Conformal trajectory generation method for flat object CT (Computed Tomography) scanning

Abstract

The invention relates to the technical field of industrial CT (Computed Tomography), in particular to a conformal track generation method for CT scanning of a flat object, which comprises the following steps of: for the flat object to be scanned, respectively carrying out perspective imaging on the main plane and the side surface of the flat object, and calculating to obtain the space size of the object; frame-selecting a to-be-scanned region of interest on a computer interface through user interaction, and calculating the spatial size of the region of interest by using an image geometrical relationship; on the basis of the space size of the object and the space size of the region of interest, generating a conformal track suitable for CT scanning through a space geometric constraint relation; the spatial geometric constraint relationship includes that the scanned object cannot collide with the radiation source and the detector, and the region of interest is always kept in the projection image in the rotation process and cannot be cut off. According to the method, the spatial sizes of the flat object and the region of interest are accurately obtained, the conformal trajectory is automatically generated through the spatial geometric constraint relation, and the scanning efficiency and the reconstruction precision are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of industrial CT technology, and in particular to a method for generating conformal trajectories for CT scanning of flat objects. Background Technology

[0002] Despite advancements in CT technology, high-resolution 3D reconstruction of regions of interest within large objects in a plane remains a challenge. To improve the imaging resolution of CT systems, many methods have been developed to modify traditional circular trajectory imaging scanning modes, enabling higher geometric magnification while avoiding collisions during the imaging process. Examples include source-moving scanning imaging, computed tomography, and oscillating finite-angle scanning imaging. However, these methods suffer from issues such as reconstruction artifacts or the need for mechanical system replacement.

[0003] Recently, some research has attempted to use variable-focus trajectory scanning imaging to acquire projection data from all directions in a single scan. By changing the source-to-sample distance (SOD) during object rotation, information gain is increased, overcoming the imaging resolution limitations of circular trajectory scanning. Existing methods have proposed adaptive scaling acquisition trajectories suitable for convex hull samples, demonstrating excellent reconstruction quality. Furthermore, some methods have tested novel approaches combining low-resolution and high-resolution scan data, further improving reconstruction quality.

[0004] Existing methods for generating variable trajectories rely on the measurement of the experimental sample and the size of the region of interest, which increases the complexity of the experiment, and geometric errors in the measurement will lead to artifacts in the reconstruction results. Summary of the Invention

[0005] To address the limitation of traditional circular trajectory CT scanning in imaging resolution of flat objects, this invention proposes a conformal trajectory generation method for CT scanning of flat objects. By combining projection geometry with user-interactive bounding box selection, the spatial dimensions of the flat object and the region of interest (ROI) are accurately obtained. Furthermore, by automatically generating a conformal trajectory suitable for CT scanning of flat objects through spatial geometric constraints, the method avoids collisions while ensuring that the ROI is always fully imaged, significantly improving scanning efficiency and reconstruction accuracy.

[0006] To achieve the above objectives, the technical solution adopted is:

[0007] This invention provides a method for generating conformal trajectories for CT scans of flat objects, comprising the following steps:

[0008] Step 1: For the flat object to be scanned, perform perspective imaging on the main plane and side of the flat object respectively, and calculate the spatial dimensions of the object using the spatial geometry of the CT system.

[0009] Step 2: Through user interaction, select the region of interest to be scanned on the computer interface, and calculate the spatial size of the region of interest using the geometric relationship of the image;

[0010] Step 3: Based on the spatial dimensions of the object and the spatial dimensions of the region of interest, generate a conformal trajectory suitable for CT scanning through spatial geometric constraints; wherein, the spatial geometric constraints include: the scanning object cannot collide with the X-ray source and detector, and the region of interest remains in the projected image without being truncated during rotation.

