JPS63166400A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To obtain high resolution and to reduce the total number of vibrators by setting at least one of the array pitches in first and second directions of two-dimensional array vibrators to irregular pitch where the outermost part of an array direction is made smallest. CONSTITUTION:If the array pitch of the array vibrators is set to the irregular pitch where the outermost part of the array direction is made smallest, a delay time difference is equalized and there is no problem as long as the delay time difference is within a tolerance, whereby ultrasonic beam focusing and side lobe suppression performance while are mostly equivalent to the case of the equal pitch can be obtained. Namely, the two-dimensional array vibrators 11 are arranged along the first direction (scan direction) (x), and the second direction (silica direction) (y) where pulse vibrators are orthogonal. The array pitch is set to regular pitch in the scan direction (x), and to the irregular pitch where outermost part of the array direction is made smallest in the slice direction (y). Thus, electronic scan such as linear electronic scan can be executed without fail, and the number of the vibrators in the second direction (silica direction) is reduced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an ultrasonic probe for transmitting and receiving ultrasonic waves used in ultrasonic diagnostic equipment, etc. This invention relates to an ultrasonic probe equipped with a transducer.

(Prior art) Ultrasonic diagnostic equipment scans the inside of the subject's body using ultrasonic waves and detects the reflected waves to obtain tomographic images. It is rapidly becoming popular. There are two types of scanning: mechanical scanning, which is performed by mechanically moving an ultrasound probe, and electronic scanning, which is performed by using an array of transducers to electronically switch and control the delay time. ” 2, electronic scanning has become mainstream. The electronic scanning method is
Broadly speaking, there are linear electronic scanning and sector electronic scanning.

Techniques for achieving high resolution in the scanning direction (azimuthal direction) in electronic scanning include the receiving dynamic focus method, which sequentially switches the focal point of the ultrasonic beam according to the time corresponding to the depth within the object during reception. , a multi-stage focusing method that repeats transmission and reception while changing the focal point, and stitches together images in the vicinity of the focal point. In addition, in the depth direction, by multilayering the matching layers of the ultrasonic transducer, a wide band is achieved, and an improvement in resolution is achieved.

However, in the direction perpendicular to the scanning plane, that is, in the slice direction, a method is used in which the ultrasound beam is focused at one point using an acoustic lens, and there is a problem in that the width of the ultrasound beam becomes wider before and after the focusing point. In the slice direction, an image is obtained by integrating the width of the ultrasound beam, so a good image can be obtained near the focal point of the acoustic lens, but the image is poor before and after the focal point where the width of the ultrasound beam becomes wider. The result is that the image becomes blurred, and microstructures such as small blood vessels cannot be clearly depicted.

In order to address these shortcomings, an attempt was made to improve the resolution in the same way as in the scanning direction by using a two-dimensional array transducer and applying reception dynamic focus and multi-step focusing in the slice direction in addition to the scanning direction. is being done.

However, when constructing such a two-dimensional array of transducers, if square transducers are simply combined, the total number of transducers becomes extremely large, making it difficult to manufacture the probe and reducing yield. In addition to lowering the voltage, it also requires a great deal of effort to connect the lead wires that connect the vibrator and the electric circuit. Therefore, there is a problem that the probe becomes expensive.

(Problems to be Solved by the Invention) As described above, in the conventional ultrasonic probe having a two-dimensional array of transducers, there was a problem that the total number of vibrations -r was extremely large, making it difficult to implement.

The present invention solves these problems and provides an ultrasonic probe that is equipped with a two-dimensional array of transducers with the number of transducers minimized and that can provide high resolution not only in the scanning direction but also in the slice direction. With the goal.

[Configuration of the Invention (Means for Solving Problems)] The present invention provides an ultrasonic probe equipped with a two-dimensional array of transducers in which a plurality of transducers are arranged along first and second directions orthogonal to each other. The tentacle is characterized in that at least one of the array pitch in the first direction and the array pitch in the second direction of the two-dimensional array vibration r is set to an unequal pitch that becomes smaller toward the outside in the array direction.

(Function) When using an array transducer, a method is used to electronically focus the ultrasound beam by controlling the delay time, but the delay time td given to the transducer at this time is as shown in Figure 2. In contrast to the ideal delay time 2, which is quantized by the arrangement pitch of the transducers and focuses the ultrasonic beam on a certain point Fo, the quantized delay time 3 shows a step-like distribution in the arrangement direction. In this case, the delay time difference between adjacent transducers of the array transducer 1 is sufficient as long as the sidelobe level at and around the focal point F caused by this delay time difference falls within the allowable value, and the array transducer 1 is arranged as shown in the figure. If the array pitch of the transducers 1 is equal, the delay time difference Δt between both ends should be within the allowable range, but if this is done, the delay time difference between the transducers other than at both ends in the arrangement direction will be smaller than necessary. Become.

