Patent Publication Number: US-2022212260-A1

Title: System and method for mitigating metal particle leakage from additive three-dimensional printed parts

Description:
BACKGROUND 
     The subject matter disclosed herein relates to imaging systems, and more particularly, to mitigating metal particle leakage from additive three-dimensional (3D) printed parts of the imaging systems. 
     Some components of an imaging system (e.g., computed tomography (CT) imaging system) may be printed or additively manufactured out of one or more materials. Some of these materials may include metal (e.g., metal powder). Loose or weakly attached powder particles (e.g., metal powder particles) may leach out from the 3D printed parts due to the nature of the additive manufacturing process. These leached out metal particles may cause image defects or the malfunction of other imaging components due to the rotating nature of a CT scanner. Typical cleaning techniques (e.g., air blowing, solvent or water rinse, ultrasound cleaning, etc.) may not be effective at completely removing these loose particles even if the cleaning is extensive (or in some cases may further promote this leakage). For example, an imaging system may include one or more collimator modules (e.g., additively manufactured collimator modules). The collimator modules may be utilized under a wide range of loads (e.g., in a high speed spin or slow rotation) and subjected to vibrations (e.g., from scanners) that cause loose particles to move around that can impact clinical images (e.g., due to density of the particles) or cause damage to other imaging components (e.g., by entering within precision ceramic bearings). 
     BRIEF DESCRIPTION 
     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 these embodiments are intended only to provide a brief summary of possible embodiments. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below. 
     In one implementation, a method is provided for mitigating metal particle leakage from a three-dimensional printed part. The method includes providing an additively manufactured part manufactured out of one or more materials, and the one or more materials comprise a metal. The method also includes applying a coating over surfaces of the additively manufactured part to keep metal particles from leaking from the additively manufactured part. 
     In a further implementation, a method is provided for mitigating metal particle leakage from a three-dimensional printed collimator. The method includes providing an additively manufactured collimator manufactured out of one or more materials, the one or more materials comprise a metal, and the additively manufactured collimator is configured to provide collimation on a beam emitted from an X-ray source of an imaging system. The method also includes applying a coating over surfaces of the additively manufactured collimator to keep metal particles from leaking from the additively manufactured collimator. 
     In an additional implementation, an imaging system is provided. The imaging system includes an additively manufactured three-dimensional (3D) collimator manufactured out of one or more materials, the one or more materials comprise a metal, and the additively manufactured (3D) collimator is configured to provide collimation on a beam emitted from an X-ray source of the imaging system. The imaging system also includes a coating disposed over surfaces of the additively manufactured 3D collimator, wherein the coating is configured to keep metal particles from leaking from the additively manufactured 3D collimator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and aspects of embodiments of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a block diagram representation of a CT system, in accordance with aspects of the present disclosure; 
         FIG. 2  is a flow chart for an embodiment of a method for producing a coated 3D printed part, in accordance with aspects of the present disclosure; 
         FIG. 3  is a schematic cross-sectional view of an embodiment of a portion of a coated 3D printed part (e.g., coated collimator), in accordance with aspects of the present disclosure; and 
         FIG. 4  is a cross-sectional view of the coated 3D printed part of  FIG. 3 , taken within line  4 - 4 , in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. 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 discussion are intended to be non-limiting, and thus additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments. 
     While aspects of the following discussion may be provided in the context of medical imaging, it should be appreciated that the present techniques are not limited to such medical contexts. Indeed, the provision of examples and explanations in such a medical context is only to facilitate explanation by providing instances of real-world implementations and applications. However, the present approaches may also be utilized in other contexts, such as imaging (e.g., in industrial use) in non-destructive inspection of manufactured parts or goods (i.e., quality control or quality review applications), and/or the non-invasive inspection of packages, boxes, luggage, and so forth (i.e., security or screening applications). Further, the present approaches may be utilized in any application where it may be beneficial to avoid the leaking of metal particles from an additively manufactured part. In general, the present approaches may be useful in any context where additive manufacturing is utilized. 
     The present disclosure provides for systems and methods for mitigating metal particle leakage from three-dimensional (3D) printed or additively manufactured parts (e.g., of an imaging system). In particular, a coating is applied to the printed part to avoid the leakage of metal particles. In the context of medical imaging, avoiding the leakage of metal particles from the printed part may avoid image defects and/or the malfunction of other imaging components. In certain embodiments, the coating may be fine-tuned (e.g., include one or more materials) to improve or alter a characteristic or function of the printed part (e.g., mechanical strength, thermal conductivity, surface finish, etc.). The coating may mitigate the need for extensive cleaning, thus, reducing the time to finish manufacturing the printed part, while avoiding both producing particle residues and damage to the printed part. 
