Probe system having magnetic resonance positioning function, and positioning method and storage medium

Abstract

The present invention relates to an MRI-PHIFU system, and in particular relates to a probe system having a magnetic resonance positioning function, and a positioning method and a storage medium. The probe system comprises a base, an ultrasonic transduction device, and a magnetic resonance positioning support, wherein the ultrasonic transduction device is fitted in the base; the magnetic resonance positioning support is connected to an outer side wall of the base; and the magnetic resonance positioning support comprises a connecting plate, several pairs of transverse columns parallel to the connecting plate, and several pairs of longitudinal columns perpendicular to the connecting plate, the longitudinal columns connecting the transverse columns to the connecting plate. Compared with the prior art, the present invention solves the problems of inaccurate positioning, complex operations, a low response speed, and the installation difficulty and unfirmness of a phased array probe in the MRI-PHIFU field in the prior art.

Description

A probe system with magnetic resonance positioning function, positioning method and storage medium Technical Field

[0001] The present invention relates to an MRI-PHIFU system, and in particular to a probe system with a magnetic resonance positioning function, a positioning method and a storage medium. Background Art

[0002] Over the past decade, magnetic resonance imaging-guided phased high-intensity focused ultrasound (MRI-PHIFU) has shown great promise in the treatment and pain relief of intracranial tumors, Parkinson's disease, essential tremor, epilepsy, uterine fibroids, adenomyosis, breast fibroadenomas, bone tumors, thyroid tumors, and prostate tumors. This technology primarily utilizes the thermal effect of ultrasound, thus posing no radiation risk to the human body and is known as "green surgery."

[0003] Ultrasound's penetrability within the human body and the focusing capabilities of spherical phased arrays allow for direct transmission of energy through tissue to the target site, eliminating the need for incisions, making it a truly noninvasive treatment. Coupled with the rapid advancements in magnetic resonance imaging and the flexibility of phased array ultrasound to switch any element on and off, this technology provides precise positioning for clinical surgical procedures. Furthermore, this technology is showing promising growth in a variety of medical applications, including tumor ablation, assisting in opening the blood-brain barrier, and assisting in inducing photosensitivity reactions.

[0004] However, as MRI-PHIFU technology continues to evolve, so too do problems. First, the HIFU system requires registration with the MRI to determine its relative position. However, according to data, there is currently no precise registration method in clinical practice. Second, most commercially available phased array probes with wiring harnesses are difficult to install and unstable. The ultrasonic transducer base and assembly can easily become loose and shift, leading to probe failure and seriously compromising overall system stability.

[0005] Therefore, existing technologies in the field of MRI-PHIFU have problems such as inaccurate positioning, complex calculations, slow response speed, difficult and unstable installation of phased array probes, and new systems need to be developed to overcome them.

[0006] Summary of the Invention

[0007] The present invention aims to address at least one of the aforementioned problems by providing a probe system, positioning method, and storage medium with magnetic resonance positioning capabilities. These solutions address the existing problems in the MRI-PHIFU field, such as inaccurate positioning, complex calculations, slow response speed, and difficult and unstable installation of phased array probes.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The first aspect of the present invention discloses a probe system with a magnetic resonance positioning function, comprising a base, an ultrasonic transducer device, and a magnetic resonance positioning bracket;

[0010] The ultrasonic transducer device is assembled in the base;

[0011] The magnetic resonance positioning bracket is connected to the outer side wall of the base; the magnetic resonance positioning bracket includes a connecting plate, several pairs of transverse columns arranged parallel to the connecting plate, and several pairs of longitudinal columns arranged perpendicular to the connecting plate, and the longitudinal columns connect the transverse columns and the connecting plate.

[0012] The magnetic resonance positioning bracket adopts staggered transverse columns and longitudinal columns with clear intersection points, and the straight lines and planes formed in the magnetic resonance positioning bracket are easier to calculate and the results are more accurate during the coordinate system conversion process, thereby ensuring the accuracy and convenience of the calculated conversion matrix and coordinate conversion results.

[0013] Preferably, the ultrasonic transducer is connected to the base via at least one limiting mechanism, which prevents the ultrasonic transducer from moving horizontally or rotating during use, ensuring that the ultrasonic transducer stably follows the movement of the base, thereby ensuring directional accuracy.

