Variable focal length transducer array and focal length adjusting method

Abstract

The invention discloses a variable focal length transducer array and a focal length adjusting method, and belongs to the technical field of ultrasonic treatment. The transducer comprises a flexible spherical-crown-shaped backing, a piezoelectric ceramic array and a focal length adjusting mechanism. The convex surface of the backing is divided into concentric rings, piezoelectric ceramic wafers arranged at equal intervals are fixed on the concave surface, and electrodes of the wafers are connected in parallel and driven by a single circuit. The focal length adjusting mechanism is composed of a thin-wall circular tube, a guide shaft, a linear bearing and an axial adjusting rod which are coaxially arranged in a sleeved mode, the axial displacement of the circular tube is controlled through a rotary knob, the curvature of the backing is changed, and the geometric focus of sound waves emitted by piezoelectric ceramics moves in the axial direction. According to the invention, a complex phased array algorithm and a multi-channel driving system are not needed, the accurate control of the focus position can be realized only through mechanical adjustment, the cost and the hardware complexity are reduced, and the method is suitable for high-intensity focused ultrasound treatment.

Description

Technical Field

[0001] This invention relates to an ultrasonic transducer, and more particularly to a variable focal length transducer array and a focal length adjustment method. Background Technology

[0002] High-intensity focused ultrasound (HIFU) is a non-invasive treatment method that focuses ultrasound waves emitted by an ultrasound transducer onto a treatment area within the body. The focused ultrasound transducer is a key component of the ultrasound therapy system; it converts electrical energy into acoustic energy and concentrates this energy onto the treatment area using a specific focusing mechanism. In its development, the focusing methods of focused ultrasound transducers have evolved from single-element lens focusing to single-element spherical self-focusing, and now to multi-element phased array focusing. Single-element spherical self-focusing has a fixed focal point, and treatment accuracy depends on the precision of the mechanical scanning. Multi-element phased array transducers, by individually controlling the excitation amplitude and phase of each element, can not only achieve focal deflection within a certain range but also compensate for beam phase distortion of ultrasound in tissues. Currently, the arrangement of the transducer array is becoming increasingly optimized, with the number of elements increasing to several thousand to tens of thousands. The manufacturing cost of multi-element phased array ultrasound therapy systems is high, with hardware costs increasing exponentially with the number of elements. The complexity of the manufacturing process places higher demands on the consistency of array elements, and the phase resolution of the drive circuit under high-density multi-channel conditions and the avoidance of array element crosstalk put significant pressure on the hardware design. To realize the practical application and promotion of ultrasound extracorporeal therapy, it is necessary to achieve therapeutic effects with lower development costs and efficient and simple focusing algorithms. This invention designs a variable focal length spherical cap-shaped focusing transducer. Through a mechanical adjustment device and focusing method, it can control the ultrasound waves emitted by each array element to be focused at a predetermined focal point along the axis. This transducer requires only a single drive circuit for excitation, avoiding complex multi-channel drive circuits and complex focusing algorithms. Summary of the Invention

[0003] This invention utilizes a flexible spherical cap-arranged piezoelectric ceramic array to design a spherical transducer array with variable focal length.

[0004] The technical solution of this invention is:

[0005] A variable focal length transducer array, comprising:

[0006] The flexible spherical backing 1 has concentric rings on its convex surface, forming multiple ring bands;

[0007] Piezoelectric ceramic elements 2 are fixed at equal intervals within the annular band of the concave surface of the backing 1, with the electrodes of each element connected in parallel;

[0008] The focal length adjustment mechanism consists of a thin-walled circular tube 3, a guide shaft 5, an axial adjustment rod 6, and a housing 7, all coaxially fitted together.

[0009] The distal end of the circular tube 3 is connected to the corresponding ring of the backing 1, and the proximal end is slidably engaged with the guide shaft 5 through the crossbeam 4; the adjusting rod 6 drives the crossbeam 4 through the thread, causing the circular tube 3 to move axially to change the curvature of the backing, thereby realizing the axial adjustment of the focal point 8.

[0010] The piezoelectric ceramic disc 2 always points to the focal point 8 in the normal direction, and the position of the focal point is adjusted by the deformation of the backing.

[0011] The central through hole of the crossbeam 4 is fixed to the outer ring of the linear bearing 10, and the guide shaft 5 passes through the linear bearing 10.

[0012] A threaded hole 9 is provided on the side of the central through hole of the crossbeam 4. The threaded hole 9 corresponds to the through hole on the near end face of the outer shell 7. The adjusting rod 6 passes through the two holes and a knob is provided on the near end of the adjusting rod 6.

