JPS6238984B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention arranges a plurality of transducers in a row, and changes the number of transducers used at the same time for each repeated pulse or for each arbitrary fixed period, thereby increasing the ultrasonic scanning line density. The present invention relates to an ultrasonic diagnostic device that improves the caliber and has a variable aperture function.

Conventionally, when obtaining a B-mode display of a subject using an ultrasonic diagnostic apparatus equipped with an ultrasonic probe in which a plurality of transducers are arranged in a row, a method for improving the scanning line density of an ultrasonic beam by the ultrasonic probe includes: A method of increasing or decreasing the number of simultaneously driven vibrators is known.

In Figure 1, the number of simultaneously driven transducers is increased or decreased by one for each repeated pulse, the number of simultaneously driven transducers is the same during transmission and reception, and the interval between ultrasonic scanning lines is changed between each transducer. A method to reduce the pitch to 1/2 is shown. In Fig. 1, during the first repeated pulse, three of the ultrasound probes (No. 1 to No. 3) having multiple transducers arranged are simultaneously driven to send an ultrasound beam inside the object. Then, the same three ultrasound echoes (No. 1 to No. 3) receive the ultrasound echoes from inside the subject. Next, at the time of the second repeated pulse, four transducers (No. 1 to No. 4), increased by one, are simultaneously driven to transmit the ultrasonic beam to the inside of the object, and the ultrasonic wave from inside the object is transmitted. The same four echoes (No. 1 to No. 4) are received. By similarly changing the number of simultaneously driven vibrators from three to four for each repeated pulse, the center of directivity of the group of simultaneously driven vibrators can be set to 1/2 of the vibrator pitch.

Figure 2 shows the feed. A method of changing the number of oscillators driven simultaneously during reception is shown. As shown in Figure 2a, three oscillators (No.
1 to No. 3) are simultaneously driven to transmit an ultrasound beam, and then the ultrasound echoes from inside the object are received by the same three transducers (No. 1 to No. 3) used during transmission. do. At the time of the next repeated pulse, the three transducers (No. 1 to No. 3) are simultaneously driven to transmit an ultrasound beam as shown in Figure 2b, and the ultrasound echoes from inside the object are detected. Reception is performed using four transducers (No. 1 to No. 4), one more than when transmitting. At the time of the third repeated pulse, as shown in Figure 2C, an ultrasonic beam is transmitted by simultaneously driving three transducers (No. 1 to No. 3) during transmission, and three transducers (No. 1 to No. 3) are driven simultaneously during reception. Ultrasonic echoes are received by simultaneously driving the transducers (No. 2 to No. 4). During the fourth repeated pulse, as shown in Figure 2 d, an ultrasonic beam is transmitted by simultaneously driving four transducers (No. 1 to No. 4) during transmission, and one transducer during reception when transmitting. Ultrasonic echoes are received by simultaneously driving the reduced number of three (No. 2 to No. 4). By repeating the above scanning, the interval between ultrasonic scanning lines can be reduced to 1/4 of the transducer pitch.
It can be done.

Furthermore, a method called variable aperture technology is known as a technology for narrowing the ultrasonic reception beam width at a short distance in depth.

This method will be explained using FIG.

In FIG. 3, numeral 10 indicates the beam pattern of the aperture D ₁₀ of the simultaneously driven transducer group, and 20 indicates the beam pattern of the aperture D ₂₀ (D ₂₀ <
The dashed line indicates the ultrasonic beam pattern of D ₁₀ ), and 30 is the aperture D ₃₀ (D ₃₀
<D ₂₀ ) ultrasonic beam pattern is shown by a dashed line.

As can be seen from this figure, when the aperture D is large, the beam becomes thinner at a position deeper than the transducer surface,
As the aperture D becomes smaller, the position where the ultrasonic beam becomes narrower shifts to a shallower position.

