Patent Publication Number: US-2023160984-A1

Title: Gradient cooling manifold assembly having additively manufactured manifolds

Description:
BACKGROUND 
     The subject matter disclosed herein relates to a magnetic resonance imaging (MRI) system and, more particularly, to a gradient cooling manifold assembly having additively manufactured manifolds. 
     Non-invasive imaging technologies allow images of the internal structures or features of a patient/object to be obtained without performing an invasive procedure on the patient/object. In particular, such non-invasive imaging technologies rely on various physical principles (such as the differential transmission of X-rays through a target volume, the reflection of acoustic waves within the volume, the paramagnetic properties of different tissues and materials within the volume, the breakdown of targeted radionuclides within the body, and so forth) to acquire data and to construct images or otherwise represent the observed internal features of the patient/object. 
     During MRI, when a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B 0 ), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency. If the substance, or tissue, is subjected to a magnetic field (excitation field B1) which is in the x-y plane and which is near the Larmor frequency, the net aligned moment, or “longitudinal magnetization”, Mz, may be rotated, or “tipped”, into the x-y plane to produce a net transverse magnetic moment, M t . A signal is emitted by the excited spins after the excitation signal B 1  is terminated and this signal may be received and processed to form an image. 
     When utilizing these signals to produce images, magnetic field gradients (G x , G y , and G z ) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradient fields vary according to the particular localization method being used. The resulting set of received nuclear magnetic resonance (NMR) signals are digitized and processed to reconstruct the image using one of many well-known reconstruction techniques. 
     The magnetic field gradients are generated by gradient field coils in a gradient coil assembly. The gradient coil assembly generates heat during imaging (e.g., due to eddy currents and resistive heating). Different types of cooling (e.g., fluidic cooling) are typically utilized to minimize heating of the gradient coil assembly. However, as the bore of MRI systems increase, minimizing the heating of the gradient coil assembly becomes more challenging. In addition, manifold assemblies for providing the fluid to cool the gradient coil assembly are costly, occupy a large footprint, and are subject to a higher risk of mechanical failure (e.g., due to the number of connections and the system demands on the manifold assemblies). 
     BRIEF DESCRIPTION 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     In one embodiment, a manifold for a gradient coil cooling manifold assembly of a MRI system is provided. The manifold includes a first main fluid passage defined by a first wall. The manifold also includes a first set of secondary fluid passages coupled to the first main fluid passage and defined by respective walls, wherein the first wall of the first main fluid passage and the respective walls of the first set of secondary fluid passages form barb connectors configured to couple to respective hoses. The manifold is formed as a single integral piece. 
     In one embodiment, a gradient coil cooling manifold assembly of a MRI system includes a plurality of hoses. The gradient coil cooling manifold assembly also includes a plurality of additively manufactured manifolds coupled to the plurality of hoses. Each additively manufactured manifold of the plurality of additively manufactured manifolds includes a main fluid passage defined by a wall. Each additively manufactured manifold of the plurality of additively manufactured manifolds also includes a set of secondary fluid passages coupled to the main fluid passage and defined by respective walls. The wall of the main fluid passage and the respective walls of the set of secondary fluid passages form barb connectors configured to couple to respective hoses of the plurality of hoses. 