[0014] Preferably, the limiting mechanism includes a first positioning unit and a second positioning unit connected to the first positioning unit, wherein the first positioning unit is disposed on the ultrasonic transducer device, and the second positioning unit is disposed on the base. The first positioning unit and the second positioning unit, which are distributed on the ultrasonic transducer device and the base, are used in combination to control the stable assembly of the ultrasonic transducer device on the base.

[0015] Further preferably, the first positioning units are positioning posts, spaced apart along the circumference of the ultrasonic transducer device, and the second positioning units are positioning slots, spaced apart along the circumference of the base. The positioning posts and slots themselves have simple structures, and their interaction does not occupy additional device volume. Therefore, the combination of positioning posts and slots can reduce changes to the original structure while meeting the positioning requirements.

[0016] Preferably, the probe system further comprises a connecting bracket connected to the outer side wall of the base, wherein the connecting bracket is used for assembling with an external structure and / or device, so that the probe system has a wider scalability.

[0017] Further preferably, a pair of connecting brackets are symmetrically arranged on the base. The pair of connecting brackets are used to connect with other components of the MRI-PHIFU system, and are mainly used for cooperation with the manipulator.

[0018] Preferably, the connecting bracket is connected to the outer wall of the base via a non-magnetic first fixing member. The non-magnetic first fixing member does not affect the magnetic resonance imaging. The detachable connection method allows the corresponding connecting bracket to be selected according to different connecting components in actual use.

[0019] Preferably, the connecting plate is connected to the outer side wall of the base via a second non-magnetic fixing member; and / or

[0020] The base also features a wire outlet extending through its sidewalls. This outlet is used to centrally route the wiring harnesses connected to the piezoelectric transducers. The connection plate provides a reference for the placement of the transverse and longitudinal columns, and prevents the magnetic resonance positioning bracket from being affected by parameters such as the base's shape and size.

[0021] Further preferably, a pair of outlets are symmetrically arranged about the base. This symmetrical arrangement allows for the wiring harness to be routed in a separate manner. The diameter of each opening for routing the wiring harness is relatively small, reducing the overall thickness and size of the probe system. Furthermore, the wiring harnesses are routed from the closest side, minimizing the possibility of entanglement and preventing the harness from running short.

[0022] Existing MRI-PHIFU systems lack cable outlets on the phased array transducer disk with cables, resulting in unstable installation and prone to loosening and displacement between the base and the ultrasonic transducer disk, leading to probe failure. By designing a double-sided cable outlet on the base, the impact of cable tension on mechanical movement is significantly reduced, ensuring a secure connection with other mechanical components of the PHIFU system and significantly improving device stability. This ensures the reliability of the MRI-PHIFU system during treatment and further ensures that calculations accurately match actual conditions.

[0023] A second aspect of the present invention discloses a magnetic resonance positioning method, comprising:

[0024] Acquiring magnetic resonance images of at least two scanning angles of the probe system according to any one of the above items through magnetic resonance;

[0025] Acquire the positioning projection point of the magnetic resonance positioning bracket from the magnetic resonance image;

[0026] Obtain the straight line where the longitudinal column is located and the positioning plane where the transverse column is located through the position information of the positioning projection point;

[0027] Acquiring position information of the intersection point in magnetic resonance according to the intersection information of the straight line and the positioning plane;

[0028] A conversion matrix is ​​calculated based on the position information of the intersection point in the magnetic resonance coordinate system and the position information of the intersection point in the breast manipulator coordinate system.

[0029] By scanning the MRI positioning stent using magnetic resonance, the coordinates of the stent in the MRI coordinate system can be obtained. Since the MRI positioning stent is connected to the robotic arm during normal use, the coordinates of the MRI positioning stent in the robotic arm coordinate system are known information. The coordinates of multiple corresponding points in two different coordinate systems can be used to calculate the transformation matrix of the two coordinate systems, and then the coordinates of each point in the probe system in the MRI coordinate system can be calculated to achieve precise positioning. Because the MRI positioning stent of the probe system has a clear intersection, it is easy to obtain the specified coordinates through magnetic resonance, which simplifies the calculation.

