Measurement method for measuring the linearity of multifocal alignment of distributed X-ray sources

Abstract

This disclosure provides a method for measuring the linearity of a multifocal array of a distributed radiation source, relating to the field of radiation scanning technology. The method includes: selecting one focal point from N focal points of the distributed radiation source as a reference focal point; determining the absolute distance along a third direction between the reference focal point and the theoretical focal arrangement line of the distributed radiation source using M markers arranged along a second direction; determining the relative positional relationship along a third direction between N-1 focal points and the reference focal point using one of the M markers; and calculating the absolute distances along a third direction between the N-1 focal points and the theoretical focal arrangement line of the distributed radiation source based on the absolute distances and the relative positional relationships along a third direction between the N-1 focal points and the reference focal point.

Description

Technical Field

[0001] This disclosure relates to the field of radiation scanning technology, and more specifically, to a measurement method for measuring the linearity of a multifocal arrangement of a distributed radiation source. Background Technology

[0002] A linear distributed X-ray source is a special type of X-ray source. While a typical X-ray source typically contains only one X-ray focus, a distributed X-ray source contains multiple X-ray focuses located at different spatial positions. When a distributed X-ray source operates, these X-ray focuses at different spatial positions can generate X-rays simultaneously or in a staggered, time-sequential manner. A linear distributed X-ray source refers to a distributed X-ray source in which multiple X-ray focuses are arranged in a straight line.

[0003] Ideally, all X-ray focal points in a linear distributed X-ray source should be aligned in a straight line. However, during manufacturing, errors can occur in the machining and assembly of parts, and parts may deform due to factors such as stress and temperature changes during processing. Therefore, the focal arrangement of a manufactured linear distributed X-ray source is often not a perfect straight line. The focal arrangement of a linear distributed X-ray source can be evaluated by measuring the linearity of the multi-focal arrangement. However, existing methods for solving linearity based on geometric calibration suffer from complex calibration structures and a large number of unknowns in the calculation process, which increases the complexity of linearity measurement.

[0004] It should be noted that the information disclosed in this section is only used to understand the background of the inventive concept of this disclosure. Therefore, the above information may include information that does not constitute prior art. Summary of the Invention

[0005] In view of at least one of the above-mentioned technical problems, this disclosure provides a measurement method for measuring the linearity of a multifocal arrangement of a distributed X-ray source, comprising: selecting one focal point from N focal points of the distributed X-ray source as a reference focal point; wherein N is a positive integer greater than 1; determining the absolute distance along a third direction between the reference focal point and the theoretical focal arrangement line of the distributed X-ray source using M markers arranged along a second direction, wherein the theoretical focal arrangement line of the distributed X-ray source extends along a first direction, the second direction is the X-ray emission direction of the distributed X-ray source, the third direction is perpendicular to the first and second directions, and M is a positive integer greater than 1; determining the relative positional relationship along the third direction between N-1 focal points and the reference focal point using one of the M markers, wherein the N-1 focal points are the focal points other than the reference focal point among the N focal points; and calculating the absolute distance along the third direction between the N-1 focal points and the theoretical focal arrangement line of the distributed X-ray source based on the absolute distance and the relative positional relationship along the third direction between the N-1 focal points and the reference focal point.

[0006] According to some exemplary embodiments, determining the absolute distance along a third direction between a reference focal point and the theoretical focal arrangement line of a distributed X-ray source using M markers arranged along a second direction includes: placing the M markers and a detector at a starting position; controlling the M markers to move along a third direction; in response to a preset step size of the movement of the M markers along the third direction, recording the movement distance of the M markers relative to the starting position along the third direction, and controlling the beam output from the reference focal point to scan and image the M markers to obtain scanned images of the M markers; determining whether the images of the M markers in the scanned images of the M markers meet preset conditions; and in response to the images of the M markers in the scanned images of the M markers meeting preset conditions, stopping the movement of the M markers along the third direction, determining that the M markers are at a reference position, and determining the total movement distance of the M markers at the reference position relative to the starting position along the third direction as the absolute distance along the third direction between the reference focal point and the theoretical focal arrangement line of the distributed X-ray source.

[0007] According to some exemplary embodiments, using one of M markers, the relative positional relationship between N-1 focal points and a reference focal point along a third direction is determined, including: when the M markers are in the reference position, removing the M-1 markers and leaving only one marker in the reference position, and identifying the one marker as the scanning marker; while the scanning marker and the detector remain stationary, controlling the beam output of the N focal points to perform N scan imaging on the scanning marker to obtain N scan images of the scanning marker; and determining the relative positional relationship between the N-1 focal points and the reference focal point along a third direction based on the position of the image of the scanning marker in the N scan images of the marker.