     In one embodiment, a MRI system is provided. The MRI system includes a gradient coil assembly including a plurality of gradient coils. The MRI system also includes a gradient coil cooling manifold assembly configured to couple to the gradient coil assembly and to regulate a temperature of the gradient coil assembly. The gradient coil cooling manifold assembly includes a plurality of manifolds. Each manifold of the plurality of manifolds includes a main fluid passage defined by a wall. Each manifold of the plurality of manifolds also includes a set of secondary fluid passages coupled to the main fluid passage and defined by respective walls. The wall of the main fluid passage and the respective walls of the set of secondary fluid passages form barb connectors configured to couple to respective hoses. Each manifold of the plurality of manifolds is formed as a single integral piece. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages 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    illustrates an embodiment of a magnetic resonance imaging (MRI) system suitable for use with the disclosed technique; 
         FIG.  2    is a schematic view of an embodiment of a cooling system coupled to a gradient coil assembly of the MRI system of  FIG.  1   , in accordance with aspects of the present disclosure; 
         FIG.  3    is a perspective view of an embodiment of a gradient coil cooling manifold assembly coupled to a gradient coil assembly, in accordance with aspects of the present disclosure; 
         FIG.  4    is front view of the gradient coil cooling manifold assembly of  FIG.  3    coupled to the gradient coil assembly, in accordance with aspects of the present disclosure; 
         FIG.  5    is a perspective view of an embodiment of a manifold of the gradient coil cooling manifold assembly of  FIG.  3    (e.g., having two main passages), in accordance with aspects of the present disclosure; 
         FIG.  6    is another perspective view of the manifold in  FIG.  5   , in accordance with aspects of the present disclosure; 
         FIG.  7    is a perspective view of an embodiment of a manifold of the gradient coil cooling manifold assembly of  FIG.  3    (e.g., having two main passages), in accordance with aspects of the present disclosure; 
         FIG.  8    is a perspective view of an embodiment of a manifold of the gradient coil cooling manifold assembly of  FIG.  3    (e.g., having a single main passage), in accordance with aspects of the present disclosure; and 
         FIG.  9    is a perspective view of an embodiment of a manifold of the gradient coil cooling manifold assembly of  FIG.  3    (e.g., having a single main passage), 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, not all features of an actual implementation are 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 subject matter, 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 are provided in the context of medical imaging, it should be appreciated that the disclosed 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 disclosed techniques may also be utilized in other contexts, such as image reconstruction for 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). In general, the disclosed techniques may be useful in any imaging or screening context or image processing or photography field where a set or type of acquired data undergoes a reconstruction process to generate an image or volume. 
     Manifold assemblies for providing fluid to cool gradient coil assemblies of MRI systems are costly, occupy a large footprint, and are subject to a higher risk of mechanical failure (e.g., due to the number of connections and the system demands on the manifold assemblies). Manufacturing manifold assemblies to meet the system demands for cooling gradient coil assemblies is difficult. Traditional fabrication techniques are insufficient. For example, copper welded/braze assemblies are too bulky and rigid and, thus, prone to damage. In addition, the cost of a welded assembly is a burden. A machined block style manifold takes up too much space and is too heavy. In addition, the machined block style includes numerous connections or joints, which increase the amount of potential leak paths. Casting necessitates complex and costly tooling, which limits design iteration. 
     The present disclosure provides a gradient cooling manifold assembly for a MRI system that includes one or more additively manufactured (e.g., via direct metal laser sintering) manifolds or manifold modules coupled to flexible rubber hosing. Each manifold module includes at least one main or primary fluid passage (e.g., inlet or outlet) defined by a first wall and a set of secondary fluid passages coupled to the main passage and defined by respective walls. The wall of at least one main fluid passage and the respective walls of the set of secondary fluid passages form barb connectors or fittings configured to couple to respective hoses. In certain embodiments, each manifold module includes two main or primary fluid passages defined by a first wall and a second wall (e.g. physically coupled via one or more structural ribs extending between the first and second walls) with each main fluid passage coupled to a respective set of secondary fluid passages having respective walls that form barb connectors. The one or more main fluid passages and the one or more sets of primary fluid passages of the manifold module are formed as a single integral piece. 
     Additive manufacturing&#39;s ability to quickly print complex geometries enables the manifold modules to be optimized to produce maximum flow with minimal volumetric space, efficient fabrication, assembly, and service ability. Critical space (e.g., axial space between the manifold assembly and the gradient coil assembly) is saved by matching the module&#39;s mainline geometry to that of the gradient coil&#39;s circular shape and targeting the branches to their destination. Fabricating this complex geometry would be substantially more difficult with traditional module fabrication techniques. Additive manufacturing allows combining otherwise separate components into a single part enable to withstand the system parameters for cooling a gradient coil assembly of a MRI system. The disclosed embodiments enable less connections in the manifold assembly, thus, lowering the risk of leaks. In addition, less braze joints/fittings enables a lower risk of mechanical failure in the manifold assembly. Further, the custom precise geometry enables better cooling with fewer failures. Even further, the disclosed embodiments enable a lower cost manifold assembly. 
