A pre-collimator with built-in alignment mechanism.

Abstract

To provide a pre-patient collimator for a CT imaging system.SOLUTION: The pre-patient collimator includes a collimator housing including multiple walls, where the multiple walls include a first wall configured to face an X-ray source when the pre-patient collimator is coupled to the CT imaging system, and a second wall and a third wall located at both sides of the first wall. The pre-patient collimator also includes a bowtie filter assembly disposed within the collimator housing and including a bowtie filter. The pre-patient collimator further includes an adjustment mechanism configured to move the bowtie filter assembly in a lateral direction between the second wall and the third wall within the collimator housing.SELECTED DRAWING: Figure 19

Description

[Technical field]

[0001] The subject matter disclosed herein relates to medical imaging systems and, more particularly, to pre-collimators having additively manufactured components. [Background technology]

[0002] In computed tomography (CT), x-rays are propagated through an object of interest, such as a patient, some of which strike a detector and image data is collected. In digital x-ray systems, a photodetector generates a signal that represents the amount or intensity of radiation that strikes individual pixel areas on the detector surface. This signal is then processed to generate an image, which may be displayed and examined. The images generated by such systems allow structures and organs within the patient's body to be identified and examined. In CT systems, the detector array includes a series of detector elements or sensors that generate similar signals at various locations as the gantry moves around the patient, allowing volumetric reconstructions to be obtained.

[0003] CT imaging systems can include a pre-collimator to ensure that the subject of interest receives the intended dose. The collimator blades of the pre-collimator are adjusted in front of the x-ray source so that the appropriate opening or aperture is set and x-rays pass through, and the scan set by the operator is performed. Adjusting the pre-patient collimator is key to obtaining a precisely shaped x-ray beam to obtain high quality images of the patient. Typically, during system adjustment, the x-ray filter (such as a bowtie filter) must be adjusted to center the x-ray beam. This requires moving the entire collimator (which is usually very heavy) or removing multiple components of the collimator (e.g., covers) to move the x-ray filter. In some cases, the x-filter must be removed during system adjustment (e.g., during an air scan), which is a tedious and time-consuming procedure. Summary of the Invention [Problem to be solved by the invention]

[0004] Certain embodiments commensurate in scope with the originally claimed subject matter are summarized below. These embodiments are not intended to limit the scope of the claimed subject matter, but rather are intended only to provide a brief summary of possible forms of the subject matter. Indeed, the subject matter may encompass a variety of forms that may be similar to or different from the embodiments set forth below. [Means for solving the problem]

[0005] In one embodiment, a pre-collimator for a CT imaging system is provided. The pre-collimator includes a collimator housing including a plurality of walls. The plurality of walls includes a first wall configured to face an X-ray source when the pre-collimator is coupled to the CT imaging system, and a second wall and a third wall located on either side of the first wall. The pre-collimator also includes a bowtie filter assembly disposed within the collimator housing and including a bowtie filter. The pre-collimator further includes an adjustment mechanism configured to laterally move the bowtie filter assembly between the second wall and the third wall within the collimator housing.

[0006] In another embodiment, the collimator for a CT imaging system is provided, the collimator including a collimator housing, the pre-collimator including a bowtie filter assembly disposed within the collimator housing and including a bowtie filter, the pre-collimator further including an adjustment mechanism configured to move the bowtie filter assembly in a first direction and a second direction within the collimator housing, the movement of the bowtie filter assembly in the first direction being independent of the movement of the bowtie filter assembly in the second direction, the first direction and the second direction being orthogonal to one another.

[0007] A further embodiment is a method of centering a bowtie filter of a collimator, the method including acquiring, in a processor, air scan data obtained by performing an air scan using a computed tomography (CT) imaging system with a bowtie filter moved out of view of an x-ray beam emitted by an x-ray source of the CT imaging system prior to an air scan to acquire air scan data, the bowtie filter being disposed in a bowtie filter assembly disposed in a collimator housing, the bowtie filter assembly being configured to be movable within the collimator housing in a first direction and a second direction, the first direction being orthogonal to the second direction, and acquiring, in the processor, alignment data obtained by performing an air scan using the CT imaging system with the bowtie filter moved in the second direction to be in the scan plane prior to an alignment scan to acquire the air scan data. The method further includes calculating, by the processor, an offset distance of the bowtie filter from a beamline path of the x-ray beam. The method further includes comparing, by the processor, the offset distance to a tolerance range for a desired center location of the bowtie filter within the x-ray beam. If the offset distance is outside the tolerance range, the method further includes calculating, by the processor, a distance to move the bowtie filter in the second direction such that the bowtie filter is centered in the x-ray beam. The method further includes, in response to a control signal from the processor, moving the bowtie filter the distance in the second direction.

[0008] These and other features, aspects and advantages of the present invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which like characters represent like parts throughout. [Brief description of the drawings]

