A cone beam CT correction phantom, correction method and device and electronic equipment

Abstract

The application relates to a correction phantom and a correction method of a cone beam CT, and the method comprises the following steps: adjusting the pose of a correction phantom to obtain a first projection of the correction phantom; moving a detector by a first distance to obtain a second projection of the correction phantom; rotating the correction phantom by 180 degrees to obtain a third projection of the correction phantom; calculating geometric parameters according to the first projection, the second projection and the third projection; and correcting the cone beam CT according to the geometric parameters. The design of the correction phantom solves the CT system geometric deviation and the calculation error generated by placing the correction phantom in the prior art. The pose of the correction phantom is adjusted to adjust the imaging angle of the light beam and the phantom according to the projection shape of the first hole and the second hole, so that the calculation precision is improved. The multiple projections obtained by adjusting the correction phantom, the data obtained by different projections and the independent calculation of each geometric parameter can avoid the introduction of accumulated errors, and the precision of the geometric parameters is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of medical and industrial imaging technology, in particular to a correction phantom and correction method of cone-beam CT. BACKGROUND

[0002] X-ray computed tomography (CT) is an imaging technology that uses X-rays to perform tomographic scanning of an object and reconstructs cross-sectional information of the object using projection data obtained from multiple angles. The level of detail in the reconstructed image of a micro-CT is a standard for judging the quality of the image. The algorithm used for reconstruction theoretically requires that the detector be parallel to the rotation axis and that the rotation angle in the plane of the detector and the rotation angle around the axis be zero. However, in the assembly process of a micro-CT system, the focal point of the radiation source and the rotation axis are physically invisible, and the installation angle of the detector cannot be guaranteed to meet the theoretical requirements when the detector is installed, making it difficult to achieve an ideal geometric relationship model. When there is a deviation between the actual geometric model and the theoretical model, geometric artifacts will be generated, thereby affecting the quality of the reconstructed image and the accuracy of the size measurement.

[0003] To obtain an accurate reconstructed image, it is necessary to eliminate geometric artifacts, so geometric correction of the system is an essential step. Yi Sun et al. proposed a point model correction method in the article "A calibration method for misaligned scanner geometry in cone-beam computed tomography", which can calculate six offset parameters of a cone-beam CT system in one projection. However, in actual acquisition of projection data, the noise in the projection data will affect the extraction of the point model in the projection, thereby affecting the calculation accuracy. Patent CN105997126B proposes a wireframe model based on the point model, which improves the noise resistance compared to the point model.

[0004] When the rotation angle of the detector around the axis is too large, the projection edge of the wireframe model is blurred, which affects the extraction of the projection edge when the above-mentioned patent installs the correction model. Theoretically, the center of the model must coincide with the center of rotation, and the distance from the radiation source to the detector and the distance from the radiation source to the center of rotation are both artificially measured, which introduces errors in the calculation of the geometric parameters. SUMMARY

[0005] The technical problem solved by the embodiments of the present application is to provide a correction phantom and correction method, device and electronic equipment of cone-beam CT to reduce the geometric deviation of the CT system and the calculation error caused by placing the correction phantom in the prior art.

[0006] In a first aspect, the embodiments of the present application provide a correction phantom for cone beam CT, comprising a phantom main body, wherein the phantom main body is provided with a first linear slot, a second linear slot, a third linear slot, a fourth linear slot, a first hole and a second hole.

[0007] The first linear slot and the second linear slot intersect, and the intersection point of the first linear slot and the second linear slot is located at the center of the phantom main body.

[0008] In a first direction, the third linear slot and the fourth linear slot are respectively arranged on the two sides of the first linear slot and the second linear slot.

[0009] In a second direction, the first hole and the second hole are respectively arranged on the two sides of the intersection point, and the first direction and the second direction are perpendicular.

[0010] The intersection point of the first linear slot extension line, the second linear slot extension line, the third linear slot extension line and the fourth linear slot extension line is the four vertices of a square.

[0011] In some embodiments, a first material part is arranged in the first linear slot, the second linear slot, the third linear slot, the fourth linear slot, the first hole and the second hole,

[0012] The density of the first material part is greater than the density of the phantom main body.

[0013] Alternatively, the density of the first material part is less than the density of the phantom main body.