     Turning now to the drawings, and referring first to  FIG.  1   , a magnetic resonance imaging (MRI) system  10  is illustrated diagrammatically as including a scanner  12 , scanner control circuitry  14 , and system control circuitry  16 . While MRI system  10  may include any suitable MRI scanner or detector, in the illustrated embodiment the system includes a full body scanner comprising a patient bore  18  into which a table  20  may be positioned to place a patient  22  in a desired position for scanning. 
     Scanner  12  includes a series of associated coils for producing controlled magnetic fields, for generating radiofrequency excitation pulses, and for detecting emissions from gyromagnetic material within the patient in response to such pulses. In the diagrammatical view of  FIG.  1   , a primary magnet coil  24  (e.g., superconducting magnet coil) is provided for generating a primary magnetic field, B 0 , generally aligned with patient bore  18 . In certain embodiments, B 0  fields on the order of 3T to 7T are contemplated, but fields higher than 7T and as low as a fraction of a Tesla are also contemplated. A series of gradient coils  26 ,  28  and  30  (e.g., magnetic gradient field coils) are grouped in a coil assembly (e.g., gradient coil assembly) for generating controlled magnetic gradient fields during examination sequences as described more fully below. A radiofrequency coil  32  is provided for generating radiofrequency pulses for exciting the gyromagnetic material. In the embodiment illustrated in  FIG.  1   , coil  32  also serves as a receiving coil. Thus, radiofrequency (RF) coil  32  may be coupled with driving and receiving circuitry in passive and active modes for receiving emissions from the gyromagnetic material and for applying radiofrequency excitation pulses, respectively. Alternatively, various configurations of receiving coils may be provided separate from RF coil  32 . Such coils may include structures specifically adapted for target anatomies, such as head coil assemblies, and so forth. Moreover, receiving coils may be provided in any suitable physical configuration, including phased array coils, and so forth. 
     In a present configuration, the magnet gradient field coils  26 ,  28  and  30  have different physical configurations adapted to their function in the imaging system  10 . As will be appreciated by those skilled in the art, the coils are comprised of conductive wires, bars or plates which are wound or cut to form a coil structure which generates a gradient field upon application of control pulses as described below. The placement of the coils within the gradient coil assembly may be done in several different orders, but in the present embodiment, a Z-axis coil is positioned at an innermost location, and is formed generally as a solenoid-like structure which has relatively little impact on the RF magnetic field. Thus, in the illustrated embodiment, gradient coil  30  is the Z-axis solenoid coil, while coils  26  and  28  are the transverse Y-axis and X-axis coils, respectively. 
     The coils of scanner  12  are controlled by external circuitry to generate desired fields and pulses, and to read signals in a controlled manner. As will be appreciated by those skilled in the art, when the material, typically bound in tissues of the patient, is subjected to the primary field, magnetic moments of the nuclei in the tissue partially align with the field. While a net magnetic moment is produced in the direction of the polarizing field, the randomly oriented components of the moment in a perpendicular plane generally cancel one another. During an examination sequence, an RF frequency pulse is generated at or near the Larmor frequency of the material of interest, resulting in rotation of the net aligned moment to produce a net transverse magnetic moment. This transverse magnetic moment precesses around the main magnetic field direction, emitting RF signals that are detected by the scanner and processed for reconstruction of the desired image. 
     Gradient coils  26 ,  28  and  30  serve to generate precisely controlled magnetic fields, the strength of which vary over a predefined field of view, typically with positive and negative polarity. When each coil is energized with known electric current, the resulting magnetic field gradient is superimposed over the primary field and produces a desirably linear variation in the Z-axis component of the magnetic field strength across the field of view. The gradient coil for each axis generates a linear magnetic field gradient in the direction of that axis. As such, the spatially-varying z-directed magnetic field varies linearly along the direction of the gradient coil axis. The three coils have mutually orthogonal axes for the direction of their variation, enabling a linear field gradient to be imposed in an arbitrary direction with an appropriate combination of the three gradient coils. 