[0009] [Figure 1] 1 shows a combination volume and block diagram of a computed tomography (CT) imaging system as described herein. [Diagram 2] 1 is a schematic diagram of an X-ray source and a multi-row X-ray detector (e.g., viewed in the XY plane) according to an embodiment of the present disclosure. [Diagram 3] 1 is a schematic diagram of an X-ray source and a multi-row X-ray detector (e.g., viewed in the YZ plane) according to an embodiment of the present disclosure. [Figure 4] FIG. 13 is a perspective view of additively manufactured components of a collimator according to aspects of the present disclosure positioned on a print bed. [Diagram 5] FIG. 13 is a cross-sectional view of a portion of a wall of an additively manufactured component of a collimator (e.g., of solid construction) according to an embodiment of the present disclosure. [Figure 6] FIG. 13 is a cross-sectional view of a portion of a wall of an additively manufactured component of a collimator (e.g., of a lattice structure) according to an embodiment of the present disclosure. [Figure 7] 1A-1D are different perspective views of an additively manufactured collimator housing according to aspects of the present disclosure. [Figure 8] 1A-1D are different perspective views of an additively manufactured collimator housing according to aspects of the present disclosure. [Figure 9] 1A-1D are different perspective views of an additively manufactured collimator housing according to aspects of the present disclosure. [Figure 10] 1A-1D are different perspective views of an additively manufactured collimator housing according to aspects of the present disclosure. [Figure 11] FIG. 11 illustrates stress distribution in the collimator housing of FIGS. 7-10 according to an embodiment of the present disclosure. [Figure 12] 11 is a deformation plot of the collimator housing in FIGS. 7-10 according to an embodiment of the present disclosure. [Figure 13] FIG. 13 is a perspective view of an additively manufactured aperture transfer plate according to aspects of the present disclosure. [Figure 14] FIG. 14 is a side view of the additively manufactured aperture transfer plate of FIG. [Figure 15] FIG. 14 is a cross-sectional view of a portion of the additively manufactured aperture transfer plate of FIG. 13 along line AA. [Figure 16] FIG. 14 is a perspective view of a portion of the mounting bracket of the additively manufactured aperture transfer plate of FIG. [Figure 17] FIG. 14 is a perspective view of a mounting bracket of the additively manufactured transfer plate of FIG. 13 , the mounting bracket coupled to an actuator, according to an embodiment of the present disclosure. [Figure 18] FIG. 14 is a perspective view of another mounting bracket of the additively manufactured transfer plate of FIG. 13 , the mounting bracket being coupled to an actuator, according to an embodiment of the present disclosure. [Figure 19] FIG. 13 is an exploded perspective view of a built-in alignment mechanism for moving a bowtie filter assembly within a collimator housing, according to an aspect of the present disclosure. [Figure 20] FIG. 2 is a perspective see-through view of a collimator housing with a bowtie filter assembly residing within and coupled to a built-in alignment mechanism in accordance with an aspect of the present disclosure. [Figure 21] FIG. 21 is a front view of the collimator housing of FIG. 20 with the bowtie filter assembly present within and coupled to the built-in alignment feature (e.g., with the bowtie filter assembly proximate to the second wall of the collimator housing). [Figure 22] FIG. 21 is a front view of the collimator housing of FIG. 20 with the bowtie filter assembly present within and coupled to the built-in alignment feature (e.g., with the bowtie filter assembly proximate to the third wall of the collimator housing). [Diagram 23] FIG. 1 is a cross-sectional side view of a collimator housing according to an aspect of the present disclosure, showing a bowtie filter assembly residing within and coupled to a built-in alignment mechanism (e.g., the bowtie filter assembly is located in the scan plane). [Figure 24]FIG. 24 is a perspective view of the collimator housing of FIG. 23 with the bowtie filter assembly residing within and coupled to the built-in alignment mechanism (e.g., the bowtie filter assembly is positioned in the scan plane). [Diagram 25] FIG. 24 is a cross-sectional side view of the collimator housing of FIG. 23 with the bowtie filter assembly residing within and coupled to the built-in alignment mechanism (e.g., the bowtie filter assembly is located outside the scan plane). [Figure 26] FIG. 24 is a perspective view of the collimator housing of FIG. 23 with the bowtie filter assembly residing within and coupled to the built-in alignment mechanism (e.g., the bowtie filter assembly is located outside the scan plane). [Figure 27] FIG. 2 is a perspective view of a pre-collimator according to an aspect of the present disclosure. [Figure 28] FIG. 13 is an exploded view of another built-in alignment mechanism for moving a bowtie filter assembly within a collimator housing, according to aspects of the present disclosure. [Figure 29] FIG. 13 is a front perspective view of a collimator housing with a bowtie filter assembly residing within and coupled to a built-in alignment mechanism (e.g., showing transverse movement of the bowtie filter assembly) according to an aspect of the disclosure. [Diagram 30] FIG. 13 is a rear perspective view of a collimator housing with a bowtie filter assembly residing within and coupled to a built-in alignment mechanism (e.g., showing lateral movement of the bowtie filter assembly) according to an aspect of the present disclosure. [Diagram 31] FIG. 2 is a perspective view of an assembled pre-collimator according to an aspect of the present disclosure. [Diagram 32] FIG. 13 is an exploded view of another built-in alignment mechanism for moving a bowtie filter assembly within a collimator housing, according to aspects of the present disclosure. [Diagram 33]33 is a schematic diagram illustrating the manipulation of the guide pin of the built-in alignment mechanism of FIG. 32 between a locked position and an unlocked position, according to an embodiment of the present disclosure. FIG. [Diagram 34] FIG. 2 is a perspective view of an assembled pre-collimator according to an aspect of the present disclosure. [Diagram 35] 1 is a flowchart of a method for centering a bowtie filter according to an aspect of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] One or more specific embodiments are described below. As it is intended to provide a concise description of these embodiments, not all features of an actual implementation are described herein. It should be understood that the development of any actual implementation, like any engineering or design project, requires numerous implementation-specific decisions to be made to achieve the developer's particular goals (such as compliance with system-related and business-related constraints that may vary from implementation to implementation). Moreover, it should be understood that such a development effort may be complex and time-consuming, but would be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill in the art having the benefit of this disclosure.

[0011] When introducing elements of various embodiments of the subject matter, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the element. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Furthermore, any numerical examples in the following description are intended to be non-limiting, and therefore other numerical values, ranges, and percentages are within the scope of the disclosed embodiments.

[0012] Although aspects of the following discussion are described in the context of medical imaging, it should be understood that the present technology is not limited to such a medical context. Indeed, the embodiments are shown and described in such a medical context merely to facilitate explanation by providing examples of real-world implementations and applications. However, the present technique can also be utilized in other contexts, such as tomographic image reconstruction for industrial computed tomography (CT) used in non-destructive testing of manufactured parts or goods (i.e., quality control or quality screening applications), and / or non-invasive inspection of packages, boxes, luggage, and the like (i.e., security or screening applications). In general, the present technique is believed to be useful in imaging or screening contexts or image processing fields, such as those utilizing collimators to control the size of an x-ray beam.

[0013] The present disclosure provides a built-in alignment mechanism disposed within a pre-collimator (e.g., an additively manufactured pre-collimator) for enabling accurate and easy adjustment of the collimator (e.g., adjustment of a bowtie filter integrated with the pre-collimator) during system alignment. In particular, the built-in alignment mechanism allows the bowtie filter to be independently adjusted laterally and transversely (e.g., centered with respect to the x-ray beam path to provide very good image quality). The configuration of the built-in alignment mechanism also allows adjustment of the bowtie filter from outside the collimator housing (e.g., via an actuator mechanism) without removing or disassembling a sub-component (e.g., the bowtie filter) from the collimator during system alignment. Furthermore, the built-in alignment mechanism can be utilized with different types of bowtie filters and is extensible for utilization with different imaging platforms.

[0014] With the above in mind, reference is now made to FIG. 1. As an example, a CT imaging system 10 is shown. The CT imaging system includes a gantry 12. The gantry 12 has an x-ray source 14. The x-ray source 14 projects a beam of x-rays 16 towards a detector assembly 15 on the opposite side of the gantry 12. The x-ray source 14 projects the beam of x-rays 16, which passes through a pre-collimator or collimator assembly 13, which determines the size of the beam of x-rays 16. The detector assembly 15 includes a collimator assembly 18 (or post-collimator assembly), a number of detector modules 20 (e.g., detector elements or sensors), and a data acquisition system (DAS) 32. The multiple detector modules 20 detect the projected x-rays that pass through a patient 22, and the DAS 32 converts the data into digital signals for further processing. Each detector module 20 in a conventional system generates an analog electrical signal that represents the intensity of the impinging x-ray beam, and hence the intensity of the beam attenuated as it passes through the patient 22. During a scan to acquire x-ray projection data, gantry 12 and the components mounted on gantry 12 rotate about a center of rotation 25 (e.g., an isocenter) to collect attenuation data from multiple view angles relative to the imaging volume.

