 22 ( _CT1 to _CTn ) provided corresponding to each vibrator, and each counter 22 has the contents corresponding to the delay time.

[Formula] becomes. If the content of each counter 22 is made into an excitation pulse by adding the clock pulse CP2, it becomes possible to deflect the ultrasonic beam to a predetermined deflection angle. Receiving section 1
0 also receives the output signal M(i) from the storage device 11 and performs phase matching using this M(i) to form a brightness modulation signal for the CRT. In this case, it is clear that M(i) functions as a delay time selection signal (for example, a tap selection signal for an LC type delay element) for the delay element installed on the output side of each transducer in the so-called differential ultrasonic wave receiving system. Needless to say. FIG. 6 is a diagram showing another embodiment of the present invention.
A sub oscillator with a slower oscillation frequency is provided which is synchronized with the main oscillator 1 shown in FIG.
During this fixed period, a sub-counter (in this embodiment, a counting function is not essentially required, but a counting function is required when displaying the scanning M mode as described later) is set in advance to an arbitrary value. If the address of the storage device is selected using the contents of , such words are used, various displays become possible.
For example, a configuration for obtaining a fan-shaped M mode (UCG) in an arbitrary angular direction at the same time as a tomographic image will be described. This M-mode method is to emit ultrasound in a certain direction, for example, the depth direction in which the ultrasound travels is set on the Y-axis of the display system, and the elapsed time is set on the X-axis, and the display system is based on the intensity of the ultrasound echo. It modulates the brightness. FIG. 6 shows an embodiment for simultaneously displaying a tomographic image and this M mode. In FIG. 6, 15 is a sub oscillator (for example, a frequency divider that divides the output of the main oscillator) that outputs an oscillation frequency slower than the main oscillation frequency synchronized with the main oscillator 1, and the output of this sub oscillator 15 is connected to the main counter 2',
This output is led to a D/A converter 17, and another
Connect to the X deflection system of CRT8'. In other words, the main counter 2' and the D/A converter 17 constitute a kind of sawtooth wave generator. Therefore, the scanning speed of the CRT 8' in the X direction is slow. On the other hand, the signal of the sawtooth wave generator 2 is
In the deflection system, the output of the receiving section 10 is connected to the changeover switch 1.
It is added to the Z signal system of CRT8' through 4'. It also includes a sub-counter 16, the output of which is applied to the storage device 11 through the changeover switch 14. With this configuration, the changeover switches 14 and 14' are switched to the b side at the timing of the sub oscillator 15, and the CRT
8' can create an M mode waveform.
Now, the main oscillator 1 is set to 5kHz, and the sub oscillator 15 is set to 5kHz.
If 500 Hz is selected, an M-mode waveform is obtained for every 10 fan-shaped lines, and tomographic images can be observed in real time with such time division, and can be viewed in any direction (the contents of the sub counter 16). An arbitrary fan-shaped line can be selected using the M-mode waveform. In this case, the set direction is clearly displayed on the CRT8. This is because the number of times the electron beam rasters in this direction is sufficiently large compared to other directions, so the brightness is much greater.
Other ways to clarify this direction
Measures such as blanking the CRT 8 may also be taken. Furthermore, by causing the sub-counter 16 to perform a counting function, it is possible to easily observe the M mode in which a tomographic image is scanned by sweeping. In addition, in the figure, the delay time control device 7 is shown included in the array type vibrator 9. FIG. 7 shows yet another embodiment of the present invention, in which narrow field selection means is provided within the data access means of FIG. In the present invention, as is clear from the above description, the maximum angle at which fan-shaped scanning can be performed, that is, the maximum deflection width (hereinafter referred to as wide field of view) is determined by the storage means 11.
Determined by the data accumulated in (Of course, resolution etc. are taken into consideration when accumulating this data.) It would be very effective if any narrow field of view (hereinafter referred to as narrow field of view) within the wide field of view could be selectively displayed. This is because, especially when observing a moving organ such as the heart, by first observing a wide field of view and then observing only the desired area with a narrow field of view, the screen creation time can be shortened. This is because it is possible to display the movements of valves and the like closer to real-time display. In this embodiment, a means for selecting a desired narrow field of view from a wide field of view set in the storage means 11 and repeatedly displaying the selected narrow field of view is disclosed. In Figure 7, 2
Reference numeral 4 denotes a region selector driven by the main oscillator 1, and the state of the starting point generator 23 is forcibly preset in the main counter 3 by a signal from the region selector 24. (In this case, the main counter 3 uses a counter that can be preset.) With this configuration, the area selector 24 can limit the field of view width, and the starting point generator 23 can arbitrarily change the scanning start position. Since the deflection area is provided, a desired deflection area can be arbitrarily selected. For example, the starting point generator 23 generates a binary code representing an address corresponding to an arbitrary deflection angle in a fan shape, and the binary code corresponding to the position of this fan shape can be freely selected. Further, the area selector 24 generates timing depending on the number of fan-shaped lines, and it goes without saying that it can also be configured with a simple counter. Next, the effects of the present invention will be described. As detailed above, according to the present invention,
Does not require nonlinear elements such as sin conversion or cos conversion,
In addition, it can be easily changed to a shape other than a fan shape, and for example, when scanning in a fan shape, the amount of transducer delay corresponding to one line of the fan, data for specifying the position of the X-Y display system, etc. Since the data is stored as a set of data, the control unit is simplified and the ultrasonic launch time can be shortened, and it is also possible to display a tomographic image and M mode in any angular direction at the same time. Further, the configuration can be easily modified to allow a desired deflection area to be selected arbitrarily. In addition to the effects described above, according to the present invention, the conventional second
Another effect is that the configuration of the delay time control device 7 in the configuration shown in the figure is simplified. In other words, the delay time τ〓 given to the vibrator for any deflection angle is l・
It is given by sinθ/v. In the range where θ is small, τ
〓 approximately satisfies l·θ/v. In such a range, when the amount of change in τ〓 is equal, the deflection angle on the CRT also changes by approximately the same deflection angle. However, as θ becomes larger, this relationship is no longer satisfied, and the direction in which the ultrasonic waves are emitted does not correspond to the emission line on the CRT. For this reason, either the deflection angle or τ must have a nonlinear element.
On the other hand, according to the present invention, even when deflected at equal deflection angles,
Alternatively, even if the deflection is performed by a uniform change of τ, the data in the storage device 11 can be created in advance so that there is always a correspondence between the emission direction of the ultrasonic wave and the bright line on the CRT, which simplifies the configuration of the device.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining the present invention,
FIG. 3 is a diagram of one embodiment of the present invention, FIG. 4 is a detailed diagram of a part thereof, FIGS. 5 and 6 are diagrams of other embodiments of the present invention, and FIG. 7 is a still further embodiment of the present invention. FIG. Explanation of symbols, 1... Main oscillator, 2... Sawtooth wave generator, 3... Main counter, 4, 17... D/A
Converter, 5...sin converter, 6...cos converter, 7
...Delay time control device, 8,8'...Cathode ray tube,
9...Array type vibrator, 10...Receiving section, 11...
...Storage device, 12, 13... Multiplier, 15... Sub-oscillator, 16... Sub-counter, 20... Shift register, 23... Starting point generator, 24... Area selector.

