JPH0155411B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic probe used in an ultrasonic diagnostic apparatus.

2. Description of the Related Art Conventionally, probe scanning methods used when obtaining a tomographic image of a subject with an ultrasonic diagnostic apparatus can be broadly classified into a linear scanning method and a sector scanning method. Although the sector scanning method is suitable for chest imaging, it has the following disadvantages compared to the linear scanning method.

(1) In the case of electronic sector scanning method (a) The electronic circuit is huge and complicated, so the cost of the entire device is high.

(b) When attempting to scan sectors up to a large deflection angle, it is difficult to obtain a good quality image because the sensitivity is insufficient for sound waves at large angles.

(2) In the case of mechanical sector scanning method (a) Since the ultrasonic transducer is moved by a motor etc., the overall shape of the probe becomes large.

(b) Cannot be scanned in any order.

(c) Scanning speed is slow.

In view of these points, it is an object of the present invention to provide an ultrasonic probe with a simple structure that performs linear electronic scanning on the transducer and sector scanning on the subject. shall be.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory main part configuration diagram (plan view) showing one embodiment of the ultrasonic probe according to the present invention.
FIG. 2 shows a side view thereof. In FIGS. 1 and 2, 10 represents a linear electronic scanning probe, 20 represents a linear sector conversion lens, and 30 represents a propagation medium. The linear electronic scanning probe 10 is composed of a packing material 12 and a transducer group 11 consisting of a plurality of transducers arranged in a plane and bonded to the packing material. Ultrasonic waves can be transmitted and received while being shifted sequentially as a group. In the linear sector conversion lens 20, an end surface 21 that is bonded to the transducer group 11 is formed into a planar shape, and the other end surface 22 opposite to this end surface 21 becomes thicker as it approaches the center in the transducer arrangement direction. It is a convex acoustic lens formed into a two-dimensional curved surface. Note that a matching layer may be interposed between the vibrator group 11 and this lens 20 for the purpose of achieving acoustic impedance matching. Propagation medium 30
has an open end 31 at the lower end and a lens 20 at the upper end.
A sound wave propagation medium formed in an inverted trapezoid shape with a concave curved surface that exactly matches the convex curved surface 22 of Ultrasonic waves are guided from the lens 20 to the aperture end 31 and conversely, the ultrasonic waves entering from the aperture end 31 are introduced into the lens 20.
Note that the propagation medium 30 preferably has an acoustic impedance close to that of the living body in order to improve the coupling with the living body. In addition, when it is made of water, gel, etc., it cannot maintain the above shape by itself, so prepare a hollow container with the above external shape made of a material that does not allow fluids to pass through, such as an acrylic resin plate, and fill this container with water. , a fluid such as gel is enclosed. In addition, considering that the opening end 31 is the part that connects with the subject, it is desirable to make it a thin film, and furthermore, the thickness of this thin film is smaller than the wavelength of the ultrasound in order to prevent the generation of pseudo-rays due to the thin film. The thickness should be sufficiently thin.
Further, an acoustic lens may be externally attached to the opening end 31 to narrow down the ultrasonic beam. Furthermore, the side surfaces 32a and 32b of the propagation medium 30 are not limited to straight shapes, but may be curved outward. Such a propagation medium 30 is bonded to the lens 20. lens 2
0, the curved surface 22 is formed so as to have a focal point at the center of the opening end 31, but the focal point does not necessarily have to be located at the opening end surface, but may be at a point shifted above or below the opening end position. It's okay.

Next, the shape of the curved surface 22 of such a lens will be described in detail. Now, let the speed of sound in the lens 20 be v ₁ and the speed of sound in the propagation medium 30 be v ₂ (v ₁ <v ₂ ). Third
As shown in the figure, in order for the sound wave that has passed through the lens 20 to converge on the focal point Pf, for example, the sound wave traveling on the x-axis from point A and the sound wave traveling on the outward path 33 from point B must reach the focal point Pf in the same elapsed time. must reach _f . In other words, in the same figure, the distance on the x-axis
The time required to propagate l ₁ and l ₂ on the outgoing path 33,
The time required to propagate _l3 must be the same. Lens 20 to satisfy such a relationship
The shape of the curved surface 22 is a hyperbola given by the following equation.

