CN109908497B - Coordinate calibration device, system, method and medium - Google Patents
Coordinate calibration device, system, method and medium Download PDFInfo
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- CN109908497B CN109908497B CN201910256465.6A CN201910256465A CN109908497B CN 109908497 B CN109908497 B CN 109908497B CN 201910256465 A CN201910256465 A CN 201910256465A CN 109908497 B CN109908497 B CN 109908497B
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Abstract
The embodiment of the invention discloses a coordinate calibration device, a system, a method and a medium, wherein the device comprises: a body and a set of calibration points corresponding to each imaging device; the calibration point groups are arranged on the body, each calibration point group at least comprises one calibration point in the scanning range of the corresponding imaging equipment, and the spatial position relationship of the calibration points among different calibration point groups is fixed. The problem that the coordinate conversion relation between the isocenters of the positioning CT and the guide CT cannot be accurately detected in the prior art is solved, so that the accuracy of isocenter detection of the positioning CT and the guide CT is improved.
Description
Technical Field
The embodiment of the invention relates to the technical field of medical equipment, in particular to a coordinate calibration device, a coordinate calibration system, a coordinate calibration method and a coordinate calibration medium.
Background
An integrated radiotherapy system generally comprises a positioning CT (Computed Tomography, CT)11 and a RT (Radiation Therapy, RT)121, as shown in fig. 1. Typically, the positioning CT 11 and RT 121 share a couch 13, and RT is disposed on a CT gantry on a side of the couch 13. In order to facilitate the image-guided radiotherapy, a detection flat plate 122 facing the RT 121 is further provided on the gantry that positions the CT 11, thereby constituting a guided CT 12 capable of rotational scanning.
In order to improve the accuracy of radiotherapy, the consistency of the positioning CT coordinates and the guiding CT (or RT) coordinates needs to be detected periodically. In the prior art, laser-assisted detection is commonly adopted, and specifically: a laser lamp 011 emitting parallel to a z axis is erected at the rotating center of a rack for positioning the CT, a flat plate 012 is arranged at a fixed position at the RT side, and the (x, y) coordinates of the rotating isocenter of the positioning CT falling on the RT known flat plate 012 are detected through projection, so that the relative coordinates between the positioning CT and the guiding CT are calculated. In the current use environment, the method has great limitation, firstly, the installation of the laser lamp 011 is difficult to ensure that the laser beam is absolutely vertical to the X-Y plane of the RT; secondly, the distance between the RT system and the CT rotation plane exceeds 2m, and the common laser beam with the diameter of 1mm is difficult to ensure the focusing under the distance, so that the diameter of a light spot is too large, and the detection precision is reduced; finally, the method cannot measure the relation between the two isocenters in the z direction, so that in actual use, the value is guaranteed by mechanical installation, and the error is large.
In summary, the prior art cannot accurately detect the coordinate relationship between the isocenter of the positioning CT and the isocenter of the guiding CT, and it is necessary to provide a coordinate calibration apparatus, which detects the coordinate transformation matrix between the positioning CT and the RT, and adjusts the spatial relationship between the positioning CT and the RT based on the coordinate transformation matrix, thereby ensuring the coordinate consistency between the positioning CT and the RT.
Disclosure of Invention
The embodiment of the invention provides a coordinate calibration device, a coordinate calibration system, a coordinate calibration method and a coordinate calibration medium, which are used for solving the problem that the coordinate relationship between isocenters of positioning CT and guide CT cannot be accurately detected in the prior art so as to improve the accuracy of isocenter detection of the positioning CT and the guide CT.
In a first aspect, an embodiment of the present invention provides a coordinate calibration apparatus, configured to calibrate coordinates between at least two imaging devices, including:
a body;
the calibration point groups corresponding to the imaging devices are arranged on the body, each calibration point group at least comprises one calibration point in the scanning range of the corresponding imaging device, and the spatial position relationship of the calibration points among different calibration point groups is fixed.
In a second aspect, an embodiment of the present invention further provides a coordinate calibration system, where the coordinate calibration device according to the first aspect includes:
the system comprises an acquisition module, a calibration module and a calibration module, wherein the acquisition module is used for acquiring an image of a part of coordinate calibration device corresponding to a scanning range of imaging equipment to be calibrated, and the image of each imaging equipment comprises position information of a target calibration point used for coordinate calculation;
and the output module is used for determining a coordinate conversion matrix between the imaging devices according to the position information of the target calibration points and the spatial position relation between the target calibration points.
In a third aspect, an embodiment of the present invention further provides a coordinate calibration method, used in cooperation with the coordinate calibration device described in the first aspect, including:
acquiring an image of a part of coordinate calibration device corresponding to a scanning range of imaging equipment to be calibrated, wherein the image of each imaging equipment comprises position information of a target calibration point used for coordinate calculation;
and determining a coordinate conversion matrix between the imaging devices according to the position information of the target calibration points and the spatial position relationship between the target calibration points.
