JPH011956A - ultrasonic probe - 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] Vibration of a transducer [Industrial field of application] The present invention is an ultrasonic diagnostic device that transmits ultrasonic waves to a subject and simultaneously detects reflected waves from within the subject. Regarding the receiving ultrasound probe, we are particularly concerned with ultrasound probes that can efficiently receive ultrasound from shallow to deep depths when diagnosing a subject.

[Conventional technology] In general, with ultrasonic diagnostic equipment, it is difficult to perform diagnosis on a subject because the absorption and scattering of ultrasonic waves within the subject increases as the cutting depth increases. Uses ultrasonic waves with high relief and low frequencies, and uses low circumferential probes in deep areas. It uses wave number ultrasound to obtain good ultrasound images.

For this reason, in the past, the frequency of the ultrasonic waves used was changed by using multiple ultrasonic probes with different transmitting and receiving characteristics and changing the material each time, depending on the depth at which the subject was to be diagnosed. was.

Alternatively, the frequency band of the ultrasonic probe can be expanded as much as possible to transmit wide-band ultrasonic waves, and a band-limiting filter is installed in the receiving circuit, and this band-limiting filter changes the passing frequency of the reflected ultrasonic waves. A technique called a dynamic filter method was used in which the frequency was changed sequentially from high to low depending on the reception time.

[Problem that the invention seeks to solve]

However, such conventional ultrasonic probes have the following problems. First, in the first conventional example, multiple ultrasound probes with different transmission and reception characteristics are required depending on each depth, which increases the number of ultrasound probes and makes it complicated to replace them. Met. In addition, in the second conventional dynamic filter method, although the number of ultrasonic probes is reduced, the transmitting and receiving characteristics of the ultrasonic probe itself are not changed, so it does not necessarily depend on each depth. However, it was not possible to receive ultrasonic waves efficiently.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ultrasonic probe that can efficiently receive ultrasonic waves from a shallow diagnostic depth to a deep diagnostic depth of a subject. shall be.

[Means for solving problems]

As shown in FIG. 1, the means of the present invention for solving the above problems consists of a vibrator 1 that converts an electric signal into an ultrasonic wave, transmits the same, and converts a received ultrasonic wave into an electric signal, and a vibrator 1 that converts the received ultrasonic wave into an electric signal. In an ultrasonic probe having a tuning coil 2 which is provided in parallel with the probe 1 to efficiently vibrate the probe, the inductance Lt of the tuning coil 2 is
This is done using an ultrasonic probe with a variable In FIG. 1, the symbol Rd is a damping resistor, and the symbol 3 is a signal line connected to an ultrasound transmitting/receiving section (not shown) that controls transmission and reception of ultrasound from the ultrasound probe.

Here, the vibrator 1 can be regarded as a kind of capacitor, and if its capacitance is C0, the resonance frequency f between the vibrator 1 and the tuning coil 2 is f=□ (1) It is expressed as 2tcfi knee. This resonant frequency f is unique to the circuit of the ultrasonic probe shown in FIG. 1, is also called a natural frequency, and determines the frequency characteristics of the ultrasonic probe.

In the present invention, the tuning coil 2
The inductance Lt is made variable, and this inductance Lt is adjusted according to the diagnostic depth of the subject.As shown in Fig. 2, in the shallow part Lt is made small to make the resonant frequency high like f, and in the deep part the resonant frequency is made high. Increase Lt to lower the resonance frequency to f2. This changes the transmission and reception characteristics of the ultrasound probe itself.

[For production]

The ultrasonic probe configured in this way changes the resonant frequency f of the ultrasonic probe by making the inductance LL of the tuning coil 2 variable. In areas where the diagnostic depth is shallow, good resolution is obtained with high ultrasonic components, and in deep areas, low ultrasonic components are efficiently received.

〔Example〕

EMBODIMENT OF THE INVENTION Below, one embodiment of the present invention will be described in detail based on the accompanying drawings.