[0015] Rotation of gantry 12 and operation of x-ray source 14 are governed by a control mechanism 26 of CT system 10. Control mechanism 26 includes an x-ray controller 28, which provides power and timing signals to x-ray source 14, a collimator controller 29, which controls the width of the aperture in pre-collimator 13 (and thus the size of x-ray beam 16), and a gantry motor controller 30, which controls the rotational speed and position of gantry 12. An image reconstructor 34 receives sampled and digitized x-ray data from DAS 32 and performs high speed reconstruction. The reconstructed image is provided as an input to a computer 36, which stores the image in a mass storage device 38. Computer 36 also receives commands and scanning parameters from an operator through a console 40. An associated display 42 allows the operator to view the reconstructed image and other data from computer 36. The operator provided commands and parameters are used by computer 36 to provide control signals and information to DAS 32, x-ray controller 28, collimator controller 29, and gantry motor controller 30. In addition, computer 36 operates a table motor controller 44. Table motor controller 44 controls a motorized table 46 to position patient 22 and gantry 12. In particular, table 46 moves a portion of patient 22 through an opening or bore 48 in the gantry.

[0016] With the above description of the overall imaging system 10 in mind, and referring to FIGS. 2 and 3, an example of an X-ray source 14 and a detector assembly 15 (e.g., an X-ray detector having multiple rows 50) are illustrated in the XY (FIG. 2) and YZ (FIG. 3) planes. For ease of illustration, the gantry 12 rotating with the X-ray source 14 is rotated from the position shown in FIG. 1 to above the gantry (+Y direction). As illustrated, the pre-collimator 13 is disposed between the X-ray source 14 and the detector assembly 15 and determines the shape of the X-ray beam 52. In particular, an opening or aperture 54 (shown in FIG. 3) between a pair of collimator blades 56 of the pre-collimator 13 shapes the X-ray beam 52. Also illustrated is the field of view 24 and the beam width 58, which corresponds to the size of the X-ray beam 52 intended to scan the patient. Proper positioning of the collimator blades 56 is important to ensure that the patient receives the proper radiation dose and that the proper area is scanned. The shape of the blade 56 is shown from different directions in Figures 2 and 3. By way of example, the blade 56 is generally curved in the XY plane and has a circular tip in the YZ plane that determines the beam size. Many other shapes are possible for the blade shape in the XY plane, including flat and angled, and the tip shape in the YZ plane may also be rectangular or triangular, for example.

[0017] FIG. 4 is a perspective view of the additively manufactured components of the pre-collimator disposed on the print bed 60. As shown in FIG. 4, the additively manufactured components of the collimator include a collimator housing 62, an aperture transfer plate 64, a motor mounting plate 66, and a sensor plate 68. In certain embodiments, other components of the collimator may be additively manufactured (e.g., a bowtie filter, a plate or cover for housing the bowtie filter, a cover plate for the collimator housing 62, etc.). The layout of the additively manufactured components on the print bed is one example of a layout configuration for additive manufacturing or three-dimensional (3D) printing of the collimator components. Other layout configurations may be utilized. Each additively manufactured component is made of lead-free material (e.g., to mitigate operational hazards that may arise from the presence of lead). In certain embodiments, the components may be formed of metallic materials (e.g., by direct metal laser sintering). In certain embodiments, some or all of the additively manufactured components may be manufactured with a solid structure 70, as shown in FIG. 5. For example, the entire sensor plate 68 is fabricated with a solid structure. The solid structure can act to block x-rays. In certain embodiments, some or all of the additively manufactured components can be fabricated with a lattice structure 72, as shown in FIG. 6. For example, the entire motor mounting plate 66 can be fabricated with a lattice structure. The lattice structure can reduce weight. The lattice structure can include a honeycomb structure or other lattice structure. As described in more detail below, some of the collimator housing 62 and the aperture transfer plate 64 are fabricated with a lattice structure and other portions are fabricated with a solid structure.

[0018] 7-10 are different perspective views of the additively manufactured collimator housing 62. The collimator housing 62 includes a plurality of walls, including a first wall 74 configured to face an x-ray source when the collimator is coupled to a gantry, a second wall 76 and a third wall 78 located on either side of the first wall 74, and a fourth wall 80 extending between the second wall 76 and the third wall 78 and adjacent to the first wall 74. Each wall 74, 76, 78, 80 includes a structural rib 82 (e.g., a structural rib integral to the respective wall 74, 76, 78, 80) that extends along at least one edge 84 of the wall 74, 76, 78, 80. For example, the first wall 74 includes a single structural rib 86 that extends along the entire edge 88. The second wall 76 includes a first structural rib 90 that extends along the entire first edge 92 (and extends from the rib 86) and a second structural rib 94 that extends along the entire second edge 96 (and extends from the rib 90). The third wall 78 includes a first structural rib 98 that extends along the entire first edge 100 (and extends from the rib 86) and a second structural rib 102 that extends along the entire second edge 104 (and extends from the rib 98). The fourth wall 80 includes ribs 94 and 102 that extend along portions of the edge 106 adjacent the second wall 76 and the third wall 78. The structural rib 86 eliminates stress concentrations at the corners of the collimator housing 62 and reduces deflection. Additionally, the rib 82 serves as a mounting surface for coupling the cover to the collimator housing 62.

[0019] Additional structural ribs 108 (e.g., structural ribs integral with the first wall 74) are disposed on the inner surface of the first wall 74 and protrude toward the interior space 110 of the collimator housing 62. The structural ribs 108 extend around an opening 112 to receive the X-ray beam from the X-ray source when the collimator is coupled to the gantry and the X-ray source. In particular, the structural ribs 108 extend between structures 114 (e.g., structures integral with the first wall 74) that allow the collimator housing 62 to be coupled to the X-ray source via fasteners. The structures 114 also protrude toward the interior space 110. The structural ribs 108 reduce both deflection and stress due to the centrifugal force of the tube (X-ray source). The structural ribs 108 also contribute to the stiffness of the collimator housing 62. The structural ribs 108 are designed to be self-supporting during additive manufacturing.

[0020] The effect of the structural ribs 86, 108 on the deflection and stress of the collimator housing 62 is shown in Figures 11 and 12, which are plots of the stress and deformation of the collimator housing 62 when it is coupled to a gantry and subjected to various load forces during gantry rotation, respectively. The ribs 86, 108 impart a uniform stress distribution across the collimator housing 62, as shown in Figure 11, with only localized stresses seen in small areas. The ribs 86, 108 also impart a uniform and symmetric deflection to the collimator housing 62, as shown in Figure 12.

[0021] 7 to 10, a receptacle 116 (e.g., a receptacle integrated with the first wall 74) disposed on the inner surface of the first wall 74 is disposed on the side of the opening 112 and is configured so that a guide for moving the bowtie filter assembly can pass through the receptacle 116. The receptacle 116 also protrudes toward the internal space 110.

[0022] Further, the stiffeners 118 (the stiffeners 118 are, for example, integral with the fourth wall 80) are disposed on the inner surface of the fourth wall 80. As shown, the stiffeners 118 are formed to have an X pattern. The pattern formed by the stiffeners 118 can be in various patterns. The stiffeners 118 add or impart rigidity to the collimator housing 62. Furthermore, the stiffeners 118 can prevent the collimator housing 62 from warping or shrinking during manufacturing and post-processing operations. The stiffeners 118 extend between the structures 120 (the structures 120 are, for example, integral with the fourth wall 80) that allow the collimator housing 62 to be coupled to the gantry bearing. Some of the structures 120 are also partially disposed on the inner surface of either the second wall 76 or the third wall 78. The structures 120 also protrude toward the interior space 110. An additional structure 122 present on the inner surface of the fourth wall 80 (the additional structure 122 is, for example, integral with the fourth wall 80) protrudes toward the interior space 110 and is configured to receive fasteners that couple the bowtie filter assembly to the collimator housing 62.