[0008] According to some exemplary embodiments, based on the position of the image of the scanned marker in N scanned images of the scanned marker, the relative positional relationship between N-1 focal points and a reference focal point along a third direction is determined, including: for one image I0 in the N scanned images corresponding to the reference focal point, recording the position p0 of the center position of the image of the scanned marker in the image plane; and for each of the N-1 scanned images I0 corresponding to the N-1 focal points in the N scanned images... i Record the position p of the center of the scanned marker image within the image plane. i And calculate the relative positions of the N-1 foci and the reference foci along the third direction according to the following formula: Where i is a positive integer greater than or equal to 1 and less than or equal to N-1. Let represent the relative positional relationship between the i-th focal point and the reference focal point along the third direction, and let r be the geometric dimension of a pixel of the detector along the third direction. Let be the magnification of a scanning imaging system that includes N focal points and detectors.

[0009] According to some exemplary embodiments, based on the absolute distances and the relative positions of the N-1 focal points and the reference focal point along a third direction, the absolute distances along a third direction between the N-1 focal points and the theoretical focal arrangement line of the distributed X-ray source are calculated, including: calculating the absolute distances along a third direction between the N-1 focal points and the theoretical focal arrangement line of the distributed X-ray source according to the following formula: ,in, Let be the absolute distance along a third direction between the i-th focus and the line of the theoretical arrangement of the focuses out of N-1 foci. The absolute distance between the reference focus and the line arranged in the focus theory along a third direction.

[0010] According to some exemplary embodiments, the M markers comprise two metal wires.

[0011] According to some exemplary embodiments, the images of the M markers in the scanned image of the M markers satisfy the preset conditions, including: in the scanned image of the two metal wires, the images of the two metal wires overlap.

[0012] According to some exemplary embodiments, for each of the N-1 scanned images corresponding to N-1 focal points, I... i Record the position p of the center of the scanned marker image within the image plane. i This includes: for each image I i The pixel matrix of the entire image is accumulated along the row direction of the pixel arrangement. The column number corresponding to the smallest element of the resulting row vector is recorded as the position p.i , where the row direction corresponds to the first direction.

[0013] According to some exemplary embodiments, the M markers include two metal strips.

[0014] According to some exemplary embodiments, during N focal beam exit processes, a metal strip covers at least half the width of the ray output window, the width of which is the dimension of the ray output window in a third direction.

[0015] According to some exemplary embodiments, the images of M markers in a scanned image of M markers satisfy preset conditions, including: the width of the brightness step in the scanned images of two metal strips is the narrowest.

[0016] According to some exemplary embodiments, for each of the N-1 scanned images corresponding to N-1 focal points, I... i Record the position p of the center of the scanned marker image within the image plane. i This includes: for each image I i The pixel matrix of the entire image is accumulated along the row direction of the pixel arrangement. The column number corresponding to the element value of the row vector obtained after accumulation that satisfies the following condition is recorded as the position p. i Position p i The element value at the given position is 0.5 * (the minimum element value of the row vector obtained after accumulation + the maximum element value of the row vector obtained after accumulation), where the row direction corresponds to the first direction.

[0017] According to some exemplary embodiments, the detector includes an area array detector; or, the detector includes a row of linear array detectors; or, the detector includes multiple rows of linear array detectors arranged along a first direction.

[0018] According to embodiments of this disclosure, by using M markers arranged along a second direction, the absolute distance between the reference focus and the theoretically arranged line of the focus can be quickly determined along a third direction. Then, based on the geometric positional relationship, the relative positional relationship between other focuses and the reference focus along the third direction can be determined. Thus, based on the absolute distance and relative positional relationship, the absolute distance between each focus and the theoretically arranged line of the focus can be determined along the third direction. This allows for rapid measurement and calculation of the linearity of the multi-focus arrangement of a distributed X-ray source. The calibration structure is simple and the calculation process does not require the introduction of a large number of additional unknowns, reducing the complexity of linearity measurement. Attached Figure Description

[0019] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0020] Figure 1This is a schematic diagram of the focal distribution of a distributed radiation source according to some exemplary embodiments of the present disclosure;

[0021] Figure 2 This is a flowchart of a measurement method according to some exemplary embodiments of the present disclosure;

[0022] Figure 3 This is a schematic diagram illustrating the measurement principle of a measurement method according to some exemplary embodiments of the present disclosure;

[0023] Figure 4 This is a schematic diagram of a reference focal point and two metal wires at different positions in a third direction, according to some exemplary embodiments of the present disclosure;

[0024] Figure 5 This is a schematic diagram of a reference focal point and two metal wires in the same position in a third direction, according to some exemplary embodiments of the present disclosure.

[0025] Figure 6 This is a schematic diagram illustrating the measurement principle of determining the relative positional relationship between a focal point and a reference focal point along a third direction using a metal wire, according to some exemplary embodiments of this disclosure.