In a fourth aspect, an embodiment of the present invention further provides a coordinate calibration method, used in cooperation with the coordinate calibration apparatus described in the first aspect, including:
positioning the coordinate calibration device to enable the calibration lines to simultaneously appear in the scanning range of the imaging equipment to be calibrated, wherein the scanning range of each imaging equipment at least corresponds to one target calibration point for coordinate calculation;
acquiring an image of a part of coordinate calibration device corresponding to a scanning range of imaging equipment to be calibrated, wherein the image of each imaging equipment comprises position information of a target calibration point used for coordinate calculation;
and determining a coordinate conversion matrix between the imaging devices according to the position information of the target calibration points and the spatial position relationship between the target calibration points.
In a fifth aspect, embodiments of the present invention also provide a storage medium containing computer-executable instructions, which when executed by a computer processor, are used to implement the coordinate calibration method according to the third aspect.
The technical scheme of the coordinate calibration device provided by the embodiment of the invention comprises a body and calibration point groups which are arranged on the body and correspond to each imaging device, wherein each calibration point group at least comprises one calibration point which is positioned in the scanning range of the corresponding imaging device, and the spatial position relationship of the calibration points among different calibration point groups is fixed, so that when each imaging device scans images of part of the coordinate calibration device in the scanning range, the spatial position relationship of the calibration points among different calibration point groups is unchanged, a coordinate conversion matrix among the imaging devices can be determined according to the actual spatial position relationship of a target point for coordinate calculation and the position information of the target point in the images.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an integrated radiotherapy system provided in the background of the invention;
fig. 2A is a schematic structural diagram of a coordinate calibration device according to an embodiment of the present invention;
fig. 2B is a schematic structural diagram of another coordinate calibration apparatus according to an embodiment of the present invention;
fig. 2C is a schematic structural diagram of another coordinate calibration apparatus according to an embodiment of the present invention;
FIG. 2D is a schematic diagram of a partial coordinate calibration apparatus for positioning a CT scan according to an embodiment of the present invention;
FIG. 2E is a schematic diagram of a partial coordinate calibration apparatus for guiding a CT scan according to an embodiment of the present invention;
FIG. 3 is a block diagram illustrating a coordinate calibration system according to a second embodiment of the present invention;
FIG. 4 is a schematic diagram of a coordinate calibration system according to a second embodiment of the present invention;
FIG. 5 is a flowchart of a coordinate calibration method according to a third embodiment of the present invention;
fig. 6 is a flowchart of a coordinate calibration method according to a fourth embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described through embodiments with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
The embodiment of the invention provides a coordinate calibration device. The device can be used for calibrating coordinates between at least two imaging devices, as shown in fig. 2A, 2B and 2C, and comprises a body 21 and a calibration point group corresponding to each imaging device, wherein the calibration point group is arranged on the body 21, each calibration point group at least comprises one calibration point 22 positioned in the scanning range of the corresponding imaging device, and the spatial position relationship of the calibration points 22 between different calibration point groups is fixed.
The imaging device of the present embodiment is generally a radiation imaging device, such as an X-ray imaging device, and the present embodiment is described by taking positioning CT and guiding CT in an integrated radiotherapy system (see fig. 1) as an example. Since the image formed by CT is usually a three-dimensional CT image or a flat film of a certain plane, and the spatial position relationship of the calibration points in the coordinate calibration device can be determined by the flat films of two orthogonal planes of the coordinate calibration device, the image described in this embodiment is a three-dimensional CT image or a flat film of at least two orthogonal planes of the coordinate calibration device scanned by each imaging device. The plain film of the present embodiment refers to a two-dimensional image of the coordinate calibration device obtained by moving the CT apparatus only along the z-axis, for example, the CT bulb is kept at a 0-degree position, and the treatment couch is moved and scanned only along the z-axis to obtain an image of the coordinate calibration device in the x-z plane, the CT bulb is kept at a 90-degree or 270-degree position, and the treatment couch is moved and scanned only along the z-axis to obtain an image of the coordinate calibration device in the y-z plane. As another example, for cone beam CT, plain film refers to the x-z plane and y-z plane images of a coordinate calibration apparatus scanned with a CT tube at 0 degrees and 90 degrees (or 270 degrees) respectively.
In order to improve the accuracy of coordinate calibration between imaging devices, the present embodiment further includes a fixing frame 23 for supporting and fixing the body 21, so that the body 21 is not deformed during the image scanning process, thereby ensuring that the spatial position relationship of the calibration points between different calibration point sets does not change relatively. In some embodiments, the fixing frame 23 is not limited to the shape shown in fig. 2A, 2B, and 2C as long as it can stably support the body 21. For example, since the imaging apparatus is generally provided with components such as a base and/or a chassis, in order that the mount 23 does not interfere with the base and/or the chassis of the imaging apparatus, the mount 23 may support only both end portions of the body 21 so as to avoid the base and/or the chassis of the imaging apparatus.
