JPH0724659B2 - Mechanical scanning ultrasonic probe - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a technique effectively applied to a probe for a mechanical scanning ultrasonic device.

[Background technology]

A probe used in a mechanical scanning ultrasonic device that performs sector scanning is, for example, as shown in FIGS. 1 and 2, in which a transducer 2 is fixed to a circumferential surface of a cylindrical rotor 1 at an equal angle. , The rotor 1 by the motor 6 through the belt 3 and the belt wheels 4 and 5.
Is rotated so that the ultrasonic beam 7 is swung in a sector shape. With such a structure, not only is the structure itself unavoidably large, but also a motor with a large torque is required when the rotor 1 rotates, so that the probe cannot be constructed compactly, and the practitioner cannot It makes it extremely difficult to grasp and move freely.

For such a probe, a small-sized probe having a simple structure as shown in FIGS. 3 to 5 has been proposed (see Japanese Patent Application No. 59-42970).

In FIGS. 3 to 5, 11 is a support for the vibrator,
It has a cylindrical shape with a hemispherical head. The support 11 is rotatably attached to a support shaft 12 that penetrates the cylinder portion. Both ends of the support shaft 12 are held by bearings on an arm 13 extending from the support member, and the support 11 can rotate about the support shaft 12. The disk-shaped vibrator 14 is fitted and fixed in the recess on the lower surface of the support body 11, and the support body 11 is reciprocally rotated to cause the ultrasonic beam to move in the plane of rotation of the support body 11. It can be shaken in sectors.

As shown in FIG. 4, the driving means for reciprocally rotating the support 11 includes a linear groove 15 provided in the hemispherical head portion so as to be parallel to the rotation center axis of the support 11, and a support body. It has a rotor 16 arranged on top of 11. This rotor 16
Has a substantially conical shape, and is attached to a rotating shaft 18 of a motor 17 so as to be rotatable about the central axis of the cone. The rotor 16 and the motor 17 are arranged such that the rotation center axis of the rotor 16 is orthogonal to the rotation center axis of the support body 11, and their positions are set by installing the motor 17 on the above-mentioned support member. It is fixed. The rotor 16 is attached so that the rotation shaft 18 is located away from the rotation center axis of the support 11. Further, the roller 19 is the rotor 16
The bearing 20 is attached to the end portion extending inward of the bearing, and the bearing 20 is fitted into the linear groove 15 of the support 11.

In this drive means, when the rotor 16 is rotated by the motor 17, the roller 19 rotates and moves along the linear groove 15, and the support 11 reciprocally rotates about the support shaft 12. That is, when the rotor 16 rotates clockwise, the roller 19 moves on a circle centered on the rotation center axis of the rotor 16. During this movement, the roller 19 moves the support 11
While moving in the upper linear groove 15 while rotating, the support 11 is simultaneously rotated counterclockwise about the support shaft 12. Support 11
When the rotor 16 rotates 90 degrees, the rotor rotates horizontally, and when the rotor 16 further rotates 90 degrees, the rotor rotates in the opposite direction. Then, when the rotor 16 rotates the remaining half circumference, the support 11 rotates clockwise and returns to the state shown in the drawing. Therefore, as the motor 17 keeps rotating the rotor 16, the ultrasonic beam emitted from the vibrator 14 is swung in a sector shape by the reciprocal rotation of the support 11.

The support body 11, the rotor 16, and the motor 17 are housed in a sealed case 21. The hermetically sealed case 21 has a window 22 through which ultrasonic waves for matching the acoustic impedance pass through in a portion through which the ultrasonic beam passes, and an internal space 25 thereof is filled with oil 23.

As the filling oil 23, an oil having an acoustic impedance at which the acoustic velocity is the same as the acoustic velocity of the ultrasonic wave passing through the living body to be inspected, or an acoustic impedance close to that, for example, high phenyl silicone oil is used. The structural formula of this high phenyl silicone oil is Is. Therefore, it may be considered that the angle of the ultrasonic beam emitted from the vibrator 14 matches the angle of the vibrator 14 which is swung in a sector shape. On the other hand, the window 22 through which the ultrasonic beam of the closed case 21 passes does not rotate the oscillator 14 because the ultrasonic beam is incident on the body surface of the subject with a small area when the ultrasonic beam is swung in a sector shape. It is formed by a curved surface having the center, that is, the center of the support shaft 12, as the center of curvature.
The shape of the entire probe including the closed case 21 is
The rotor 16 and the support 11 are arranged in a substantially straight line, and the rotor 16 is formed in a conical shape.
Since it is located inside, it can be elongated. Therefore, at the time of inspection, the practitioner can easily and firmly grasp the probe, and the inspection can be performed easily.