[0011] According to the conformal trajectory generation method for CT scanning of flat objects of the present invention, step 1 further includes:

[0012] Establish a CT scan spatial coordinate system and set the coordinates of the X-ray source as O. S (0,0), the detector length is L D The distance from the X-ray source to the scanned object is L. SOD The distance from the X-ray source to the detector is L. SDD The detector's center coordinates are O D (0,L SDD The detector pixel size is H. D ×W D ;

[0013] Acquire projection images F1 where the main plane of the flat object is parallel to the detector plane, and F2 where the main plane of the flat object is perpendicular to the detector plane;

[0014] The spatial coordinates of the projected images F1 and F2 are extracted using an image recognition algorithm, and the spatial dimensions of the object V1 = {(L...} are calculated based on the projection magnification ratio. o W o )}.

[0015] According to the conformal trajectory generation method for CT scanning of flat objects of the present invention, the spatial dimension V1 of the object is further calculated by the following formula:

[0016]

[0017] Among them, L o W is the length of the object. o For the width of the object, {(u 11 ,v 11 ),(u 12 ,v 12 ),(u 13 ,v 13 ),(u 14 ,v 14 )} represents the spatial coordinates of the projected image F1, {(u 21,v 21 ),(u 22 ,v 22 ),(u 23 ,v 23 ),(u 24 ,v 24 )} represents the spatial coordinates of the projected image F2.

[0018] According to the conformal trajectory generation method for CT scanning of flat objects of the present invention, step 2 further includes:

[0019] Select the region of interest within the projected image F1 and obtain its spatial coordinates O3 = {(u 31 ,v 31 ),(u 32 ,v 32 ),(u 33 ,v 33 ),(u 34 ,v 34 )};

[0020] Calculate the size of the region of interest V2 = {(L) using image geometric relationships R W R )},in:

[0021]

[0022] According to the conformal trajectory generation method for CT scanning of flat objects of the present invention, step 3 further includes:

[0023] The initial scanning angle is set at the position where the main plane of the flat object is parallel to the detector plane, and the center of the region of interest is used as the rotation center.

[0024] Calculate the distance and angle between the vertices of the object and the center of rotation, as well as the distance and angle between the vertices of the region of interest and the center of rotation;

[0025] Calculate the spatial coordinates of an object and a region of interest at any rotation angle;

[0026] Based on spatial geometric constraints, the optimal SOD value is determined for each rotation angle, and a conformal trajectory is generated.

[0027] According to the conformal trajectory generation method for CT scanning of flat objects of the present invention, the distance and angle between the vertex of the object and the center of rotation are further calculated by the following formula:

[0028]

[0029] Where L1 is the distance from the center of rotation along the major axis to one end of the object, and L2 is the distance from the center of rotation along the major axis to the other end of the object, satisfying L1 + L2 = L o ,β o1 β o2 β o3 β o4 L is the angle between the lines connecting the four vertices of the object to the center of rotation and the perpendicular line from the center of the minor axis. o1 L o2 L o3 L o4 The distances from the four vertices of the object to the center of rotation.

[0030] According to the conformal trajectory generation method for CT scanning of flat objects of the present invention, the distance and angle between the vertex of the region of interest and the center of rotation are further calculated by the following formula:

[0031]

[0032] Where, β R1 β R2 β R3 β R4 Let L be the angle between the line connecting the four vertices of the region of interest to the center of rotation and the perpendicular line from the center of the minor axis. R1 L R2 L R3 L R4 Let be the distances from the four vertices of the region of interest to the center of rotation.

[0033] According to the conformal trajectory generation method for CT scanning of flat objects of the present invention, the spatial coordinates of the object and the region of interest at any rotation angle are further calculated by the following formula:

[0034] For the vertex coordinates of the object:

[0035] O ob i,1 =(L SOD +L o1 *sin(α i -β o1 ),L o1 *cos(α i -β o1 ))

[0036] O ob i,2 =(L SOD +L o2 *sin(α i +β o2 ),L o2 *cos(α i +γo2 ))

[0037] o ob i,3 =(L SOD -L o3 *sin(α i -β o3 ),-L o3 *cos(α i -β o3 ))