[0030] The probe system is mounted on the breast manipulator via a connecting bracket, so the breast manipulator coordinate system described here is actually consistent with the ultrasound coordinate system.

[0031] Preferably, it includes:

[0032] The positioning projection points include corresponding transverse projection points formed by the transverse column on the sagittal plane of the magnetic resonance scan and corresponding longitudinal projection points formed by the longitudinal column on the cross-sectional plane of the magnetic resonance scan; and / or

[0033] The straight line where the longitudinal column is located is calculated based on the position information of at least two cross sections; and / or

[0034] The positioning plane of the transverse column is calculated by using position information of at least two sagittal planes; and / or

[0035] The intersection point is obtained by calculating the intersection position information of the straight line and the positioning plane; and / or

[0036] The transformation matrix is ​​calculated based on the position information of the intersection point in the magnetic resonance coordinate system and the position information of the intersection point in the breast manipulator coordinate system;

[0037] Based on this transformation matrix, the position information in the magnetic resonance image is converted to the multi-element phased high-intensity focused ultrasound system. By calculating relatively simple lines and planes and their corresponding intersection points, the transformation matrix between coordinate systems can be calculated. This is more convenient and more accurate than the existing spherical point selection and calculation methods.

[0038] Preferably,

[0039] The coordinates of any four non-coplanar points in magnetic resonance are:

[0040] The coordinates of any four non-coplanar points in the breast manipulator in the magnetic resonance image are:

[0041] According to the magnetic resonance coordinates and the breast manipulator coordinates, the transformation matrix is ​​obtained:

[0042] According to the magnetic resonance coordinates and the transformation matrix, the coordinates of the corresponding points in the multi-element phased high-intensity focused ultrasound system are obtained as follows:

[0043] As shown above, a simple conversion method is shown. The corresponding transformation matrix can be obtained through any four non-coplanar points. The coordinates of the four points in the two coordinate systems can be easily obtained.

[0044] A third aspect of the present invention discloses a computer storage medium, wherein when a computer program is executed by a processor, the computer storage medium implements the magnetic resonance positioning method as described in any one of the above items.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The existing MRI-PHIFU system suffers from inaccurate conversion matrices between the probe coordinate system and the magnetic resonance coordinate system, resulting in large positioning errors. This invention utilizes a magnetic resonance positioning bracket and a magnetic resonance belt for two-level scanning, quickly determining the projection points of the bracket on a plane and, consequently, the relative positional relationship between the magnetic resonance and the probe. The linear equation is simpler and more accurate than the calculation of the positioning plane, making calculations faster and the resulting conversion matrix more accurate and adaptable. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a schematic diagram of the structure of the probe system;

[0048] FIG2 is a schematic structural diagram of an ultrasonic transducer device and a base;

[0049] FIG3 is a schematic structural diagram of the connection bracket and the base;

[0050] FIG4 is a schematic structural diagram of the base after the connecting bracket is removed;

[0051] FIG5 is a schematic structural diagram of a magnetic resonance positioning bracket and a base;

[0052] FIG6 is a schematic diagram of the top view of the probe system;

[0053] FIG7 is a schematic diagram of the sagittal plane when the probe system is positioned;

[0054] FIG8 is a schematic diagram of a cross section of the probe system during positioning;

[0055] FIG9 is a schematic diagram of the positioning plane when the probe system is positioned;

[0056] In the figure: 001-base; 002-ultrasonic transducer; 003-connecting bracket; 004-magnetic resonance positioning bracket; 005-first positioning unit; 006-second positioning unit; 007-connecting bracket through hole; 008-connecting bracket threaded hole; 009-first fixing piece; 010-positioning bracket threaded hole; 011-wire outlet; 012-positioning bracket through hole; 013-second fixing piece; 014-sagittal plane; 015-transverse projection point; 016-transverse column; 017-cross section; 018-longitudinal projection point; 019-longitudinal column; 020-first positioning plane; 021-second positioning plane. DETAILED DESCRIPTION

[0057] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] The existing MRI-PHIFU system suffers from inaccurate conversion matrices between the probe coordinate system and the magnetic resonance coordinate system, resulting in large positioning errors. This invention utilizes an MRI positioning bracket and a two-level scanning system using an MRI belt. This allows for rapid determination of the projection points of the bracket on a plane, thereby determining the relative positional relationship between the MRI and the probe.