In the example of the conventional probe described above, the rotor and the support are connected by the roller, but, for example,
The rotor having a hemispherical head may be connected to the support.

The probe having the above structure is characterized by its simple structure, small size, and low cost.
Since the swing angles of 14 are not proportional to each other, when the ultrasonic pulses are emitted at equal intervals, there is a drawback that the intervals of the ultrasonic beams cannot be swung in a sector shape at equal angles.
That is, in the probe having the structure shown in FIG. 1 which is one of the conventional examples, the rotor 1 in which the swing terminal 2 is fixed to the rotation angle of the motor 6 is used.
Since the rotation angle is proportional, the images are formed by sector-shaped ultrasonic beams at equal angular intervals when ultrasonic waves are emitted at equal intervals as long as the motor is rotated at a constant speed. On the other hand, in the probe having the structure shown in FIG. 3, the ultrasonic beams form a dense image at both ends of the sector-shaped image. In order to avoid such drawbacks, it is better to make the ultrasonic wave emission timing interval longer as the deflection angle of the ultrasonic beam becomes larger, but this means discarding the amount of information to be captured within a limited time, and in real time. A device intended to obtain a good image is not desirable because it leads to deterioration of image quality.

[Object of the Invention]

An object of the present invention is to provide a technical means capable of obtaining a good image in real time in a small and lightweight probe for a mechanical scanning ultrasonic device.

[Outline of Invention]

In order to achieve such an object, a probe for a mechanical scanning ultrasonic device according to the present invention is basically a motor in which a rotation axis is aligned with an imaginary straight line, and this motor. And an ultrasonic oscillator fixed to a support body that oscillates around a support shaft that is arranged orthogonally to the virtual straight line by the drive of A curved curved ultrasonic irradiation window, the support,
It swings because a protrusion that rotates with the rotation of the motor is fitted into a groove formed on the motor side and parallel to the support shaft at a certain distance from the rotation shaft of the motor. In the probe for mechanical scanning ultrasonic device,
The support shaft is close to the ultrasonic wave irradiation window at a distance smaller than the radius of curvature of the ultrasonic wave irradiation window, and the velocity of sound is slower than that of a living body and acoustic in the envelope formed by the ultrasonic wave irradiation window. A liquid having an impedance close to that of a living body is enclosed.

According to the probe for a mechanical scanning ultrasonic device configured as described above, first, the support shaft of the support body that oscillates the ultrasonic probe is moved at a distance smaller than the radius of curvature of the ultrasonic irradiation window. It is placed close to the ultrasonic irradiation window.

As a result, the motor and the mechanism for swinging the ultrasonic probe by the motor can be brought close to the ultrasonic irradiation window. Therefore, in particular, the distance between the parts in the axial direction of the rotating shaft of the motor can be increased. Can be narrowed, and miniaturization can be achieved in this direction.

Further, by enclosing a liquid whose sound velocity is slower than that of the living body and whose acoustic impedance is close to that of the living body in an envelope composed of an ultrasonic wave irradiation window, the ultrasonic waves from the ultrasonic probe are When passing through, the light is refracted outward in the direction of the extension line and is irradiated.

Therefore, the oscillation angle of the ultrasonic probe is small, that is,
It is possible to reduce the distance from the motor shaft of the protrusion that fits into the groove of the support member, and in particular, it is possible to reduce the size of the motor in the radial direction with respect to the rotation shaft.

As described above, according to the present invention, the probe can be downsized both in the rotation axis direction of the motor and in the radial direction with respect to the rotation axis. Therefore, the entire probe can be significantly downsized.

Then, by bringing the support shaft of the support body that swings the ultrasonic probe close to the ultrasonic irradiation window at a distance smaller than the radius of curvature of the ultrasonic irradiation window, detailed description will be given in the section of Examples described later. As long as the rotation speed of the motor is constant,
The displacement amount of the ultrasonic sector can be made constant.

Therefore, a good image can be obtained in real time.

[Principle of Invention]

The probe of the present invention has the structure shown in FIG.
The rotation of the motor is converted into the pendulum operation of the vibrator. First, the pendulum operation will be described with reference to FIG.

As shown in FIG. 6, when the rotor rotation angle is φ, the pendulum deflection angle is θ, the roller rotation radius is r ₀ , and the distance between the rotor rotation center and the pendulum rotation center is l, the pendulum is In order to make the deflection angle of ± 45 °, r ₀ = 1.

When the rotor is rotated by an angle φ, the swing angle θ of the pendulum is given by the following equation.