[0023] Furthermore, a side structure 124 (the side structure 124 is, for example, integrated with the second wall 76) present on the inner surface of the second wall 76 protrudes toward the internal space 110. The side structure 124 is configured to be coupled to a rail guide (for example, directly to the rail guide) and an actuator (for example, indirectly to the actuator via the rail guide) to move the aperture transfer plate. A side structure 126 (the side structure 126 is, for example, integrated with the third wall 78) disposed on the inner surface of the third wall 78 protrudes toward the internal space 110. Also, the side structure 126 is configured to be coupled to a rail guide (for example, directly to the rail guide) and an actuator (for example, indirectly to the actuator via the rail guide) to move the aperture transfer plate.

[0024] In certain embodiments, the portions of the structures protruding from the interior surface of the walls 74, 76, 78, and 100 may be located in different regions or may not be present. Furthermore, because of the ribs 82 along the edges and other structures protruding from the walls 74, 76, 78, and 80 toward the interior space 110, the thickness 128 of each of the walls 74, 76, 78, and 80 may vary according to the length of the ribs or other structures. Also, for certain walls, such as the fourth wall 80, in areas where no structures or ribs are located, the thickness 128 of the fourth wall varies, as shown in FIG. 10. Furthermore, the thickness 128 of each of the walls 74, 76, 78, and 80 may be approximately 3.5 millimeters (in areas where no structures or ribs are located) (which is approximately 5 to 35 percent of the thickness of a typical collimator housing wall).

[0025] Furthermore, a portion of the collimator housing 62 is manufactured with a solid structure (as shown in FIG. 5 ) and a portion of the collimator housing 62 is manufactured with a lattice structure (as shown in FIG. 6 ). With respect to the first wall 74, the structure 114 and the rib 108 are manufactured with a solid structure, and the rib 88, the receptacle 116, and the remaining portion of the first wall are manufactured with a lattice structure. With respect to the second wall 76, the first portion 130 of the side structure 124 (the first portion 130 is, for example, directly connected to the rail guide) and the ribs 90, 94 are manufactured with a lattice structure. The second portion 132 of the side structure 124 (the second portion 132 is, for example, closest to the inner surface of the second wall 76) and the remaining portion of the second wall 76 are manufactured with a solid structure. With respect to the third wall 78, the ribs 98, 102, the side structure 126, and the corner 134 of the third wall 78 are manufactured with a lattice structure. The remainder of the third wall 78 is fabricated from a solid construction. With respect to the fourth wall 80, the portions along the edges 106 of the ribs 94, 102 are fabricated from a lattice construction. The remainder of the fourth wall 80 (including the stiffeners 118, the structures 120, and the structures 122) is fabricated from a solid construction.

[0026] The use of solid construction in portions of the walls 74, 76, 78, and 80 provides a tight, integrated X-ray shield, eliminating the need to attach additional attenuating material to the collimator housing 62. The tight X-ray shielding prevents X-rays from escaping the pre-collimator except through the apertures in the aperture transfer plate 64. The use of a lattice construction allows the collimator housing 62 and the collimator to be lightweight. For example, the collimator housing 62 may weigh approximately 3.3 kilograms (kg), which is approximately 23.5 percent of the weight of a typical collimator housing. In addition, the footprint (area) of the collimator housing 62 and the collimator is reduced. The reduced footprint and weight of the collimator allows the collimator to be handled with one hand and easily rotated (torqued) when coupled to the gantry.

[0027] 13 and 14 are diagrams of an additively manufactured aperture transfer plate 64. The aperture transfer plate 64 includes a plate portion 136 and a mounting bracket 138 integrated as a single piece. The plate portion 136 includes a number of apertures 140 having different widths 142. Which openings 140 are utilized during radiation emission determines the size of the x-ray beam emitted from the collimator. The plate portion 136 has a thickness 143 that varies along its length. The plate portion 136 is manufactured of a solid construction (to attenuate x-rays) as shown in FIG. 15. Returning to FIGS. 13 and 14, mounting brackets 138 are provided at the longitudinal ends 144, 146 of the plate portion 136. Each mounting bracket 138 includes a first portion 148 extending perpendicular to the plate portion 136 and a second portion 150 extending parallel to the plate portion 136 and toward the other mounting bracket 138. Because the first and second portions 148, 150 are not critical to the attenuation of x-rays, both portions 148, 150 are fabricated with a lattice structure. Figure 16 shows the lattice structure of the second portion 150 of the mounting bracket 138.

[0028] The second portion 150 of the mounting bracket 138 is configured to be attached to an actuator and rail guide that moves (e.g., mechanically or electrically) the aperture transfer plate 64 in and out of the path of the x-ray beam. FIG. 17 shows the second portion 150 of the mounting bracket 152 (see FIGS. 13 and 14 ) coupled (e.g., via fasteners) to an actuator 154 that is coupled to a rail guide 156. The rail guide 156 is coupled to a side structure 124 in the collimator housing 62. The actuator 154 moves along the rail guide 156 to move the aperture transfer plate 64. FIG. 18 shows the second portion 150 of the mounting bracket 158 ​​(see FIGS. 13 and 14 ) coupled (via fasteners) to an actuator 160 that is coupled to a rail guide 162. The rail guide 162 is coupled to a side structure 126 in the collimator housing 62. The actuators may be driven by a motor that drives both actuators 154 , 160 to move along their respective rail guides 156 , 162 and thus the aperture transfer plate 64 .

[0029] 13 and 14, the additively manufactured aperture transfer plate 64 may weigh approximately 0.3 kg, which is approximately 23 percent of the weight of the components that make up a typical aperture transfer plate in a typical collimator. Additively manufacturing the laminated transfer plate 64 eliminates the need for spacer blocks and pins that are typically utilized to mount an aperture transfer plate in a typical collimator.

[0030] The use of additively manufactured components can result in significant mass reduction (e.g., 70% mass reduction compared to a typical collimator (e.g., a low-cost collimator)), assembly time reduction (e.g., 50% reduction compared to a typical collimator), cost reduction (e.g., 25% reduction compared to a typical collimator), and part count efficiencies (e.g., 81% reduction compared to a typical collimator). Furthermore, the use of additively manufactured components to reduce the mass of the collimator reduces the mass of the rotating CT gantry, which in turn reduces the power consumed by the gantry drive, resulting in significant operational cost reductions (e.g., 17%-18% reduction compared to a typical collimator).