FIG. 3 is a circuit diagram showing a first embodiment of the ultrasonic probe according to the present invention. In this embodiment, a plurality of tuning coils 2a, 2b, 2C having different inductances are provided in parallel as a means for making the inductance Lt of the tuning coil 2 in FIG. 1 variable, and these tuning coils 28 to 2c are connected in parallel. The overall inductance is changed by switching the state using analog switches SW, SW2. That is, the first tuning coil 2a with inductance L1
and a second tuning coil 2 with an inductance L2.
b and a third tuning coil 2C with an inductance L are connected in parallel, and a first analog switch SW□ is provided on the ground side of the second tuning coil 2b, and the third tuning coil 2C is connected to the ground side. A second analog switch SW2 is provided on the side. A control signal line 4a connected to the first analog switch SW and a second analog switch SW
Control signals S□, S2 are input from a control circuit (not shown) to the control signal line 4b connected to the first and second analog switches sw1. sw,
By sequentially opening and closing the tuning coils 28 to 2C, the parallel connection combination of the three tuning coils 28 to 2C is changed, and the overall inductance is changed. The operation will be explained. First, a control signal output from an ultrasonic transmitter/receiver (not shown) is inputted from the signal line 3, and ultrasonic waves are transmitted and received from the transducer 1. At this time, as the ultrasonic waves are transmitted, the reception of reflected echoes from the shallow part of the diagnostic depth starts, so the first control signal S□ and the second Two control signals S2 are respectively input. That is, as shown in Fig. 4 (a) to (c), a signal that switches between H (high) and L (low) as time passes after the ultrasonic wave is emitted is input, and when the signal is set to I, the analog switch is Turn on SW, SW, and when it is L, analog switch sw,, sw.

control to turn off. Immediately after the ultrasonic wave is emitted, the reflected echo from the shallow part is received, and since both the second and second control signals S□ and S2 are H, the second control signal S□ and S2 are both H, as shown in FIG. and a second analog switch SW.

Both SW2 are turned on. Therefore, in FIG. 3, the first to third tuning coils 2a to 2C are all connected in parallel, and each inductance L1. L...
The overall inductance (
(corresponding to the inductance Lt in FIG. 1) is minimized. As a result, it is clear from the above equation (1) and as shown in FIG.

At this time, the resonant frequency f becomes maximum.

Next, at time t2 when a reflected echo from a deeper part than at time t is received, the first control signal S1 is L and the second control signal S2 is H, so as shown in FIG. As shown in , the first analog switch SW is turned off and the second analog switch SW2 is turned on. Therefore, in Fig. 3, the first tuning coil 2a and the third tuning coil 2C are connected in parallel, and the overall inductance (Lt) as a result of connecting their inductances L, , L3 in parallel is different from the previous one. also becomes larger. As a result, the resonant frequency f at this time becomes smaller than the previous time according to equation (1).

Next, at time t3 when a reflected echo from a deeper part than at time t2 is received, the first control signal S1 is H and the second control signal S2 is L, so as shown in FIG. As shown in , the first analog switch SW1 is turned on, and the second analog switch SW1 is turned on.
W2 is turned off, so in FIG. 3, the first tuning coil 2a and the second tuning coil 2b
are connected in parallel, and their inductances L1, L
The overall inductance (Lt
) becomes even larger than the previous time (however, Lx >
L 3). As a result, the resonant frequency f at this time becomes even smaller than the previous time according to equation (1).

Next, it is the time when the reflected echo from the deepest part is received just before the end of the ultrasonic emission, and since the first and second control signals S□ and S2 are both L,
As shown in FIG. 5, the first and second analog switches sw1. sw and are both turned off. Therefore, in FIG. 3, only the first tuning coil 2a is connected,
The overall inductance (Lt) is determined only by this inductance L1, and its value is the largest and largest so far. As a result, the resonant frequency f at this time is
According to equation (1), it becomes even smaller than the previous time and becomes the minimum.

In this way, as time elapses after the ultrasonic wave is emitted, the diagnostic depth of the subject shifts from a shallow part to a deep part.
By appropriately turning on and off the W and SW2, the overall inductance (Lt) of the first to third tuning coils 28 to 2c can be sequentially increased. As a result.

By changing the resonance frequency f, it is possible to obtain good resolution with high ultrasonic components in areas where the diagnosis depth is shallow, and to efficiently receive low ultrasonic components in deep areas.

In addition, in FIG. 3, three tuning coils 2
Although a to 2c are shown as being provided in parallel, the present invention is not limited to this. Two tuning coils or four or more tuning coils may be provided in parallel, and the state of parallel connection of these tuning coils may be changed to one or more. The overall inductance may be changed by switching using three or more analog switches.

FIG. 6 is a circuit diagram showing a second embodiment of the present invention. In this embodiment, the first and second analog switches sw1. sw2 is replaced with a first and second diode switch D□tD2, respectively. In addition, in FIG. 6, the symbol Cc represents the second and third tuning coils 2b.

2c are coupling capacitors that pass only alternating current, and symbols R and R2 are resistors. and a second control signal S output from a control circuit not shown from the control signal lines 4a and 4b;
S2 are respectively input, and the bias current that switches between H and L with the passage of time after ultrasonic wave emission is applied to the first and second diode switches D1 and D2, as shown in FIGS. 4(a) to 4(c). By conducting, the diode switches D, D2 are turned on and off similarly to the analog switches SW□ and SW2 shown in FIG. As a result, different inductances L, L2 . The overall inductance (Lt) can be changed by switching the parallel connection state of the three tuning coils 2a, 2b, and 2c. In this case, the overall inductance (Lt) can be changed more smoothly than in the embodiment shown in FIG. In this embodiment as well, two tuning coils or four or more tuning coils are provided in parallel, and the state of the parallel connection of these tuning coils is switched using one or three or more diode switches, so that the overall The inductance may also be changed.

