System and method for three-dimensional printing of collimators

Abstract

A method for forming a metal lattice structure includes printing, with 3D printing, a first layer of a first wall section of the metal lattice structure in a first direction along a first vector offset from a centerline of the first wall section by half a first distance of a first width of the first wall section orthogonal to the centerline. The method further includes printing, using 3D printing, a second layer of the first wall section on the first layer in a second direction along a second vector offset from a first line of the first wall section by half the first distance of the first width of the first wall section, where the second direction is opposite the first direction, and the first vector and the second vector are disposed on opposite sides of the centerline.

Description

Background Art

[0001] The subject matter disclosed herein relates to three-dimensional (3D) printing of collimators.

[0002] Various mechanical and micromechanical systems may employ gratings or grids that include some form of grooves or other openings at least partially defined by sidewalls (e.g., vertical sidewalls or diaphragms). Such gratings or grids may be used to limit or collimate the transfer of energy or material from one side of the grating or grid to the opposite side or may perform other functions where the grooves or other sidewall structures contribute to the function of the overall system.

[0003] The use of additive manufacturing technology in industrial environments is becoming more and more popular. The manufacturability of various materials (e.g., 316L, J13Iconel 718, 625, AlSi10Mg, etc.) is well known. However, refractory materials still pose a challenge, especially for laser powder bed fusion (LPBF) technology. At the same time, tungsten printing is a niche market, and limited industries invest in it. For example, the manufacture of computed tomography (CT) collimators using 3D printing is challenging due to thin walls, tight manufacturing tolerances, and the use of tungsten materials. 3D printed collimators that require multiple layers (for building thickness) using LPDF currently produce products with less than acceptable density and rough surfaces, which causes quality problems. Summary of the invention

[0004] Certain embodiments commensurate with the scope of the originally claimed subject matter are summarized below. These embodiments are not intended to limit the scope of the claimed subject matter, but rather, these embodiments are intended only to provide a brief overview of possible embodiments. In fact, the disclosed subject matter may include a variety of forms that may be similar to or different from the embodiments described below.

[0005] In one embodiment, a method for forming a metal grid structure is provided. The method includes using three-dimensional (3D) printing to print a first layer of a first wall segment of the metal grid structure in a first direction along a first vector, the first vector offset from a first centerline of the first wall segment by half of a first distance of a first width of the first wall segment orthogonal to the first centerline. The method also includes using 3D printing to print a second layer of the first wall segment on the first layer in a second direction along a second vector, the second vector offset from the first centerline of the first wall segment by half of a first distance of the first width of the first wall segment, wherein the second direction is opposite to the first direction, and the first vector and the second vector are disposed on opposite sides of the first centerline.

[0006] In another embodiment, a method for forming a collimator configured for use with an X-ray detector of an X-ray imaging system is provided. The method includes using three-dimensional (3D) printing to alternately print layers of a first group of membranes extending along a first direction by alternately using a first vector and a second vector when printing the layers of the first group of membranes of the collimator, wherein the first vector and the second vector are oriented in opposite directions along the first direction, are disposed on opposite sides of a first centerline of corresponding membranes of the first group of membranes, and are offset from the first centerline by half of a first distance of a first width of corresponding membranes of the first group of membranes. The method also includes using 3D printing to alternately print layers of a second group of membranes extending along a second direction by alternately using a third vector and a fourth vector when printing the layers of the second group of membranes of the collimator, wherein the third vector and the fourth vector are oriented in opposite directions along the second direction and are disposed on opposite sides of a second centerline of corresponding membranes of the second group of membranes, and are offset from the second centerline by half of a second distance of a second width of corresponding membranes of the second group of membranes, wherein the first direction is orthogonal to the second direction.

[0007] In another embodiment, a system for forming a collimator configured for use with an X-ray detector of an X-ray imaging system is provided. The system includes a memory encoding a processor executable routine. The system also includes a processing circuit configured to access the memory and execute the processor executable routine, wherein the routines, when executed by the processing circuit, cause the processing circuit to perform an action. The action includes using three-dimensional (3D) printing to alternately print layers of a first set of diaphragms extending along a first direction by alternatingly using a first vector and a second vector when printing the layers of the first set of diaphragms of the collimator, wherein the first vector and the second vector are oriented in opposite directions along the first direction, are disposed on opposite sides of a first centerline of a corresponding diaphragm of the first set of diaphragms, and are offset from the first centerline by half of a first distance of a first width of the corresponding diaphragm of the first set of diaphragms. The actions also include utilizing 3D printing to alternately print layers of a second set of diaphragms extending along a second direction by alternately utilizing a third vector and a fourth vector when printing the layers of the second set of diaphragms of the collimator, wherein the third vector and the fourth vector are oriented in opposite directions along the second direction and are disposed on opposite sides of a second centerline of respective diaphragms of the second set of diaphragms and are offset from the second centerline by half a second distance of a second width of respective diaphragms of the second set of diaphragms, wherein the first direction is orthogonal to the second direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] These and other features, aspects, and advantages of the present subject matter will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters refer to like parts throughout the several views, and in which:

[0009] Figure 1Components of a computed tomography imaging system according to certain aspects of the present disclosure are shown;

[0010] Figure 2 schematically illustrates a side view of a channel of a detector with a collimator blade disposed thereon according to certain aspects of the present disclosure;

[0011] Figure 3 shows a top view of a portion of a collimator according to certain aspects of the present disclosure;

[0012] Figure 4 A conventional printing strategy for printing the walls or diaphragms of a collimator (e.g., using a single vector) is schematically shown;

[0013] Figure 5 A conventional printing strategy (e.g., utilizing a dual vector strategy) for printing the walls or diaphragms of a collimator is schematically shown;

[0014] Figure 6 Schematically illustrates a zigzag printing strategy (eg, utilizing a single vector printing strategy) for printing a wall or diaphragm of a collimator according to aspects of the present disclosure;

[0015] Figure 7 Shown from the use of Figure 5 An image above of a portion of a collimator printed using a conventional printing strategy;

[0016] Figure 8 The invention shows the use of various aspects of the present disclosure. Figure 6 An image above of a portion of a collimator printed using a zigzag printing strategy;

[0017] Fig. 9 Schematically illustrates a zigzag printing strategy (eg, utilizing an alternating vector printing strategy) for printing a wall or diaphragm of a collimator according to aspects of the present disclosure;

[0018] Fig.10 schematically illustrates an overall zigzag printing strategy for forming joints between intersecting walls or membranes of a collimator in accordance with aspects of the present disclosure;

[0019] Fig.11 Schematically illustrates a method for printing according to various aspects of the present disclosure. Fig.10 Top view of the printing strategy for the initial layer of the wall or membrane in FIG.