Here, f is the focal length.

Note that if the aperture of the lens 20 is small, this hyperbola may be approximated by a circular arc curve with a radius of curvature R expressed by the following equation.

R=f(v ₂ /v ₁ −1) The thicknesses of the lens 20 and the propagation medium 30 are substantially constant as shown in FIG. 2.

FIG. 4 shows the state of scanning with the ultrasonic probe having such a configuration. i.e. group Gi
The ultrasonic beam Ba generated by simultaneously exciting the transducers of the linear sector conversion lens 20
After traveling straight through the propagation medium 30, its open end surface 3
1, converging toward the focal point P _f at the center of the image. Furthermore, the ultrasonic waves emitted from the open end surface 31 avoid the rib cage 41 and travel straight into the interior of the subject 40 . On the other hand, when scanning progresses and the oscillators of group Gj are simultaneously excited,
Beam B _b is emitted into the subject in a manner similar to that described above. These beams Ba and B _b always pass through the focal point P _f , and as is clear from the figure, when the transducer group 11 is linearly scanned by electrons, the object 40 is subjected to sector scanning.

FIG. 5 is a diagram showing the state of the beam when the vibrator is driven in a delayed manner. In FIG. 4, the transducers are driven simultaneously, but in the case of FIG. drive As a result, the focal position of the lens 20 does not coincide with the convergence point of the beam, but the beam width within the subject becomes narrower than in the case of Fig. 4, and as a result, a tomographic image with good resolution can be obtained. .

Note that the acoustic impedance of the probe 10 is generally larger than the acoustic impedance of the subject.
Therefore, in order to guide the power of the probe to the subject with as little loss as possible, it is desirable to select the respective acoustic impedances as follows.

IpI _L I _M I _B where Ip is the acoustic impedance of the probe 10, IL is the acoustic impedance of the lens 20, I _M is the acoustic impedance of the propagation medium 30, _and I _B is the acoustic impedance of the subject 40.

Note that the reflected wave travels backward along the beam path shown in FIGS. 4 and 5, and can be received by the vibrator 11.

As explained above, according to the present invention, with a simple configuration, the transducer is subjected to linear electronic scanning, but the object to be examined is subjected to high-quality sector scanning, and there is no reduction in scanning speed. An ultrasonic probe capable of linear sector conversion can be realized.

Furthermore, if the ultrasound probe of the present invention is used, there is no need for a complicated and expensive electronic circuit for swinging the ultrasound beam, and a simple and inexpensive linear electronic scanning circuit is used, which is suitable for chest imaging, etc. This has the effect of realizing sector scanning. Also, if we focus on the transducer, the ultrasonic beam enters and exits almost from the front.
The vibrator can always perform sector scanning in the direction of maximum sensitivity, producing a unique effect not found in conventional sector scanning.

[Brief explanation of drawings]

Fig. 1 is an explanatory main part configuration diagram showing an embodiment of an ultrasonic probe according to the present invention, Fig. 2 is a side view of the probe shown in Fig. 1, and Fig. 3 is a linear sector conversion lens. FIGS. 4 and 5 are explanatory diagrams illustrating the state of linear sector conversion. 10...Linear electronic scanning probe, 11...
Oscillator group, 20... linear sector conversion lens,
30... Propagation medium, 31... Open end.

Claims (1)

[Scope of Claims] 1 A vibrator group consisting of a plurality of vibrators arranged in a straight line has one end face formed into a flat shape, and the other end face opposite to this face which is thicker as it gets closer to the center. A linear sector conversion lens formed into a curved surface is bonded so that its planar end face faces the vibrator group, and has an aperture end face formed in a flat or curved shape and faces this aperture end face. The other side of the linear
A propagation medium formed into a curved surface that matches the curved surface of the sector conversion lens and exhibiting a sound speed faster than the sound speed in the linear sector conversion lens is bonded so that the curved surface faces the curved surface of the linear sector conversion lens, An ultrasonic probe characterized in that a sector-scanning ultrasonic beam can be emitted from an aperture end face by linearly scanning the group of transducers.