[0038] O ob i,4 =(L SOD -L o4 *sin(α i +β o4 ),-L o4 *cos(α i +β o4 ))

[0039] Among them, O ob i,j This indicates that the j-th vertex of the object rotates at an angle α. i The coordinates below;

[0040] For the vertex coordinates of the region of interest:

[0041] O R i,1 =(L SOD +L R1 *sin(α i -β R1 ),L R1 *cos(α i -β R1 ))

[0042] O R i,2 =(L SOD +L R2 *sin(α i +β R2 ),L R2 *cos(α i +β R2 ))

[0043] O R i,3 =(L SOD -L R3 *sin(α i -β R3 ),-L R3 *cos(α i -β R3 ))

[0044] O R i,4 =(L SOD -L R4 *sin(α i +β R4 ),-L R4 *cos(α i +β R4 ))

[0045] Among them, O R i,j This indicates that the j-th vertex of the region of interest is rotated by angle α. i The coordinates below.

[0046] According to the conformal trajectory generation method for CT scanning of flat objects of the present invention, the optimal SOD value further needs to satisfy the following basic conditions:

[0047] 0 <O ob i,j <L SDD

[0048]

[0049] Where, θ i,j O represents the angle between the line connecting the vertex of the region of interest and the ray source and the central axis; ob i,j This indicates that the j-th vertex of the object rotates at an angle α. i The coordinates below, O R i.j (y) represents the position of the j-th vertex of the region of interest at a rotation angle α. i The vertical coordinate value below, O R i.j (x) represents the j-th vertex of the region of interest at a rotation angle α. i The x-axis value below.

[0050] According to the conformal trajectory generation method for CT scanning of flat objects of the present invention, the optimal SOD value at each rotation angle is further calculated:

[0051] {L SOD1 |min(O R i,j (x))=l s}

[0052]

[0053] L SODi =max{L SOD1 ,L SOD2}

[0054] Among them, l s For a safe distance, θ s From a safety perspective.

[0055] The beneficial effects achieved by adopting the above technical solution are:

[0056] ① This invention can automatically adapt to flat objects of different sizes and shapes, without the need for complex settings and adjustments for each sample, greatly improving the flexibility and versatility of scanning.

[0057] ② This invention innovatively combines two imaging operations (0° and 90° projection) with user-interactive ROI selection, which can accurately obtain the spatial geometric information of objects and regions of interest without manual measurement. This effectively reduces the complexity of the experiment, reduces the number of operation steps and time costs, and makes the CT scanning process more efficient and convenient. It significantly improves the automation level and reconstruction accuracy of the scanning process, and can provide higher quality data support for subsequent image analysis and research.

[0058] ③ This invention automatically generates optimized scanning trajectories through spatial geometric constraints, ensuring full visibility of the ROI and avoiding collisions. While avoiding collisions, it also ensures the integrity of the ROI data, thus balancing both safety and imaging quality. Attached Figure Description

[0059] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0060] Figure 1 This is a flowchart illustrating a method for generating conformal trajectories for CT scanning of flat objects according to an embodiment of the present invention.

[0061] Figure 2 This is a schematic diagram of a CT system simulation according to an embodiment of the present invention;

[0062] Figure 3 This is a schematic diagram of the CT system composition structure according to an embodiment of the present invention;

[0063] Figure 4 This is a schematic diagram of the CT scan spatial coordinate system parameter settings according to an embodiment of the present invention;

[0064] Figure 5 This is a schematic diagram illustrating the process of establishing the spatial geometry of the region of interest according to an embodiment of the present invention;

[0065] Figure 6 This is a geometric space schematic diagram of the conformal trajectory generation process according to an embodiment of the present invention;

[0066] Figure 7 This is a schematic diagram illustrating the calculation of the distance and angle between the object and the vertex of the region of interest and the rotation center in an embodiment of the present invention. Detailed Implementation

[0067] The exemplary solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art.