If the array pitch of the array transducers is set to an unequal pitch that becomes smaller toward the outside in the array direction, the delay time difference will be equalized, but as long as this delay time difference is within the allowable range, there will be no problem, and it will be almost the same as when the pitch is equal. The same ultrasonic beam focusing performance and sidelobe suppression performance can be obtained. Therefore, for example, if the present invention is applied to an ultrasonic probe for linear electronic scanning, the arrangement pinch in the first direction of the two-dimensional array transducer is set to A pitch, and the arrangement pinch in the second direction is By setting the pitch to a constant pitch and selecting the first direction as the scanning direction, linear electronic scanning': 9 electronic scanning can be performed without any problem, and the number of oscillators can be reduced in the second direction (slicing direction). This greatly reduces the total number of vibrations.

(Embodiment) FIG. 1 is an exploded perspective view showing a schematic configuration of an ultrasound probe according to an embodiment of the present invention. In the figure, the two-dimensional array of transducers 11 has a number of stages of transducers arranged along a first direction (scanning) (j direction) and a second direction (slice h' direction) y, which are perpendicular to each other. , the array pitch is in the scanning direction
In the slicing direction y, the pitch is equal, and in the slicing direction y, the pitch becomes smaller toward the outside in the arrangement direction. The two-dimensional array vibrator 11 is composed of a piezoelectric plate, a common electrode formed on one surface of the plate, and individual electrodes corresponding to each vibrator formed on the other side. In this case, Only the individual electrodes may be divided between each vibrator, and the piezoelectric body plate may also be divided by cutting.When cutting the piezoelectric body, do not cut the entire bending direction, but cut the piezoelectric body to an appropriate depth. The cutting may be performed at the same angle.

For example, the surface of this two-dimensional array vibrator 11 on which individual electrodes are formed is adhered to a backing material 12, and the surface on the opposite side, for example, J (on which conductive rods are formed), is bonded to an acoustic matching layer X3. He is covered.

The acoustic matching layer 13 is made of a single layer or a multilayer (1M structure), and its sound velocity and thickness are adjusted so that acoustic impedance matching between the piezoelectric material and the subject (living body) can be achieved.

Parameters such as acoustic impedance are regulated.

FIG. 3 is a plan view showing a more detailed configuration of the two-dimensional array vibrator 11. In this example, the number of elements in the scanning direction X is 17 elements, and the number of elements in the slicing direction y is 9 elements. When performing linear electronic scanning, a predetermined number of transducers are shifted by one element in the X direction for each transmission and reception of ultrasonic waves. Drive as a do position. In that case, -1
If a delay time as shown in FIG. 2 is given to the vibrator driven as the 11th position, the ultrasonic beam can be electronically focused.

Furthermore, since the two-dimensional array transducers 1] are arranged at equal pitches in the scanning direction X, linear electronic scanning can be performed correctly in fixed steps determined by the arrangement pitch. In other words, if the arrangement pitch of the transducers in the scanning direction If the pitch is constant, correct linear electronic scanning is possible without any change from conventional methods.

On the other hand, in the slice direction y, in order to focus the ultrasonic beam, it is sufficient to give the delay time symmetrically around the center transducer y5 in the X direction, so yl and V9. V2 and ye.

y3 and y7. Each vibrator pair of Y4 and ye is electrically connected and can be electrically considered as five elements.

Here, in FIG. 3, by applying common hatching, cross hatching, etc. to the vibrators with the same delay time given for electron focusing during transmission and reception,
The delay time given to each vibrator can be easily identified. Further, the distribution of the delay time td given to each vibrator at this time in the scanning direction X and the slice direction y is shown as t dx and t dy in the figure. Both tdx and tdy are ideal delay time distributions warmed by the arrangement pitch of the vibrators.

Here, as for the scanning direction X, as explained in FIG.
If the childization error becomes a problem in practice, it becomes a problem.

On the other hand, regarding the quantization error of the delay time distribution tdy in the slice direction y, let the number of oscillators counted in one direction from the center in the slice direction y be n (n-5 in this case), and from this center to the end. When the length of the arrayed vibrator is L, the array direction of the vibrator 1" from the center (X direction)
It can be minimized by setting the length y+ in as follows.

Yi = (i ・L2/n)"' = (i-ya215)l/y a-y 1(i-5), y b =
y 1 (i=4), -.

y O−y i(+−1). This corresponds to Fresnel division of the two-dimensional array vibrator 11 in the slice direction y. By doing so, even in the slice direction y, electron focusing can be performed with small quantization errors and suppressed site lobes even though the array pitch of the transducers is unequal. Note that in this slice direction y, unlike in the scanning direction X, linear electronic scanning of the ultrasonic beam is not performed, so it goes without saying that there is no problem even if the array pitch of the transducers is set to be unequal.

Next, another embodiment of the present invention will be described. In the embodiment shown in FIG. 4, an acoustic lens 14 is further bonded and fixed to -L of the acoustic matching layer 13 of the ultrasonic probe shown in the embodiment of FIG. This acoustic lens 14 has, for example, a cylindrical shape as shown in the figure, and has convergence tjf only in the slice direction y.