As mentioned above, when the swing angle of the pendulum is designed to be ± 45 °,
Since r ₀ = l, θ = tan ⁻¹ (sin φ).

FIG. 7 shows an example of numerical calculation between the rotation angle φ and the deflection angle θ of the motor, that is, the rotor. Here, A is a case where r ₀ = 1 and is an example of a probe having a large sector angle.
B is a case where r ₀ = 0.7l, and is an example of a probe that makes the sector angle small.

As can be seen from the calculation example of FIG. 7, the swing angle θ of the pendulum is not proportional to the rotation angle φ of the rotor. The increase in the deflection angle θ decreases as the rotation angle φ increases.

On the other hand, as shown in FIG. 8, consider a case where an acoustic medium having a refractive index n is enclosed in a thin plastic having a curved surface L and a vibrator is placed in this medium. Here, the cross section of the curved surface L is assumed to be a circle, and the center of curvature thereof is O. It is assumed that the radius of this circle, that is, the radius of curvature, is r, and the sound source (vibrator) A is located at a position distant from the center O of the circle by y ₀ forward. The ultrasonic beam emitted from the sound source A by vibrating the oscillator travels in the medium at an angle θ with respect to the extension line of the straight line OA and is refracted at the intersection B with the interface of the plastic. During this refraction, the incident angle and the radiation angle with respect to the normal line OB at the point B are α and β, respectively. Since the cross section of the curved surface L is a circle whose center is O, OB has a value of r. The other angles BOA and OAB are γ ₁ and γ ₂ , respectively, as shown in the figure.

When the symbols shown in the figure are defined as above, the following equation can be obtained from the equation of refraction: nsin α = sin β …… (1) At ΔOAB, γ ₁ + γ ₂ + α = 180 ° …… (2) On the straight line OC At point A, θ + γ ₂ = 180 ° (3) If the deflection angle of the ultrasonic beam is Θ, then Θ = γ ₁ + β (4)

From the equations (2) and (3), γ ₁ + α−θ = 0 (5) From the equation (1), sin β = nsin α β = sin ⁻¹ (nsin α) (6) Applying the sine formula to ΔOAB, Becomes This formula gives Given that the refractive index n, the radius of curvature r, the radius of curvature-distance between oscillators y ₀ , and the deflection angle θ are given, it is found that the deflection angle Θ can be obtained from the above equation.

It is convenient to use the following equation as a numerical calculation equation for obtaining Θ, given n, r, y ₀ , θ.

γ ₁ = θ−α β = sin ⁻¹ (nsin α) Θ = γ ₁ + β As a medium to be enclosed in plastic, for example, a sound velocity of 882 [m / se, which has good acoustic impedance matching with a living body.
c] using a low-polymerization product of trifluorochloroethylene, the relationship between the deflection angle θ and the deflection angle θ when the refractive index n = 1.75 and the radius of curvature r = 60 [mm] is set as the parameter y ₀ = 0,10. , 20,30,4
Calculate as 0,50 [mm].

The numerical calculation results obtained in this way are shown in FIG.

In y ₀ = 0, but of course the deflection angle (deflection angle) of the deflection angle θ and the ultrasonic beam oscillator Θ proportional, with respect to the increase of θ in accordance with a large value of the parameter y ₀ as shown in FIG. 9 The increasing rate of Θ, that is, the value of dΘ / dθ increases with θ. That is, the curve of Θ = f (θ) becomes a downward convex curve as the parameter y ₀ increases. Looking at this relationship in FIG. 8, when y ₀ = 0, γ ₁ = 0, and Θ =
θ. Then, as y ₀ increases, the angle β, that is, the refraction increases, so that the change rate of Θ increases with respect to the change of θ. Therefore, when the value of y ₀ is set to an appropriate value, the increase rate of the deflection angle θ of the vibrator with respect to the rotation angle φ of the rotor in the structure shown in FIG. As described above, it is possible to correct that φ decreases as φ increases. Example 10 of these actual numerical calculations
Shown in the figure. Here, the relational expression between the rotation angle φ of the rotor and the deflection angle θ of the vibrator In the above, an example in which r ₀ = 1 is calculated. The horizontal axis represents the rotation angle φ of the rotor, and the vertical axis represents the deflection angle Θ of the ultrasonic beam.
However, when r = 60 [mm], the parameter yo = 0,10,20,3
It was set to 0, 40, 50 [mm].