The body is preferably made of rigid materials, and the rigid materials can simply and conveniently keep the spatial position relationship of the calibration points among different calibration point groups fixed; of course, the body may also be made of a flexible material as long as the fixing frame 23 can keep the spatial positional relationship between the calibration points of different calibration point sets unchanged.
Preferably, the calibration points of the different calibration point groups are arranged linearly (see fig. 2A and 2B) to simplify the spatial positional relationship between the coordinate calibration points, thereby reducing the amount of operation for determining the coordinate conversion matrix between the imaging devices according to the spatial positional relationship in the image of the calibration points of the different calibration point groups.
In order to make the calibration points of different calibration point sets be arranged linearly, the calibration points of different calibration point sets of this embodiment may be disposed on the same characteristic line of the body (see fig. 2A and 2C), or disposed on the same identification line (see fig. 2B), and the identification line is located inside or on the surface of the body. The characteristic line is a line carrying characteristic information of the body, such as a sideline or an axis line of the body, and the identification line can be any line arranged in the body. Optionally, the attenuation coefficient of the identification line to the ray is usually different from that of the body to the ray, so that the identification line can be displayed on the image.
It is understood that, if each calibration point group includes a plurality of calibration points, the correspondence relationship of the target calibration points for coordinate calculation needs to be determined when determining the coordinate conversion matrix between the imaging devices from the position information of the calibration points in the image. To facilitate determination of the correspondence, the shapes of the respective calibration points 22 (see fig. 2B) or attenuation coefficients of the rays in the calibration point groups of the present embodiment are different so that the shapes or gradation values of the calibration points on the image are different, so that the target calibration points for coordinate calculation in different calibration point groups can be determined according to the shapes or gradation values of the calibration points on the image.
In this embodiment, calibration point 22 and body 21 are composed of different materials, so that calibration point 22 can be identified in an image scanned by a corresponding imaging device. For example, for a radiographic imaging device, calibration points 22 and body 21 do not attenuate radiation differently. Alternatively, calibration point 22 may be a metal ball disposed within body 21, or calibration point 22 may be a hole formed within body 21.
The technical scheme of the coordinate calibration device provided by the embodiment of the invention comprises a body and calibration point groups which are arranged on the body and correspond to each imaging device, wherein each calibration point group at least comprises one calibration point which is positioned in the scanning range of the corresponding imaging device, and the spatial position relationship of the calibration points among different calibration point groups is fixed, so that when each imaging device scans images of part of the coordinate calibration device in the scanning range, the spatial position relationship of the calibration points among different calibration point groups is unchanged, a coordinate conversion matrix among the imaging devices can be determined according to the actual spatial position relationship of a target point for coordinate calculation and the position information of the target point in the images.
Example two
Fig. 3 is a block diagram of a coordinate calibration system according to a second embodiment of the present invention. The coordinate calibration system is used in cooperation with the coordinate calibration device described in the previous embodiment, and includes an acquisition module 31 and an output module 32, where the acquisition module 31 is configured to acquire an image of a portion of the coordinate calibration device corresponding to a scanning range of an imaging device to be calibrated, and the image of each imaging device includes position information of a target calibration point used for coordinate calculation; the output module 32 is used for determining a coordinate transformation matrix between the imaging devices according to the position information of the target calibration points and the spatial position relationship between the target calibration points. The spatial positional relationship between the target calibration points may be determined in advance and stored in the memory of the coordinate calibration system.
It can be understood that an image corresponding to the CT imaging apparatus is generally a three-dimensional CT image or a planar flat sheet, and a spatial position relationship of any calibration point can be determined by the flat sheets of two orthogonal planes of the coordinate calibration device, so the image described in this embodiment is a three-dimensional CT image of a part of the coordinate calibration device or a flat sheet of at least two orthogonal planes. The plain film of the present embodiment refers to a two-dimensional image of the coordinate calibration device obtained by moving the CT apparatus only along the z-axis, for example, the CT bulb is kept at a 0-degree position, and the treatment couch is moved and scanned only along the z-axis to obtain an image of the coordinate calibration device in the x-z plane, the CT bulb is kept at a 90-degree or 270-degree position, and the treatment couch is moved and scanned only along the z-axis to obtain an image of the coordinate calibration device in the y-z plane. As another example, for cone beam CT, plain film refers to the x-z plane and y-z plane images of a coordinate calibration apparatus scanned with a CT tube at 0 degrees and 90 degrees (or 270 degrees) respectively.
It is understood that if coordinate calibration between two imaging devices can be realized, coordinate calibration between any number of imaging devices can be realized, and for convenience of explanation of the technical solution, this embodiment takes correction of coordinates of two imaging devices as an example.