[0026] Figure 7 This is a schematic diagram illustrating the measurement principle of determining the relative positional relationship between a focal point and a reference focal point along a third direction using a metal strip, according to some exemplary embodiments of this disclosure. Detailed Implementation

[0027] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0029] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0030] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0031] In the embodiments of this disclosure, an X-ray source refers to a device capable of generating X-rays, specifically including an electron source, an accelerating electric field, and a metal target. Electrons emitted by the electron source are accelerated by the accelerating electric field and then strike the metal target, thereby generating X-rays. The focal point of the X-ray source is the location where the electrons strike the metal target, which is also the location where the X-rays are generated.

[0032] A linear distributed X-ray source is a special type of X-ray source. While a typical X-ray source typically contains only one X-ray focus, a distributed X-ray source contains multiple X-ray focuses located at different spatial positions. When a distributed X-ray source operates, these X-ray focuses at different spatial positions can generate X-rays simultaneously or in a staggered, time-sequential manner. A linear distributed X-ray source refers to a distributed X-ray source in which multiple X-ray focuses are arranged in a straight line.

[0033] Figure 1 This is a schematic diagram of the focal distribution of a distributed radiation source according to some exemplary embodiments of this disclosure. For example... Figure 1 As shown, an X-ray output window 11 is provided at the wall 12 of the X-ray source tube of the distributed X-ray source. The X-ray output window 11 can be rectangular, rounded rectangular, or other shapes that can meet the X-ray emission requirements of multiple X-ray sources. The distributed X-ray source can include N focal points, where N is a positive integer greater than 1. Ideally, all X-ray focal points contained in a linear distributed X-ray source should be arranged on the same theoretical straight line, which can be the center line 13 of the X-ray output window. However, during the manufacturing process, there are errors in the processing and installation of parts, and parts may also deform due to factors such as stress and temperature changes during processing. Therefore, the focal point arrangement of the manufactured distributed X-ray source is often not a perfect straight line. See also Figure 1 In the embodiments of this disclosure, the distributed radiation source includes focal spot q1, focal spot q2, focal spot q3, ..., focal spot q N-1 and focus q N The ideal focal positions of each focus are shown by the circular markers in the figure, and the actual focal positions are shown by the square markers. It can be seen that there is a positional deviation between the actual and ideal focal positions. The distribution pattern of the focal points can be reflected by the linearity of the focal alignment, that is, the positional deviation between the actual and ideal focal positions.

[0034] However, existing methods for measuring linearity generally suffer from complex calibration structures and numerous unknowns in the calculation process, increasing the complexity of linearity measurement. For example, related technologies employ geometric calibration methods, using a phantom containing multiple metal spheres as the calibration structure. The intrinsic and extrinsic parameters of the imaging system are calculated through one or more X-ray imaging results of the calibration structure, and then the linearity of the focal alignment of the X-ray source in the imaging system can be solved based on these parameters. However, this method requires solving for a large number of unknown geometric parameters during the calculation of intrinsic and extrinsic parameters, making the calculation process complex and cumbersome. Furthermore, to ensure parameter fitting accuracy, the calibration structure needs to include multiple layers of metal spheres as markers, resulting in a relatively complex overall structure.

[0035] To address the aforementioned issues, embodiments of this disclosure provide a measurement method that measures the linearity of a multifocal arrangement of a distributed X-ray source based on markers positioned along the X-ray emission direction, thereby reducing the complexity of linearity measurement.

[0036] Figure 2 This is a flowchart of a measurement method according to some exemplary embodiments of this disclosure. For example... Figure 2 As shown, the measurement method provided in the embodiments of this disclosure is used to measure the linearity of the multifocal arrangement of a distributed X-ray source, including operations S210 to S240.

[0037] In operation S210, one focal point is selected from the N focal points of the distributed ray source as the reference focal point, where N is a positive integer greater than 1.

[0038] In the embodiments of this disclosure, a reference focus is first selected during measurement. By measuring the absolute distance between the reference focus and the theoretically arranged line of focus, as well as the relative positional relationships between the other focuses and the reference focus, the absolute distances between each focus and the theoretically arranged line of focus can be determined, thus obtaining the linearity measurement result. For ease of operation, the reference focus can be selected from the N focuses of the distributed X-ray source located at the edge, for example... Figure 1 The focus q1 in the middle.

[0039] In operation S220, using M markers arranged along the second direction, the absolute distance between the reference focus and the theoretical arrangement line of the focal point of the distributed ray source along the third direction is determined. The theoretical arrangement line of the focal point of the distributed ray source extends along the first direction, the second direction is the ray emission direction of the distributed ray source, the third direction is perpendicular to the first and second directions, and M is a positive integer greater than 1.

[0040] In operation S230, using one of the M markers, the relative positional relationship between the N-1 foci and the reference foci along the third direction is determined, where the N-1 foci are the foci other than the reference foci among the N foci.

[0041] In operation S240, based on the absolute distance and the relative positional relationship between the N-1 focal points and the reference focal point along the third direction, the absolute distances between the N-1 focal points and the theoretical focal arrangement line of the distributed X-ray source along the third direction are calculated.