[0020] Fig.12 Schematically illustrates a method for printing according to various aspects of the present disclosure. Fig.10 Top view of the printing strategy for the next layer of the wall or membrane in FIG.

[0021] Fig.13Schematically illustrates a method for printing according to various aspects of the present disclosure. Fig.10 A top view of the printing strategy for the initial layer and the next layer of overlapping walls or membranes; and

[0022] Fig.14 A laser powder bed fusion system for printing a wall or diaphragm of a collimator according to aspects of the present disclosure is schematically illustrated. DETAILED DESCRIPTION

[0023] One or more specific embodiments will be described below. In order to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be understood that in the development of any such actual implementation, as in any engineering or design project, many implementation-specific decisions must be made to achieve the developer's specific goals, such as complying with system-related and business-related constraints that may vary from implementation to implementation. In addition, it should be understood that such development efforts may be complex and time-consuming, but are still routine tasks for design, fabrication, and manufacturing for ordinary technicians who benefit from this disclosure.

[0024] When introducing elements of various embodiments of the present subject matter, the articles "a," "an," "the," and "said" are intended to indicate that there are one or more elements. The terms "comprising," "including," and "having" are intended to be inclusive, and mean that there may be additional elements in addition to the listed elements. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and thus the additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments.

[0025] Although the various aspects discussed below may be provided in the context of medical imaging, it should be understood that the present technology is not limited to such medical contexts. In fact, examples and explanations are provided in such medical contexts only to facilitate explanation by providing examples of realistic specific implementations and applications. However, the present method may also be used in other contexts, such as for tomographic image reconstruction of industrial computed tomography (CT) used in non-destructive inspection of manufactured parts or manufactured products (i.e., quality control or quality audit applications) and / or non-invasive inspection of packages, boxes, luggage, etc. (i.e., security inspection or screening applications). Generally speaking, the present method may be used in any imaging or screening context utilizing an X-ray imaging grating (such as a collimator or anti-scatter grid). Moreover, although discussed in the context of CT imaging, the present method may be utilized in any imaging system utilizing a collimator or an anti-scatter grid (e.g., conventional X-ray imaging system, positron emission tomography imaging, etc.).

[0026] The present technology relates to various aspects of additive manufacturing, e.g., three-dimensional (3D) printing of x-ray gratings or metal grid structures (e.g., collimators or x-ray grids). The present technology provides a customized single-vector zigzag printing strategy (i.e., a single vector per layer of a given wall or a given wall segment) that utilizes alternating vectors that are offset in opposite directions from the center of a diaphragm (e.g., wall) by half of the vector distance. For example, 3D printing can be used to print a collimator (e.g., made of multiple layers) for use with an x-ray detector of an x-ray imaging system, wherein 3D printing is used to alternately print layers of a first set of diaphragms extending along a first direction by alternatingly utilizing a first vector and a second vector when printing the layers of the first set of diaphragms of the collimator. The first vector and the second vector are oriented in opposite directions along the first direction, are disposed on opposite sides of a first centerline of respective diaphragms of the first set of diaphragms, and are offset from the first centerline by a first distance (e.g., a vector distance) of half of a first width of respective diaphragms of the first set of diaphragms. 3D printing is also used to alternately print layers of a second group of membranes extending along a second direction by alternately utilizing a third vector and a fourth vector when printing layers of a second group of membranes of a collimator. The third vector and the fourth vector are oriented in opposite directions along the second direction and are disposed on opposite sides of a second centerline of a corresponding membrane of the second group of membranes, and are offset from the second centerline by half of a second distance of a second width of a corresponding membrane of the second group of membranes. The first direction is orthogonal to the second direction. This forms an article (i.e., a collimator) having a smoother finish and a higher density (where conventional processes would require a multi-vector strategy for a given thickness (i.e., greater than 100 microns)). The disclosed technology also improves production capacity, unifies membrane properties, and enables printing of symmetrical walls. In addition, the disclosed technology improves measurement capabilities when utilizing a collimator due to the use of a backlight source and a smoother finish that facilitates edge detection. Further, the disclosed technology reduces cleaning time and reduces / removes the presence of residual particles adhering to the membrane surface.

[0027] Considering the above discussion, Figure 1 An embodiment of an imaging system 10 for acquiring and processing image data according to the structures and methods discussed herein is illustrated. That is, the type of imaging system 10 depicted is an example of one type of imaging system that may benefit from or otherwise utilize components made according to the techniques described herein (e.g., a multi-layer X-ray grating, such as an anti-scatter grid or a collimator). However, as described herein, other types of systems (e.g., non-imaging systems, non-medical systems, etc.) may also utilize components made according to the techniques described herein.

[0028] In the illustrated example, the system 10 is a computed tomography (CT) system designed to acquire X-ray projection data and reconstruct the projection data into volume reconstructions for display and analysis. The CT imaging system 10 includes one or more X-ray sources 12, such as one or more X-ray tubes or solid-state emission structures that allow generation of X-rays at one or more energy spectra during an imaging phase.

[0029] In some implementations, the source 12 can be positioned proximate to a pre-patient collimator and / or filter assembly 22, which can be used to steer the X-ray beam 20, define the shape (such as by limiting off-angle emission) and / or range of high-intensity regions of the X-ray beam 20, control or define the energy distribution of the X-ray beam 20, and / or otherwise limit X-ray exposure to those portions of the patient 24 that are not within the region of interest. In practice, the filter assembly or beam shaper 22 can be incorporated into a gantry between the source 12 and the imaging volume.