If there are two imaging devices, the output module 32 of the present embodiment includes: a reference image determining unit 321, a virtual calibration point determining unit 322, and a coordinate conversion matrix determining unit 323, the reference image determining unit 321 being configured to take one of the imaging devices as a reference imaging device and take an image of the reference imaging device as a reference image; the virtual calibration point determining unit 32 is configured to determine, based on the spatial positional relationship between the stored target calibration points and the positional information of the target calibration points in the reference image, positional information of virtual calibration points corresponding to another imaging device in the coordinate system in which the reference image is located; the coordinate conversion matrix determination unit 323 is configured to determine a coordinate conversion matrix between the two imaging devices based on the position information of the virtual calibration point and the position information of the target calibration point of the other imaging device.
Illustratively, as shown in fig. 2D and 2E, the body of the coordinate calibration device is a cylindrical structure, and the axis of the body is provided with a marking line, on which a calibration point P1 and a calibration point P2 are provided, and the two imaging devices are respectively a positioning CT and a guiding CT of the integrated radiotherapy system (see fig. 1). The set calibration point P1 corresponds to a positioning CT, and the positioning CT corresponds to a mapLike an fbct (fan beam CT) image (see fig. 2D), the calibration point P2 corresponds to a pilot CT, and the image corresponding to the pilot CT is a cbct (cone beam CT) image (see fig. 2E). Based on the actual spatial position relationship between the calibration point P1 and the calibration point P2, a virtual calibration point P21 corresponding to P1 is determined in the coordinate system of the CBCT image (see the dotted line portion outside the CBCT image in fig. 2E) using the CBCT image as a reference image, and assuming that the coordinate conversion matrix of the positioning CT with respect to the guide CT is TCR, the coordinates of the positioning CT and the guide CT satisfy: p21(x,y)＝TCRP1(x,y)。
Coordinate P of P1 in the preceding formula1(x, y) is known, the coordinates of P21 can be determined from the coordinates of P2 and the spatial position relationship between the two coordinates of P2 and P1, and therefore the coordinates of P1 and P21 and the coordinate transformation matrix can be calculated. After the coordinate transformation matrix is calculated, all relations between coordinate systems are established between the positioning CT and the guiding CT, so that the method can be applied to image guiding and other workflows. For example, the coordinate system for guiding the central coordinates of the CT to the positioning CT may be adjusted according to the coordinate transformation matrix by using the positioning CT as a reference device. The coordinates of P1 and P21 are determined through the CBCT image and the FBCT image, the accuracy of the determined coordinates can reach a sub-pixel level, and therefore compared with the prior art that the rotation centers of the two imaging devices can only be roughly calibrated in an x-y plane, the three-dimensional coordinates of the isocenter of the two imaging devices can be accurately calibrated.
It is to be understood that, in order to improve the accuracy of coordinate calibration between the imaging devices, each imaging device may correspond to a plurality of calibration points, that is, each imaging device includes a plurality of target calibration points for coordinate calculation in an image thereof, and at this time, the coordinate conversion matrix determination unit may determine an initial coordinate conversion matrix between the two imaging devices based on position information of a virtual calibration point corresponding to each target calibration point and position information of a target calibration point of the other imaging device, and determine a coordinate conversion matrix between the two imaging devices based on the initial coordinate conversion matrix between the two imaging devices.
It is to be understood that the coordinate conversion matrix determining unit may determine and store the weight coefficient of each target calibration point in advance when determining the coordinate conversion matrix between the two imaging devices based on the initial coordinate conversion matrix between the imaging devices, and then determine the coordinate conversion matrix between the two imaging devices based on the initial coordinate conversion matrix between the imaging devices and the weight coefficient of each target calibration point. For example, when each imaging device corresponds to two target calibration points, the weight coefficient of each target calibration point is 0.5, that is, the average value of the coordinate transformation matrices corresponding to the two target calibration points is taken.
For convenience of description of the technical solution, the coordinate directions of the positioning CT and the guiding CT in the embodiment are consistent (see fig. 1), but it can be understood that even if the coordinate directions of the positioning CT and the guiding CT are not consistent, for example, the treatment couch for positioning CT moves along the z-axis and the treatment couch for guiding CT moves along the y-axis, the coordinate transformation matrices of the positioning CT and the guiding CT can be obtained according to any embodiment of the present invention.
Optionally, as shown in fig. 4, the system further includes a processor 201, a memory 202, an input device 203, and an output device 204; the number of the processors 201 in the device may be one or more, and one processor 201 is taken as an example in fig. 4; the processor 201, the memory 202, the input device 203 and the output device 204 in the apparatus may be connected by a bus or other means, and fig. 4 illustrates the connection by a bus as an example.