[0042] According to embodiments of this disclosure, by using M markers arranged along a second direction, the absolute distance between the reference focus and the theoretically arranged line of the focus can be quickly determined along a third direction. Then, based on the geometric positional relationship, the relative positional relationship between other focuses and the reference focus along the third direction can be determined. Thus, based on the absolute distance and relative positional relationship, the absolute distance between each focus and the theoretically arranged line of the focus can be determined along the third direction. This allows for rapid measurement and calculation of the linearity of the multi-focus arrangement of a distributed X-ray source. The calibration structure is simple and the calculation process does not require the introduction of a large number of additional unknowns, reducing the complexity of linearity measurement.

[0043] In the embodiments of this disclosure, since the distance between the marker and the focal point can be measured, and the image of the marker by the X-ray emitted through the focal point can be detected and received by a detector set in the second direction, and the distance between the detector and the marker can also be measured, the relative position between the focal point and the marker in the third direction can be determined based on the image of each marker by the focal point.

[0044] In operation S220, using M markers arranged along the second direction, the absolute distance along the third direction between the reference focus and the theoretical focal arrangement line of the distributed radiation source is determined, including: placing the M markers and the detector in the initial position; controlling the movement of the M markers along the third direction; in response to a preset step size of the movement of the M markers along the third direction, recording the movement distance of the M markers relative to the initial position along the third direction, and controlling the beam output from the reference focus to scan and image the M markers to obtain scanned images of the M markers; determining whether the images of the M markers in the scanned images of the M markers meet preset conditions; in response to the images of the M markers in the scanned images of the M markers meeting preset conditions, stopping the movement of the M markers along the third direction, determining that the M markers are in the reference position, and determining the total movement distance of the M markers in the reference position relative to the initial position along the third direction as the absolute distance along the third direction between the reference focus and the theoretical focal arrangement line of the distributed radiation source.

[0045] Figure 3 This is a schematic diagram illustrating the measurement principle of a measurement method according to some exemplary embodiments of this disclosure. The following is in conjunction with... Figure 3 The measurement methods of the embodiments of this disclosure will be explained and described.

[0046] For ease of description, in the embodiments of this disclosure, the first direction x, the second direction y, and the third direction z are described respectively. The first direction x is the direction of the theoretically arranged line of the focal point of the distributed ray source, the second direction y is the ray emission direction of the distributed ray source, and the third direction z is perpendicular to the first direction x and the second direction y. For example, the first direction x corresponds to the length direction of the distributed ray source, the second direction y corresponds to the height direction of the distributed ray source, and the third direction z corresponds to the width direction of the distributed ray source.

[0047] In the embodiments of this disclosure, the marker 2 can be a metal wire, and M markers 2 are multiple metal wires arranged in the second direction y. The measurement principle of the embodiments of this disclosure will be explained below using the marker 2 as a metal wire as an example.

[0048] When marker 2 is a metal wire, the metal wire extends along a first direction x, and adjacent metal wires are spaced a certain distance apart in a second direction y. M metal wires can move simultaneously along a third direction z. The metal wire can have good toughness and a strong absorption rate for X-rays to ensure clear imaging edge contours and improve measurement accuracy. The interfaces of the metal wires in the extension direction should be kept as uniform as possible. In some embodiments, the metal wire can be a tungsten wire with a diameter of 0.1 mm.

[0049] like Figure 3 As shown, M markers 2 are positioned along the second direction y of the X-ray output window 1, meaning the projections of the M markers 2 onto the X-ray output window 1 coincide, where M is a positive integer greater than 1. The scanning imaging signal of the markers 2 from the distributed X-ray source 1 can be received and imaged by a detector 3 positioned at the second direction y of the distributed X-ray source 1. The boundary lines of the detector plane of the detector 3 in two directions are parallel to the first direction x and the third direction z, respectively. The normal direction of the detector 3 is parallel to the second direction y, and the center of the detector 3 can be aligned with the center of the X-ray output window 1 in the first direction x to improve imaging quality.

[0050] Figure 4 This is a schematic diagram of a reference focal point and two metal wires at different positions in a third direction, according to some exemplary embodiments of the present disclosure; Figure 5 This is a schematic diagram of a scanned image showing a reference focal point and two metal wires at the same position in a third direction, according to some exemplary embodiments of this disclosure. Figures 4-5As shown, taking M=2 as an example, when the positions of the two metal wires and a focal point of the distributed X-ray source 1 are different in the second direction y, the detector 3 can receive images of each metal wire from the X-rays emitted from that focal point at different positions. That is, the detector 3 can receive a first image 311 for one metal wire and a second image 312 for the other metal wire. When the positions of the M markers 2 and the focal point are the same in the second direction y, the images of each metal wire from the X-rays emitted from that focal point received by the detector 3 coincide. That is, the detector 3 can receive a third image 313 formed by the overlapping images of the two metal wires. Therefore, by moving the markers 2, when the images received by the detector 3 coincide, it can be determined that the markers 2 and the reference focal point are at the same position in the third direction z. This measurement method does not require complex calculations or image processing, greatly improving measurement efficiency.