[0013] The adjusting rod 6 adopts a micrometer structure, and the knob has scale lines on the outside.

[0014] The wall of the circular tube 3 is provided with limiting teeth 11, which slide with the adjacent circular tube to limit radial deviation.

[0015] The backing 1 is made of flexible insulating material with a thickness of 0.5-5mm.

[0016] A focal length adjustment method, comprising:

[0017] Calculate the distance each ring needs to move based on the target focal length R:

[0018] Δd n =d n -d 0n -R+R0;

[0019] in, dn is the axial distance between the far end of the circular tube (3) and the focal point, R is the adjusted focal length, and D n Let n be the diameter of the circular tube (3), n ≤ m, and m be the number of circular tubes (3);

[0020] d0n is the axial distance between the far end of the circular tube (3) and the initial focal point, and R0 is the initial focal length;

[0021] Rotate the knob to the corresponding scale, and the adjusting rod (6) will drive the circular tube (3) to move axially by Δdn, so that the focal point moves to the point corresponding to the focal length R.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention fixes a piezoelectric ceramic sheet onto a flexible spherical cap backing. By controlling the shape of the backing, the geometric focus of the sound wave emitted by the piezoelectric ceramic can move along the axial direction. All ceramics are in phase and excited by a single electrical system, avoiding the use of complex phased array algorithms and control systems. This allows for controllable axial movement of the focus while keeping the transducer position unchanged. Attached Figure Description

[0024] Figure 1 This is a three-dimensional diagram of the flexible spherical cap and piezoelectric ceramic arrangement of the present invention;

[0025] Figure 2 It is a three-dimensional diagram of the overall structure of the transducer.

[0026] Figure 3 This is a front view of the transducer structure of the present invention;

[0027] Figure 4 This is a structural diagram of the back of the transducer of the present invention;

[0028] Figure 5 This is a schematic diagram of the method for adjusting the transducer focus according to the present invention;

[0029] Figure 6 This is a structural diagram of the connection method between the circular tube and the guide shaft of the present invention;

[0030] Figure 7 This is a partial structural diagram of the axial adjusting rod and threaded sleeve of the present invention;

[0031] Figure 8 This is a schematic diagram of the position of the limiting teeth in this invention.

[0032] The components are: 1. Flexible backing; 2. Piezoelectric ceramic; 3. Round tube; 4. Crossbeam; 5. Guide shaft; 6. Adjusting rod; 7. Housing; 8. Focusing point; 9. Threaded hole; 10. Linear bearing; 11. Limiting tooth; 20. Crown base; 21. Crown top. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings.

[0034] Figure 1 A three-dimensional diagram of the flexible spherical crown and piezoelectric ceramic arrangement. The spherical crown backing 1 is made of flexible insulating material with a thickness ranging from 0.5 to 5 mm. The center of the backing 1 can be opened. The flexible material is made of insulating materials such as rubber, polyurethane, and silicone.

[0035] The surface of the spherical crown-shaped backing 1 is divided into concentric rings. Adjacent rings divide the backing 1 into rings of equal width. There are a total of 9 rings in the figure, forming 8 rings. The width of the rings is greater than the diameter of the piezoelectric ceramic disc 2. The width of the rings is generally in the range of 5-20mm.

[0036] Two piezoelectric ceramic discs are arranged at equal intervals within the ring and fixedly connected to the backing 1. The discs are arranged with the same polarity. The discs are evenly distributed within and between the rings, and small gaps are left between the edges of the discs to accommodate the slight changes in the position and orientation of the discs caused by the pull of the surrounding backing 1.

[0037] The electrode leads of the piezoelectric ceramic 2 are connected in parallel, and all the piezoelectric ceramics 2 are excited by a single electric drive, so that the sound waves emitted by them can be focused at the set focal point.

[0038] Figure 2 This is a 3D diagram of the overall structure of the transducer. The distal end of the thin-walled circular tube 3 is connected to the convex backing 1 of the spherical crown. The diameter of the circular tube 3 corresponds one-to-one with the diameter of the convex ring of the spherical crown. The circular tube 3 is made of metal. Each circular tube 3 is coaxially arranged. The proximal end of each circular tube 3 is fixedly connected to the corresponding crossbeam 4. The guide shaft 5 passes through the central through hole of each crossbeam 4, so that each circular tube 3 can only move along the axial direction. The central through hole of the crossbeam 4 can fix the outer ring of a linear bearing. The guide shaft 5 passes through the linear bearing, making the direction of displacement of the circular tube 3 more stable and the movement smoother.