[0014] In a second aspect, the embodiments of the present application provide a correction method for cone beam CT, wherein the correction method is based on the correction phantom of the first aspect to correct the cone beam CT, comprising:

[0015] Adjusting the pose of the correction phantom to obtain a first projection of the correction phantom;

[0016] Moving the detector by a first distance to obtain a second projection of the correction phantom;

[0017] Rotating the correction phantom by 180 degrees to obtain a third projection of the correction phantom;

[0018] Calculating geometric parameters according to the first projection, the second projection and the third projection;

[0019] Correcting the cone beam CT according to the geometric parameters.

[0020] In some embodiments, the geometric parameters include: the distance from the ray source to the detector; the distance from the ray source to the rotation center; the in-plane rotation angle of the detector; the rotation angle of the detector around the center; and the projection coordinates of the rotation center on the detector.

[0021] In some embodiments, the first hole and the second hole in the calibration phantom are both circular holes, and adjusting the pose of the calibration phantom includes:

[0022] Obtain the projected shape of the circular hole and measure the roundness of the projected shape of the circular hole, so that the correction phantom is perpendicular to the central beam.

[0023] In some embodiments, before adjusting the pose of the correction phantom, the method further includes:

[0024] Adjust the orientation of the X-ray source, detector, and stage so that the central beam emitted by the X-ray source is perpendicular to the rotation center of the detector and the stage.

[0025] In some embodiments, calculating geometric parameters based on the first projection, the second projection, and the third projection includes:

[0026] Based on the first projection and the second projection, calculate the distance from the X-ray source to the detector, the distance from the X-ray source to the rotation center, and the ordinate of the projection of the rotation center onto the detector;

[0027] According to the formula Calculate the distance SOD from the ray source to the center of rotation, where, The distance the detector moves. Let be the side length of the square. Let be the side length of the square in the first projection. For the square in the second projection and The side length of the corresponding side;

[0028] According to the formula Calculate the distance from the radiation source to the detector. ,in, The distance the detector moves. Let be the side length of the square in the first projection. For the square in the second projection and L1 The side length of the corresponding side;

[0029] According to the formula Calculate the ordinate of the projection of the rotation center onto the detector. ,in, Let be the ordinate of the center of the corrected phantom corresponding to the first projection. Here is the ordinate of the center of the corrected phantom corresponding to the second projection. The distance the detector moves. This represents the distance from the X-ray source to the detector.

[0030] In some embodiments, the calculating the geometric parameters according to the first projection, the second projection and the third projection further comprises:

[0031] calculating a horizontal coordinate of a projection of the rotation center on the detector and an in-plane rotation angle of the detector according to the second projection and the third projection;

[0032] calculating the horizontal coordinate of the projection of the rotation center on the detector according to the formula wherein, is a horizontal coordinate of the corrected phantom center corresponding to the second projection, is a horizontal coordinate of the corrected phantom center corresponding to the third projection;

[0033] calculating the in-plane rotation angle of the detector according to ;

[0034] wherein, is a horizontal coordinate of the vertex A in the third projection, is a horizontal coordinate of the vertex C in the third projection, the vertex A and the vertex C being vertices of two adjacent corners of the square in the third projection, is a preset parameter.

[0035] In a third aspect, an embodiment of the present application provides a correction device for a cone beam CT, comprising:

[0036] an adjusting module configured to adjust a pose of the corrected phantom to obtain a first projection of the corrected phantom; a moving module configured to move the detector by a first distance to obtain a second projection of the corrected phantom; a rotating module configured to rotate the corrected phantom by 180 degrees to obtain a third projection of the corrected phantom; a calculating module configured to calculate geometric parameters according to the first projection, the second projection and the third projection; and a correcting module configured to correct the cone beam CT according to the geometric parameters.

[0037] In a fourth aspect, an embodiment of the present application provides an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method in any one of the second aspect.

