JP5416627B2 - 3D ultrasound probe - Google Patents

Description

  The present invention relates to an ultrasonic probe used in an ultrasonic diagnostic apparatus, and more particularly to a probe for acquiring a three-dimensional ultrasonic image.

  2. Description of the Related Art An ultrasonic probe for acquiring a three-dimensional ultrasonic image is of a type that mechanically scans a transducer array in which vibration elements are arranged one-dimensionally in a direction that intersects the arrangement direction. . In this type of ultrasonic probe, scanning in the direction of the one-dimensional array of vibration elements (main scanning) is performed electronically, and mechanical scanning is performed in the sub-scanning direction intersecting with the main scanning, thereby obtaining a three-dimensional region. Get ultrasonic echo information. In mechanical scanning, it is necessary to reciprocate the transducer array within a predetermined range. As a method for reciprocating the vibration array, a method using a motor that can rotate in forward and reverse directions and a method using a link mechanism or a cam mechanism while rotating the motor in one direction are known.

  Patent Document 1 below discloses a method in which a motor is rotated in one direction and converted into a reciprocating motion using a link mechanism or a cam mechanism.

Japanese Patent Laid-Open No. 60-135034

  The method of rotating the motor in one direction and converting it into a reciprocating motion using a link mechanism and a cam mechanism does not require the motor to be reversed, and is advantageous for positional errors and noise due to backlash of the transmission system accompanying the reversal. Further, in order to reverse the motor, it is necessary to generate a large torque because the inertia of the rotating part of the motor is added in addition to the inertia of the vibrator array or the like. ) A small motor is sufficient.

  Patent Document 1 discloses a mechanical scanning mechanism of an ultrasonic probe using a swash plate cam. However, there is no disclosure about changing the mechanical scanning range when using a swash plate cam.

  An object of the present invention is to make it possible to change a sub-scanning range in a mechanical scanning mechanism using a cam having a cam surface inclined with respect to a rotation axis of an ultrasonic probe.

  The three-dimensional ultrasonic probe of the present invention is rotationally driven around a rotation axis, has an inclined cam having a cam surface inclined with respect to the rotation axis, and one end abuts on the cam surface of the inclined cam. Two rods arranged symmetrically, a rod holder that regulates the rotation of the rod and guides the slide in the rotation axis direction, and contacts the other end of the rod, and swings perpendicular to the rotation axis by the slide of the rod An oscillating plate that oscillates about an axis, and a one-dimensional ultrasonic transducer array disposed on the oscillating plate. The rod holder can be rotated about the rotation axis. Thus, the position where the rod comes into contact with the swing plate is changed, the swing range of the swing plate is changed, and the sub-scanning range of the ultrasonic beam is changed.

  Further, the inclined cam has a cam profile that makes the rocking speed of the rocking plate constant within a range of at least 70% of the rocking range of the rocking plate when the rod holder is set to a specific rotational position. You can

  In the swing mechanism of the ultrasonic transducer array using the tilt cam, the swing range can be changed.

It is a perspective view which shows the principal part structure inside the three-dimensional ultrasonic probe of this embodiment. It is a front view which shows the principal part structure inside the three-dimensional ultrasonic probe of this embodiment. It is a figure for demonstrating the shape of a cam profile. It is a figure which shows the relationship between rotation angle (phi) of an inclination cam, and inclination angle (theta) of a rocking | swiveling board (vibrator array). It is a figure which shows the relationship between the rotation angle (phi) of an inclination cam, and the rocking | fluctuation speed (d (theta) / d (phi)) of a rocking | swiveling board (vibrator array). It is a figure which shows the change of the position of the rod with respect to the rocking | fluctuation axis | shaft by rotation of a rod holder. It is a figure which shows the amount h 'of rod advance / retreat when the rotation position (psi) of a rod holder is changed. It is a figure which shows inclination | tilt angle (theta) 'of a rocking | fluctuation board (vibrator array) when changing the rotation position (psi) of a rod holder.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are views showing the internal structure of the three-dimensional ultrasonic probe 10 of the present embodiment, particularly the structure relating to the oscillation of the transducer array 12, FIG. 1 is a perspective view, and FIG. FIG. The case 14 of the ultrasonic probe 10 is broken so that the inside can be seen. The transducer array 12 is one-dimensionally arranged so that the vibration elements draw an arc. In another example, it can be arranged in a straight line. The probe 10 is capable of electronic scanning of ultrasonic waves within the plane formed by the one-dimensionally arranged vibration elements. The transducer array 12 is fixed on a swing plate 18 that swings about a swing shaft 16. The swing shaft 16 is supported by the case 14 so that its axis does not move. One end of two rods 20 is in contact with the swing plate 18, and the other end of these rods is in contact with the cam surface 24 of the inclined cam 22.