[0039] The outer shell 7 is cylindrical, with its distal opening diameter matching the crown base 20. The proximal end of the outer shell 7 is closed, and a guide shaft 5 is axially fixed at the center of the proximal end face of the outer shell 7. The guide shaft 5 passes through the through holes of each crossbeam 4 and extends to the crown top 21. A threaded hole is provided beside the central through hole of each crossbeam 4, and a through hole corresponding axially to the threaded hole on each crossbeam 4 is provided on the proximal end face of the outer shell 7. An axial adjustment rod 6 is provided between the two holes. Rotating the knob located on the proximal end face of the outer shell 7 drives the adjustment rod 6 to move the crossbeam 4 axially, thereby moving the corresponding distal backing 1 of the circular tube 3, and moving the piezoelectric ceramic disc 2. A scale line is provided on the circumferential side of the knob to indicate the displacement distance.

[0040] Figure 3 This is a front view of the transducer, where 1 is the flexible backing; 2 is the piezoelectric ceramic disc; and 7 is the transducer housing. Nine rings forming eight bands are also clearly visible.

[0041] Figure 4 This is a structural diagram of the back of the transducer. The outer shell 7 is cylindrical and closed at the near end. An axial adjustment rod 6 knob is provided on the near end face of the outer shell. The number of knobs corresponds to the number of cylindrical tubes 3. Scale lines are provided on the outer side of the knobs along the circumference.

[0042] Figure 5 This is a schematic diagram of the adjustment transducer to achieve focusing at the set focal point. The spherical crown is divided into three rings and four circular rings. The radius of the spherical crown is R. The diameters of each circular ring from the inside (crown top 21) to the outside (crown bottom 20) are D1 to D4 respectively. 8 is the focal point position. The center normal of each circular plate points to the focal point. d1 to d4 are the axial distances from the far end of each circular tube 3 to the focal point.

[0043] Figure 6This is a structural diagram showing the connection between the round tube and the guide shaft; the thin-walled round tube 3 is fixedly connected to the crossbeam 4 at its near end, the guide shaft 5 passes through the central through hole of the crossbeam 4, and there is a threaded hole 9 on the side of the central through hole. A linear bearing 10 is provided at the central through hole of the crossbeam 4, the outer ring of the linear bearing 10 is fixed to the central through hole of the crossbeam 4, and the guide shaft 5 passes through the linear bearing 10.

[0044] Figure 7 This is a partial structural diagram of the axial adjusting rod and threaded sleeve, where 6 is the axial adjusting rod and 11 is the threaded sleeve. This structure is designed to ensure displacement accuracy, with an adjustment accuracy equivalent to that of a micrometer.

[0045] Figure 8 This is a schematic diagram of the position of the limiting tooth. The limiting tooth 11 is set on the wall of the circular tube 3 away from the crossbeam 4. The limiting tooth 11 slides with the wall of the adjacent circular tube 3, which can effectively ensure the overall axial displacement of each circular tube 3 and prevent radial deviation.

[0046] Focus adjustment method:

[0047] Suppose the spherical cap is divided into m rings, corresponding to m thin-walled circular tubes 3 and m-1 annular bands, with diameters of D1, D2, D3, ... D from the inside out. n , n≤m. Diameter D1 corresponds to the opening at crown 21, diameter D n Corresponding to position 20 at the crown base, the initial focal point of the transducer is set to R0. The knob of adjustment rod 6 is returned to zero, and the center normal of each piezoelectric ceramic disc 2 points to the initial focal point. The axial distance between the distal end of each circular tube 3 and the focal point is:

[0048]

[0049] Where: 1≤n≤m;

[0050] When the transducer needs to be adjusted to the focal length R, the axial distance between the far end of each circular tube 3 and the focal point is:

[0051]

[0052] The distance that the concentric circles on each backing 1 need to move is:

[0053] Δd n =d n -d 0n -R+R0

[0054] When R > R0, Δdn is positive; when R < R0, Δdn is negative. The positive or negative value of Δdn indicates the direction of displacement of the circular tube 3, which also corresponds to the rotation direction of the knob. The circular tube 3 is displaced through the axial adjusting rod 6 and the crossbeam. When Δdn is positive, the circular tube 3 moves away from the focal point; conversely, it moves towards the focal point.