[0038] ​​​​​The beneficial effects of the embodiments of the present application: different from the related art, the correction phantom and the correction method of the cone beam CT provided by the embodiments of the present application, the method comprises: adjusting the pose of the correction phantom, obtaining the first projection of the correction phantom; moving the detector by a first distance, obtaining the second projection of the correction phantom; rotating the correction phantom by 180 degrees, obtaining the third projection of the correction phantom; calculating the geometric parameters according to the first projection, the second projection and the third projection; correcting the cone beam CT according to the geometric parameters. The design of the correction phantom solves the CT system geometric deviation and the calculation error generated by placing the correction phantom in the prior art. By observing the projection shape of the first hole and the second hole, the pose of the correction phantom is adjusted to adjust the imaging angle of the light beam and the phantom, and the calculation precision is improved. By adjusting the correction phantom to obtain a plurality of projections, the data obtained by different projections are independently calculated for each geometric parameter to avoid the introduction of cumulative error, and the accuracy of the obtained geometric parameters is effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0039] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are schematic and not intended to be limiting of the embodiments, and in which like reference numerals designate similar items in the figures, in which: the drawings do not limit the proportion.

[0040] Figure 1 is a structure diagram of a correction phantom of a cone beam CT provided by the embodiments of the present application;

[0041] Figure 2 is a flow diagram of a correction method of a cone beam CT provided by the embodiments of the present application;

[0042] Figure 3 is a correction scene diagram of a cone beam CT provided by the embodiments of the present application;

[0043] Figure 4 is a structure diagram of a correction device of a cone beam CT provided by the embodiments of the present application;

[0044] Figure 5 is a structure diagram of an electronic device provided by the embodiments of the present application. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0046] It should be noted that the various features of the embodiments of the present application can be combined, unless otherwise explicitly stated, and are within the scope of the present application. In addition, although the division of functional modules is made in the device schematic diagram, and the logical order is shown in the flow chart, in some cases, the steps shown or described can be executed in a manner different from the module division in the device schematic diagram or the order in the flow chart. In addition, the "first", "second", "third" and the like used herein do not limit the data and execution order, but only distinguish the same items or similar items with basically the same function and effect.

[0047] Unless otherwise defined, all technical and scientific terms used in the specification are the same as those commonly understood by those skilled in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not used to limit the present application.

[0048] Please refer to Figure 1 , Figure 1 is a structure diagram of a correction phantom of a cone beam CT provided by an embodiment of the present application, as shown in Figure 1 , the correction phantom comprises a phantom main body 300, the phantom main body 300 is provided with a first linear groove 301, a second linear groove 302, a third linear groove 303, a fourth linear groove 304, a first hole 305 and a second hole 306, the first linear groove 301 and the second linear groove 302 intersect, and the intersection point of the first linear groove 301 and the second linear groove 302 is located at the center of the phantom main body, along a first direction, the third linear groove 303 and the fourth linear groove 304 are respectively arranged on the two sides of the first linear groove 301 and the second linear groove 302, along a second direction, the first hole 305 and the second hole 306 are respectively arranged on the two sides of the intersection point, the first direction and the second direction are perpendicular, and the intersection point of the extension line of the first linear groove 301, the extension line of the second linear groove 302, the extension line of the third linear groove 303 and the extension line of the fourth linear groove 304 is the four vertices of a square. Wherein, the first direction is along the Y direction as shown in Figure 1 , and the second direction is the X direction perpendicular to the Y direction.

[0049] In some embodiments, the first direction can be along the X direction as shown in Figure 1 , and the second direction can be the Y direction perpendicular to the X direction.

[0050] It should be noted that the third slot 303 and the fourth slot 304 are arranged in parallel on the phantom main body 300, and the distance from the center of the phantom main body to the third slot 303 is equal to the distance from the center of the phantom main body to the fourth slot 304, and the first hole 305 and the second hole 306 are equal in distance from the center of the phantom main body, and the first hole 305 and the second hole 306 can be circular holes, square holes, equilateral triangular holes, etc. Regular polygon holes are convenient for observation during projection.

[0051] The first hole and the second hole can be used to adjust the perpendicularity of the correction plate and the central beam. By obtaining the projection shape of the circular hole, the circularity of the projection shape of the circular hole is measured to be as large as possible, so that the correction phantom is perpendicular to the central beam.

[0052] Among them, the intersection of the first slot 301 extension line, the second slot 302 extension line, the third slot 303 extension line and the fourth slot 304 extension line is the four vertices of a square, and the line connecting the four vertices is the four sides of a square. The distance of the four sides of the square is known when designing the correction phantom of the present application.