[0031] In addition to the additively manufactured components, the pre-collimator disclosed herein includes a built-in alignment mechanism for adjusting the positioning of the bowtie filter assembly. FIG. 19 is an exploded view of the built-in alignment mechanism 164 for moving the bowtie filter assembly 166 within the collimator housing 62. The bowtie filter assembly 166 includes a base plate or filter mounting plate 168, a bowtie filter 170 (e.g., a bowtie filter manufactured using polytetrafluoroethylene), and a cover 172 (e.g., a front cover). The base plate 168 supports the bowtie filter 170 and the built-in alignment mechanism 164 components. The base plate 168 and the cover 172 partially surround the bowtie filter 170. The cover 172 does not extend around the top and bottom of the bowtie filter 170. A radiation shielding layer 174 (e.g., a shielding layer made using a tungsten-based polymer) is disposed on a surface of the base plate 168 that forms a direct interface with the bowtie filter 170. A radiation shielding layer 176 is disposed on a surface of the cover 172 that forms a direct interface with the bowtie filter 170. The base plate 168 and the cover 172 are configured to accommodate different types of bowtie filters 170. The bowtie filter 170 is coupled or attached to the base plate 168 via fasteners 178 (e.g., screws) that pass through corresponding openings in the bowtie filter 170 and the base plate 168. The cover 172 is coupled or attached to the base plate 168 to surround the bowtie filter 170 via fasteners (e.g., screws, not shown) that pass through corresponding openings in the cover 172 and the base plate 168.

[0032] The built-in alignment mechanism 164 includes an adjustment mechanism 180 configured to move the bowtie filter 170 in a first direction 182 (e.g., lateral or X-direction) and a second direction 184 (e.g., transverse or Z-direction, which is the same direction as the movement of the CT table). The movement in the lateral direction 182 is independent of the movement in the transverse direction 184. The movement in the lateral direction 182 occurs between the second wall 76 and the third wall 78 of the collimator housing 62. The movement in the transverse direction 184 occurs toward and away from the fourth wall 80 of the collimator housing 62. The lateral direction 182 is perpendicular to the transverse direction 184.

[0033] The adjustment mechanism 180 includes a frame 186 that is part of and extends from the base plate 168. The single frame 186 allows for movement in both the lateral direction 182 and the transverse direction 184 independently of one another. The frame 186 extends in a direction 184 parallel to the second wall 76 and the third wall 78. The frame 186 includes a slot 188 and a pair of openings 190, 192. The slot 188 is located closer to the fourth wall 80 of the collimator housing 62 than the openings 190, 192.

[0034] The built-in alignment mechanism 164 includes polymer guides 194, 196, 198 for moving the bowtie filter assembly 166. A portion (e.g., a threaded portion) of each of the polymer guides 194, 196 passes through an opening in the base plate 168 and is coupled to the base plate 168 via a fastener 200 (e.g., a nut) on the back side of the base plate 168. The polymer guides 194, 196 pass through a receptacle 116 (see FIG. 8 ) in the first wall 74. The polymer guide 198 is coupled to a structure (e.g., structure 122 in FIG. 8 ) in the fourth wall 80. The polymer guide 198 passes through an opening 202 in the base plate 168. The receptacle 116 and the opening 202 define a range of movement of the bowtie filter assembly 166 in the lateral direction 182. Fasteners 204 (e.g., mounting screws) coupled to ends 206 (ends farther from fourth wall 80) of polymer guides 194, 196 limit the range of movement of bowtie filter assembly 166 in transverse direction 184. These fasteners 204 also hold bowtie filter 170 firmly in the scan plane during operation. In certain embodiments, fasteners 204 are loosened prior to adjustment in lateral direction 182. In certain embodiments, fasteners 204 are removed prior to adjustment in transverse direction 184.

[0035] The adjustment mechanism 180 includes an adjustment screw 208 that adjusts the movement of the bowtie filter assembly 166 in the lateral direction 182 within the collimator housing 62. The adjustment screw 208 allows the bowtie filter assembly 166 to be adjusted so that the bowtie filter 170 is located at the isocenter of the x-ray beam. A portion of the adjustment screw 208 extends through a nut 210 (e.g., a lock nut) on the exterior of the collimator housing 62 and into the interior space 110 of the collimator housing 62 (through an opening in the second wall 76). Within the collimator housing 62, a portion of the adjustment screw 208 extends through a slot 188 and is secured to the frame 186 by a fastener 212 (e.g., a nut). Rotating the adjustment screw 208 moves the bowtie filter assembly 166 in the lateral direction 182. Each end of the slot 188 acts as a limit to the movement of the bowtie filter assembly 166 in the transverse direction 184. Once the adjustment is complete, a lock nut 210 can be utilized to lock the position of the bowtie filter assembly 166. The adjustment screw 208 can be mechanically actuated. In certain embodiments, the adjustment screw 208 can be automatically actuated (in response to a control signal from the processing circuitry of the collimator controller 29 of FIG. 1) by a motorized actuator 213 coupled to the adjustment screw 208. Rotating the adjustment screw 208 in a circumferential direction 218 toward the fourth wall 80, as shown in FIG. 20, moves the bowtie filter assembly 166 in a lateral direction 182 (+X direction) toward the second wall 76, as shown in FIG. 21. Rotating the adjustment screw 208 in a circumferential direction 220 away from the fourth wall 80, as shown in FIG. 20, moves the bowtie filter assembly 166 in a lateral direction 182 (-X direction) toward the third wall 78, as shown in FIG. 22.

[0036] Returning to FIG. 19, the adjustment mechanism 180 also includes a locking pin 214 coupled to a locking pin spring mechanism 216 that adjusts the movement of the bowtie filter assembly 166 in the transverse direction 184 within the collimator housing 62. The locking pin spring mechanism 216 is disposed outside the collimator housing 62. The locking pin 214 extends from the exterior of the collimator housing 62 into the interior space 110 of the collimator housing 62 (through an opening in the second wall 76). A portion of the locking pin 214 passes through one of the openings 190, 192 of the frame 186. When the locking pin 214 is disposed within the opening 190, the bowtie filter assembly 166 is disposed such that the bowtie filter 170 is located within a scan plane 217 (passing through the opening 112 in the first wall 74), as shown in FIGS. 23 and 24. When the locking pin 214 is positioned in the opening 192, the bowtie filter assembly 166 is positioned near the fourth wall 80 and outside the scan plane 217, as shown in Figures 25 and 26. When the locking pin mechanism 216 is moved away from the collimator housing 62, the locking pin 214 is withdrawn from whichever opening 190, 192 the locking pin 214 is positioned in, allowing the bowtie filter assembly 166 to move in the transverse direction 184 along the polymer guides 194, 196, 198. When the locking pin mechanism 216 is released, the locking pin 214 can pass through the desired opening 190, 192 when the locking pin 214 is aligned with that opening. The locking pin mechanism 216 may be mechanically actuated or automatically actuated by a motorized actuator.

[0037] 27 is a perspective view of the assembled pre-collimator 13. The collimator 13 includes the additively manufactured collimator housing 62, the additively manufactured aperture transfer plate 64, and the additively manufactured motor mounting plate 66, as described above. Additionally, the collimator 13 includes a built-in alignment mechanism 164, an adjustment mechanism 180, and a motor 222 coupled to the motor mounting plate 66 and configured to move the aperture transfer plate 64 (by means of an actuator and a rail guide).