Therefore, after transmitting ultrasonic waves with a predetermined number of transducers between repeated pulses, if the number of simultaneously driven transducers for wave reception is changed at a constant cycle,
As shown in FIG. 3, since the position where the beam narrows changes in the depth direction, an image with good overall resolution can be obtained. In other words, the narrower the beam width, the sharper the ultrasonic echoes reflected inside the object, which improves the resolution in the azimuth direction.The wider the narrow beam can be obtained inside the object, the higher the resolution. The image obtained is as follows.

However, in this case, the number of vibrators to be increased or decreased must be an even number; if the number is odd, the center of directivity of the group of simultaneously driven vibrators will shift.

Figure 3 shows the method for drawing ultrasonic beam width using a concave transducer, given the ultrasonic frequency, transducer group aperture, and focal point. This was calculated by Kazuhiro Iinuma et al. Ultrasonic frequency, transducer group diameter D ₁₀
[In this case, it is expressed as D ₁₀ = (oscillator pitch) x (number of transducers), and the number of transducers is now n.] The beam pattern 10 when a focal point is given is represented by a solid line, and then the simultaneous The number of driving oscillators is set to (n-2),
The beam pattern 20 when the transducer group diameter D ₂₀ (<D ₁₀ ) is represented by a broken line, and the number of simultaneously driven transducers is (n-4), and the transducer group diameter D ₃₀ (<
D ₂₀ ), the beam pattern 30 is represented by a dashed line, and the intersections of the beam pattern 10 and the beam pattern 20 are A and beam pattern 2, respectively.
If the intersection point of 0 and beam pattern 30 is B, then
Switch the number of simultaneously driven vibrators from (n-4) to (n-2) at point B in the depth direction from the vibrator surface,
By switching from (n-2) beam patterns to n beam patterns at point A, each beam pattern can be combined most effectively.

As described above, it has been found that, given the ultrasound frequency, transducer aperture, and focal point, there is the most effective variable aperture switching point for narrowing the ultrasound beam overall, and that the switching point The point can be determined by the above-mentioned "method for drawing ultrasonic beam width using a concave transducer."

Figure 4 shows the synthesized beam pattern when the number of simultaneously driven oscillators is switched between n, (n-2), and (n-4) in the most effective manner as shown in figure 3. is shown.

By the way, as mentioned above, there is a method of increasing the ultrasonic scanning line density by changing the number of simultaneously driven transducers for each repeated pulse or any fixed period, and that it is possible to obtain high-resolution images (especially in the azimuth direction) over a wide range. When using both methods, if the variable aperture switching point is fixed, it will not be possible to obtain the desired optimal beam pattern.

In order to increase the ultrasonic scanning line density, the present invention changes the number of transducers that are driven simultaneously for each repeated pulse or for each arbitrary fixed period, and also varies the number of driven transducers during reception at a fixed period. The purpose of the present invention is to provide an ultrasonic diagnostic device that is equipped with a function to narrow an ultrasonic beam over a range, and in this case, an adjustment function that optimally switches the aperture of a group of transducers in response to an increase or decrease in the number of transducers. shall be.

For example, if the ultrasonic frequency is 3 MHz, the focus is 10 cm, and the transducer spacing is 1.5 mm, and the number of simultaneously driven transducers is 8 and 7 during transmission for each repeated pulse, and when 8 transducers are simultaneously driven during transmission, the reception Switches the number of simultaneously driven vibrators from 4 to 6 to 8 at regular intervals,
When seven vibrators are simultaneously driven during transmission, the number of simultaneously driven vibrators is switched to three, five, and seven at regular intervals during reception. The beam pattern when such variable aperture switching is performed is shown in Fig. 5. 40 indicates that the number of simultaneously driven transducers is 8 during transmission, and the number of driven oscillators is 4 and 6 at fixed intervals during reception.
The solid line shows the composite beam pattern when the number of transducers is 8, and 50 indicates the number of simultaneously driven oscillators during transmission, which is 3,
The combined beam patterns in the case of 5 and 7 beams are shown by broken lines. In this case, as is clear from Figure 5, if the number of simultaneously driven oscillators during transmission is 8, there is ₁ switching point B from 4 oscillators to 6 oscillators...
......3.5cm Switching point A from 6 oscillators to 8 oscillators ₁ point...
………5.2cm If the number of simultaneously driven vibrators during transmission is 7, switching point B from 3 vibrators to 5 vibrators is ₂ points……
………2.4cm Switching point A from 5 oscillators to 7 oscillators ₂ points……
......It will be 4.4cm.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 6, 60 is a repetitive pulse generator, 61 is a control circuit that controls the drive vibrator, and 62
63 is a transmitting electronic focusing circuit, 63 is a circuit that generates a pulse to drive the transducer, 64 is an ultrasonic probe, 65 is an amplifier that amplifies the ultrasonic echo, 66 is a receiving electronic focusing circuit 67 is a receiving transducer. 68 is a circuit that controls the switching time of the variable aperture switching circuit 67, and 69 is an addition circuit that adds the ultrasonic echoes obtained from a plurality of transducer groups. 70 is an amplification and detection circuit for amplifying and detecting the received echo signal, 71
is a display section such as a CRT that modulates the brightness using the signal from the amplification/detection circuit 70 and displays the B mode inside the object.