[0030] An X-ray beam 20 enters an area in which a subject (e.g., a patient 24) or an object of interest (e.g., a manufactured part, luggage, a package, etc.) is located. The subject attenuates at least a portion of the X-ray photons 20, resulting in attenuated X-ray photons 26, which impinge on a pixelated detector array 28 formed of a plurality of detector elements (e.g., pixels) arranged in an array. In the depicted example, the attenuated X-ray photons 26 pass through a collimator 18 (e.g., an anti-scatter grid) before reaching the detector array 28. As discussed herein, the collimator 18 may be composed of a plurality of blades or other elements aligned substantially perpendicular to the surface of the detector array 28 and formed of an attenuating material that limits or prevents X-ray photons 26 traveling at stray angles (e.g., scattered X-rays) from reaching the detector array 28. Electrical signals reaching the detector array 28 are detected and processed to generate one or more projection data sets. In the depicted example, the detector 28 is coupled to a system controller 30, which commands acquisition of digital signals generated by the detector 28.

[0031] The system controller 30 commands the operation of the imaging system 10 to perform filtering, inspection and / or calibration schemes, and may process the acquired data. The system controller 30 provides power, focus position, control signals, etc. for the X-ray inspection sequence relative to the X-ray source 12. According to certain embodiments, the system controller 30 may control the operation of the filter assembly 22, the CT gantry (or other structural support to which the X-ray source 12 and the detector 28 are attached), and / or the translation and / or tilting of the patient support during the inspection process.

[0032] In addition, via the motor controller 36, the system controller 30 can control the operation of the linear positioning subsystem 32 and / or the rotation subsystem 34 for moving the subject 24 and / or components of the imaging system 10, respectively. For example, in a CT system, the radiation source 12 and the detector 28 rotate around the object (e.g., the patient 24) to collect X-ray transmission data over a series of angular views. Therefore, in a real-world implementation, the imaging system 10 is configured to generate X-ray transmission data corresponding to each of a plurality of angular positions (e.g., 360°, 180°+fan beam angle (α), etc.) covering the entire scanning area of ​​interest.

[0033] The system controller 30 may include signal processing circuitry and associated memory circuitry. In such embodiments, the memory circuitry may store programs, routines, and / or coded algorithms that are executed by the system controller 30 to operate the imaging system 10 (including the x-ray source 12 and / or the filter assembly 22) and process the digital measurements acquired by the detector 28. In one embodiment, the system controller 30 may be implemented as all or part of a processor-based system.

[0034] The source 12 may be controlled by an X-ray controller 38 included within the system controller 30. The X-ray controller 38 may be configured to provide power, timing signals, and / or focal spot size and focal spot position to the source 12. Additionally, in some embodiments, the X-ray controller 38 may be configured to selectively activate the source 12 so that tubes or emitters at different locations within the system 10 may operate synchronously with or independently of each other, or to switch the source between different energy profiles during an imaging session.

[0035] The system controller 30 may include a data acquisition system (DAS) 40. The DAS 40 receives data collected by the readout electronics of the detector 28, such as digital signals from the detector 28. The DAS 40 may then convert and / or process the data for subsequent processing by a processor-based system, such as a computer 42. In certain implementations discussed herein, circuitry within the detector 28 may convert the detector's analog signals to digital signals before transmission to the data acquisition system 40. The computer 42 may include or communicate with one or more non-transitory memory devices 46 capable of storing data processed by the computer 42, data to be processed by the computer 42, or instructions to be executed by the image processing circuitry 44 of the computer 42. For example, a processor of the computer 42 may execute one or more sets of instructions stored on a memory 46, which may be a memory of the computer 42, a memory of a processor, firmware, or the like. By way of example, the image processing circuitry 44 of the computer 42 may be configured to generate a diagnostic image.

[0036] The computer 42 may also be adapted to control features enabled by the system controller 30 (i.e., scanning operations and data acquisition), such as in response to commands and scanning parameters provided by an operator via an operator workstation 48. The system 10 may also include a display 50 coupled to the operator workstation 48 that allows the operator to view relevant system data, imaging parameters, raw imaging data, reconstructed data or images, etc. In addition, the system 10 may include a printer 52 that is coupled to the operator workstation 48 and is configured to print any desired measurement results. The display 50 and printer 52 may also be connected to the computer 42 (e.g., directly or via the operator workstation 48). Figure 1 ). Further, the operator workstation 48 may include or be coupled to a picture archiving and communication system (PACS) 54. The PACS 54 may be coupled to a remote system or client 56, a radiology department information system (RIS), a hospital information system (HIS), or an internal or external network to enable others at different locations to access the image data.

[0037] Considering the foregoing discussion of the overall imaging system 10, and turning to Figure 2 , an example of a detector 28 and collimator 18 arrangement is shown in a cross-sectional side view. In this example, the detector 28 is shown as an array of pixels 58 that each correspond to a readout channel. A set of collimator blades 60 of the collimator 18 are shown to be associated with the pixel array 58 so that each pixel is individually collimated. The blades 60 are shown to be placed where the pixels are joined so that the shadows attributable to the blades 60 are primarily located at these joints, so that most of the active area of ​​the pixel 58 is relatively free of shadows produced by the blades. In this way, each pixel 58 is relatively uniformly and evenly affected by the collimator blades 60.

[0038] Figure 3 A top view of a portion of the collimator 18 (e.g., a metal grid structure) is shown. As depicted, the collimator 18 includes a first group 62 of diaphragms 64 (e.g., walls) extending along a first direction 66. The collimator 18 also includes a second group 68 of diaphragms 64 (e.g., walls) extending along a second direction 70 that is orthogonal to the first direction 66. Each diaphragm 64 in both the first group 62 of diaphragms 64 and the second group 68 of diaphragms 64 has a width 72 (e.g., thickness) extending along the second direction 70 and the first direction 66, respectively. In some embodiments, the width 72 is greater than 100 microns. The first group 62 of diaphragms 64 and the second group 68 of diaphragms 64 intersect or meet to form a junction or intersection 74. In some embodiments, Figure 2 and Figure 3 The collimator 18 in can be 3D printed and formed from multiple layers, as described in more detail below. In some embodiments, Figure 2 and Figure 3The collimator 18 may be made of tungsten.