[0068] This embodiment discloses a method for generating conformal trajectories for CT scans of flat objects, such as... Figure 1 As shown, it includes the following steps:

[0069] Step S1: For the flat object to be scanned, perform perspective imaging on the main plane and side of the flat object respectively, and calculate the spatial dimensions of the object using the spatial geometric relationship of the CT system.

[0070] like Figure 2 As shown, step S1 specifically includes the following sub-steps:

[0071] Step S11: The CT system mainly consists of an X-ray source, detector, mechanical system, and software, such as... Figure 3 As shown. The object is placed on the platform of the mechanical system and can move back and forth along the scaling axis.

[0072] Step S12: Establish the CT scan spatial coordinate system, such as... Figure 4 As shown. Parameter settings are as follows: ray source coordinates are O. S (0,0), the detector length is L D The distance from the X-ray source to the scanned object (SOD) is L. SOD The distance from the X-ray source to the detector (SDD) is L. SDD The detector's center coordinates are O D (0,L SDD The detector pixel size is H. D ×W D H D W represents the detector's height. D Indicates the width of the detector.

[0073] Step S13: Acquire the projection image F1 (corresponding to acquisition angle 0°) of the main plane of the flat object to be scanned parallel to the detector plane, and acquire the projection image F2 (corresponding to acquisition angle 90°) of the main plane of the flat object to be scanned perpendicular to the detector plane.

[0074] Step S14: Extract the spatial coordinates of the projected image F1 using an image recognition algorithm: {(u11 ,v 11 ),(u 12 ,v 12 ),(u 13 ,v 13 ),(u 14 ,v 14 The spatial coordinates of the projected image F2 are: {(u)} 21 ,v 21 ),(u 22 ,v 22 ),(u 23 ,v 23 ),(u 24 ,v 24 )}.

[0075] Step S15: Using the projection magnification ratio of the CT system, calculate the spatial dimension V1 of the object according to the following formula: V1 = {(L o W o )}.

[0076]

[0077] Among them, L o W is the length of the object. o This represents the width of the object.

[0078] Step S2: Select the region of interest (ROI) to be scanned on the computer interface through user interaction, and calculate the spatial size of the ROI using the geometric relationship of the image.

[0079] like Figure 5 As shown, the specific process of establishing the spatial geometry of the region of interest through user interaction in step S2 includes:

[0080] Step S21: In the computer system, select the region of interest (ROI) in the projected image F1 and obtain the spatial coordinates of the ROI O3 = {(u 31 ,v 31 ),(u 32 ,v 32 ),(u 33 ,v 33 ),(u 34 ,v 34 )}.

[0081] Step S22: Calculate the spatial size V2 of the region of interest using image geometric relationships. R W R )},in:

[0082]

[0083] WR =W o

[0084] Step S3: Based on the spatial dimensions of the object and the spatial dimensions of the region of interest, generate a conformal trajectory (the optimal position of the object's motion trajectory) suitable for CT scanning through spatial geometric constraints; further, the spatial geometric constraints include: the scanned object cannot collide with the X-ray source and the detector, and the region of interest remains in the projected image without being truncated during rotation.

[0085] like Figure 6 As shown, step S3, which involves the system automatically generating a conformal trajectory suitable for CT scans using two spatial geometries, includes the following steps:

[0086] Step S31: Take the position where the main plane of the flat object is parallel to the detector plane as the initial scanning angle (0°), and take the center of ROI as the rotation center.

[0087] Step S32: Calculate the distance and angle between the vertex of the object and the center of rotation, such as... Figure 7 As shown.

[0088]

[0089] Where L1 is the distance from the center of rotation along the major axis to one end of the object, and L2 is the distance from the center of rotation along the major axis to the other end of the object, satisfying L1 + L2 = L o . β o1 β o2 β o3 β o4 L is the angle between the lines connecting the four vertices of the object to the center of rotation and the perpendicular line from the center of the minor axis. o1 L o2 L o3 L o4 The distances from the four vertices of the object to the center of rotation.