     With the foregoing discussion in mind,  FIG. 1  illustrates an embodiment of an imaging system  10  for acquiring and processing image data that may utilize 3D additively manufactured or printed parts in accordance with aspects of the present disclosure. Although the following embodiments are discussed in terms of the computed tomography (CT) imaging system, the embodiments may also be utilized with other imaging systems (e.g., X-ray, PET, CT/PET, SPECT, nuclear CT, etc.). In the illustrated embodiment, system  10  is a computed tomography (CT) system designed to acquire X-ray projection data, to reconstruct the projection data into a tomographic image, and to process the image data 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 which allow X-ray generation at one or more locations and/or one or more energy spectra during an imaging session. 
     In certain implementations, the source  12  may be positioned proximate to a collimator  22  used to define the size and shape of the one or more X-ray beams  20  that pass into a region in which a subject  24  (e.g., a patient) or object of interest is positioned. The subject  24  attenuates at least a portion of the X-rays. Resulting attenuated X-rays  26  impact a detector array  28  formed by a plurality of detector elements. Each detector element produces an electrical signal that represents the intensity of the X-ray beam incident at the position of the detector element when the beam strikes the detector  28 . Electrical signals are acquired and processed to generate one or more scan datasets. 
     A system controller  30  commands operation of the imaging system  10  to execute examination and/or calibration protocols and to process the acquired data. With respect to the X-ray source  12 , the system controller  30  furnishes power, focal spot location, control signals and so forth, for the X-ray examination sequences. The detector  28  is coupled to the system controller  30 , which commands acquisition of the signals generated by the detector  28 . In addition, the system controller  30 , via a motor controller  36 , may control operation of a linear positioning subsystem  32  and/or a rotational subsystem  34  used to move components of the imaging system  10  and/or the subject  24 . 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 encoded algorithms executed by the system controller  30  to operate the imaging system  10 , including the X-ray source  12 , and to process the data acquired by the detector  28  in accordance with the steps and processes discussed herein. In one embodiment, the system controller  30  may be implemented as all or part of a processor-based system such as a general purpose or application-specific computer system. 
     The source  12  may be controlled by an X-ray controller  38  contained within the system controller  30 . The X-ray controller  38  may be configured to provide power and timing signals to the source  12 . In addition, in some embodiments the X-ray controller  38  may be configured to selectively activate the source  12  such that tubes or emitters at different locations within the system  10  may be operated in synchrony with one another or independent of one another. 
     The system controller  30  may include a data acquisition system (DAS)  40 . The DAS  40  receives data collected by readout electronics of the detector  28 , such as sampled analog signals from the detector  28 . The DAS  40  may then convert the data to digital signals for subsequent processing by a processor-based system, such as a computer  42 . In other embodiments, the detector  28  may convert the sampled analog signals to digital signals prior to transmission to the data acquisition system  40 . The computer may include processing circuitry  44  (e.g., image processing circuitry). The computer  42  may include or communicate with one or more non-transitory memory devices  46  that can store data processed by the computer  42 , data to be processed by the computer  42 , or instructions to be executed by a processor (e.g., processing circuitry  44 ) of the computer  42 . For example, the processing circuitry  44  of the computer  42  may execute one or more sets of instructions stored on the memory  46 , which may be a memory of the computer  42 , a memory of the processor, firmware, or a similar instantiation. 
     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, and so forth. Additionally, the system  10  may include a printer  52  coupled to the operator workstation  48  and configured to print any desired measurement results. The display  50  and the printer  52  may also be connected to the computer  42  directly or via the operator workstation  48 . Further, the operator workstation  48  may include or be coupled to a picture archiving and communications system (PACS)  54 . PACS  54  may be coupled to a remote system  56 , radiology department information system (RIS), hospital information system (HIS) or to an internal or external network, so that others at different locations can gain access to the image data. 
       FIG. 2  is a flow chart for an embodiment of a method  58  for producing a coated 3D printed part. The method  58  includes additively manufacturing or providing an additively manufacturing 3D printed part (block  60 ). The printed part may be made of one or more materials. These materials may include one or more different metals (e.g., metal powders) depending on the part. In certain embodiments, the parts may be components of an imaging system (e.g., imaging system  10 ). For example, the parts may be a frame, circuitry, a collimator, or any other component that can be additively manufactured. The printed part may be additively manufactured via any additive manufacturing technique (e.g., laser powder bed fusion, photopolymerization, material jetting, binder jetting, material extrusion, sheet lamination, direct energy deposition, etc.). 
     The method  58  also includes cleaning the printed part (block  62 ). Typically, in the absence of a coating, printed parts undergo extensive cleaning repeatedly that is both time consuming and leaves particle residues (even after multiple days of cleaning). In addition, the extensive cleaning may physically damage the printed part. Extensive cleaning may include compressed air cleaning and blowing, solvent- or water-based cleaning, ultrasonic cleaning, or the addition of filtration units. With the coating, less cleaning of the printed parts may be needed compared to printed parts without the coating. For example, passive cleaning may be utilized before the application of the coating. Passive cleaning may include mechanical vibration or de-powdering. 