FIG. 7 is a circuit diagram showing a third embodiment of the present invention. In this embodiment, a direct current 'il! By flowing a current, magnetic saturation is forcibly caused in the core material, and its inductance L is changed. That is, the core material of the tuning coil 2 undergoes magnetic saturation when the current flowing through the tuning coil 2 exceeds a certain level.

This has the property that the inductance L of the tuning coil 2 appears to be smaller, and this is utilized. In addition, in FIG. 7, the symbol Cc is a coupling capacitor connected to the tuning coil 2 and passes only alternating current, and the symbol R is a resistor. Then, by inputting a DC current i output from a control circuit (not shown) through the control signal line 5 and flowing this DC current i through the tuning coil 2, magnetic saturation is forcibly caused in the core material, and the As shown in FIG. 5, the inductance L of the tuning coil 2 can be changed from the minimum value to the maximum value as the diagnostic depth moves from a shallow portion to a deep portion. In this case, the number of parts can be reduced compared to the embodiments shown in FIGS. 3 and 6. In addition.

As shown in FIG. 8, for the tuning coil 2 in which the inductance L is made variable due to the above magnetic saturation,
Inductance. Another tuning coil 2' in which the tuning coil 2' is fixed may be provided in parallel.

In the above explanation, the vibrator 1 is illustrated and explained as one piece, but the present invention is not limited to the mechanical scanning type.
The present invention can be similarly applied to an electronic scanning type ultrasonic probe in which a large number of transducers (transducer elements) 1.1, . . . are arranged in rows at regular intervals in a phased array configuration. In this case, many of the same circuits as shown in FIGS. 3, 6, 7, and 8 will be incorporated into the same ultrasonic probe.

〔Effect of the invention〕

Since the present invention is configured as described above, the inductance of the tuning coil can be sequentially changed as time passes after the ultrasonic wave is emitted, and as the diagnostic depth of the subject moves from a shallow part to a deep part as the ultrasound is received. According to
The resonance frequency between the vibrator and the tuning coil can be changed. Therefore, the transmission and reception characteristics of the ultrasound probe itself can be changed depending on the diagnostic depth of the subject. From this, it is possible to efficiently receive ultrasound from a shallow diagnostic depth to a deep diagnostic depth using a standard ultrasound probe. In this case, low ultrasonic components can be efficiently received. Therefore, an ultrasound image with high diagnostic value can be obtained.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing the basic principle of the ultrasonic probe according to the present invention, Fig. 2 is a graph showing how the resonant frequency changes due to changes in the inductance of the tuning coil, and Fig. 3 is a diagram showing the basic principle of the ultrasonic probe according to the present invention. FIG. 4 is a timing diagram showing the first and second control signals;
FIG. 5 is an operation explanatory diagram showing a state in which the inductance changes and the resonance frequency changes in accordance with a change in the diagnostic depth. FIG. 6 is a circuit diagram showing a second embodiment of the invention, FIG. 7 is a circuit diagram showing a third embodiment of the invention, and FIG. 8 is a circuit diagram showing a modification thereof. 1... Vibrator, 2.2', 2a to 2C... Tuning coil, 3... Signal line, 4a, 4b,
5...Control signal line, L, L, L1~L
3,5Lt...Tuning coil inductance, 'SW work, SW,...Analog switch (selector switch), D,,D,...Diode switch (selector switch), Sl, S,...Control Signal, i...DC current.

Claims (3)

[Claims] (1) A vibrator that converts electric signals into ultrasonic waves and transmits them, and converts received ultrasonic waves into electric signals, and a tuning coil that is installed in parallel with this vibrator to efficiently perform the vibration. An ultrasonic probe comprising: an ultrasonic probe having a tuning coil having a variable inductance; (2) The means for making the inductance of the tuning coil variable is a method in which a plurality of tuning coils with different inductances are arranged in parallel, and the state of parallel connection of these tuning coils is changed by a changeover switch to change the overall inductance. The ultrasonic probe according to claim 1, characterized in that: (3) A patent characterized in that the means for making the inductance of the tuning coil variable is such that by passing a direct current through the tuning coil, magnetic saturation is forcibly caused in the core material of the tuning coil, thereby changing the inductance. An ultrasonic probe according to claim 1.