The memory 202 is a computer-readable storage medium for storing software programs, computer-executable programs, and modules, and the processor 201 executes various functional applications and data processing of the device by executing the software programs, instructions, and modules stored in the memory 202, that is, functions of the coordinate calibration system described above.
The memory 202 may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created according to the use of the terminal, and the like. Further, the memory 202 may include high speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some examples, the memory 202 may further include memory located remotely from the processor 201, which may be connected to the device over a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The input device 203 may be used to receive input numeric or character information and generate key signal inputs related to user settings and function controls of the apparatus.
The output device 204 may include a display device such as a display screen, for example, of a user terminal.
The technical scheme of the coordinate calibration system provided by the embodiment of the invention comprises an acquisition module and an output module, wherein the acquisition module is used for acquiring the image of a part of the coordinate calibration device corresponding to the scanning range of the imaging equipment to be calibrated, and the image of each imaging equipment comprises the position information of a target calibration point used for coordinate calculation; the output module is used for determining a coordinate conversion matrix between the imaging devices according to the position information of the target calibration points and the stored spatial position relationship between the target calibration points. Compared with the prior art, the system can determine the coordinate transformation matrix between the imaging devices simply and quickly.
EXAMPLE III
Fig. 5 is a flowchart of a coordinate calibration method according to a third embodiment of the present invention. The embodiment of the present invention corresponds to the coordinate calibration system described in the foregoing embodiment, and the method includes:
s101, acquiring an image of a part of the coordinate calibration device corresponding to the scanning range of the imaging equipment to be calibrated, wherein the image of each imaging equipment comprises position information of a target calibration point used for coordinate calculation.
Taking an integrated radiotherapy system as an example, the integrated radiotherapy system generally comprises a positioning CT and a guiding CT, after the coordinate calibration device is positioned, the positioning CT is controlled to acquire FBCT images of part of the coordinate calibration device in the scanning range of the positioning CT, and the guiding CT is controlled to acquire CBCT images of part of the coordinate calibration device in the scanning range of the guiding CT. Since the scan ranges of the positioning CT and the pilot CT correspond to at least one calibration point set, both the FBCT image and the CBCT image contain target calibration points that can be used for coordinate calculation, and since both the FBCT image and the CBCT image are three-dimensional images, they contain spatial position information of the target calibration points.
And S102, determining a coordinate conversion matrix between the imaging devices according to the position information of the target calibration points and the stored spatial position relationship between the target calibration points.
After the images of the coordinate calibration device shot by the two imaging devices are acquired, the coordinate conversion matrix between the imaging devices can be determined according to the position information of the target calibration points in the two images and the stored spatial position relationship between the target calibration points.
Preferably, one of the imaging devices is taken as a reference imaging device, and the image of the reference imaging device is taken as a reference image; determining position information of a virtual calibration point corresponding to another imaging device in a coordinate system in which the reference image is located according to the stored spatial position relationship between the target calibration points and the position information of the target calibration points in the reference image; then, a coordinate conversion matrix between the isocenters of the two imaging apparatuses is determined based on the position information of the virtual calibration point and the position information of the target calibration point of the other imaging apparatus.
Illustratively, as shown in fig. 2D and 2E, the body of the coordinate calibration device is a cylindrical structure, and the axis of the body is provided with a marking line, on which a calibration point P1 and a calibration point P2 are provided, and the two imaging devices are respectively a positioning CT and a guiding CT of the integrated radiotherapy system (see fig. 1). The calibration point P1 is set to correspond to a positioning CT, the image corresponding to the positioning CT is an fbct (fan beam CT) image (see fig. 2D), the calibration point P2 corresponds to a guiding CT, and the image corresponding to the guiding CT is a cbct (cone beam CT) image (see fig. 2E). Based on the actual spatial position relationship between the calibration point P1 and the calibration point P2, a virtual calibration point P21 corresponding to P1 is determined in the coordinate system of the CBCT image (see the dotted line portion outside the CBCT image in fig. 2E) using the CBCT image as a reference image, and assuming that the coordinate conversion matrix of the positioning CT with respect to the guide CT is TCR, the coordinates of the positioning CT and the guide CT satisfy: p21(x,y)＝TCRP1(x,y)。
Coordinate P of P1 in the preceding formula1(x, y) is known, P21 can be determined from the coordinates of P2 and the spatial positional relationship between the two coordinates of P2 and P1, and therefore the coordinates of P1 and P21 and the coordinate conversion matrix can be calculated. After the coordinate transformation matrix is calculated, all relations between coordinate systems are established between the positioning CT and the guiding CT, so that the method can be applied to image guiding and other workflows. For example, the coordinate system for guiding the central coordinates of the CT to the positioning CT may be adjusted according to the coordinate transformation matrix by using the positioning CT as a reference device. The coordinates of P1 and P21 are determined through the CBCT image and the FBCT image, the accuracy of the determined coordinates can reach a sub-pixel level, and therefore compared with the prior art that the rotation centers of the two imaging devices can only be roughly calibrated in an x-y plane, the three-dimensional coordinates of the isocenter of the two imaging devices can be accurately calibrated.