Next, according to FIG. 7, the variable diameter switching circuit 6
7 and the specific configuration of the switching time control circuit 68. In this case, a case will be described in which the number of vibrators driven simultaneously at the beginning during transmission is changed from 8 to 7 for each repeated pulse.

Reception signals e ₁ to e ₈ from each of the eight transducers driven during reception are input to input lines 72 to 79, respectively. Delay lines 80 to 87 are connected to the input lines 72 to 79, respectively, and a switch element 8 is connected between each input line 72 to 79 and the adder 69.
8 to 95 are connected, and this switch element 8
8 to 95 turn on the transmission of input signals e ₁ to e ₈ to the adder 69. This is for off control. Switch elements 88-95 are connected to control circuits 96-103, respectively, which control switching timing.
Control circuits 96 to 1 that control each switching timing
03, the switch elements 88 to 95 correspond to the number of vibrators (8 and 7 in this embodiment, respectively) that are simultaneously driven for each repetitive pulse.
Time constant switching means 104 to 111 are connected in parallel for selecting a time constant for determining the switching timing. In this example, two types of oscillators, 8 and 7, are used, but if the number of oscillators to be switched for each repeated pulse is various, it is necessary to provide a number of time constant switching means corresponding to the types. There is. Control circuit 9 that controls each switching timing
Control signals 6 to 103 from a control circuit 61 for controlling the drive vibrator are inputted through signal lines 104, respectively.

In FIG. 8, a is a repetitive pulse signal, b is a control signal to switch elements 88 (S ₁ ), 95 (S ₈ ), and C is a control signal to switch elements 89 (S ₂ ),
94 (S ₇ ).

Switch elements 89 (S ₂ ) and 94 (S ₇ ) are at time TB ₁
The switch elements 88 (S ₁ ) and 95 (S ₈ ) are switched from the OFF state to the ON state at time TA ₁ . However, if TB ₁ > TA ₁ , in this case, from the time the ultrasound is transmitted until time TB ₁
Since S ₁ , S ₂ , S ₇ , and S ₈ are in the off state, the oscillator 4
Only the signals from the four transducers (No. 3 to No. 6) are input to the adder 69, and in this case, the vibrator diameter is equal to four vibrators.

Next, between time TB ₁ and TA ₁ , the switch element 88
(S ₁ ), 95 (S ₈ ) are in the off state, and switch elements 89 (S ₂ ), 94 (S ₇ ) are in the on state,
The group of simultaneously driven vibrators consists of six elements, and only the signals from the six vibrators (No. 2 to No. 7) are input to the adder 69.

Furthermore, after TA ₁ , switch elements 88 (S ₁ ), 95
(S ₈ ) is also turned on, so the number of simultaneously driven oscillators is 8.
Only the signals from eight transducers (No. 1 to No. 8) are input to the adder 69.

In this way, the number of simultaneously driven transducers during reception is switched between 4, 6, and 8, and the switching time at that time is: TB ₁ ... time equivalent to depth 3.5 cm TA ₁ ... depth 5.2 cm The control circuits 96 to 103 that control the switching timing are operated so that the switching timing is at the appropriate time.