  The rod 20 is supported by the rod holder 26 so that the rod itself can slide along the axial direction of the rod 20. The rod holder 26 has a substantially cylindrical shape and can be rotated around its axis. A holder drive motor 28 is provided to rotate the rod holder 26, and the driving force of this motor is transmitted to the rod holder 26 by an appropriate transmission element. The transmission element can be constituted by, for example, a pinion 30 fixed to the output shaft of the holder drive motor 28 and a ring-shaped gear 32 provided on the outer peripheral surface of the rod holder 26. The tilt cam 22 is rotationally driven by a swing motor 34. The shape of the cam surface 24 of the inclined cam 22, that is, the cam profile will be described in detail later.

  The rotation axes of the swing motor 34 and the inclined cam 22 are the same. The axes of the two rods are arranged in parallel to the rotational axis of the inclined cam 22 and symmetrically with respect to this axis. Further, the axis of the swing shaft 16 is arranged so as to be orthogonal to the rotation axis of the inclined cam 22. The axis of the oscillating shaft 16 is further positioned within the plane formed by the transducer elements of the transducer array 12, that is, the plane of the ultrasonic scanning plane, and is orthogonal to the central axis of the ultrasonic scanning plane. It can also be arranged at a position parallel to this axial arrangement.

  When the inclined cam 22 rotates, the rod 20 relatively moves on the cam surface 24 and slides in the axial direction due to the shape of the cam surface 24. The rod 20 that slides and advances advances the rocking plate 18, and at this time, the other rod 20 is retracted so as not to obstruct the movement of the rocking plate 18. As a result, the rotational motion in one direction of the swing motor 34 is converted into the swing motion of the swing plate 18 and the transducer array.

  The cam profile of the inclined cam 22 will be described. FIG. 3 shows the shape of the cam surface 24 and a coordinate system for explanation. Further, in the following description regarding the cam surface shape, a coordinate system fixed on the inclined cam 22 will be used for the sake of simplicity.

  The z axis coincides with the rotation axis of the inclined cam 22, and the intersection of the z axis and the cam surface 24 is defined as O. The x axis and the y axis are orthogonal to the z axis and orthogonal to each other. As described above, the xyz coordinate system is a system that rotates together with the tilt cam 22, and the x axis and the y axis rotate together with the tilt cam 22. A curve s is a locus of contact points A and B between the cam surface 24 and the rod 20. The positions of the contact points A and B on the xy plane are represented by an angle φ. In an actual probe, this angle φ corresponds to the rotation angle of the tilt cam. The distance from the z-axis of the contact points A and B is L / 2. Therefore, the distance between the points where the contact points A and B are projected onto the xy plane is L. This distance L is the distance between the two rods 20. Further, the inclination of the line segment AB with respect to the xy plane is defined as θ. In addition, a difference between z coordinates of the point O and the contact point A is set as h. This h corresponds to the sliding amount of the rod.

  FIG. 4 is a graph showing the relationship between the angular position φ of the contact point A and the inclination θ of the line segment AB. The graph is a straight line in a certain range (−θ1 to θ1) centering on θ = 0. In addition, a sine waveform is formed outside this range. When the plane including the two rods 20 is orthogonal to the swing shaft 16, the inclination θ of the line segment AB becomes the tilt of the swing plate 18. Therefore, by making the graph a straight line in a predetermined section, the rotational speed of the rocking plate 18 is constant in that section. If the rotation speed is constant and ultrasonic main scanning is performed at a constant time interval, the scanning plane becomes a constant angular interval. Also, outside this range, the graph has a sine waveform.

  When φ at θ = θ1 is φ1, the relationship between the angular position φ and the inclination θ is as follows.