[0051] See you again Figure 1 For ease of description, in the embodiments of this disclosure, focus q1 is selected as the reference focus. Based on the above method, the absolute distance along the third direction between the reference focus and the theoretically arranged line of the distributed ray source can be obtained. .

[0052] In other embodiments, considering that the relative distance between each marker in the second direction can be measured, it is also possible to directly obtain the scanning image of the M markers by the reference focus without moving the M markers. Based on the relative distance between the images of the M markers and the correspondence between the relative distances of the M markers in the second direction, the relative distance between the M markers and the reference focus in the third direction is determined. Then, based on the relative distance and the current position of the M markers, the distance between the reference focus and the theoretical focal arrangement line of the distributed X-ray source in the third direction is determined.

[0053] In the embodiments of this disclosure, M=2, that is, the number of markers 2 is 2. In some other embodiments, M can also be other integers greater than 1, such as 3, 4, 5, etc., that is, the number of markers 2 can be 3, 4, 5 or other numbers.

[0054] In the embodiments of this disclosure, the starting positions of the M markers can be the same as the positions of the theoretically arranged lines of the focal points of the distributed X-ray source in the third direction z. When the markers are metal wires, the images of the M markers satisfy preset conditions, which can be that the images of the M markers coincide, or the distance between the images of the M markers is less than a preset threshold.

[0055] In operation S230, using one of the M markers, the relative positional relationship between the N-1 focal points and the reference focal point along a third direction is determined, including: with the M markers in the reference position, removing the M-1 markers, leaving only one marker in the reference position, and designating the one marker as the scanning marker; with the scanning marker and detector remaining stationary, controlling the beam output of the N focal points to perform N scan imaging on the scanning marker to obtain N scan images of the scanning marker; and determining the relative positional relationship between the N-1 focal points and the reference focal point along a third direction based on the position of the image of the scanning marker in the N scan images of the marker.

[0056] In the embodiments of this disclosure, when M markers are in the reference position, the reference focus and the position of the marker in the third direction z can be considered known. The relative positional relationship between the remaining N-1 foci and the reference position can be determined. Based on the relative positional relationship and the absolute distance along the third direction between the reference position and the theoretical arrangement line of the focus, the absolute distance along the third direction between the N-1 foci and the theoretical arrangement line of the focus can be calculated.

[0057] In embodiments of this disclosure, based on the position of the scanned marker image in N scanned images of the scanned marker, the relative positional relationship between N-1 focal points and a reference focal point along a third direction is determined, including: for one image I0 corresponding to the reference focal point in the N scanned images, recording the position p0 of the center position of the scanned marker image in the image plane; for each image I0 in the N-1 scanned images corresponding to the N-1 focal points... i Record the position p of the center of the scanned marker image within the image plane. i And calculate the relative positions of the N-1 foci and the reference foci along the third direction according to the following formula:

[0058] ,

[0059] Where i is a positive integer greater than or equal to 1 and less than or equal to N-1. Let represent the relative positional relationship between the i-th focal point and the reference focal point along the third direction, and let r be the geometric dimension of a pixel of the detector along the third direction. Let be the magnification of a scanning imaging system that includes N focal points and detectors.

[0060] Figure 6 This is a schematic diagram illustrating the measurement principle of determining the relative positional relationship between a focal point and a reference focal point along a third direction using a metal wire, according to some exemplary embodiments of this disclosure. Figure 6 As shown, when the scanning marker is a metal wire 21, for the i-th focal point qi The position of the center of the image corresponding to it in the scanned image 31 of detector 3 within the image plane is p. i Let p0 be the position of the image of the metal wire 21 corresponding to the reference focus in the image plane. Since the positions of the lines containing each focus in the second direction y, the position of the metal wire 21 in the second direction y, and the position of the detector 3 in the second direction y are fixed and can all be directly measured, based on the principle of triangle similarity, according to p i The focus q can be obtained by calculating the relative distance between it and p0. i The relative distance between the reference focus and the reference focus, according to p0 and p i The positional relationship between them can be used to determine the focus q. i The relative positional relationship between the reference focus and the reference focus.

[0061] Let SOD be the distance between the position of the line containing each focal point in the second direction y and the position of the metal wire 21 in the second direction y, and let SDD be the distance between the position of the line containing each focal point in the second direction y and the position of the detector 3 in the second direction y. Then the magnification of the scanning imaging system including N focal points and detectors is... It can be represented as:

[0062] ,

[0063] Let the reference focus and focus q be... i The distance between them in the third direction z is Reference focus and focus q i The distance of the image of the corresponding metal wire 21 in the image plane is ,have Where r is the geometric dimension of a pixel of the detector along a third direction, in millimeters per pixel (mm / pixel). Then, according to the principle of triangle similarity, we can obtain:

[0064] ,

[0065] After sorting, you will get: .