At the time of the next repeated pulse, the time constant switching means 104 to 111 are switched to different terminals from those in the case of eight transducers, the number of transmitting transducers is set to seven, and the number of driving transducers at the time of reception is set to three and five. and 7 pieces respectively.
The first exchange is performed at the timing of TB ₂ and TA ₂ (TB ₂ < TA ₂ ). In this case, the control circuits 96 to 103 that control the switching timing are activated so that the switching timing is TB ₂ ...the time corresponding to a depth of 2.4 cm and TA ₂ ...the time corresponding to a depth of 4.4 cm. be.

In this way, when transmitting an ultrasound beam, n+1 or n transducers are driven as a group, and when receiving an echo, the transducers used for receiving the ultrasound beam are symmetrically driven with respect to the central axis of the ultrasound beam. The number will be increased sequentially. Note that n mentioned above is a positive number.

Control circuit 96-1 for controlling switching timing
As 03, a multivibrator may be used.

As described above, according to the present invention, a plurality of transducers are arranged in a line, and the number of transducers used at the same time is changed for each repeated pulse or for each arbitrary fixed period, thereby improving the ultrasonic scanning line density. In addition, it is equipped with a variable aperture function that changes the number of simultaneously driven transducers during reception in increments of an even number to narrow the ultrasonic beam over a wide range and improve resolution in that area. By controlling this, an effective beam pattern can be obtained.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a scanning line density increasing method in which the number of drive transducers during transmission is varied for each repetitive pulse;
Figure 2 is an explanatory diagram of a method for increasing the scanning line density by varying the number of simultaneously driven transducers during transmission and reception, and Figure 3 is a diagram showing the beam pattern when the aperture of the simultaneously driven transducer group is varied. , Figure 4 shows the actual beam pattern when changing the number of simultaneously driven transducers during reception, and Figure 5 shows the actual beam pattern when the number of simultaneously driven transducers during transmission is 8 and 7, and when receiving A diagram showing a beam pattern when variable aperture technology is adopted, FIG. 6 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 7 is a diagram showing the switching circuit and switching timing control shown in FIG. 6. Specific configuration diagram of the circuit, No. 8
The figure is a diagram showing a time chart of an embodiment of the ultrasonic diagnostic apparatus of the present invention. 60...Repetitive pulse generator, 61...Control circuit for controlling the driving transducer, 62...Electronic focusing circuit for transmission, 63...Circuit for generating pulses to drive the transducer, 64...Ultrasonic probe, 65...Amplifier for amplifying ultrasonic echoes, 6
6...Electronic focusing circuit for reception, 67...
Variable aperture switching circuit that selects the ultrasonic echo from the receiving transducer and changes the aperture, 68...
A circuit for controlling the switching timing of the switching circuit, 69...Adder, 70...Amplification and detection circuit, 71...Display unit.

Claims (1)

[Claims] 1. In an ultrasonic device that scans an ultrasound beam by arranging a plurality of transducers in a line and sequentially selecting a group of transducers that transmit or receive waves as a set from among the plurality of transducers, Ultrasonic waves are transmitted by sequentially selecting and driving either a first transducer group in which the number of transducers constituting the transducer group is n+1 or a second transducer group in which the number of transducers is n+1. The number of beam transmitting means and the number of transducers used to receive echoes from the ultrasonic beams sequentially transmitted from the transmitting means, relative to the central axis of the ultrasonic beams transmitted from each transducer group. and ultrasonic beam receiving means for increasing the number of ultrasonic beams sequentially in a symmetrical relationship, and the receiving means further receives echoes of the ultrasonic beam transmitted from the first transducer group at a period T1. a first switching means for sequentially increasing the number of transducers provided to the wave; and a first switching means for receiving echoes from the ultrasonic beam transmitted from the second transducer group at a period T2 (however, T1>T2); An ultrasonic diagnostic apparatus comprising: second switching means for sequentially increasing the number of transducers exposed to waves.