[0090] Step S33: Calculate the distance and angle between the vertices of the region of interest and the center of rotation.

[0091]

[0092] Where, β R1 β R2 β R3 β R4 Let L be the angle between the line connecting the four vertices of the region of interest to the center of rotation and the perpendicular line from the center of the minor axis. R1 L R2 L R3 L R4 Let be the distances from the four vertices of the region of interest to the center of rotation.

[0093] Step S34: Calculate the spatial coordinates of the object at any rotation angle. The formula for calculating the vertex coordinates of the object is:

[0094] O ob i,1 =(L SOD +L o1 *sin(α i -β o1 ),L o1 *cos(α i -β o1 ))

[0095] O ob i,2 =(L SOD +L o2 *sin(α i +β o2 ),L o2 *cos(α i +β o2 ))

[0096] O ob i,3 =(L SOD -L o3 *sin(α i -β o3 ),-L o3 *cos(α i -β o3 ))

[0097] O ob i,4 =(L SOD -L o4 *sin(α i +β o4 ),-L o4 *cos(α i +β o4 ))

[0098] Among them, O ob i,j This indicates that the j-th vertex of the object rotates at an angle α. i The coordinates below.

[0099] Step S35: Calculate the spatial coordinates of the region of interest under any rotation angle. The formula for calculating the vertex coordinates of the region of interest is:

[0100] O R i,1 =(L SOD +L R1 *sin(α i -βR1 ),L R1 *cos(α i -β R1 ))

[0101] O R i,2 =(L SOD +L R2 *sin(α i +β R2 ),L R2 *cos(α i +β R2 ))

[0102] O R i,3 =(L SOD -L R3 *sin(α i -β R3 ),-L R3 *cos(α i -β R3 ))

[0103] O R i,4 =(L SOD -L R4 *sin(α i +β R4 ),-L R4 *cos(α i +β R4 ))

[0104] Among them, O R i,j This indicates that the j-th vertex of the region of interest is rotated by angle α. i The coordinates below.

[0105] Step S36: For each rotation angle, calculate the corresponding optimal SOD value. The judgment principle is that the object will not collide with the X-ray source and detector, the region of interest is always in the projected image, and the optimal SOD value must meet the following basic conditions:

[0106] 0 <O ob i,j <L SDD

[0107]

[0108] Where, θ i,j This represents the angle between the line connecting the vertex of the region of interest and the ray source and the central axis. R i.j (y) represents the position of the j-th vertex of the region of interest at a rotation angle α.i The vertical coordinate value (y component) below, O R i.j (x) represents the j-th vertex of the region of interest at a rotation angle α. i The x-axis value (x component) below.

[0109] Collision constraint: All vertices (O) of the object ob i,j During rotating scanning, the device must always be positioned between the X-ray source and the detector to avoid mechanical collisions. When O ob i,j When ≤0, the object will collide with the radiation source; when O ob i,j ≥L SDD The object will collide with the detector.

[0110] ROI Field of View Constraints: CT 3D reconstruction relies on complete projection data captured from different angles. If the ROI is truncated in the projection at a certain angle (partially outside the detector's field of view), the reconstruction algorithm will produce artifacts (such as stripes, blurring, or distortion) due to data loss. The ROI is typically a localized area requiring focused observation (such as solder joints or material defects on a chip). If the ROI is truncated, its high-resolution imaging target will fail directly. This embodiment of the invention limits: all vertices of the ROI (O... R i,j During projection, the projection angle (θ) of the ROI vertex at the current angle. i,j The angle must be smaller than the maximum angle that the detector can receive to ensure the integrity of the ROI data; otherwise, the ROI will be truncated.

[0111] Step S37: To ensure efficient calculation, set a safe distance l s and safety angle θ s Calculate the optimal SOD value at each rotation angle to obtain the conformal trajectory.