[0039] Figure 4 A conventional printing strategy (eg, using a single vector) for printing the walls or membranes of a collimator is schematically shown. Figure 4 As depicted, vertical box 76 represents a wall or diaphragm of the collimator extending in direction 80 (e.g., Y direction). Wall or diaphragm 76 includes centerline 78. Wall or diaphragm 76 is 3D printed in multiple layers 82, where each layer 82 is printed as a laser patch on top of other layers 82, such that wall or diaphragm 76 extends in direction 84 (e.g., Z direction). Each layer 82 includes a layer thickness 86 (e.g., L in direction 84). t ). Wall or membrane 76 includes a width 88 (e.g., wall thickness) extending in a direction 90 (e.g., X direction) orthogonal to direction 80. Width 88 is 100 microns or less. Centerline 78 is centered within width 88. A single layer 82 of wall or membrane 76 is printed in direction 80 with a single vector exposure 92 (e.g., having a thickness of 100 microns or less).

[0040] If the walls or membrane of the collimator have a wall thickness greater than 100 microns, a different strategy needs to be utilized. Figure 5 A conventional printing strategy (eg, using a dual vector strategy) for printing the walls or membranes of a collimator is schematically shown. Figure 5 As depicted, vertical box 94 represents a portion of a wall or diaphragm 96 of the collimator extending in direction 80 (e.g., the Y direction) printed using a first vector exposure 98 (e.g., having a thickness of 100 microns or less). Vertical box 100 represents a portion of a wall or diaphragm 96 printed using a second vector exposure 102 (e.g., having a thickness greater than 100 microns). Wall or diaphragm 96 includes centerline 104. Wall or diaphragm 96 is 3D printed in multiple layers 82, each layer 82 being printed as a laser patch on top of other layers 82 (of the same vector exposure) such that wall or diaphragm 96 extends in direction 84 (e.g., the Z direction). Each layer 82 includes a layer thickness 86 (e.g., L in the direction 84). t). The wall or diaphragm 96 includes a width 106 (e.g., wall thickness) extending in a direction 90 (e.g., X direction) orthogonal to the direction 80. The width 106 is greater than 140 microns. The centerline 78 is centrally located within the width 106. A single layer 82 of the wall or diaphragm 96 is printed using two adjacent vectors, a first vector exposure 98 in the direction 80 and a second vector exposure 102 in a direction 108 opposite to the direction 80. Portion 94 of the wall or diaphragm 96 is formed by laser patch printing layers 82 on top of each other using the first vector exposure 98 to form portion 94. Portion 100 of the wall or diaphragm 96 is formed by laser patch printing layers 82 on top of each other using the second vector exposure 102 to form portion 100. Specifically, each layer of the wall 96 is printed via the first vector exposure 98 and the second vector exposure 102. The vector distance 110, (e.g., L Dxy ) represents the distance between the first vector exposure 98 and the second vector exposure 102 along the direction 90.

[0041] Figure 4 The printing strategy in works well for printing the walls or membranes of the collimator less than 100 microns. However, when the walls or membranes of the collimator are larger than 100 microns, the printing strategy in Figure 5 The depicted multi-vector strategy (for printing a single layer), which leads to the following problems or challenges. These problems include increased surface roughness and reduced wall density relative to the designed (desired) wall density. These problems also include asymmetric wall properties (e.g., greater roughness and less density in the second vector patch). These problems further include that the measured wall thickness is not representative of the designed wall thickness. Specifically, residual particles and porosity on the diaphragm surface typically result in thicker walls but reduced density, all of which degrades collimator performance. These problems further include longer post-processing (e.g., ultrasonic cleaning to remove particles loosely attached to the diaphragm surface).

[0042] Provided below is a zigzag printing strategy utilizing a single vector printing strategy that can be used for 3D printing (eg, via LPBF) of collimators (eg, made of tungsten) having membranes or walls with wall thickness greater than 100 microns. Figure 6 A zigzag printing strategy (eg, using a single vector printing strategy) for printing a wall or membrane 112 of a collimator, or a section of a wall or membrane 112 is schematically shown. Figure 6As depicted, the wall or diaphragm 112 of the collimator extends along direction 80 (e.g., Y direction). The wall or diaphragm 112 includes a centerline 114. The wall or diaphragm 112 is 3D printed in multiple layers 116, wherein each layer 116 is printed as a laser patch on top of the other layers 116, so that the wall or diaphragm 112 extends along direction 84 (e.g., Z direction). Each layer 116 includes a layer thickness 86 (e.g., Lt) in direction 84. The wall or diaphragm 112 includes a width 118 (e.g., wall thickness) extending along a direction 90 (e.g., X direction) orthogonal to the direction 80. The width 118 is greater than 100 microns. The centerline 114 is centered within the width 118. The individual layers 116 of the wall or diaphragm 112 are printed alternately using two different vectors (e.g., each layer 116 uses a single vector). As depicted, an initial layer 120 (layer n) is printed along a first vector 122 (V1) in a first direction (i.e., Y direction 80) using a first vector exposure. The first vector 122 is offset from the centerline 114 by half of the distance of width 118 (or vector distance 136). A next layer 124 (layer n+1) is printed on the initial layer 120 with a laser patch along a second vector 126 (V2) in a second direction 128 opposite to the first direction 80. The second vector 126 is offset from the centerline 114 by half of the distance of width 118 (or vector distance 136). The first vector 122 and the second vector 126 are respectively disposed on opposite sides 130, 132 of the centerline 114. The layer 124 has the same thickness as the initial layer 120. The layers 120, 124 together have a layer thickness 134 (2xL t ). Vector distance 136 (eg, L Dxy ) represents the distance between the first vector 122 and the second vector 126 along the direction 90. The vector distance 136 represents the distance moved between the first vector 122 and the second vector 126 to print the corresponding layer 116. The vector distance 136 is determined based on a combination of laser power and laser speed to achieve the desired printing results. In this case, the vector distance 136 is the same as the width 118 of the wall 112. In some embodiments, vectors of different directions can be used to print layers of membranes or walls to improve the density and surface finish of the printed collimators. In some embodiments, different vectors can be used for different (and adjacent) sections of a wall or membrane on the same layer, where a single vector is used for each section of the wall or membrane.