[0038] FIG. 28 is an exploded view of another built-in alignment mechanism 224 for moving the bowtie filter assembly 166 within the collimator housing 62. The built-in alignment mechanism 224 includes a base plate 226 coupled to the bowtie filter assembly 166. The bowtie filter assembly 166 includes a filter mounting plate 228, a bowtie filter 170 (e.g., a bowtie filter made of polytetrafluoroethylene), and a cover 172 (e.g., a front cover). The base plate 168 supports the bowtie filter assembly 166 and the components of the built-in alignment mechanism 224. The filter mounting plate 228 and the cover 172 partially surround the bowtie filter 170. The cover 172 does not extend around the top and bottom of the bowtie filter 170. A radiation shielding layer 174 (e.g., a shielding layer made of a tungsten-based polymer) is disposed on a surface of the filter mounting plate 228 that forms a direct interface with the bowtie filter 170. A radiation shielding layer 176 is disposed on a surface of the cover 172 that forms a direct interface with the bowtie filter 170. The filter mounting plate 228 and the cover 172 are configured to accommodate different types of bowtie filters 170. The bowtie filters 170 are coupled or attached to the filter mounting plate 228 by fasteners 178 (e.g., screws) that pass through corresponding openings in the bowtie filter 170 and the filter mounting plate 228. The cover 172 is coupled or attached to the filter mounting plate 228 to surround the bowtie filter 170 by fasteners (not shown, e.g., screws) that pass through corresponding openings in the cover 172 and the filter mounting plate 228.

[0039] The built-in alignment mechanism 224 includes an adjustment mechanism 180 configured to move the bowtie filter assembly 166 in a first direction 182 (e.g., lateral direction) and a second direction 184 (e.g., transverse direction). Movement in the lateral direction 182 is independent of movement in the transverse direction 184. Movement in the lateral direction 182 occurs between the second wall 76 and the third wall 78 of the collimator housing 62. Movement in the transverse direction 184 occurs toward and away from the fourth wall 80 of the collimator housing 62. The lateral direction 182 is orthogonal to the transverse direction 184.

[0040] The built-in alignment mechanism 224 includes surface-contacting rail guides 230, 232 for moving the bowtie filter assembly 166 and the base plate 226. The surface-contacting rail guides 230, 232 are coupled to mounting plates 234, 236, respectively, that are attached to the fourth wall 80 of the collimator housing 62. The base plate 226 is disposed on the surface-contacting rail guides 230, 232. The adjustment mechanism 180 includes an actuator screw assembly 238 that includes an actuator screw 240, a knob 242 coupled to the actuator screw 240, and a receiver 244 that includes a threaded portion. The receiver 244 is attached to a receptacle portion 246 of the base plate 226 that includes an opening for the threaded portion of the receptacle 244. The actuator screw 240 is configured to move in and out of the threads of the receptacle to move the bowtie filter assembly 166 in the transverse direction 184 (e.g., in and out of the scan plane) along the surface contacting rail guides 230, 232. The actuator screw 240 may be mechanically actuated or automatically actuated by a motorized actuator. Actuation of the actuator screw 240 (via the knob 242), as shown by arrow 248 in FIG. 29, moves the bowtie filter assembly 166 and base plate 226 in the transverse direction 184. Fasteners 204 (e.g., mounting screws) coupled to the ends 206 (ends farther from the fourth wall 80) of the surface contacting rail guides 230, 232 limit the range of movement of the bowtie filter assembly 166 in the transverse direction 184. These fasteners 204 also hold the bowtie filter 170 rigidly in the scan plane during operation.

[0041] Adjustment mechanism 180 includes a frame 250 that is part of and extends from filter mounting plate 228. Frame 250 allows bowtie filter assembly 166 to move in lateral direction 182 independent of movement in transverse direction 184. Frame 250 extends in direction 184 parallel to second wall 76 and third wall 78. Frame 250 includes a slot 252.

[0042] The adjustment mechanism 180 includes an adjustment screw 208 that adjusts the movement of the bowtie filter assembly 166 in the lateral direction 182 within the collimator housing 62 (without moving the base plate 226). The adjustment screw 208 allows the bowtie filter assembly 166 to be adjusted so that the bowtie filter 170 is located at the isocenter of the x-ray beam. A portion of the adjustment screw 208 passes through a nut 210 (e.g., a lock nut) on the outside of the collimator housing 62 and extends into the interior space 110 of the collimator housing 62 (through an opening in the second wall 76). Within the collimator housing 62, a portion of the adjustment screw 208 passes through a slot 252 and is secured to the frame 250 via a fastener 212 (e.g., a nut). Rotating the adjustment screw 208 moves the bowtie filter assembly 166 in the lateral direction 182. Each end of the slot 252 acts as a limit to the movement of the bowtie filter assembly 166 in the transverse direction 184. Once adjustment is complete, a lock nut 210 can be utilized to lock the position of the bowtie filter assembly 166. The adjustment screw 208 can be mechanically actuated. In certain embodiments, the adjustment screw 208 can be automatically actuated (in response to a control signal from the processing circuitry of the collimator controller 29 of FIG. 1) by a motorized actuator 213 coupled to the adjustment screw 208. As shown in FIG. 30, rotating the adjustment screw 208 in a circumferential direction (indicated by arrow 254) toward the fourth wall 80 moves the bowtie filter assembly 166 in a lateral direction 182 toward the second wall 76, and rotating the adjustment screw 208 in a circumferential direction away from the fourth wall 80 moves the bowtie filter assembly 166 in a lateral direction 182 toward the third wall 78.

[0043] FIG. 31 is a perspective view of an assembled pre-collimator 13. The collimator 13 includes the additively manufactured collimator housing 62, the additively manufactured aperture transfer plate 64, and the additively manufactured motor mounting plate 66 described above, but with some modifications. For example, the aperture transfer plate 64 does not include a mounting bracket. The plate portion 136 of the aperture transfer plate 64 is coupled (e.g., indirectly via guide rails and actuators) to integral side structures 256, 258 of the collimator housing 62. The side structures 256, 258 are located further away from the first wall 74 compared to the similar side structures in the collimator housing 62 of FIGS. 7-10. Additionally, the collimator 13 includes a built-in alignment mechanism 224, an adjustment mechanism 180, and a motor 222 coupled to the motor mounting plate 66 and configured to move the aperture transfer plate 64 (via actuators and rail guides).

[0044] 32 is an exploded view of another built-in alignment mechanism 260 for moving the bowtie filter assembly 166 within the collimator housing. The bowtie filter assembly 166 includes a base plate or filter mounting plate 262, a bowtie filter 170 (e.g., a bowtie filter fabricated using polytetrafluoroethylene), and a cover 172 (e.g., a front cover). The filter mounting plate 262 and the cover 172 partially surround the bowtie filter 170. The cover 172 does not extend around the top and bottom of the bowtie filter 170. In a particular embodiment, a radiation shielding layer (e.g., a shielding layer fabricated using a tungsten-based polymer) is disposed on a surface of the filter mounting plate 262 that forms a direct interface with the bowtie filter 170. In a particular embodiment, the radiation shielding layer is disposed on a surface of the cover 172 that forms a direct interface with the bowtie filter 170. Filter mounting plate 262 and cover 172 are configured to accommodate different types of bowtie filters 170. Bowtie filter 170 is coupled or attached to filter mounting plate 262 via fasteners 178 (e.g., screws) that pass through corresponding openings in bowtie filter 170 and filter mounting plate 228. Cover 172 is coupled or attached to filter mounting plate 262 to surround bowtie filter 170 via fasteners (not shown, e.g., screws) that pass through corresponding openings in cover 172 and filter mounting plate 262.