When y ₀ = 0, the increase rate of the deflection angle Θ of the ultrasonic beam decreases as the rotor rotation angle φ increases, but the curvature radius-transducer distance y ₀ is increased and y ₀ = 50 [ mm], φ and Θ are close to a proportional relationship, and it can be understood that they approximate to a straight line. Looking at this relationship in FIG. 8, θ = tan ⁻¹
Since (sin φ), when y ₀ = 0, Θ = θ to Θ =
It becomes tan ^-1 (sin φ) and draws a sin curve. Then, since the apex of the sin curve becomes larger as y ₀ becomes larger, the range of Θ is limited to some extent, so that it becomes an approximately straight line. When a medium that propagates ultrasonic waves at a low speed is used in this way, in the mechanical scanning mechanism having the structure shown in FIG. By setting the rotation center of the oscillator, the deflection angle of the ultrasonic beam can be made to be close to the rotation angle of the rotor.

On the other hand, in the above numerical calculation method, y ₀ = 50 mm was set, and the relationship between φ and Θ was calculated when r = 60,65,70,75 mm with the radius of curvature r as a parameter. The calculation result is shown in FIG. As can be seen from FIG. 11, the smaller r is, the larger the value of Θ with respect to φ is. Therefore, if the radius of curvature r is reduced with an increase in φ to reduce the radius of curvature r of the curved surface of the window through which the ultrasonic beam passes, then
It can be approximated to a proportional relationship with an increase of.

〔Example〕

FIG. 12 is a cross-sectional view for explaining the configuration of an embodiment of the present invention, parts having the same functions as those in FIG. 4 are designated by the same reference numerals, and the repeated description thereof will be omitted.

This embodiment, as shown in FIG. 12, is constructed based on the principle of the present invention, and its closed case 21
Has a radius of curvature of r = 60 [mm], and the center of rotation of the pendulum motion of the oscillator 14 is placed in front of the radius of curvature of the window 24 through which the ultrasonic beam passes, thereby reducing the size.

〔effect〕

As described above, according to the novel technical means disclosed in the present application, the following effects can be obtained.

(1) By placing the center of rotation of the pendulum motion of the oscillator in front of the radius of curvature of the window through which the ultrasonic beam passes, so that the deflection angle of the ultrasonic beam is proportional to the rotation angle of the motor, Since the sound wave pulse can be emitted, the frame rate of the display image can be increased.

(2) The size of the device can be reduced by placing the center of rotation of the pendulum motion of the oscillator in front of the radius of curvature of the window of the closed case through which the ultrasonic waves pass.

Although the present invention has been specifically described based on the principle and the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

[Brief description of drawings]

1 and 2 are schematic configuration diagrams showing an example of a conventional probe used in a mechanical scanning ultrasonic device for performing sector scanning, and FIGS. 3 to 5 are conventional simple structures. For explaining the structure of the small-sized probe of FIG. 6, FIG. 6 to FIG. 11, a diagram for explaining the principle of the probe of the present invention, and FIG. It is a sectional view for explaining the composition of one example. In the figure, 11 ... Support, 12 ... Support shaft, 13 ... Arm, 14
…… Vibrator, 15 …… Linear groove, 16 …… Rotor, 17 …… Motor, 18 …… Rotary axis, 19 …… Roller, 20 …… Bearing axis, 21 ……
Airtight case, 22,24 ... Window through which ultrasonic waves pass, 23 ... Oil, 25
…… Internal space.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-58-89251 (JP, A) JP-A-58-50943 (JP, A) JP-A-54-112587 (JP, A) JP-A-57- 112853 (JP, A) JP 58-138443 (JP, A) JP 56-168547 (JP, A)

Claims (1)

[Claims] 1. A motor arranged with its rotation axis aligned with an imaginary straight line, and a super-motor fixed to a support body that oscillates about a support shaft arranged orthogonal to the imaginary straight line. An ultrasonic wave oscillator, a rotary body fixed to the rotary shaft of the motor and arranged in contact with the support, and a curved ultrasonic irradiation window that also serves as an envelope of the motor and the ultrasonic vibrator. In the probe for mechanical scanning type ultrasonic device, wherein the ultrasonic transducer oscillates along the curved surface of the ultrasonic irradiation window, the support is set to a radius of curvature of the ultrasonic irradiation window. While supporting by the support shaft provided between the center and the inner surface of the ultrasonic irradiation window, a liquid whose sound velocity is slower than that of the living body and whose acoustic impedance is similar to that of the living body is provided in the envelope including the ultrasonic irradiation window. Enclose it and keep it outside the rotating core of the rotating body and the ultrasonic irradiation window. Ultrasonic beam deflection angle and the mechanical scanning type ultrasonic device for probe is characterized in that as a substantially proportional relationship.