[0043] like Figure 6As depicted, layers 116 are alternately printed by alternating use of a first vector 122 and a second vector 126 for printing the corresponding layer 116. This alternating use of the first vector 122 and the second vector results in a zigzag pattern 138 in the direction 84. Utilization of the zigzag strategy improves production capacity, improves collimator surface finish, and increases wall density to up to 99.9% (excluding cracks). Utilization of the zigzag strategy also unifies diaphragm characteristics and enables printing of symmetrical walls. Utilization of the zigzag strategy further provides measurement capability improvements (e.g., the use of a backlight and a smoother surface finish facilitates edge detection). Utilization of the zigzag strategy further reduces cleaning time and reduces or eliminates the presence of residual particles adhering to the diaphragm surface. In summary, utilization of the zigzag strategy enables faster printing with better quality that meets key quality standards.

[0044] Figure 7 and Figure 8 The difference between a collimator printed using a conventional zigzag printing strategy and a custom zigzag printing strategy is illustrated. Figure 7 shows the output from using conventional printing strategies (e.g. Figure 5 Image 140 above of a portion of a collimator 142 printed using the dual vector strategy in FIG. Figure 8 Shown from the use of Figure 6 (and / or Fig. 9 and / or Fig.10 ). As depicted in image 140, the wall 148 of the collimator 142 has visible asymmetry. In addition, the wall 148 of the collimator 142 is rough and has density issues. In contrast, as depicted in image 144, the wall 150 of the collimator 146 is more asymmetric. In addition, the wall 150 is denser and smoother. Further, the wall 150 has fewer residual particles. The target wall thickness for both collimators 142, 146 is 150 microns.

[0045] As described above, multiple vectors may be utilized in 3D printing (eg, via LPBF) of a collimator (eg, made of tungsten) having a membrane or wall having a wall thickness greater than 100 microns. Fig. 9 A zigzag printing strategy (eg, using an alternating vector printing strategy) for printing the walls or membranes of a collimator is schematically shown. Fig. 9As depicted, the wall or diaphragm 112 of the collimator extends along direction 80 (e.g., the Y direction). Specifically, the wall or diaphragm 112 is printed in two portions or sections 152 and 154. Portions 152 and 154 are printed adjacent to each other and aligned along direction 80. The printing of portion 152 utilizes a zigzag printing strategy that alternates the use of two vectors when printing the layers of portion 152. The printing of portion 154 utilizes a zigzag printing strategy that alternates the use of the same two vectors (utilized in printing portion 152) but utilizes the two vectors in a different order when printing the layers of portion 154.

[0046] Wall or diaphragm 112 includes centerline 114 of both portion 152 and portion 154. Portion 152 is 3D printed in multiple layers 116, where each layer 116 is printed as a laser patch on top of other layers 116, so that portion 152 extends along direction 84 (e.g., Z direction). Each layer 116 includes a layer thickness 86 (e.g., Lt) in direction 84. Portion 152 includes a width 118 (e.g., wall thickness) extending along direction 90 (e.g., X direction) orthogonal to direction 80. Width 118 is greater than 100 microns. Centerline 114 is centered within width 118. Individual layers 116 of portion 152 are alternately printed using two different vectors (e.g., each portion of layer 116 uses a single vector). As depicted, an initial layer 120 (layer n) of portion 152 is printed along a first vector 122 (V1) in a first direction (i.e., Y direction 80) using a first vector exposure. The first vector 122 is offset from the center line 114 by half the distance of width 118 (or vector distance 136). The next layer 124 (layer n+1) of the portion 152 is printed on the initial layer 120 with a laser patch along the second vector 126 (V2) in a second direction 128 opposite to the first direction 80 using a second vector exposure. The second vector 126 is offset from the center line 114 by half the distance of width 118 (or vector distance 136). The first vector 122 and the second vector 126 are respectively disposed on opposite sides 130, 132 of the center line 114 when printing the portion 152. The layer 124 has the same thickness as the initial layer 120. The layers 120, 124 of the portion 152 together have a layer thickness 134 (2xL t ). Vector distance 136 (eg, L Dxy ) represents the distance between the first vector 122 and the second vector 126 along the direction 90. The vector distance 136 represents the distance moved between the first vector 122 and the second vector 126 to print the corresponding layer 116 of the portion 152. The vector distance 136 is determined based on a combination of laser power and laser speed to achieve the desired printing result. In this case, the vector distance 136 is the same as the width 118 of the wall 112.

[0047] Portion 154 is 3D printed in multiple layers 116 (corresponding to the same layers 116 in portion 152), wherein each layer 116 is printed as a laser patch on top of the other layers 116 such that portion 154 extends along direction 84 (e.g., Z direction). Each layer 116 of portion 154 also includes the same layer thickness 86 (e.g., Lt) in direction 84. Portion 154 includes the same width 118 (e.g., wall thickness) as portion 152 extending along direction 90 (e.g., X direction) orthogonal to direction 80. The individual layers 116 of portion 154 are alternately printed using the same two different vectors (e.g., each portion of layer 116 using a single vector) as used in printing portion 152. As depicted, an initial layer 120 (layer n) of portion 154 is printed along a second vector 126 (V2) in a second direction 128 opposite to first direction 80 using a second vector exposure. The second vector 126 is offset from the center line 114 by half the distance of width 118 (or vector distance 136). The next layer 124 (layer n+1) of the portion 154 is printed on the initial layer 120 with laser patching along the first vector 122 (V1) in the first direction 80 using the first vector exposure. The first vector 122 is offset from the center line 114 by half the distance of width 118 (or vector distance 136). The first vector 122 and the second vector 126 are respectively disposed on opposite sides 130, 132 of the center line 114 when printing the portion 154. The layer 124 has the same thickness as the initial layer 120. The layers 120, 124 of the portion 154 together have the same layer thickness 134 (2xL t ). Vector distance 136 (eg, L Dxy ) represents the distance between the first vector 122 and the second vector 126 along the direction 90. The vector distance 136 represents the distance moved between the first vector 122 and the second vector 126 to print the corresponding layer 116 of the portion 152. The vector distance 136 is determined based on a combination of laser power and laser speed to achieve the desired printing result. In this case, the vector distance 136 is the same as the width 118 of the wall 112. This printing strategy of utilizing alternating vectors when printing adjacent portions of the wall 112 reduces residual stress and improves the quality of the wall 112.