[0066] See you again Figure 1 In the embodiments of this disclosure, focus points q2, q3, ..., q can be sequentially focused on. N-1 , focus q N By performing the above operations, the relative positional relationship between each focal point and the reference focal point along a third direction is obtained. , , ... , .

[0067] In operation S240, based on the absolute distances and the relative positions of the N-1 focal points and the reference focal point along a third direction, the absolute distances along a third direction between the N-1 focal points and the theoretical focal arrangement line of the distributed X-ray source are calculated, including: calculating the absolute distances along a third direction between the N-1 focal points and the theoretical focal arrangement line of the distributed X-ray source according to the following formulas: ,in, Let be the absolute distance along a third direction between the i-th focus and the line of the theoretical arrangement of the focuses out of N-1 foci. The absolute distance between the reference focus and the line arranged in the focus theory along a third direction.

[0068] In the embodiments of this disclosure, the calculated This represents the relative positional relationship between the i-th focus and the reference focus along the third direction z. The absolute distance between the reference focus and the theoretically arranged line of the focus along the third direction z has been obtained by moving the marker. Therefore, the sum of the two can be used to obtain the absolute distance between the i-th focus and the theoretically arranged line of the focus along the third direction z.

[0069] See you again Figure 1 Taking focus q2 as an example, in the embodiments of this disclosure, the relative positional relationship between the focus and the reference focus along a third direction is obtained according to the aforementioned operations. The absolute distance along a third direction between the lines of the theoretical arrangement of the reference focus and the distributed ray source focus. This allows us to calculate the absolute distance along a third direction between the focal point and the theoretically arranged line of the distributed ray source's focal points. Similarly, for focus q3, ..., focus q... N-1 , focus q N The corresponding absolute distances can be obtained respectively. ... , .

[0070] In the embodiments of this disclosure, the M markers 2 can be two metal wires. Correspondingly, the images of the M markers in the scanned image of the M markers satisfy a preset condition, which can include the images of the two metal wires overlapping in the scanned image of the two metal wires. In other embodiments, the preset condition may also include that the distance between the images of the two metal wires in the scanned image of the two metal wires is less than a preset threshold, or that the distance between the images of the two metal wires reaches a minimum value during the movement of the two metal wires.

[0071] When the scanning marker is a metal wire 21, the position of the center of the image of the scanning marker within the image plane can be determined by the pixel value in the image. Because the metal wire has a strong absorption rate for X-rays, the pixel value at the corresponding position in the image obtained by scanning the metal wire is smaller than the pixel value at other positions within the image plane. In the embodiments of this disclosure, each of the N-1 scanning images corresponding to N-1 focal points is I... i Record the position p of the center of the scanned marker image within the image plane. i This includes: for each image I i The pixel matrix of the entire image is accumulated along the row direction of the pixel arrangement. The column number corresponding to the smallest element of the resulting row vector is recorded as the position p. i , where the row direction corresponds to the first direction.

[0072] The metal wire extends in the first direction x. In order to ensure that all focal points can image the metal wire, the length of the metal wire in the first direction x is not less than the length of the X-ray output window 11 in the first direction x.

[0073] In some embodiments, the pixel matrix of the entire image can be accumulated along the row direction of the pixel arrangement. In other embodiments, the pixel matrix of only a portion of the image can be accumulated along the row direction of the pixel arrangement, thereby reducing the amount of computation and improving measurement efficiency.

[0074] It should be noted that, unless otherwise specified, the content and features described above can be combined with the embodiments described below. To save space, the various embodiments below will not be repeated. For example, in the embodiments described below, another embodiment of this disclosure is illustrated using M markers including two metal strips as an example. It should be understood that the metal strip structure markers described below are only for illustrative purposes and may include not only metal wires but also other structural forms. Those skilled in the art should understand that the structural form of the markers can be designed according to specific needs.

[0075] In some other embodiments, the M markers 2 may also include two metal strips.

[0076] To facilitate the determination of the edges of the metal strip image, in this embodiment, during the beam exit process at N focal points, the metal strip covers at least half the width of the X-ray output window, the width of which is the dimension of the X-ray output window in the third direction. At this time, the scanned image on detector 3 is the image of the metal strip formed by X-rays.

[0077] Figure 7 This is a schematic diagram illustrating the measurement principle of determining the relative positional relationship between a focal point and a reference focal point along a third direction using a metal strip, according to some exemplary embodiments of this disclosure. Figure 7 As shown, when the scanning marker is a metal strip 22, for the i-th focal point q i Because it has a certain width and is not an ideal point light source, some X-rays emitted through this focal point can pass through the edge of the metal strip, while some X-rays are blocked and cannot pass through the edge of the metal strip. Figure 7 Taking the direction shown as an example, for the direction via the focus q i leftmost edge q iL The X-rays emitted from position I, after passing the edge of metal strip 22, will land at the corresponding position I on detector 3. iR Then detector 3 in I iR The area to its right can receive the focus q. i All emitted X-rays; for those passing through focus q i rightmost edge q iR The X-rays emitted from position I, after passing the edge of metal strip 22, will land at the corresponding position I on detector 3. iL Then detector 3 in I iL The area to its left, due to the obstruction of the metal strip 22, cannot receive the focus q. i All emitted X-rays; while for detector 3 located at I iL with I iR The area between them can receive part of the signal via the focal point q. i The emitted X-rays. Therefore, for the image of the edge portion of the metal strip, i.e., located at I... iL to I iR The region between these two points appears as a stepped area of ​​brightness variation in the image, with brightness distribution curve 32 being a curve that continuously changes from the lowest brightness to the highest brightness.