[0055] Example

[0056] Let the spherical piezoelectric ceramic array have a base diameter of 100mm (crown bottom 20) and a crown diameter of 20mm (crown top 21). The backing 1 is divided into m-1=8 concentric rings (m=9 in total), with 5mm diameter circular piezoelectric ceramic sheets evenly spaced. The diameters of the circular tubes 3 are D1=20.26mm, D2=32.96mm, D3=44.35mm, D4=55.06mm, D5=65.02mm, D6=75.59mm, D7=85.09mm, D8=94.23mm, and D9=103.98mm. Assume the initial focal length is R0=70mm, and crown top 21 is the position base point. Then, according to the formula: The initial axial distances between each ring and the focal point are: d01 = 69.26 mm, d02 = 68.03 mm, d03 = 66.39 mm, d04 = 64.36 mm, d05 = 61.99 mm, d06 = 58.92 mm, d07 = 55.59 mm, d08 = 51.77 mm, and d09 = 46.87 mm. At this time, the knob position scale of the corresponding axial adjustment rod 6 is zero.

[0057] Assuming the required focal length is R = 80mm, then according to the formula: The axial distances between the set focal points and each ring are: d1 = 79.36 mm, d2 = 78.28 mm, d3 = 76.86 mm, d4 = 75.11 mm, d5 = 73.10 mm, d6 = 70.51 mm, d7 = 67.75 mm, d8 = 64.65 mm, d9 = 60.80 mm.

[0058] According to the formula: Δd n =d n -d 0n If -R+R0, then the knobs need to be adjusted to move each rotation away from the focal point by the following distances: △d1=0.10mm, △d2=0.25mm, △d3=0.47mm, △d4=0.75mm, △d5=1.11mm, △d6=1.59mm, △d7=2.16mm, △d8=2.88mm, △d9=3.93mm.

[0059] Rotate the knobs corresponding to the nine round tubes to the corresponding scale values ​​to adjust the focal length.

Claims

1. A variable focal length transducer array, characterized in that, include: The flexible spherical backing (1) has concentric rings on its convex surface, forming multiple ring bands; Piezoelectric ceramic elements (2) are fixed at equal intervals in the annular band of the concave surface of the backing (1), and the electrodes of each element are connected in parallel; The focal length adjustment mechanism consists of a thin-walled circular tube (3) coaxially sleeved, a guide shaft (5), an axial adjustment rod (6) and a housing (7); The distal end of the circular tube (3) is connected to the corresponding ring of the backing (1), and the proximal end is slidably engaged with the guide shaft (5) through the crossbeam (4); the adjusting rod (6) drives the crossbeam (4) through the thread, thereby causing the circular tube (3) to move axially to change the curvature of the backing and realize the axial adjustment of the focal point (8).

2. The transducer array according to claim 1, characterized in that, The piezoelectric ceramic (2) disc always points to the focal point (8) in the normal direction, and the position of the focal point is adjusted by the deformation of the backing.

3. The transducer array according to claim 2, characterized in that, The central through hole of the crossbeam (4) is fixed to the outer ring of the linear bearing (10), and the guide shaft (5) passes through the linear bearing (10).

4. The transducer array according to claim 3, characterized in that, The crossbeam (4) has a threaded hole (9) on the side of the central through hole. The threaded hole (9) corresponds to the through hole on the near end face of the outer shell (7). The adjusting rod (6) passes through the two holes and has a knob on the near end of the adjusting rod (6).

5. The transducer array according to claim 4, characterized in that, The adjusting rod (6) adopts a micrometer structure, and the knob has scale lines on the outside.

6. The transducer array according to claim 5, characterized in that, The wall of the circular tube (3) is provided with limiting teeth (11), which slide with the adjacent circular tube to limit radial deviation.

7. The transducer array according to claim 6, characterized in that, The backing (1) is made of flexible insulating material with a thickness of 0.5-5mm.

8. A focal length adjustment method, based on the transducer array according to any one of claims 1-7, characterized in that, include: Calculate the distance each ring needs to move based on the target focal length R: Δd n =d n -d 0n -R+R0; in, dn is the axial distance between the far end of the circular tube (3) and the focal point, R is the adjusted focal length, and D n Let n be the diameter of the circular tube (3), n ≤ m, and m be the number of circular tubes (3); d0n is the axial distance between the far end of the circular tube (3) and the initial focal point, and R0 is the initial focal length; Rotate the knob to the corresponding scale, and the adjusting rod (6) will drive the circular tube (3) to move axially by Δdn, so that the focal point moves to the point corresponding to the focal length R.

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