[0045] The built-in alignment mechanism 260 includes an adjustment mechanism 180 configured to move the bowtie filter assembly 166 in a first direction 182 (e.g., lateral direction) and a second direction 184 (e.g., transverse direction). The movement in the lateral direction 182 is independent of the movement in the transverse direction 184. The movement in the lateral direction 182 occurs between the second wall 76 and the third wall 78 of the collimator housing 62 in FIGS. 7-10. The movement in the transverse direction 184 occurs toward and away from the fourth wall 80 of the collimator housing 62 in FIGS. 7-10. The lateral direction 182 is orthogonal to the transverse direction 184.

[0046] The built-in alignment mechanism 260 includes guides 264, 266 for moving the bowtie filter assembly 166. The guides 264, 266 are coupled to extensions 268, 270 that are part of the filter mounting plate 262 and extend in the transverse direction 184 (e.g., away from the fourth wall 80 in FIGS. 7-10). The guides 264, 266 support the bowtie filter assembly 166. The guides 264, 266 pass through receptacles 116 on the first wall 74 of the collimator housing 62 in FIGS. 7-10.

[0047] The adjustment mechanism 180 includes three guide pins 272 that extend through respective receptacles 274 in the filter mounting plate 262 to respective quarter-turn bushings 276 (e.g., bushings made using a wear-resistant material) disposed within support pads 278. The support pads 278 are coupled to the fourth wall 80 of the collimator housing 62, FIGS. 7-10, via fasteners 280. The receptacles 274 allow the bowtie filter assembly 166 to move in both the lateral direction 182 and the transverse direction 184. As shown in FIG. 33, the guide pins 272 are configured to rotate a quarter turn in each direction, as indicated by arrows 282, between a locked position 284 and an unlocked position 286. Each guide pin 272 includes a first set of projections 288 and a second set of projections 290 at different axial positions along the respective guide pin 272. The first set of protrusions 288 and the second set of protrusions 290 define two distinct axial positions for bowtie filter assembly 166 as it moves in transverse direction 184, one axial position where bowtie filter 170 is in the scan plane and the other axial position where bowtie filter 172 is outside of the scan plane. In the unlocked position, the first set of protrusions 288 and / or the second set of protrusions 290 penetrate receptacles 274 to allow bowtie filter assembly 166 to move in transverse direction 184. In the locked position, the first set of protrusions 288 or the second set of protrusions 290 interface with a wall defining receptacle 274 to prevent bowtie filter assembly 166 from moving in transverse direction 184.

[0048] The adjustment mechanism 180 includes a frame 292 that is part of the filter mounting plate 262 and extends from the filter mounting plate 262. The frame 292 allows the bowtie filter assembly 166 to move in the lateral direction 182 independently of its movement in the transverse direction 184. The frame 292 extends in a direction 184 parallel to the second wall 76 and the third wall 78 of the collimator housing 162 in Figures 7-10. The frame 292 includes a slot 294.

[0049] The adjustment mechanism 180 includes an adjustment screw 208 that adjusts the movement of the bowtie filter assembly 166 in the lateral direction 182 within the collimator housing 62 of FIGS. 7-10. The adjustment screw 208 allows the bowtie filter assembly 166 to be adjusted so that the bowtie filter 170 is located at the isocenter of the x-ray beam. A portion of the adjustment screw 208 extends through a nut 210 (e.g., a lock nut) on the exterior of the collimator housing 62 and into the interior space 110 of the collimator housing 62 (through an opening in the second wall 76). Within the collimator housing 62, a portion of the adjustment screw 208 extends through a slot 294 and is secured to the frame 292 by a fastener 212 (e.g., a nut). As the adjustment screw 208 rotates, the bowtie filter assembly 166 moves in the lateral direction 182. Each end of the slot 294 acts as a limit to the movement of the bowtie filter assembly 166 in the transverse direction 184. Once adjustment is complete, a lock nut 210 can be utilized to lock the position of the bowtie filter assembly 166. The adjustment screw 208 can be mechanically actuated. In certain embodiments, the adjustment screw 208 can be automatically actuated (in response to a control signal from the processing circuitry of the collimator controller 29, FIG. 1) by a motorized actuator coupled to the adjustment screw 208. Rotating the adjustment screw 208 in a circumferential direction toward the fourth wall 80 moves the bowtie filter assembly 166, FIGS. 7-10, in a lateral direction 182 toward the second wall 76 of the collimator housing 62, while rotating the adjustment screw 208 in a circumferential direction away from the fourth wall 80 moves the bowtie filter assembly 166 in a lateral direction 182 toward the third wall 78.

[0050] 34 is a perspective view of the assembled pre-collimator 13. The collimator 13 includes the additively manufactured collimator housing 62, the additively manufactured aperture transfer plate 64, and the additively manufactured motor mounting plate 66. Additionally, the collimator 13 includes a built-in alignment mechanism 260, an adjustment mechanism 180, and a motor 222 coupled to the motor mounting plate 66 and configured to move the aperture transfer plate 64 (by means of an actuator and a rail guide).

[0051] FIG. 35 is a flow chart of a method 296 for aligning a bowtie filter to the center of the x-ray beam. The method 296 can be performed using one or more components (e.g., computer 36, collimator controller 29, etc.) of the CT system 10 of FIG. 1. The method 296 includes performing an air scan to obtain air scan data after the bowtie filter (e.g., as part of a bowtie filter assembly) in the pre-collimator is moved out of the view or out of the scan plane (block 298). The bowtie filter can be moved out of the scan plane using one of the adjustment mechanisms for moving the bowtie filter assembly in the transverse direction described above. The bowtie filter is not removed from the collimator during block 298. The method 296 also includes obtaining alignment scan data (e.g., by a center body filter scan) after the bowtie filter is moved transversely into the scan plane (block 300). The method 296 further includes calculating or determining (e.g., by processing circuitry) an offset value or offset distance from the center of the beamline path based on the air scan data and the alignment scan data (block 302). The method 296 further includes comparing the offset value to an acceptable or desired range of bowtie filter center positions (e.g., the center of the bowtie filter coincides with the isocenter alignment) (block 304). If the offset value is outside the acceptable range, the method 296 includes calculating (e.g., by processing circuitry) a value or distance to move the bowtie filter laterally to achieve the desired center position (e.g., within the acceptable range) (block 306). The method 296 further includes moving the bowtie filter laterally the calculated value or distance (e.g., in millimeters) using one of the adjustment mechanisms (e.g., adjustment screw 208) described above (block 308).The lateral adjustment of the bowtie filter may be performed automatically based on a control signal provided (e.g., from collimator controller 29) to an actuator coupled to an adjustment mechanism (e.g., adjustment screw 208) for moving the bowtie filter laterally. Method 296 then repeats blocks 298-304. If the offset value is within the acceptable range, method 296 ends (block 310).