[0059] Example 1

[0060] A probe system with a magnetic resonance positioning function, as shown in Figures 1 to 9, includes a base 001, an ultrasonic transducer device 002, and a magnetic resonance positioning bracket 004; the ultrasonic transducer device 002 is assembled in the base 001; the magnetic resonance positioning bracket 004 is connected to the outer wall of the base 001; the magnetic resonance positioning bracket 004 includes a connecting plate, several pairs of transverse columns 016 arranged parallel to the connecting plate, and several pairs of longitudinal columns 019 arranged perpendicular to the connecting plate, and the longitudinal columns 019 connect the transverse columns 016 and the connecting plate.

[0061] The magnetic resonance positioning bracket 004 includes a connecting plate, several pairs of transverse columns 016 arranged parallel to the connecting plate, and several pairs of longitudinal columns 019 arranged perpendicular to the connecting plate. The longitudinal columns 019 connect the transverse columns 016 and the connecting plate, and have a more three-dimensional complete structure. Compared with the use of spherical positioning markers: the center and edge points of the circle corresponding to each spherical positioning marker are determined by a circle positioning algorithm, and the center of the sphere corresponding to the spherical positioning marker is fitted as the positioning marker point; it has the characteristics of simple calculation method and easier fitting.

[0062] More specifically, in this embodiment:

[0063] The probe system as a whole comprises a base 001, an ultrasonic transducer 002, a connecting bracket 003, and an MRI positioning bracket 004, as shown in Figures 1 to 6. The ultrasonic transducer 002 is mounted in the base 001, and the connecting bracket 003 and the MRI positioning bracket 004 are respectively mounted on the outer wall of the base 001.

[0064] The ultrasonic transducer device 002 is a spherical structure, as shown in Figures 1 and 2 , with several mounting holes for piezoelectric transducers. The ultrasonic transducer device 002 has a plurality of first positioning units 005 spaced circumferentially on its back (convex) surface. In conjunction with these, a plurality of second positioning units 006 are spaced circumferentially on the inner side of the base 001. The first positioning units 005 and the second positioning units 006 are connected to each other, allowing the ultrasonic transducer device 002 to be positioned within the base 001. This ultrasonic transducer device 002 can utilize an ultrasonic transducer disk, with the first positioning units 005 being positioning posts and the second positioning units 006 being positioning slots. Insertion of the positioning posts into the slots secures the ultrasonic transducer device 002 to the base 001. More specifically, the ultrasonic transducer disk adopts a spherical structure, on which are distributed several mounting holes for mounting piezoelectric transducers; in particular, this embodiment adopts detachable mounting holes, such as threaded connection, to facilitate the replacement of a single piezoelectric transducer, thereby avoiding the difficulty of replacement under the traditional adhesive fixing method, and the situation where multiple piezoelectric transducers can only be scrapped when they are damaged, thereby improving the use efficiency.

[0065] Connecting brackets 003 are used to connect to other components of the MRI-PHIFU system. As shown in Figures 3 and 4, they are symmetrically positioned on either side of base 001. They are removable and connected to the outer wall of base 001 via non-magnetic first fixing members 009. More specifically, a protruding flat surface is formed on the side of base 001 for mounting connecting brackets 003. This flat surface is provided with multiple threaded holes 008 for connecting brackets. Connecting brackets 003 have through-holes 007 corresponding to the threaded holes 008. Non-magnetic fixing screws (first fixing members 009) pass through these holes and are screwed into the threaded holes 008, securing connecting brackets 003 to the outer wall of base 001. Connecting brackets 003 are designed to connect to other components of the MRI-PHIFU system. Therefore, they are removable and interchangeable, making them easily adaptable to different connection requirements.