[0048] As described above, partial vectors may be utilized in 3D printing (e.g., via LPBF) of a collimator (e.g., made of tungsten) having a membrane or wall having a wall thickness greater than 100 microns, where the partial vectors enable the formation of joints or intersections between intersecting or orthogonal walls of the collimator. Fig.10 The overall zigzag printing strategy for forming the joints between the intersecting walls or membranes 156 and 158 of the collimator is schematically shown. Fig.11 Schematically shows the method for printing Fig.10Top view of the printing strategy for the initial layer 160 (layer n) of walls or membranes 156 and 158 in FIG. Fig.12 Schematically shows the method for printing Fig.10 Top view of the printing strategy for the next layer 162 (layer n+1) of walls or membranes 156 and 158 in FIG. Fig.13 Schematically shows the method for printing Fig.10 Top view of the printing strategy for an initial layer 160 and a next layer 162 of overlapping walls or membranes 156 and 158.

[0049] like Figures 10 to 13 As depicted, the collimator wall or membrane 156 extends in direction 80 (eg, the Y direction). The wall or membrane 156 includes a centerline 164. Figures 11 to 13 As depicted, the wall or diaphragm 158 of the collimator extends in direction 90 (e.g., X direction). The wall or diaphragm 158 includes a centerline 166. Both the wall 156 and the wall 158 are 3D printed in multiple layers 116, wherein each layer 116 is printed as a laser patch on top of the other layers 116, so that the wall or diaphragm 156 and the wall or 158 extend in direction 84 (e.g., Z direction). Each layer 116 of the wall 156 and the wall 158 includes a layer thickness 86 (e.g., Lt) in direction 84. The wall 156 and the wall 158 each include a width 118 (e.g., wall thickness) extending in directions 90 (e.g., X direction) and direction 80, respectively, which are orthogonal to each other. The width 118 is greater than 100 microns. The centerline 164 and the centerline 166 are centered within the corresponding width 118.

[0050] The individual layers 116 of each wall 156 and 158 are printed alternately using different vectors (each section of a particular layer 116 using a single vector). Fig.10 , Fig.11 and Fig.13As depicted, an initial layer 160 (layer n) of the wall 156 is printed along a first vector 168 for a portion of the wall 156 in the first direction 80 before switching to printing along a second vector 170 for another portion of the wall 156 in the first direction (i.e., the Y direction 80). Both the first vector 168 and the second vector 170 are offset from the centerline 164 by half the distance of the width 118 (or the vector distance 136 between the first vector 168 and the second vector 170). The first vector 168 and the second vector 170 are disposed on opposite sides 130, 132 of the centerline 164, respectively. In certain embodiments, a gap is formed when printing the wall 156 where printing switches between the first vector 168 and the second vector 170. Where printing switches between the first vector 168 and the second vector 170 is where the wall 156 and the wall 158 form a joint 171. Switching between the first vector 168 and the second vector 170 may occur multiple times in the first direction 80 at locations where the wall 156 will form a joint with another wall. The corresponding areas of the initial layer 160 of the wall 156 having the first vector 168 and the second vector 170 may be considered to be different adjacent sections of the wall 156 (thus, each layer of wall sections has a single vector).

[0051] like Fig.10 , Fig.11 and Fig.13 As depicted, an initial layer 160 (layer n) of the wall 158 is printed along a third vector 172 in a second direction 174 for a portion of the wall 158 before switching to printing along a fourth vector 176 in a second direction 174 (i.e., opposite the X direction 90) for another portion of the wall 158. Both the third vector 172 and the fourth vector 176 are offset from the centerline 166 by half the distance of the width 118 (or the vector distance 136 between the third vector 172 and the fourth vector 176). The third vector 172 and the fourth vector 176 are disposed on opposite sides 178, 180 of the centerline 166, respectively. In certain embodiments, a gap is formed when printing the wall 158, where printing switches between the third vector 172 and the fourth vector 176. Where printing switches between the third vector 172 and the fourth vector 176 is where the wall 156 and the wall 158 form a joint 171. Switching between the third vector 172 and the fourth vector 176 may occur multiple times in the second direction 174 at locations where the wall 158 will form a joint with other walls. Corresponding areas of the initial layer 160 of the wall 158 having the third vector 172 and the fourth vector 176 may be considered to be different adjacent segments of the wall 156 (thus, each layer of wall segments has a single vector).

[0052] The initial layer 160 of printing wall 156 using first vector 168 and second vector 170 intersects with the initial layer 160 of printing wall 158 using third vector 172 and fourth vector 176 at a location that forms joint 171. Specifically, the printing of initial layer 160 of wall 156 and wall 158 intersects at the respective vectors used to print the respective wall 156 and wall 158. In certain embodiments, to form joint 171, the printing of initial layer 160 of wall 156 fills the gap where the printing of wall 158 switches between third vector 172 and fourth vector 176, and the printing of initial layer 160 of wall 158 fills the gap where the printing of wall 156 switches between first vector 168 and second vector 170.