[0053] In some embodiments, a first material part is arranged in the first slot, the second slot, the third slot, the fourth slot, the first hole and the second hole, and the density of the first material part is greater than the density of the phantom main body; or the density of the first material part is less than the density of the phantom main body.

[0054] It can be understood that when the cone beam CT system is corrected, in order to obtain the collected data, there need to be high-density and low-density areas in the correction phantom. If the overall density of the correction phantom is close, the image in the projection is not easy to distinguish, and the subsequent image data segmentation processing is difficult to operate.

[0055] When the density of the phantom main body is large, the phantom main body can be a high-density iron plate, copper plate, alloy plate, etc., and the first material part can be a low-density organic glass or air; when the density of the phantom main body is small, the phantom main body can be a low-density organic glass plate, and the first material part can be a high-density iron, copper, etc. For example, when the first hole and the second hole are circular holes, and the first material part is iron, a spherical object made of iron can be filled into the first hole and the second hole, and a rod-shaped object made of iron can be filled into the first slot, the second slot, the third slot and the fourth slot.

[0056] The correction phantom for cone beam CT provided by the embodiments of the present application adjusts the position and posture of the correction phantom to adjust the imaging angle of the light beam and the phantom by observing the projection shape of the first hole and the second hole, and improves the calculation accuracy.

[0057] Referring to Figure 2 , Figure 2 is a flowchart of a correction method of a cone beam CT provided by an embodiment of the present application, as Figure 2 shown, the correction method corrects the cone beam CT based on the above-mentioned correction phantom, and comprises the following steps:

[0058] Step S1: adjusting the pose of the correction phantom to obtain a first projection of the correction phantom;

[0059] Step S2: moving the detector by a first distance to obtain a second projection of the correction phantom;

[0060] Step S3: rotating the correction phantom by 180 degrees to obtain a third projection of the correction phantom;

[0061] Step S4: calculating geometric parameters according to the first projection, the second projection and the third projection;

[0062] Step S5: correcting the cone beam CT according to the geometric parameters.

[0063] The pose of the correction phantom is the position and attitude of the correction phantom. Before obtaining the first projection of the correction phantom, the pose of the correction phantom needs to be adjusted. By observing the projection shape of the first hole and the second hole in the correction phantom, the correction phantom is made perpendicular to the central beam.

[0064] In some embodiments, the first hole and the second hole in the correction phantom are both circular holes, and the adjusting the pose of the correction phantom comprises: obtaining the projection shape of the circular hole, measuring the circularity of the projection shape of the circular hole, and making the correction phantom perpendicular to the central beam.

[0065] It can be understood that when the pose of the correction phantom is measured in a non-perpendicular state with the central beam, errors will exist in the subsequently collected data. By obtaining the projection shape of the circular hole and measuring the circularity of the projection shape of the circular hole as large as possible, the correction phantom is made perpendicular to the central beam.

[0066] When the detector is moved by the first distance, the detector can be moved towards the correction phantom. The moving distance should not be too far or too close. The first distance of the movement can be one-fifth of the distance between the correction phantom and the detector, so that the first projection and the second projection are well distinguished, and the images of the first projection and the second projection can be completely presented on the detector.

[0067] The embodiment of the present application provides a correction method of a cone beam CT, and the method comprises the following steps: adjusting the pose of a correction phantom, obtaining a first projection of the correction phantom; moving a detector by a first distance, obtaining a second projection of the correction phantom; rotating the correction phantom by 180 degrees, obtaining a third projection of the correction phantom; calculating geometric parameters according to the first projection, the second projection and the third projection; and correcting the cone beam CT according to the geometric parameters. By adjusting the correction phantom to obtain multiple projections, the data obtained by different projections are used to independently calculate each geometric parameter, so that the cumulative error is avoided, and the accuracy of the geometric parameters is effectively improved.

[0068] In some embodiments, the geometric parameters comprise the distance from a ray source to a detector, the distance from the ray source to a rotation center, the in-plane rotation angle of the detector, the rotation angle of the detector around the center thereof, and the projection coordinates of the rotation center on the detector.

[0069] In some embodiments, before the pose of the correction phantom is adjusted, the method further comprises the following steps: adjusting the poses of a ray source, a detector and a stage, so that a central beam emitted by the ray source is perpendicular to the rotation center of the detector and the stage.