[0052] Technical effects of the disclosed embodiments include providing a built-in alignment mechanism disposed within the pre-collimator for accurate and easy adjustment of the collimator during system alignment. In particular, the built-in alignment mechanism can adjust the bowtie filter both laterally and transversely independently of one another (e.g., centered with respect to the x-ray beam path for high image quality). The built-in alignment mechanism configuration also allows the bowtie filter to be adjusted from outside the collimator housing (e.g., via an actuator mechanism) without removing or disassembling a sub-component (e.g., bowtie filter) from the collimator during system alignment. Furthermore, the built-in alignment mechanism is configured for use with different types of bowtie filters and is extensible for use with different imaging platforms.

[0053] The technology presented and claimed herein has been applied to specific examples and tangible objects of a practical nature that demonstrably improve upon the state of the art, and as such is not abstract, intangible, or purely theoretical. Moreover, where a claim contains one or more elements specified as "means for [performing] [a function]..." or "steps for [performing] [a function]...", such elements are intended to be construed under 35 U.S.C. 112(f). However, for claims containing elements specified in any other manner, it is intended that such elements not be construed under 35 U.S.C. 112(f).

[0054] The description herein uses examples to disclose the subject matter described herein, including the best mode, and also to enable one skilled in the art to practice the disclosure, including making and using any devices or systems and performing any methods incorporated therein. The patentable scope of the subject matter is defined in 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 that do not differ insubstantial from the literal language of the claims. [Explanation of symbols]

[0055] 10 CT system 13 Precollimator 14 X-ray source 62 Collimator housing 74 Receptacle 76 Wall 78 Wall 80 Wall 166 Bowtie Filter Assembly 170 Bowtie Filter 182 Lateral direction

Claims

1. A pre-collimator (13) for a computed tomography (CT) imaging system (10), comprising: a collimator housing (62) including a plurality of walls (74, 76, 78, 80), the plurality of walls (74, 76, 78, 80) including a first wall (74) configured to face an X-ray source (14) when the pre-collimator (13) is coupled to the CT imaging system (10), a second wall (76) and a third wall (78) located on either side of the first wall (74), the plurality of walls (74, 76, 78, 80) including a fourth wall (80) extending between the second wall (76) adjacent to the first wall (74) and the third wall (78); a bowtie filter assembly (166) disposed within the collimator housing (62) and including a bowtie filter (170); and an adjustment mechanism (180) configured to move the bowtie filter assembly (166) in a lateral direction (182) between the second wall (76) and the third wall (78) within the collimator housing (62), the adjustment mechanism (180) configured to move the bowtie filter assembly (166) in a transverse direction (184) toward and away from the fourth wall (80); Including, movement of the bowtie filter assembly (166) in a lateral direction (182) is independent of movement of the bowtie filter assembly (166) in a transverse direction (184); The adjustment mechanism (180) a frame (186) disposed within the collimator housing (62), the frame being coupled to the bowtie filter assembly (166); an adjustment screw (208) coupled to the frame (186), the adjustment screw (208) adjusting movement of the bowtie filter assembly (166) in the lateral direction (182); a locking pin (214) coupled to the frame (186), the locking pin (214) controlling movement of the bowtie filter assembly (166) in the transverse direction (184); Including, The frame (186) is a first opening (192) for receiving the locking pin (214) when the bowtie filter assembly (166) moves in the transverse direction (184) away from a scan plane (217); a second opening (190) for receiving the locking pin (214) when the bowtie filter assembly (166) moves in the transverse direction (184) into the scan plane (217); and a pre-collimator including

2. 2. The pre-collimator of claim 1, wherein the frame includes a slot through which the adjustment screw passes, the slot holding the adjustment screw passing through the slot when the bowtie filter assembly moves in the lateral direction.

3. 2. The pre-collimator (13) of claim 1, wherein the adjustment mechanism (180) is operated from outside the collimator housing (62) so that the bowtie filter assembly (166) moves in the lateral direction (182) and the transverse direction (184) within the collimator housing (62).

4. 2. The pre-collimator of claim 1, further comprising: a motorized actuator coupled to the adjustment mechanism, the motorized actuator configured to, in response to a control signal from a processor, actuate the adjustment mechanism to move the bowtie filter assembly in the lateral direction to center the bowtie filter relative to the X-ray beam emitted from the X-ray source.

5. 2. The pre-collimator of claim 1, wherein the bowtie filter assembly includes a cover that partially encloses the bowtie filter of the bowtie filter assembly and a filter mounting plate.

6. 6. The pre-collimator (13) of claim 5, wherein radiation shielding material is disposed on each side of both the filter mounting plate (168, 228, 262) and the cover (172) facing the bowtie filter.

7. The pre-collimator (13) of claim 5, wherein the filter mounting plate (168, 228, 262) and cover (172) are configured to partially enclose different types of bowtie filters.

8. A pre-collimator (13) for a computed tomography (CT) imaging system (10), comprising: Collimator housing (62), a bowtie filter assembly (166) disposed within the collimator housing (62) and including a bowtie filter (170), the bowtie filter assembly (166) including a cover (172) and a filter mounting plate (168, 228, 262) that partially enclose the bowtie filter (170) of the bowtie filter assembly (166); and an adjustment mechanism (180) configured to move the bowtie filter assembly (166) in a first direction (182) and a second direction (184) within the collimator housing (62), wherein movement of the bowtie filter assembly (166) in the first direction (182) is independent of movement of the bowtie filter assembly (166) in the second direction (184), and wherein the first direction (182) and the second direction (184) are orthogonal to one another; Including, the filter mounting plate (168, 228, 262) supports the bowtie filter (170) and components of the adjustment mechanism (180); The adjustment mechanism (180) a frame (186) disposed within the collimator housing (62), the frame being coupled to the bowtie filter assembly (166); an adjustment screw (208) coupled to the frame (186), the adjustment screw (208) adjusting movement of the bowtie filter assembly (166) in the first direction (182); a locking pin (214) coupled to the frame (186), the locking pin (214) regulating movement of the bowtie filter assembly (166) in the second direction (184); Including, The frame (186) is a first opening (192) for receiving the locking pin (214) when the bowtie filter assembly (166) is moved in the second direction (184) away from a scan plane (217); a second opening (190) for receiving the locking pin (214) when the bowtie filter assembly (166) is moved in the second direction (184) into the scan plane (217); and a pre-collimator including

9. 9. The pre-collimator (13) of claim 8, wherein the collimator housing (62) includes a first wall (74) configured to face an X-ray source (14) when the pre-collimator (13) is coupled to the CT imaging system (10), and the first direction (182) and the second direction (184) are perpendicular to each other along parallel planes within the first wall (74).

10. 10. The pre-collimator of claim 8, wherein the collimator housing includes a plurality of walls, the plurality of walls including a first wall configured to face an X-ray source when the pre-collimator is coupled to the CT imaging system, and a second wall and a third wall located on either side of the first wall, and the adjustment mechanism is configured to move the bowtie filter assembly in the first direction between the second wall and the third wall.

11. 11. The pre-collimator (13) of claim 10, wherein the plurality of walls (74, 76, 78, 80) includes a fourth wall (80) extending between the second wall (76) adjacent the first wall (74) and the third wall (78), and the adjustment mechanism (180) moves the bowtie filter assembly (166) in a second direction (184) toward and away from the fourth wall (80).

Images