[0112] {L SOD1 |min(O R i,j (x))=l s}

[0113]

[0114] L SODi =max{L SOD1 ,L SOD2}

[0115] In L SOD1 In the calculation formula, min(O R i,j (x) represents the position of the ROI vertex at rotation angle α. iThe closest distance to the radiation source (i.e., the minimum value of the X-axis coordinate). Find the minimum value min(O). R i,j (x)), and force the minimum value to be equal to the preset safety distance l. s (Avoid objects being too close to the ray source); ensure that the nearest vertex of the ROI is at least l away from the ray source. s To prevent mechanical collisions.

[0116] In l SOD2 In the calculation formula, the maximum value is found among the projection angles of all ROI vertices. And force this maximum value to be equal to the preset safety angle θ. s This ensures that all vertices of the ROI do not exceed the detector's field of view during projection.

[0117] Unless otherwise specifically stated, the relative steps, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0118] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0119] The units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations are not considered to be beyond the scope of this invention.

[0120] Those skilled in the art will understand that all or part of the steps in the above methods can be implemented by a program instructing related hardware, and the program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk. Optionally, all or part of the steps in the above embodiments can also be implemented using one or more integrated circuits. Accordingly, each module / unit in the above embodiments can be implemented in hardware or as a software functional module. This invention is not limited to any particular combination of hardware and software.

[0121] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for generating conformal trajectories for CT scanning of flat objects, characterized in that, Includes the following steps: Step 1: For the flat object to be scanned, perform perspective imaging on the main plane and side of the flat object respectively, and calculate the spatial dimensions of the object using the spatial geometry of the CT system. Step 2: Through user interaction, select the region of interest to be scanned on the computer interface, and calculate the spatial size of the region of interest using the geometric relationship of the image; Step 3: Based on the spatial dimensions of the object and the spatial dimensions of the region of interest, generate a conformal trajectory suitable for CT scanning through spatial geometric constraints; wherein, the spatial geometric constraints include: the scanning object cannot collide with the X-ray source and detector, and the region of interest remains in the projected image without being truncated during rotation.

2. The method for generating conformal trajectories for CT scanning of flat objects according to claim 1, characterized in that, Step 1 specifically includes: Establish a CT scan spatial coordinate system and set the coordinates of the X-ray source as O. S (0,0), the detector length is L D The distance from the X-ray source to the scanned object is L. SOD The distance from the X-ray source to the detector is L. SDD The detector's center coordinates are O D (0,L SDD The detector pixel size is H. D ×W D ; Acquire projection images F1 where the main plane of the flat object is parallel to the detector plane, and F2 where the main plane of the flat object is perpendicular to the detector plane; The spatial coordinates of the projected images F1 and F2 are extracted using an image recognition algorithm, and the spatial dimensions of the object V1 = {(L...} are calculated based on the projection magnification ratio. o W o )}.

3. The method for generating conformal trajectories for CT scanning of flat objects according to claim 2, characterized in that, The spatial dimension V1 of the object is calculated using the following formula: Among them, L o W is the length of the object. o For the width of the object, {(u 11 ,v 11 ),(u 12 ,v 12 ),(u 13 ,v 13 ),(u 14 ,v 14 )} represents the spatial coordinates of the projected image F1, {(u 21 ,v 21 ),(u 22 ,v 22 ),(u 23 ,v 23 ),(u 24 ,v 24 )} represents the spatial coordinates of the projected image F2.

4. The method for generating conformal trajectories for CT scanning of flat objects according to claim 2, characterized in that, Step 2 specifically includes: Select the region of interest within the projected image F1 and obtain its spatial coordinates O3 = {(u 31 ,v 31 ),(u 32 ,v 32 ),(u 33 ,v 33 ),(u 34 ,v 34 )}; Calculate the size of the region of interest V2 = {(L) using image geometric relationships R W R )},in: IN R =In o 。 5. The method for generating conformal trajectories for CT scanning of flat objects according to claim 1, characterized in that, Step 3 specifically includes: The initial scanning angle is set at the position where the main plane of the flat object is parallel to the detector plane, and the center of the region of interest is used as the rotation center. Calculate the distance and angle between the vertices of the object and the center of rotation, as well as the distance and angle between the vertices of the region of interest and the center of rotation; Calculate the spatial coordinates of an object and a region of interest at any rotation angle; Based on spatial geometric constraints, the optimal SOD value is determined for each rotation angle, and a conformal trajectory is generated.