[0053] like Fig.10 , Fig.12 and Fig.13 As depicted, the next layer 162 (layer n+1) of the wall 156 is printed along the fifth vector 182 for a portion of the wall 156 in the third direction 184 before switching to printing along the sixth vector 186 for another portion of the wall 156 in the third direction 184 (i.e., opposite the Y direction 80). Both the fifth vector 182 and the sixth vector 186 are offset from the centerline 164 by half the distance of the width 118 (or the vector distance 136 between the fifth vector 182 and the sixth vector 186). The fifth vector 182 and the sixth vector 186 are disposed on opposite sides 130, 132 of the centerline 164, respectively. In certain embodiments, a gap is formed when printing the wall 156 where printing switches between the fifth vector 182 and the sixth vector 186. Where printing switches between the fifth vector 182 and the sixth vector 186 is where the wall 156 and the wall 158 form the joint 171. Switching between the fifth vector 182 and the sixth vector 186 may occur multiple times in the third direction 184 at locations where the wall 156 will form a joint with other walls. The corresponding areas of the next layer 162 of the wall 158 having the fifth vector 182 and the sixth vector 186 may be considered to be different adjacent segments of the wall 158 (thus, each layer of wall segments has a single vector).

[0054] like Fig.10 , Fig.12 and Fig.13As depicted, the next layer 162 (layer n+1) of the wall 158 is printed along the seventh vector 188 for a portion of the wall 158 in the fourth direction 90 before switching to printing along the eighth vector 190 for another portion of the wall 158 in the fourth direction (i.e., the X direction 90). Both the seventh vector 188 and the eighth vector 190 are offset from the centerline 166 by half the distance of the width 118 (or the vector distance 136 between the seventh vector 188 and the eighth vector 190). The seventh vector 188 and the eighth vector 190 are disposed on opposite sides 180, 178 of the centerline 166, respectively. In certain embodiments, a gap is formed when printing the wall 158, wherein printing switches between the seventh vector 188 and the eighth vector 190. Where printing switches between the seventh vector 188 and the eighth vector 190 is where the wall 156 and the wall 158 form the joint 171. Switching between the seventh vector 188 and the eighth vector 190 may occur multiple times in the fourth direction 90 at locations where the wall 158 will form a joint with other walls. The corresponding areas of the next layer 162 of the wall 158 having the seventh vector 188 and the eighth vector 190 may be considered to be different adjacent segments of the wall 158 (thus, each layer of wall segments has a single vector).

[0055] The next layer 162 of printing the wall 156 using the fifth vector 182 and the sixth vector 186 intersects the initial layer 160 of printing the wall 158 using the seventh vector 188 and the eighth vector 190 at a location where the joint 171 is formed. Specifically, the printing of the next layer 162 of the wall 156 and the wall 158 intersects at the respective vectors used to print the respective wall 156 and the wall 158. In certain embodiments, to form the joint 171, the printing of the next layer 162 of the wall 156 fills the gap where the printing of the wall 158 switches between the seventh vector 188 and the eighth vector 190, and the printing of the initial layer 160 of the wall 158 fills the gap where the printing of the wall 156 switches between the fifth vector 182 and the sixth vector 186.

[0056] As mentioned above, the collimator can be 3D printed using LPBF, which is also known as direct metal laser sintering (DMLS), selective laser melting (SLM), or direct metal printing (DMP). Fig.14An LPBF system 192 for printing a wall or diaphragm of a collimator is schematically shown. The LPBF system 192 includes a metal powder reservoir 194 (e.g., of tungsten powder) located on a powder platform 196 coupled to a piston 198. The LPBF system 192 also includes a powder bed 200 (e.g., of tungsten powder) located on a build platform 202 coupled to a piston 204. The LPBF system 192 further includes a powder roller 206 to transfer (e.g., spread) powder from the powder reservoir 194 to the powder bed 200 between the formation of layers of the wall or diaphragm 207 of the collimator. The LPBF system 192 still further includes a laser 208, which can direct the laser via a mirror 210 or directly onto the powder bed 200 to form the layers of the wall or diaphragm 207.

[0057] The LPBF system 192 still further includes a controller 212 coupled to the laser 208. The controller 212 includes a processor 214 (e.g., a processing circuit) and a memory 216 (e.g., a memory circuit). The processor 214 may include multiple microprocessors, one or more "general purpose" microprocessors, one or more special purpose microprocessors and / or one or more application specific integrated circuits (ASICS), system on a chip (SoC) devices, or some other processor configuration. For example, the processor 214 may include one or more reduced instruction set (RISC) processors or complex instruction set (CISC) processors. The processor 214 may execute instructions to perform various zigzag printing strategies as described above to form the walls or diaphragms of the collimator. These instructions may be encoded in a program or code stored in a tangible, non-transitory computer readable medium (e.g., an optical disk, a solid-state device, a chip, firmware, etc.), such as the memory 216. The controller 212 controls the operation of the laser 208 and the LPBF system 192.

[0058] To form the collimator wall or diaphragm 207, a layer of powder (e.g., tungsten powder) is spread on the build platform 202 (e.g., via powder roller 206). The laser 208 fuses this first layer of the wall or diaphragm 207. A new layer of powder is then spread over the previous layer (e.g., via powder roller 206), and another layer is fused and added to the initial layer. This process is repeated until the entire wall or diaphragm 207 is formed (i.e., the desired height of the wall or diaphragm is reached). The loose, unfused powder is then removed in a post-processing process.

[0059] The technical effects of the disclosed embodiments include providing a customized single-vector zigzag printing strategy for 3D printing of collimators (i.e., a single vector per layer of a given wall) that utilizes alternating vectors that are offset from the center of the diaphragm (e.g., wall) by half the vector distance in opposite directions. The technical effects of the disclosed embodiments also include forming an article (i.e., a collimator) with a smoother finish and higher density (wherein for a given thickness (i.e., greater than 100 microns), conventional processes would require a multi-vector strategy). The technical effects of the disclosed embodiments further include improving production capacity, unifying diaphragm properties, and enabling the printing of symmetrical walls. The technical effects of the disclosed embodiments even further include improving measurement capabilities due to the use of a backlight source and a smoother finish that facilitates edge detection when a collimator is utilized. The technical effects of the disclosed embodiments still further include reducing cleaning time and reducing / removing the presence of residual particles adhering to the surface of the diaphragm.

[0060] The technology presented and claimed herein is referred to and applied to physical and specific examples of a practical nature that clearly improves upon the present state of the art and, therefore, is not abstract, intangible, or purely theoretical. In addition, if any claim appended to the end of this specification contains one or more elements designated as "means for [performing] the function of ..." or "steps for [performing] the function of ...," it is intended that such elements be interpreted under 35 U.S.C. § 112(f). However, for any claim containing elements designated in any other manner, it is not intended that such elements be interpreted under 35 U.S.C. § 112(f).