When such an acoustic lens 14 is provided, the slice direction y
The maximum delay time (delay time difference) given relative to the transducers arranged in the X direction for electron focusing in is the maximum delay time (delay time difference) given to the transducers arranged in the X direction for electron focusing in order to move the focal point of the ultrasonic wave from the focal point determined by the acoustic lens 14 to the desired position. Whatever value you need is fine. Therefore, when the acoustic lens 14 is not used in combination, it is possible to reduce the number of divisions of the vibrator in the X direction,
The total number of transducers can be further reduced.

In Fig. 5, an acoustic lens is not used as in Fig. 4, but the transducer array surface of the two-dimensionally arranged transducer 11 is made concave with respect to the slice direction, and the ultrasonic beam is focused on the center of the curvature of the concave surface. It is something. In this case, it is preferable that the backing material 12 also has a concave shape to match the shape of the two-dimensionally arranged camera element 1 as shown in the figure. Note that the acoustic matching layer is omitted in FIG.

Next, an embodiment in which the present invention is applied to an electronic sector ultrasonic probe using a two-dimensional array will be described with reference to FIGS. 6 and 7.

Figure 7 shows an example of an ultrasonic probe for sector electronic scanning according to the prior art, in which two square transducers are combined.
In the scanning direction A delay time of 25 is given to the array vibrator in the X direction. When ultrasonic waves are transmitted and received in this state, the ultrasonic beams are deflected in the novo direction determined by the delay time 23 required for sector scanning. For the slice direction y perpendicular to the scanning direction X, the delay time required for electron focusing is 22
is quantized at intervals in the y-novo direction of the vibrator, and a stepped delay time 26 is given to the array vibrator in the x-direction.

On the other hand, FIG. 6 shows an ultrasonic probe for sector electronic scanning using a two-dimensional array transducer 27 according to an embodiment of the present invention. The quantization error 30 (shaded area) of the delay time 28 calculated is clearly smaller than that shown in FIG. This also applies to the X direction.

From this result, according to the present invention, it is possible to reduce the quantization error in delay time when the number of elements is the same. When actually performing sector electronic scanning, the number of elements is divided by several tenths in both the It turns out.

[Effects of the Invention] According to the present invention, at least one of the arrangement pitch in the first direction and the arrangement pitch in the second direction of the two-dimensionally arranged vibrator is set to an unequal pitch that becomes smaller toward the outside in the arrangement direction. By doing so, the ultrasonic beam has excellent focusing properties and sidelobe suppression characteristics in both the scanning direction and the slicing direction, and high resolution can be obtained, so the total number of transducers is greatly reduced. Therefore, according to the present invention, it is possible to easily manufacture an ultrasonic probe, improve the yield, and thereby reduce the price of the ultrasonic probe.

[Brief explanation of the drawing]

FIG. 1 shows an ultrasonic probe (11) according to an embodiment of the present invention.
Figure 2 is a diagram for explaining the electric r-focusing method using the array vibration r, Figure 3 is the details of the same array oscillator (second order) in the same example. 4 and 5 are exploded perspective views showing the configuration of an ultrasonic probe according to another embodiment of the present invention, and FIG. 6 is an exploded perspective view showing the configuration of an ultrasonic probe according to another embodiment of the present invention. FIG. 7 is a diagram showing the structure of an ultrasonic probe for sector electronic scanning using a two-dimensional array of transducers according to the prior art. DESCRIPTION OF SYMBOLS 11... Two-dimensional array vibrator, 12... Backing material, 13... Acoustic matching layer, 14... Acoustic lens, X... Scanning direction, y... Slice direction, 22-2
6°28-30...Curve showing delay time. Applicant's agent Patent attorney Takehiko Suzuta (Shun Ashikagata) District 1 DL Figure 2 Figure 4 (L square 1 clause) Figure 5

Claims (6)

[Claims] (1) In an ultrasound probe equipped with a two-dimensionally arrayed transducer in which a plurality of transducers are arranged along first and second orthogonal directions, the first direction of the two-dimensionally arrayed transducer is An ultrasonic probe characterized in that at least one of the array pitch and the array pitch in the second direction is an unequal pitch that becomes smaller toward the outside in the array direction. (2) Claims characterized in that the arrangement pitch in the first direction of the two-dimensionally arrayed vibrator is approximately equal, and the arrangement pitch in the second direction is an uneven pitch that becomes smaller toward the outside in the arrangement direction. The ultrasonic probe according to item 1. (3) The ultrasonic probe according to claim 1 or 2, wherein the first direction is a scanning direction of electronic scanning, and the second direction is a slicing direction. (4) Two acoustic lenses with focusing properties in the second direction
The ultrasonic probe according to claim 1, 2, or 3, characterized in that it is arranged in front of a dimensionally arrayed transducer. (5) The ultrasonic probe according to claim 1, 2, 3, or 4, characterized in that the array surface of the two-dimensionally arrayed transducers is concave with respect to the second direction. Child. (6) Claims 1, 2, and 3, characterized in that vibrator pairs located at symmetrical positions from the center of the two-dimensionally arrayed vibrator in the second direction are electrically connected. The ultrasonic probe according to item 4 or 5.