6. The method for generating conformal trajectories for CT scanning of flat objects according to claim 5, characterized in that, The distance and angle between the vertex of the object and the center of rotation are calculated using the following formula: L2=L o -L1 Where L1 is the distance from the center of rotation along the major axis to one end of the object, and L2 is the distance from the center of rotation along the major axis to the other end of the object, satisfying L1 + L2 = L o ,β o1 β o2 β o3 β o4 L is the angle between the lines connecting the four vertices of the object to the center of rotation and the perpendicular line from the center of the minor axis. o1 L o2 L o3 L o4 The distances from the four vertices of the object to the center of rotation.

7. The method for generating conformal trajectories for CT scanning of flat objects according to claim 5, characterized in that, The distance and angle between the vertex of the region of interest and the center of rotation are calculated using the following formula: Where, β R1 β R2 β R3 β R4 Let L be the angle between the line connecting the four vertices of the region of interest to the center of rotation and the perpendicular line from the center of the minor axis. R1 L R2 L R3 L R4 Let be the distances from the four vertices of the region of interest to the center of rotation.

8. The method for generating conformal trajectories for CT scanning of flat objects according to claim 5, characterized in that, The spatial coordinates of the object and the region of interest at any rotation angle are calculated using the following formula: For the vertex coordinates of the object: The ob i,1 =(L SOD +L o1 *sin(a i -b o1 ),L o1 *cos(a i -b o1 )) The ob i,2 =(L SOD +L o2 *sin(a i +b o2 ),L o2 *cos(a i +g o2 )) the ob i,3 =(L SOD -L o3 *sin(a i -b o3 ),-L o3 *cos(a i -b o3 )) The ob i,4 =(L SOD -L o4 *sin(a i +b o4 ),-L o4 *cos(a i +b o4 )) Among them, O ob i,j This indicates that the j-th vertex of the object rotates at an angle α. i The coordinates below; For the vertex coordinates of the region of interest: The R i,1 =(L SOD +L R1 *sin(a i -b R1 ),L R1 *cos(a i -b R1 )) The R i,2 =(L SOD +L R2 *sin(a i +b R2 ),L R2 *cos(a i +b R2 )) The R i,3 =(L SOD -L R3 *sin(a i -b R3 ),-L R3 *cos(a i -b R3 )) The R i,4 =(L SOD -L R4 *sin(a i +b R4 ),-L R4 *cos(a i +b R4 )) Among them, O R i,j This indicates that the j-th vertex of the region of interest is rotated by angle α. i The coordinates below.

9. The method for generating conformal trajectories for CT scanning of flat objects according to claim 5, characterized in that, The optimal SOD value must meet the following basic conditions: 0<O ob i,j <L SDD Where, θ i,j O represents the angle between the line connecting the vertex of the region of interest and the ray source and the central axis; ob i,j This indicates that the j-th vertex of the object rotates at an angle α. i The coordinates below, O R i.j (y) represents the position of the j-th vertex of the region of interest at a rotation angle α. i The vertical coordinate value below, O R i.j (x) represents the j-th vertex of the region of interest at a rotation angle α. i The x-coordinate value below.

10. The method for generating conformal trajectories for CT scanning of flat objects according to claim 9, characterized in that, Calculate the optimal SOD value for each rotation angle: {L SOD1 |min(O R i,j (x))=l s } L SODi <max{L SOD1 ,L SOD2 } Among them, l s For a safe distance, θ s From a safety perspective.

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