[0070] The pose of the stage is adjusted with the center of the detector as the coordinate origin, so that the beam emitted by the ray source is perpendicular to the center of the detector.

[0071] Before the pose of the correction phantom is adjusted, the poses of the ray source, the detector and the stage are adjusted, so that the central beam emitted by the ray source is perpendicular to the rotation center of the detector and the stage, the cone beam CT system is preliminarily corrected, and the accuracy of the geometric parameters is further improved.

[0072] Please refer to Figure 3 , Figure 3 is a correction scene schematic diagram of a cone beam CT provided by the embodiment of the present application, as shown in Figure 3 The center of the detector is the coordinate origin, the line connecting the center of the detector and the ray source S is the Z axis, the line perpendicular to the horizontal plane of the line where the Z axis is located is the X axis, and the line perpendicular to the lines where the X axis and the Z axis are located is the Y axis. The pose of the correction phantom 10 is adjusted to obtain a first projection 30. It should be noted that the image of the first projection is on the detector, and the detector is not shown in the figure, but the image of the first projection should be completely presented on the detector. The detector is moved by a first distance d, obtaining the second projection 20, rotating the correction phantom 10 by 180 degrees to obtain the third projection, it should be noted that the image of the third projection coincides with the first projection in the absence of errors, but there may be deviations in the rotation process, so that the third projection and the first projection cannot be completely overlapped. It should be noted that the intersection of the first slot extension line, the second slot extension line, the third slot extension line and the fourth slot extension line in the correction phantom is the four vertices of the square, and the first hole and the second hole are circular holes.

[0073] In some embodiments, the calculating the geometric parameters according to the first projection, the second projection and the third projection comprises:

[0074] According to the first projection and the second projection, the distance from the ray source to the detector, the distance from the ray source to the rotation center and the longitudinal coordinate of the projection of the rotation center on the detector are calculated;

[0075] Specifically, referring to Figure 3 , the distance from the ray source to the rotation center SOD is calculated according to the formula , wherein, is the moving distance of the detector, is the side length of the square, is the side length of the square in the first projection, is the side length of the square in the second projection and L1 the corresponding side;

[0076] It should be noted that in the measurement process L1 and L2 the same side length in the projection must meet the length.

[0077] The distance from the ray source to the detector SOD is calculated according to the formula , wherein, is the moving distance of the detector, is the side length of the square in the first projection, is the side length of the square in the second projection and the corresponding side; The longitudinal coordinate of the projection of the rotation center on the detector is calculated according to the formula

[0078] , wherein, is the longitudinal coordinate of the center of the correction phantom corresponding to the first projection, is the longitudinal coordinate of the center of the correction phantom corresponding to the second projection, is the moving distance of the detector, is the distance from the ray source to the detector. In some embodiments, the calculating the geometric parameters according to the first projection, the second projection and the third projection further comprises:

[0079] In some embodiments, the calculating the geometric parameters according to the first projection, the second projection and the third projection further comprises:​

[0080] Based on the second and third projections, calculate the abscissa of the projection of the rotation center onto the detector and the in-plane rotation angle of the detector.

[0081] According to the formula Calculate the x-coordinate of the projection of the rotation center onto the detector. ,in, Let x be the x-coordinate of the center of the corrected phantom corresponding to the second projection. The x-coordinate of the center of the corrected phantom corresponding to the third projection;

[0082] according to Calculate the in-plane rotation angle of the detector ;

[0083] in, Let A be the x-coordinate of vertex A in the third projection. Let be the x-coordinate of vertex C in the third projection. Vertices A and C are the two adjacent corner vertices of the square in the third projection. , , , These are preset parameters.

[0084] Among them, the vertex corresponding to point A (x, y) and the vertex corresponding to point C In (x',y'), , , , The value was calculated using the method described by Yi Sun et al. in “A calibration method for misaligned scanner geometry in cone-beam computed tomography”.

[0085] In some embodiments, the detector's rotation angle around its center is calculated via a third projection; specifically, see [link to relevant documentation]. Figure 3 To distinguish the side lengths of the first projection and the third projection, the upper side length of the third projection is named L. AB The lower side length is named L. CD Using the method described by Yi Sun et al. in "A calibration method for misaligned scanner geometry in cone-beam computed tomography", the L... AB and L CD The ratio is used to obtain the detector's rotation angle outAng around its center.