It is to be understood that, in order to improve the accuracy of coordinate calibration between the imaging devices, each imaging device may correspond to a plurality of calibration points, that is, each imaging device includes a plurality of target calibration points for coordinate calculation in an image thereof, and at this time, the coordinate conversion matrix determination unit may determine an initial coordinate conversion matrix between the two imaging devices based on position information of a virtual calibration point corresponding to each target calibration point and position information of a target calibration point of the other imaging device, and determine a coordinate conversion matrix between the two imaging devices based on the initial coordinate conversion matrix between the two imaging devices.
It can be understood that, besides the three-dimensional CT image of the coordinate transformation device, a planar sheet of a certain plane of the coordinate transformation device can be obtained through CT, and the planar sheets of two orthogonal planes can determine the spatial position relationship of the target calibration point, so the image of the embodiment is the three-dimensional CT image of the coordinate calibration device or the planar sheets of two orthogonal planes of the coordinate calibration device.
Compared with the coordinate calibration method in the prior art, the embodiment utilizes the existing positioning CT and guide CT to obtain the image of the coordinate calibration device, does not need to add an additional mechanical precision detection device, has low implementation difficulty and low cost, can achieve the detection precision of a sub-pixel level, is higher than the common mechanical detection precision, and reduces the system error influence of the related workflow of the positioning CT and the guide CT.
Example four
Fig. 6 is a flowchart of a coordinate calibration method according to a fourth embodiment of the present invention. The coordinate calibration method provided by the embodiment of the invention is used for calibrating the coordinates of at least two imaging devices by adopting the coordinate calibration device and the coordinate calibration system described in the previous embodiment, and the method comprises the following steps:
s201, the coordinate calibration device is placed, so that the calibration lines are simultaneously present in the scanning range of the imaging equipment to be calibrated, and the scanning range of each imaging equipment at least corresponds to one target calibration point for coordinate calculation.
When the coordinate calibration device and the coordinate calibration system described in the foregoing embodiments are used to perform coordinate calibration on at least two imaging devices, the coordinate calibration device needs to be positioned first, so that the body of the coordinate calibration device is located in the scanning ranges of the two imaging devices at the same time, and at least one calibration point group appears in the scanning range of each imaging device. Wherein each set of calibration points comprises at least one calibration point.
It is to be understood that, in order to improve the accuracy of coordinate calibration between the imaging devices, each imaging device may correspond to a plurality of calibration points, that is, each imaging device includes a plurality of target calibration points for coordinate calculation in an image thereof, and at this time, the coordinate conversion matrix determination unit may determine an initial coordinate conversion matrix between the two imaging devices based on position information of a virtual calibration point corresponding to each target calibration point and position information of a target calibration point of the other imaging device, and determine a coordinate conversion matrix between the two imaging devices based on the initial coordinate conversion matrix between the two imaging devices.
S202, acquiring an image of a part of the coordinate calibration device corresponding to the scanning range of the imaging equipment to be calibrated, wherein the image of each imaging equipment comprises position information of a target calibration point used for coordinate calculation.
Taking an integrated radiotherapy system as an example, the imaging device is generally a positioning CT and a guiding CT, after the coordinate calibration device is positioned, the positioning CT is controlled to acquire FBCT images of part of the coordinate calibration device in the scanning range, and the guiding CT is controlled to acquire CBCT images of part of the coordinate calibration device in the scanning range. Since the scan ranges of the positioning CT and the pilot CT correspond to at least one calibration point set, both the FBCT image and the CBCT image contain target calibration points that can be used for coordinate calculation, and since both the FBCT image and the CBCT image are three-dimensional images, they contain spatial position information of the target calibration points.
And S203, determining a coordinate conversion matrix between the imaging devices according to the position information of the target calibration points and the spatial position relationship between the target calibration points.
After the images of the coordinate calibration device shot by the two imaging devices are acquired, the coordinate conversion matrix between the imaging devices can be determined according to the position information of the target calibration points in the two images and the stored spatial position relationship between the target calibration points.
Preferably, one of the imaging devices is taken as a reference imaging device, and the image of the reference imaging device is taken as a reference image; determining position information of a virtual calibration point corresponding to another imaging device in a coordinate system in which the reference image is located according to the stored spatial position relationship between the target calibration points and the position information of the target calibration points in the reference image; then, a coordinate conversion matrix between the isocenters of the two imaging apparatuses is determined based on the position information of the virtual calibration point and the position information of the target calibration point of the other imaging apparatus.