[0061] This written description uses examples to disclose the subject matter, including the best mode, and also to enable those skilled in the art to practice the subject matter, including making and using any devices or systems and performing any included methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insignificant differences from the literal language of the claims.

Claims

1. A method for forming a metal grid structure, the method comprising: Use three-dimensional (3D) printing to: printing a first layer of a first wall segment of the metal grid structure in a first direction along a first vector, the first vector being offset from a first centerline of the first wall segment by half a first distance of a first width of the first wall segment orthogonal to the first centerline; as well as Printing a second layer of the first wall segment on the first layer in a second direction along a second vector, the second vector being offset from the first center line of the first wall segment by half of the first distance of the first width of the first wall segment, wherein the second direction is opposite to the first direction and the first vector and the second vector are arranged on opposite sides of the first center line. 2 . The method of claim 1 , further comprising printing layers of the first wall segment alternately in the first direction along the first vector and in the second direction along the second vector until a desired height of the first wall segment is reached.

3. The method of claim 2, further comprising alternately printing corresponding layers of a plurality of walls of the metal grid structure in the first direction along the first vector and in the second direction along the second vector until a desired height of each of the plurality of walls is reached, wherein the first vector and the second vector utilized in printing each wall are offset from and disposed on opposite sides of a corresponding first centerline of each wall.

4. The method of claim 1, further comprising utilizing 3D printing to: printing a first layer of a second wall segment of the metal grid structure in a third direction along a third vector that is offset from a second centerline of the second wall segment by half a second distance of a second width of the second wall segment that is orthogonal to the second centerline; and Printing a second layer of the second wall segment on the first layer in a fourth direction along a fourth vector, the fourth vector being offset from the second center line of the second wall segment by half of the second distance of the second width of the second wall segment, wherein the fourth direction is opposite to the third direction, the third vector and the fourth vector are disposed on opposite sides of the second center line, and both the third direction and the fourth direction are orthogonal to both the first direction and the second direction. 5 . The method of claim 4 , further comprising alternately printing layers of the second wall segment in the third direction along the third vector and in the fourth direction along the fourth vector until a desired height of the second wall segment is reached. The method of claim 4 , wherein the first wall segment and the second wall segment are joined at an intersection.

7. The method of claim 1, further comprising utilizing 3D printing to: printing a first layer of a second wall segment of the metal grid structure in the second direction along the second vector; and A second layer of the second wall segment is printed on the first layer in the first direction along the first vector, wherein the first wall segment and the second wall segment are adjacent to each other and aligned along the first direction.

8. The method of claim 1, wherein the first vector and the second vector comprise unique vectors along the first direction and the second direction, respectively, for printing the first wall segment.

9. The method of claim 1, wherein the metal grid structure comprises an anti-scatter grid or a collimator configured for use with an X-ray detector of an X-ray imaging system.

10. The method of claim 9, wherein the metal grid structure comprises tungsten.

11. The method of claim 1 , wherein the 3D printing comprises laser powder bed fusion.

12. The method of claim 1, wherein the first distance of the first width of the first wall segment is greater than 100 microns.

13. A method for forming a collimator configured for use with an X-ray detector of an X-ray imaging system, the method comprising: Use three-dimensional (3D) printing to: printing the layers of the first set of diaphragms of the collimator extending along a first direction by alternately utilizing a first vector and a second vector when printing the layers of the first set of diaphragms, wherein the first vector and the second vector are oriented in opposite directions along the first direction, are disposed on opposite sides of a first centerline of respective diaphragms of the first set of diaphragms, and are offset from the first centerline by a first distance of half a first width of the respective diaphragms of the first set of diaphragms; as well as The layers of the second group of diaphragms of the collimator extending along a second direction are alternately printed by alternately utilizing a third vector and a fourth vector when printing the layers of the second group of diaphragms, wherein the third vector and the fourth vector are oriented in opposite directions along the second direction and are disposed on opposite sides of a second centerline of respective diaphragms of the second group of diaphragms and are offset from the second centerline by a second distance of half a second width of the respective diaphragms of the second group of diaphragms, wherein the first direction is orthogonal to the second direction.

14. The method of claim 13, further comprising alternately printing the layers of both the first set of diaphragms and the second set of diaphragms until a desired height of both the first set of diaphragms and the second set of diaphragms is reached.

15. The method of claim 13, wherein the first set of diaphragms and the second set of diaphragms are joined at an intersection. The method of claim 13 , wherein the collimator comprises tungsten.

17. The method of claim 13, wherein the first distance and the second distance are each greater than 100 microns.

18. A system for forming a collimator configured for use with an X-ray detector of an X-ray imaging system, the system comprising: a memory encoding a processor-executable routine; and a processing circuit configured to access the memory and execute the processor-executable routine, wherein the routine, when executed by the processing circuit, causes the processing circuit to: Use three-dimensional (3D) printing to: printing the layers of the first set of diaphragms of the collimator extending along a first direction by alternately utilizing a first vector and a second vector when printing the layers of the first set of diaphragms, wherein the first vector and the second vector are oriented in opposite directions along the first direction, are disposed on opposite sides of a first centerline of respective diaphragms of the first set of diaphragms, and are offset from the first centerline by a first distance of half a first width of the respective diaphragms of the first set of diaphragms; as well as The layers of the second group of diaphragms of the collimator extending along a second direction are alternately printed by alternately utilizing a third vector and a fourth vector when printing the layers of the second group of diaphragms, wherein the third vector and the fourth vector are oriented in opposite directions along the second direction and are disposed on opposite sides of a second centerline of respective diaphragms of the second group of diaphragms and are offset from the second centerline by a second distance of half a second width of the respective diaphragms of the second group of diaphragms, wherein the first direction is orthogonal to the second direction.

19. The system of claim 18, wherein the first distance and the second distance are each greater than 100 microns.

20. The system of claim 19, wherein the first set of diaphragms and the second set of diaphragms are joined at an intersection.

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