[0086] Please refer to Figure 4 , Figure 4 is a kind of correction device structure schematic diagram of the cone beam CT provided in the embodiment of the application, the device 100 includes: adjustment module 101, moving module 102, rotating module 103, calculation module 104 and correction module 105.

[0087] Adjustment module 101 is used to adjust the pose of the correction phantom, to obtain the first projection of the correction phantom.Moving module 102 is used to move the detector by a first distance, to obtain the second projection of the correction phantom.Rotating module 103 is used to rotate the correction phantom by 180 degrees, to obtain the third projection of the correction phantom.Calculation module 104 is used to calculate geometric parameters according to the first projection, the second projection and the third projection.Correction module 105 is used to correct the cone beam CT according to the geometric parameters.

[0088] In the embodiment of the application, the correction device of the cone beam CT can also be built by hardware devices, for example, the correction of the cone beam CT can be built by one or more than two chips, and each chip can work in coordination with each other to complete the application of the correction method for the cone beam CT described in each embodiment. For another example, the correction device of the cone beam CT can also be built by various logic devices, such as general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), single-chip microcomputers, ARM (Acorn RISC Machine) or other programmable logic devices, discrete gates or transistor logic, discrete hardware components or any combination of these components.

[0089] The correction device of the cone beam CT in the embodiment of the application can be a device with an operating system. The operating system can be an Android operating system, can be an ios operating system, and can also be other possible operating systems, and the embodiment of the application does not make specific limitations.

[0090] It should be noted that the above-mentioned correction device of the cone beam CT can execute the correction method of the cone beam CT provided in the embodiment of the application, and has the function modules and beneficial effects corresponding to the execution method. The technical details not described in detail in the embodiment of the correction device of the cone beam CT can be referred to the correction method of the cone beam CT provided in the embodiment of the application.

[0091] The application also provides an electronic device, please refer to Figure 5 , Figure 5is a structural schematic diagram of an electronic device provided by an embodiment of the present application. The electronic device 200 comprises at least one processor 201 and a memory 202 connected with the at least one processor 201 in communication, wherein the memory 202 stores instructions executable by the at least one processor 201, and the instructions are executed by the at least one processor 201 to enable the at least one processor 201 to perform the correction method of cone beam CT in any of the above method embodiments. The processor 201 and the memory 202 can be connected by a bus or other means, Figure 5 take the bus connection as an example.

[0092] The processor 201 can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), a hardware chip or any combination thereof; it can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD) or a combination thereof. The above-mentioned PLD can be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL) or any combination thereof.

[0093] The memory 202 is a non-transitory computer readable storage medium, which can be used to store non-transitory software programs, non-transitory computer executable programs and modules, such as program instructions / modules corresponding to the correction method of cone beam CT in the embodiments of the present application. The processor 201 can implement the correction method of cone beam CT in any of the above method embodiments by running the non-transitory software programs, instructions and modules stored in the memory 202, for example, can implement the whole process of Figure 2 .

[0094] The embodiments of the present application provide a computer readable storage medium, for example, a memory including program codes, the program codes being executable by a processor to complete the correction method of the cone beam CT in the above embodiments. For example, the computer readable storage medium can be a Read-Only Memory (ROM), a Random Access Memory (RAM), a Compact Disc Read-Only Memory (CDROM), a magnetic tape, a floppy disk and an optical data storage device, etc.

[0095] The embodiments of the present application provide a computer program product, which includes one or more program codes stored in a computer readable storage medium. The processor of the electronic device reads the program codes from the computer readable storage medium, and the processor executes the program codes to complete the steps of the correction method of the cone beam CT provided in the above embodiments.

[0096] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above, which are not provided in details for simplicity; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand: the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A correction phantom for cone beam CT, characterized by, The phantom body comprises a first wire slot, a second wire slot, a third wire slot, a fourth wire slot, a first hole and a second hole; The first wire slot and the second wire slot intersect, and the intersection point of the first wire slot and the second wire slot is located at the center of the phantom body; In the first direction, the third wire slot and the fourth wire slot are respectively arranged on the two sides of the first wire slot and the second wire slot; In the second direction, the first hole and the second hole are respectively arranged on the two sides of the intersection point, and the first direction and the second direction are perpendicular; The intersection point of the first wire slot extension line, the second wire slot extension line, the third wire slot extension line and the fourth wire slot extension line is the four vertices of a square.