Illustratively, as shown in fig. 2D and 2E, the body of the coordinate calibration device is a cylindrical structure, and the axis of the body is provided with a marking line, on which a calibration point P1 and a calibration point P2 are provided, and the two imaging devices are respectively a positioning CT and a guiding CT of the integrated radiotherapy system (see fig. 1). The calibration point P1 is set to correspond to a positioning CT, the image corresponding to the positioning CT is an fbct (fan beam CT) image (see fig. 2D), the calibration point P2 corresponds to a guiding CT, and the image corresponding to the guiding CT is a cbct (cone beam CT) image (see fig. 2E). Based on the actual spatial positional relationship between the calibration point P1 and the calibration point P2, a virtual calibration point P21 corresponding to P1 is determined in the coordinate system of the CBCT image (see the virtual calibration point P21 outside the CBCT image in FIG. 2E)Line part), assuming that the coordinate transformation matrix of the positioning CT with respect to the guiding CT is TCR, the coordinates of the positioning CT and the guiding CT satisfy: p21(x,y)＝TCRP1(x,y)。
Coordinate P of P1 in the preceding formula1(x, y) is known, the coordinates of P21 can be determined from the coordinates of P2 and the spatial position relationship between the two coordinates of P2 and P1, and therefore the coordinates of P1 and P21 and the coordinate transformation matrix can be calculated. After the coordinate transformation matrix is calculated, all relations between coordinate systems are established between the positioning CT and the guiding CT, so that the method can be applied to image guiding and other workflows. For example, the coordinate system for guiding the central coordinates of the CT to the positioning CT may be adjusted according to the coordinate transformation matrix by using the positioning CT as a reference device. The coordinates of P1 and P21 are determined through the CBCT image and the FBCT image, the accuracy of the determined coordinates can reach a sub-pixel level, and therefore compared with the prior art that the rotation centers of the two imaging devices can only be roughly calibrated in an x-y plane, the three-dimensional coordinates of the isocenter of the two imaging devices can be accurately calibrated.
It is to be understood that, in order to improve the accuracy of isocenter calibration between imaging devices, each imaging device may correspond to a plurality of calibration points, that is, each imaging device includes a plurality of target calibration points for coordinate calculation in an image thereof, and at this time, the coordinate conversion matrix determination unit may determine an initial coordinate conversion matrix between the two imaging devices according to position information of a virtual calibration point corresponding to each target calibration point and position information of a target calibration point of the other imaging device, and determine a coordinate conversion matrix between the two imaging devices according to the initial coordinate conversion matrix between the two imaging devices.
It can be understood that, besides the three-dimensional CT image of the coordinate transformation device, a planar sheet of a certain plane of the coordinate transformation device can be obtained through CT, and the planar sheets of two orthogonal planes can determine the spatial position relationship of the target calibration point, so the image of the embodiment is the three-dimensional CT image of the coordinate calibration device or the planar sheets of two orthogonal planes of the coordinate calibration device.
Compared with the coordinate calibration method in the prior art, the coordinate calibration device in the embodiment has simple positioning, only needs to position the CT and guide the CT to obtain the image of the coordinate calibration device, does not need to add an additional mechanical precision detection device, has low realization difficulty and low cost, can achieve the detection precision of a sub-pixel level, is higher than the common mechanical detection precision, and reduces the system error influence of positioning the CT and guiding the related workflow of the CT.
EXAMPLE five
An embodiment of the present invention further provides a storage medium containing computer-executable instructions, where the computer-executable instructions, when executed by a computer processor, implement the coordinate calibration method described in the foregoing embodiment, and the method includes:
acquiring an image of a part of coordinate calibration device corresponding to a scanning range of imaging equipment to be calibrated, wherein the image of each imaging equipment comprises position information of a target calibration point used for coordinate calculation;
and determining a coordinate conversion matrix between the imaging devices according to the position information of the target calibration points and the stored spatial position relationship between the target calibration points.
From the above description of the embodiments, it is obvious for those skilled in the art that the present invention can be implemented by software and necessary general hardware, and certainly, can also be implemented by hardware, but the former is a better embodiment in many cases. Based on such understanding, the technical solutions of the present invention or portions thereof that contribute to the prior art may be embodied in the form of a software product, where the computer software product may be stored in a computer-readable storage medium, such as a floppy disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a FLASH Memory (FLASH), a hard disk or an optical disk of a computer, and includes several instructions to enable a computer device (which may be a personal computer, a server, or a network device) to implement corresponding technical effects of the coordinate calibration system.