     The method  58  also includes preparing a coating (block  64 ). Preparing the coating may be as simple as getting it ready (e.g., mixing, if needed) for application depending of the composition of the coating. For example, the coating may include a mixture of materials. The coating may made of organic polymers or polymer composites. In certain embodiments, the coating may be made of non-reactive polymers, 1-part reactive polymers, or 2-part reactive polymers. In certain embodiments, the coating may be made of thermosetting polymers or thermoplastic polymers. In certain embodiments, the coating may be made of one or more of epoxies, polyurethanes, polyacrylics, cyanoacrylates, silicones, polyolefins, polyvinyl alcohol, rubbers, polyvinyl chloride, phenol formaldehyde, nylon, and polyacrylonitrile. In certain embodiments, the coating may be made of pure polymers or polymer blends. In certain embodiments, the coating may be made of a polymer composite that may include inorganic fillers, ceramic precursors, or fine metal particles. In certain embodiments, the coating may be fined tuned (e.g., include one or more materials) to improve or alter a characteristic or function of the printed part (e.g., mechanical strength, thermal conductivity, surface finish, etc.) depending on the application. For example, the coating may include a heavy metal powder (e.g., tungsten) configured to increase radiation shielding. 
     The method  58  further includes applying the coating to the printed part (block  66 ). For example, applying the coating may include immersing the printed part within the coating, spraying the coating on the printed part, brush coating the coating, or another technique. In certain embodiments, a coating with monomers or oligomers with crosslinkers may be coated to the surfaces of the printed part and then chemical crosslinking performed. In certain embodiments, the surfaces of the printed part may be coated with a polymer solution and then the polymer solution may be solidified via evaporation or cooling down of melted polymers. Typically, the coating may be a liquid that penetrates through the surfaces of the printed part to anywhere that the metal particles have the potential to leak out to and prevent the movement of the particles after curing or solidification. The coating may be applied separately to individual printed parts or applied to multiple printed parts at the same time. 
       FIG. 3  is a schematic cross-sectional view of a portion of a coated 3D printed part. As depicted,  FIG. 3  includes a 3D printed part  68  and a coating  70  disposed over the surfaces of the 3D printed part  68 . As noted above, the 3D printed part  68  may be any type of printed part that includes metal particles. For example, the printed part  68  may be any component of an imaging system (e.g., imaging system  10 ). For example, the printed part  68  may be a frame, electronics, collimator, or other component of the imaging system. As depicted in  FIG. 3 , the printed part  68  is a two-dimensional (2D) collimator. In the case of the coating  70  for the collimator, the coating  70  is almost transparent to radiation (i.e., the coating does not affect the functionality of the collimator with regard to collimation. A thickness of the coating  70  (e.g., of a few micrometers) is such that it does not influence the geometry of the printed part  68  nor cause the printed part  68  to exceed its engineering tolerance. 
     As mentioned above, the coating  70  may be fine-tuned (e.g., include one or more materials) to improve or alter a characteristic or function of the printed part  68  (e.g., mechanical strength, thermal conductivity, surface finish, etc.) depending on the application.  FIG. 4  is a cross-sectional view of the coated 3d printed part  68  of  FIG. 3 , taken within line  4 - 4 . As depicted, the coating  70  includes inorganic fillers, ceramic precursors, or fine metal particles  72 . In certain embodiments, the coating  70  includes a heavy metal powder (e.g., tungsten) to increase radiation shielding when the printed part  68  is a collimator as in  FIGS. 3 and 4 . 
     Certain printed parts, such as a collimator are very fragile due to most walls being very thin (e.g., between approximately 30 micrometers and 300 micrometers). In the case of collimator, it is subject to a wide range of loads (e.g., from a high-speed spin to a slow rotation) that (in the absence of a coating) cause loose metal particles to leak from the collimator. The addition of the coating  70  to the collimator increases the collimator&#39;s mechanical strength and toughness. For example, a printed tungsten tensile bar (e.g., having the dimensions of approximately 250 millimeters (mm) for the length, 23.7 mm for the width, and 1.82 mm for the thickness) under a tensile strength test may have a maximum load (N) of 2753. However, the same bar coated in a first epoxy-based coating and a second epoxy-based coating has maximum loads of 3613 and 2954, respectively. Thus, the coating increases the mechanical strength of the printed part (such as a collimator). 
     As discussed herein, technical effects of the disclosed subject matter include providing a coating on an additively manufactured or printed 3D part (e.g., imaging system component such as a collimator). The coating applied to the printed part minimizes or avoids the leakage of metal particles from the printed part. In the context of medical imaging, avoiding the leakage of metal particles from the printed part may avoid image defects and/or the malfunction of other imaging components. In certain embodiments, the coating may be fine-tuned (e.g., include one or more materials) to improve or alter a characteristic or function of the printed part (e.g., mechanical strength, thermal conductivity, surface finish, etc.). The coating may mitigate the need for extensive cleaning, thus, reducing the time to finish manufacturing the printed part and avoiding both producing particle residues and damage to the printed part during the cleaning. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention 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 insubstantial differences from the literal languages of the claims.