2. The correction phantom of claim 1, wherein, The first material part is arranged in the first wire slot, the second wire slot, the third wire slot, the fourth wire slot, the first hole and the second hole, The density of the first material part is greater than the density of the phantom body; Or, the density of the first material part is less than the density of the phantom body.

3. A correction method of cone beam CT, characterized by, The correction method corrects the cone beam CT based on the correction phantom of claim 1 or 2, comprising: adjusting the pose of the correction phantom to obtain the first projection of the correction phantom; moving the detector by a first distance to obtain the second projection of the correction phantom; rotating the correction phantom by 180 degrees to obtain the third projection of the correction phantom; calculating the geometric parameters according to the first projection, the second projection and the third projection; correcting the cone beam CT according to the geometric parameters.

4. The correction method of claim 3, wherein The geometric parameters include: the distance from the ray source to the detector; the distance from the ray source to the rotation center; the in-plane rotation angle of the detector; the rotation angle of the detector around the center; and the projection coordinates of the rotation center on the detector.

5. The correction method of claim 3, wherein The first hole and the second hole in the correction phantom are circular holes, and the adjusting the pose of the correction phantom comprises: obtaining the projection shape of the circular hole, measuring the roundness of the projection shape of the circular hole, so that the correction phantom is perpendicular to the central beam.

6. The correction method of claim 3, wherein Before adjusting the pose of the correction phantom, the method further comprises: adjusting the pose of the ray source, the detector and the object table, so that the central beam emitted by the ray source is perpendicular to the rotation center of the detector and the object table.

7. The correction method of claim 4, wherein The calculation of the geometric parameters according to the first projection, the second projection and the third projection comprises: calculating the distance from the ray source to the detector, the distance from the ray source to the rotation center and the longitudinal coordinate of the projection of the rotation center on the detector according to the first projection and the second projection; The distance SOD of the ray source to the rotation center is calculated according to the formula , wherein, is the moving distance of the detector, is the side length of the square, is the side length of the square in the first projection, is the side length of the square in the second projection and L1 is the corresponding side of the square. The distance of the ray source to the detector is calculated according to the formula wherein is the distance of the ray source to the detector, is the distance of the detector movement, is the length of the side of the square in the first projection, is the length of the side of the square in the second projection corresponding to the side of the square in the first projection, and is the length of the side of the square in the second projection corresponding to the side of the square in the first projection. According to the formula Calculate the ordinate of the projection of the rotation center onto the detector. ,in, Let be the ordinate of the center of the corrected phantom corresponding to the first projection. Here is the ordinate of the center of the corrected phantom corresponding to the second projection. The distance the detector moves. This represents the distance from the X-ray source to the detector.

8. The correction method of claim 4, wherein, The calculation of the geometric parameters according to the first projection, the second projection and the third projection further comprises: calculating the horizontal coordinate of the projection of the rotation center on the detector and the in-plane rotation angle of the detector according to the second projection and the third projection. The horizontal coordinate of the projection of the center of rotation on the detector is calculated according to the formula wherein is the horizontal coordinate of the center of the second projection on the detector, is the horizontal coordinate of the center of the second projection on the detector, is the horizontal coordinate of the center of the third projection on the detector. According to Computing an in-plane rotation angle of a detector ; wherein, is a horizontal coordinate of a vertex A in the third projection, is a horizontal coordinate of a vertex C in the third projection, the vertex A and the vertex C being vertices of two adjacent corners of the square in the third projection, , , , is a preset parameter.

9. A correction device for cone beam CT, characterized by comprising: an adjusting module for adjusting the pose of the correction phantom of any one of claims 1 or 2 to obtain the first projection of the correction phantom; a moving module for moving the detector by a first distance to obtain the second projection of the correction phantom; a rotating module for rotating the correction phantom by 180 degrees to obtain the third projection of the correction phantom; a calculating module, configured to calculate a geometric parameter according to the first projection, the second projection and the third projection; a correcting module, configured to correct the cone beam CT according to the geometric parameter.

10. An electronic device, comprising: comprise: at least one processor; and, a memory connected with the at least one processor in communication; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method in any one of claims 3 to 8.

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