[0078] In this embodiment, the images of the M markers in the scanned images of the M markers satisfy the preset conditions, including: the width of the brightness step in the scanned images of the two metal strips is the narrowest. During the movement of the metal strips, the relative position between the focal point and the edge of the metal strip continuously changes, causing the width of the brightness step in the scanned image to change accordingly. When the width of the brightness step is the narrowest, the focal point and the edge of the metal strip are at the same position in the third direction z. At this point, the position of the reference focal point and the absolute distance along the third direction between the reference focal point and the theoretical focal arrangement line of the distributed X-ray source can be determined based on the position of the metal strip edge.

[0079] When the marker is a metal strip, in the aforementioned steps, for each of the N-1 scanned images corresponding to N-1 focal points, I... i Record the position p of the center of the scanned marker image within the image plane. i This includes: for each image I iThe pixel matrix of the entire image is accumulated along the row direction of the pixel arrangement. The column number corresponding to the element value of the row vector obtained after accumulation that satisfies the following condition is recorded as the position p. i Position p i The element value at the given position is 0.5 * (the minimum element value of the row vector obtained after accumulation + the maximum element value of the row vector obtained after accumulation), where the row direction corresponds to the first direction.

[0080] See you again Figure 7 In this embodiment, the image of the edge portion of the metal strip is represented on the image as a stepped region with varying brightness, and the center position of this stepped region represents the focal point q. i The position of the image of the corresponding metal strip edge in the image plane, and the corresponding focal point q. i The center position of the image of the metal strip edge can be determined by the position where the brightness changes to half in the brightness gradient. By using the pixel matrix to accumulate along the rows, the center position of the image of the scanned marker in the image plane can be quickly determined. i Then, the absolute distance along the third direction between the focal point and the theoretical focal arrangement line of the distributed ray source is calculated.

[0081] In the embodiments of this disclosure, the structure of the detector 3 can be determined according to actual needs. For example, in some embodiments of this disclosure, the detector includes an area array detector; or, in some embodiments, the detector includes a row of linear array detectors; or, in other embodiments, the detector includes multiple rows of linear array detectors arranged along a first direction.

[0082] When detector 3 includes a row of linear array detectors, the row of linear array detectors is equivalent to a row of the two-dimensional image of the area array detector. In this case, when determining the position of the center of the marker image in the image plane, it is not necessary to accumulate the pixel matrix of the entire image along the row direction of the pixel arrangement. The pixel value of a linear array detector is equivalent to accumulating the element value of the corresponding row vector along the row direction.

[0083] In the case where detector 3 includes multiple rows of linear array detectors, the linear array detector matrix formed by the multiple rows of linear array detectors is equivalent to part or all of a planar array detector.

[0084] In the embodiments of this disclosure, by using M markers arranged along the second direction, the absolute distance between the reference focus and the theoretically arranged line of the focus can be quickly determined along the third direction. Then, based on the geometric positional relationship, the relative positional relationship between other focuses and the reference focus along the third direction can be determined. Thus, based on the absolute distance and relative positional relationship, the absolute distance between each focus and the theoretically arranged line of the focus can be determined along the third direction. The linearity of the multi-focus arrangement of the distributed X-ray source can be quickly measured and calculated. The calibration structure is simple and the calculation process does not require the introduction of a large number of additional unknowns, which reduces the complexity of linearity measurement.

[0085] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A measurement method for measuring the linearity of a multifocal arrangement of a distributed X-ray source, characterized in that, The method includes: One focal point is selected from the N focal points of the distributed ray source as the reference focal point, where N is a positive integer greater than 1; Using M markers arranged along the second direction, the absolute distance between the reference focal point and the theoretical focal arrangement line of the distributed ray source along the third direction is determined, wherein the theoretical focal arrangement line of the distributed ray source extends along the first direction, the second direction is the ray emission direction of the distributed ray source, the third direction is perpendicular to the first direction and the second direction, and M is a positive integer greater than 1. Using one of the M markers, determine the relative positional relationship along a third direction between N-1 foci and the reference foci, wherein the N-1 foci are the foci other than the reference foci among the N foci; and Based on the absolute distance and the relative positional relationship between the N-1 focal points and the reference focal point along a third direction, the absolute distances along a third direction between the N-1 focal points and the theoretical focal arrangement line of the distributed ray source are calculated respectively.