[0066] The magnetic resonance positioning bracket 004 is used to assist the probe system in the positioning conversion between the magnetic resonance coordinate system and the breast manipulator coordinate system (ultrasound coordinate system). As shown in Figure 5, it is connected to the outer wall of the base 001 and is assembled by a non-magnetic second fixing member 013. More specifically, the positioning bracket is composed of a connecting plate, a transverse column 016 and a longitudinal column 019. A pair of protrusions matching the size of the connecting plate are formed on the base 001, and the positioning bracket through holes 012 are symmetrically arranged on the protrusions. The side of the connecting plate is provided with a positioning bracket threaded hole 010 corresponding to the positioning bracket through hole 012. The positioning bracket is firmly assembled on the outer wall of the base 001 by passing a non-magnetic positioning bracket screw (second fixing member 013) through the positioning bracket through hole 012 and screwing it to the positioning bracket threaded hole 010. The positioning bracket adopts a truss structure, which is formed by four transverse columns 016 and six longitudinal columns 019. The transverse columns 016 are arranged parallel to the connecting plate, and the longitudinal columns 019 are arranged perpendicular to the connecting plate. The longitudinal columns 019 connect the transverse columns 016 and the connecting plate to form a rectangular parallelepiped.

[0067] To further enhance assembly stability, the probe system features a cable outlet 011 for centralized cable routing. As shown in Figure 6, this dual-side cable routing structure allows the numerous cables connected to the piezoelectric transducers mounted on the ultrasonic transducer 002 to be routed from a specific location, mitigating the potential for cable tension to hinder the probe system's movement and ensuring the secure installation of the ultrasonic transducer 002 within the base 001. These dual-side cable outlets 011 also feature a symmetrical structure, located on either side of the MRI positioning bracket 004. These outlets 011 extend through the sidewalls of the base 001 and face outward, allowing the cables to continue extending outward without affecting the structure and movement of the probe system or the MRI-PHIFU system.

[0068] After the probe system is assembled on the MRI-PHIFU system, the position information of the positioning bracket in the breast manipulator coordinate system (ultrasound coordinate system) can be obtained and is known information. To obtain the transformation matrix between the magnetic resonance coordinate system and the ultrasound coordinate system, the position information of the positioning bracket in the magnetic resonance coordinate system needs to be measured. Specifically, for this probe system, referring to Figures 7 to 9, a sagittal plane 014 and a transverse plane 017 can be obtained through magnetic resonance scanning. The four transverse columns 016 form four corresponding transverse projection points 015 on the sagittal plane 014, and the six longitudinal columns 019 form six corresponding longitudinal projection points 018 on the transverse plane 017. Therefore, by scanning two transverse planes 017 at different positions, the equations of the six straight lines on which the six longitudinal columns 019 lie in the magnetic resonance coordinate system can be calculated. By scanning two sagittal planes 014 at different positions, the position information of the two positioning planes (first positioning plane 020 and second positioning plane 021) on which the four transverse columns 016 lie can be calculated. The six straight lines mentioned above will intersect with the two positioning planes to form twelve intersection points, and the coordinate information of the twelve intersection points can be calculated based on the linear equations obtained above and the position information of the positioning planes. Combined with the known coordinate information of the positioning bracket (the twelve intersection points mentioned above) in the thermal manipulator coordinate system, the transformation matrix between the magnetic resonance coordinate system and the ultrasound coordinate system (breast manipulator coordinate system) can be calculated. Compared with the calculation of linear equations and positioning planes, the calculation is simpler and more accurate, so the calculation is faster, the resulting transformation matrix is ​​more accurate, and the applicability is stronger.

[0069] More specifically, four points on any different planes of the twelve intersection points are selected, and their coordinates in the magnetic resonance coordinate system are as follows (1), and their coordinates in the breast manipulator coordinate system are as follows (2):

[0070] The conversion matrix can be obtained as formula (3):

[0071] Furthermore, the transformation relationship between the magnetic resonance coordinate system and the breast manipulator coordinate system is formula (4):

[0072] In summary, in this design, the magnetic resonance positioning bracket 004 is used and magnetic resonance is used to perform multi-angle and multi-plane scanning, thereby obtaining the projection point of the magnetic resonance positioning bracket 004 on the scanning plane and the position information of the intersection point in the magnetic resonance coordinate system. Based on the known position information of the intersection point in the breast manipulator coordinate system, the transformation relationship between the two coordinate systems can be calculated; compared with other shapes, such as spherical markers, the fitting difficulty is reduced, and it has the characteristics of simple calculation method and easier fitting.