  In the section corresponding to Equation (2), a sine wave having a half wavelength from φ1 to (π−φ1) is obtained. The same applies to the section corresponding to Equation (4). Since it is desirable that the speed is continuous at the boundary of each section corresponding to the expressions (1) to (4), the differential value of the expression (2) at φ = φ1 is the speed (θ1 / φ1 of the section corresponding to the expression 1). ), It is as follows, and a in equations (2) and (4) is obtained.

  If θ1 = 60 ° and φ1 = 30 °, a = 0.167 rad = 9.55 °. Therefore, the range of the swing angle of the swing plate 18 is ± 39.55 °. If the scanning of the ultrasonic wave is performed in a range where the rotation speed of the rocking plate 18 is constant, the range is about 76% of the rocking range.

  The relationship between the displacement h of the contact point A in the z-axis direction and the angular position φ is shown below.

  The cam profile is determined by the displacement h shown in the equations (6) to (9).

  FIG. 5 shows the rotational speed dθ / dφ of the rocking plate 18 with respect to the angular position φ. If the rotation speed of the rocking plate 18 is constant, the ultrasonic main scanning is performed at a constant time interval, whereby the angular interval between the main scanning surfaces is constant.

  6 is a view showing a state in which the rod holder 26 is viewed from above in FIG. 1 or FIG. As described above, the rod holder 26 is rotatable around its own cylindrical axis. This axis coincides with the rotational axis of the inclined cam 22. By rotating the rod holder 26, the distance S between the two rods in the direction perpendicular to the swing shaft 16 changes.

  The time when the two rods 20 are aligned in the direction orthogonal to the swing shaft 16 is indicated by reference numerals 20-1 and 20-1 in FIG. At this time, the interval S in the orthogonal direction of the swing axis of the rod 20 is the distance L of the rod 20 (S = L). When the rod holder 26 is rotated by an angle ψ, the two rods are in positions indicated by reference numerals 20-2 and 20-2, and the interval S in the direction perpendicular to the swing shaft 16 is shortened to L ′ (L ′ = Lcosψ).

  Since the displacement h in the z-axis direction of the contact point A does not change, when the interval S is shortened from L to L ′, the swing range of the swing plate 18 is widened. In the inclined cam 22 having the cam profile obtained by applying θ1 = 60 °, φ1 = 30 °, and S = L to the above-described formulas (1) to (9), the rod holder 26 is rotated so as to be spaced. FIG. 7 and FIG. 8 show the displacement h ′ of the rod 20 and the inclination θ ′ of the swing plate 18 when S is shortened. FIG. 8 also shows a graph of the inclination θ shown in FIG. 4 for comparison.

The inclination θ ′ when the rod holder 26 is rotated and the interval S is set to L ′ is expressed as follows in the section of −φ1 to φ1.

  As shown in Expression (10), θ ′ is not a linear function of φ, and the graph of θ ′ is not completely a straight line in the interval of −φ1 to φ1.

  In the above embodiment, when the two rods 20 are arranged in a direction perpendicular to the swing shaft 16, the cam profile of the tilt cam is determined so that the swing speed of the transducer array is constant within a predetermined range. did. However, when the two rods 20 are in other arrangements, the cam profile can be designed so that the oscillation speed of the transducer array is constant within a predetermined range.

  10 Three-dimensional ultrasonic probe, 12 transducer array, 16 rocking shaft, 18 rocking plate, 20 rod, 22 inclined cam, 24 cam surface, 26 rod holder.

Claims (2)

An inclined cam that is rotationally driven about a rotation axis and has a cam surface that is inclined with respect to the rotation axis;
One end abuts against the cam surface of the inclined cam, and two rods arranged symmetrically with respect to the rotational axis;
A rod holder that regulates the rotation of the rod and guides the slide in the rotation axis direction;
An oscillating plate that contacts the other end of the rod and oscillates around an oscillating axis perpendicular to the rotation axis by sliding the rod;
A one-dimensional ultrasonic transducer array disposed on an oscillating plate;
Have
The rod holder can be rotated around the rotation axis, and by this rotation, the position where the rod contacts the swing plate is changed, the swing range of the swing plate is changed, and the sub-scanning range of the ultrasonic beam is changed. Change the
3D ultrasonic probe. The three-dimensional ultrasonic probe according to claim 1,
The inclined cam has a cam profile that makes the rocking speed of the rocking plate constant within a range of at least 70% of the rocking range of the rocking plate when the rod holder is set to a specific rotation position.
3D ultrasonic probe.

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