2. The method according to claim 1, characterized in that, The step of determining the absolute distance along a third direction between the reference focal point and the theoretical focal arrangement line of the distributed ray source using M markers arranged along the second direction includes: Place the M markers and detectors in the starting position; Control the movement of the M markers along the third direction; In response to the M markers moving a preset step length along the third direction, the movement distance of the M markers relative to the starting position along the third direction is recorded, and the beam is controlled from the reference focus to scan and image the M markers to obtain scanned images of the M markers; Determine whether the images of the M markers in the scanned images of the M markers meet preset conditions; and In response to the M markers' images in the scanned image satisfying a preset condition, the movement of the M markers along the third direction is stopped, the M markers are determined to be at a reference position, and the total movement distance of the M markers at the reference position relative to the starting position along the third direction is determined as the absolute distance along the third direction between the reference focus and the theoretical focal arrangement line of the distributed X-ray source.

3. The method according to claim 2, characterized in that, The step of determining the relative positional relationship between N-1 foci and the reference foci along a third direction using one of the M markers includes: When the M markers are at the reference position, remove M-1 markers, leaving only one marker at the reference position, and identify the one marker as the scan marker; With the scanning marker and the detector remaining stationary, the N focal beams are controlled to emit light from each of the N focal points, performing N scans on the scanning marker to obtain N scan images of the scanning marker; and Based on the position of the image of the scanned marker in N scanned images of the marker, the relative positional relationship between the N-1 focal points and the reference focal point along a third direction is determined.

4. The method according to claim 3, characterized in that, The step of determining the relative positional relationship between the N-1 focal points and the reference focal point along a third direction based on the position of the image of the scanning marker in N scanned images of the scanning marker includes: For one image I0 among the N scanned images corresponding to the reference focal point, record the position p0 of the center position of the scanned marker's image in the image plane; and For each of the N-1 scanned images corresponding to the N-1 focal points, I... i Record the position p of the center of the image of the scanned marker in the image plane. i And the relative positional relationship between the N-1 foci and the reference foci along the third direction is calculated according to the following formula: ， Where i is a positive integer greater than or equal to 1 and less than or equal to N-1. Let r represent the relative positional relationship between the i-th focal point and the reference focal point along the third direction, where r is the geometric dimension of a pixel of the detector along the third direction. The magnification is the magnification of the scanning imaging system that includes the N focal points and the detector.

5. The method according to claim 1, characterized in that, The step of calculating the absolute distances along a third direction between the N-1 focal points and the theoretical focal arrangement line of the distributed radiation source, based on the absolute distances and the relative positional relationships between the N-1 focal points and the reference focal point along a third direction, includes: The absolute distances along a third direction between the N-1 foci and the theoretically arranged line of the distributed ray source's foci are calculated using the following formulas: ， in, The absolute distance along a third direction between the i-th focus among the N-1 foci and the line of the theoretical arrangement of the foci. The absolute distance along a third direction between the reference focus and the line of the theoretical arrangement of the focus.

6. The method according to claim 4, characterized in that, The M markers include two metal wires.

7. The method according to claim 6, characterized in that, The images of the M markers in the scanned images of the M markers satisfy the preset conditions, including: in the scanned images of the two metal wires, the images of the two metal wires overlap.

8. The method according to claim 7, characterized in that, For each of the N-1 scanned images corresponding to the N-1 focal points, I... i Record the position p of the center of the image of the scanned marker in the image plane. i ,include: For each image I i The pixel matrix of the entire image is accumulated along the row direction of the pixel arrangement. The column number corresponding to the smallest element of the resulting row vector is recorded as the position p. i , wherein the row direction corresponds to the first direction.

9. The method according to claim 4, characterized in that, The M markers include two metal strips.

10. The method according to claim 9, characterized in that, During the N focal beam output processes, the metal strip covers at least half the width of the ray output window, the width being the dimension of the ray output window in the third direction.

11. The method according to claim 10, characterized in that, The images of the M markers in the scanned images of the M markers meet the following preset conditions: in the scanned images of the two metal strips, the width of the brightness step is the narrowest.

12. The method according to claim 11, characterized in that, For each of the N-1 scanned images corresponding to the N-1 focal points, I... i Record the position p of the center of the image of the scanned marker in the image plane. i ,include: For each image I i The pixel matrix of the entire image is accumulated along the row direction of the pixel arrangement. The column number corresponding to the element value of the row vector obtained after accumulation that satisfies the following condition is recorded as the position p. i : Position p i The element value at that location = 0.5 * (the minimum element value of the row vector obtained after accumulation + the maximum element value of the row vector obtained after accumulation). Wherein, the row direction corresponds to the first direction.

13. The method according to claim 2, characterized in that, The detector includes an area array detector; or... The detector comprises a row of linear array detectors; or... The detector includes a multi-row linear array detector, which is arranged along the first direction.

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