[0073] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A probe system with magnetic resonance positioning function, characterized in that: It comprises a base (001), an ultrasonic transducer device (002), and a magnetic resonance positioning bracket (004); The ultrasonic transducer device (002) is assembled in the base (001); The magnetic resonance positioning bracket (004) is connected to the outer wall of the base (001); the magnetic resonance positioning bracket (004) comprises a connecting plate, a plurality of pairs of transverse columns (016) arranged parallel to the connecting plate, and a plurality of pairs of longitudinal columns (019) arranged perpendicular to the connecting plate, wherein the longitudinal columns (019) connect the transverse columns (016) and the connecting plate.

2. A probe system with magnetic resonance positioning function according to claim 1, characterized in that: The ultrasonic transducer device (002) and the base (001) are connected via at least one limiting mechanism.

3. A probe system with magnetic resonance positioning function according to claim 2, characterized in that: The limiting mechanism comprises: a first positioning unit (005), and a second positioning unit (006) connected to the first positioning unit (005), wherein the first positioning unit (005) is arranged on the ultrasonic transducer device (002), and the second positioning unit (006) is arranged on the base (001).

4. The probe system with magnetic resonance positioning function according to claim 1, characterized in that: The probe system further comprises a connecting bracket (003) connected to the outer side wall of the base (001).

5. A probe system with magnetic resonance positioning function according to claim 4, characterized in that: The connecting bracket (003) is connected to the outer side wall of the base (001) via a non-magnetic first fixing member (009).

6. The probe system with magnetic resonance positioning function according to claim 1, characterized in that: The connecting plate is connected to the outer side wall of the base (001) via a non-magnetic second fixing member (013); and / or The base (001) is also provided with a wire outlet (011), and the wire outlet (011) passes through the side wall of the base (001).

7. A magnetic resonance positioning method, characterized in that: include: Acquiring magnetic resonance images of at least two scanning angles of the probe system according to any one of claims 1 to 6 by magnetic resonance; Acquiring a positioning projection point of a magnetic resonance positioning bracket (004) from the magnetic resonance image; The straight line where the longitudinal column (019) is located and the positioning plane where the transverse column (016) is located are obtained through the position information of the positioning projection point; According to the intersection information of the straight line and the positioning plane, the position information of the intersection point in the magnetic resonance is obtained. interest; A conversion matrix is ​​calculated and acquired according to the position information of the intersection point in the magnetic resonance coordinate system and the position information of the intersection point in the breast manipulator coordinate system.

8. A magnetic resonance positioning method according to claim 7, characterized in that: include: The positioning projection points include a transverse column (016) forming a corresponding transverse projection point (015) on the sagittal plane (014) of the magnetic resonance scan and a longitudinal column (019) forming a corresponding longitudinal projection point (018) on the cross-sectional plane (017) of the magnetic resonance scan; and / or The straight line on which the longitudinal column (019) is located is calculated from the position information of at least two cross-sections (017); and / or The positioning plane where the transverse column (016) is located is calculated through the position information of at least two sagittal planes (014); and / or The intersection point is obtained by calculating the intersection position information of the straight line and the positioning plane; and / or The transformation matrix is ​​calculated based on the position information of the intersection point in the magnetic resonance coordinate system and the position information of the intersection point in the breast manipulator coordinate system; According to the conversion matrix, the position information in the magnetic resonance image is converted into a multi-element phased high-intensity focused ultrasound system.

9. A magnetic resonance positioning method according to claim 8, characterized in that: The coordinates of any four non-coplanar points in magnetic resonance are: The coordinates of any four non-coplanar points in the breast manipulator in the magnetic resonance image are: According to the magnetic resonance coordinates and the breast manipulator coordinates, the transformation matrix is ​​obtained: According to the magnetic resonance coordinates and the transformation matrix, the corresponding points in the multi-element phased high-intensity focused ultrasound system are obtained. The coordinates are:

10. A computer storage medium, characterized in that: When the computer program is executed by a processor, the magnetic resonance positioning method according to any one of claims 7 to 9 is implemented.

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