Claims (1)

[Scope of Claims] 1. A plurality of ultrasonic transducers are arranged in an array and each transducer is given a desired amount of delay, thereby transmitting and receiving ultrasonic waves at a deflection angle corresponding to the amount of delay, and generating the received signal. In an electronic scanning type ultrasonic tomography device that displays a tomographic image of a subject on a display means, a delay amount signal given to each transducer and a display position designation signal consisting of a sine value and a cosine value given to the display means are used for each deflection. It consists of a storage means that has been stored in advance as set data for each angle, and a main counter that counts the main oscillator and its oscillation frequency.A delay amount signal and a display position designation signal for the deflection angle according to the output of this main counter are read from the storage means. and a second display means in addition to the display means, the data access means in addition to the main oscillator and the main counter;
a sub-oscillator that is synchronized with the main oscillator and has an oscillation frequency slower than the oscillation frequency of the main oscillator; and means for interrupting reading by the main counter and selecting an address corresponding to a predetermined deflection angle when the sub-oscillator oscillates. An ultrasonic tomography apparatus characterized in that the received signal obtained by the delay amount signal of the address is used as the Z signal of the second display means. 2. In the device according to claim 1,
An ultrasonic tomography apparatus characterized in that the data access means comprises narrow field selection means. 3. In the device according to claim 2,
A data access means to which the narrow field selection means is attached is connected to a main oscillator, a presettable main counter for counting the output of the main oscillator, and a preset input of the presettable main counter, A start point generator to which a signal designating an address where data related to the scan start point is stored is set, and a signal to which the output of the main counter is input and causes the main counter to preset the address designation signal of the start point generator. An ultrasonic tomography apparatus comprising: a region selector that generates an area selector;