It should be noted that, in the embodiment of the coordinate calibration system, the included units and modules are merely divided according to functional logic, but are not limited to the above division as long as the corresponding functions can be implemented; in addition, specific names of the functional units are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present invention.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (11)
1. A coordinate calibration apparatus for calibrating coordinates between at least two imaging devices of an integrated radiotherapy system, comprising:
a body;
the calibration point groups corresponding to each imaging device are arranged on the body, each calibration point group at least comprises one calibration point in the scanning range of the corresponding imaging device, and the spatial position relationship of the calibration points among different calibration point groups is fixed;
the imaging equipment is used for imaging the corresponding calibration point group to determine the three-dimensional space position information of the target calibration point;
the coordinate calibration device determines a coordinate transformation matrix between the imaging devices based on the three-dimensional spatial position information determined by the imaging devices and the spatial position relationship, and comprises:
a reference image determining unit configured to take one of the imaging devices as a reference imaging device and take an image of the reference imaging device as a reference image;
a virtual calibration point determining unit for determining position information of a virtual calibration point corresponding to another imaging apparatus in a coordinate system in which the reference image is located, based on a spatial positional relationship between target calibration points and position information of the target calibration points in the reference image;
and the coordinate conversion matrix determining unit is used for determining a coordinate conversion matrix between the two imaging devices according to the position information of the virtual calibration point and the position information of the target calibration point of the other imaging device.
2. The apparatus of claim 1, further comprising:
the fixing frame is used for supporting the body so as to fix the position of the body.
3. The device of claim 1, wherein the body is made of a rigid material.
4. The device of claim 2, wherein the body is made of a flexible material, and the spatial positional relationship between the calibration points of different sets of calibration points is maintained by the fixture.
5. A device according to any of claims 1-4, wherein the calibration points of the different sets of calibration points are linearly distributed.
6. A coordinate calibration system, characterized in that the coordinate calibration apparatus according to any one of claims 1 to 5 comprises:
the system comprises an acquisition module, a calibration module and a calibration module, wherein the acquisition module is used for acquiring an image of a part of coordinate calibration device corresponding to a scanning range of imaging equipment to be calibrated, and the image of each imaging equipment comprises three-dimensional space position information of a target calibration point used for coordinate calculation;
the output module is used for determining a coordinate conversion matrix between the imaging devices according to the three-dimensional space position information of the target calibration points and the three-dimensional space position relationship between the target calibration points;
the output module includes:
a reference image determining unit configured to take one of the imaging devices as a reference imaging device and take an image of the reference imaging device as a reference image;
a virtual calibration point determining unit for determining position information of a virtual calibration point corresponding to another imaging apparatus in a coordinate system in which the reference image is located, based on a spatial positional relationship between target calibration points and position information of the target calibration points in the reference image;
and the coordinate conversion matrix determining unit is used for determining a coordinate conversion matrix between the two imaging devices according to the position information of the virtual calibration point and the position information of the target calibration point of the other imaging device.
7. The system according to claim 6, wherein if the calibration point group of each imaging device includes at least two target calibration points, the coordinate conversion matrix determination unit is configured to determine an initial coordinate conversion matrix between the two imaging devices based on the position information of the virtual calibration point corresponding to each target calibration point and the position information of the target calibration point of the other imaging device, and determine a coordinate conversion matrix between the two imaging devices based on the initial coordinate conversion matrix between the two imaging devices.
8. The system according to any one of claims 6-7, wherein the image is a CT image or a flat slice of two orthogonal planes.
9. A coordinate calibration method for use with the coordinate calibration device of any one of claims 1-5, comprising:
acquiring an image of a part of coordinate calibration device corresponding to a scanning range of imaging equipment to be calibrated, wherein the image of each imaging equipment comprises position information of a target calibration point used for coordinate calculation;
determining a coordinate transformation matrix between the imaging devices according to the position information of the target calibration points and the spatial position relationship between the target calibration points;
the determining a coordinate transformation matrix between the imaging devices according to the position information of the target calibration points and the spatial position relationship between the target calibration points comprises:
taking one imaging device as a reference imaging device, and taking an image of the reference imaging device as a reference image;
determining position information of a virtual calibration point corresponding to another imaging device in a coordinate system of the reference image according to the spatial position relationship between the target calibration points and the position information of the target calibration points in the reference image;
and determining a coordinate conversion matrix between the two imaging devices according to the position information of the virtual calibration point and the position information of the target calibration point of the other imaging device.
10. A coordinate calibration method for use with the coordinate calibration device of any one of claims 1-5, comprising:
positioning the coordinate calibration device to enable the calibration points to be positioned in the scanning range of the imaging equipment to be calibrated, wherein the scanning range of each imaging equipment at least corresponds to one target calibration point for coordinate calculation;
acquiring an image of a part of coordinate calibration device corresponding to a scanning range of imaging equipment to be calibrated, wherein the image of each imaging equipment comprises position information of a target calibration point used for coordinate calculation;
and determining a coordinate conversion matrix between the imaging devices according to the position information of the target calibration points and the spatial position relationship between the target calibration points.
11. A storage medium containing computer-executable instructions for implementing the coordinate calibration method of any one of claims 9-10 when executed by a computer processor.
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