     The pulsed gradient fields perform various functions integral to the imaging process. Some of these functions are slice selection, frequency encoding and phase encoding. These functions can be applied along the X-, Y- and Z-axis of the original coordinate system or along other axes determined by combinations of pulsed currents applied to the individual field coils. 
     The slice select gradient determines a slab or cross-section of tissue or anatomy to be imaged in the patient. The slice select gradient field may be applied simultaneously with a frequency selective RF pulse to excite a known volume of spins within a desired slice that precess at the frequencies equal to the excitation bandwidth of the RF pulse. The slice thickness is determined by the bandwidth of the RF pulse and the gradient strength across the field of view. 
     The frequency encoding gradient is also known as the readout gradient and is usually applied in a direction perpendicular to the slice select gradient. The frequency encoding gradient encodes positional information of spins with the plane excited by the RF pulse. In general, the frequency encoding gradient waveforms comprises of a dephasing lobe that dephases the spins, and a readout gradient lobe that rephases the spins at the center of the readout gradient waveform to form an echo. Spins with a nuclear magnetic moment encoded with a spatially varying phase (as they precess at different frequencies) according to their spatial position along the gradient field. By Fourier transformation, acquired signals may be analyzed to identify their location in the selected slice by virtue of the frequency encoding. 
     Finally, the phase encode gradient is generally applied before the readout gradient and after the slice select gradient. Localization of spins in the gyromagnetic material in the phase encode direction is accomplished by sequentially inducing variations in phase of the precessing protons of the material using slightly different gradient amplitudes that are sequentially applied during the data acquisition sequence. The phase encode gradient permits phase differences to be created among the spins of the material in accordance with their position in the phase encode direction, similar in principle to the phase accumulated by spins in the readout gradient waveform at different time points. 
     As will be appreciated by those skilled in the art, a great number of variations may be devised for pulse sequences employing the exemplary gradient pulse functions described above as well as other gradient pulse functions not explicitly described here. Moreover, adaptations in the pulse sequences may be made to appropriately orient both the selected slice and the frequency and phase encoding to excite the desired material and to acquire resulting MR signals for processing. 
     The coils of scanner  12  are controlled by scanner control circuitry  14  to generate the desired magnetic field and radiofrequency pulses. In the diagrammatical view of  FIG.  1   , control circuitry  14  thus includes a control circuit  36  for commanding the pulse sequences employed during the examinations, and for processing received signals. Control circuit  36  may include any suitable programmable logic device, such as a CPU or digital signal processor of a general purpose or application-specific computer. Control circuit  36  further includes memory circuitry  38 , such as volatile and non-volatile memory devices for storing physical and logical axis configuration parameters, examination pulse sequence descriptions, acquired image data, programming routines, and so forth, used during the examination sequences implemented by the scanner. 
     Interface between the control circuit  36  and the coils of scanner  12  is managed by amplification and control circuitry  40  and by transmission and receive interface circuitry  42 . Circuitry  40  includes amplifiers for each gradient field coil to supply drive current to the field coils in response to control signals from control circuit  36 . Interface circuitry  42  includes additional amplification circuitry for driving RF coil  32 . Moreover, where the RF coil serves both to emit the radiofrequency excitation pulses and to receive MR signals, circuitry  42  will typically include a switching device for toggling the RF coil between active or transmitting mode, and passive or receiving mode. A power supply, denoted generally by reference numeral  34  in  FIG.  1   , is provided for energizing the primary magnet  24 . Finally, circuitry  14  includes interface components  44  for exchanging configuration and image data with system control circuitry  16 . It should be noted that, while in the present description reference is made to a horizontal cylindrical bore imaging system employing a superconducting primary field magnet assembly, the present technique may be applied to various other configurations, such as scanners employing vertical fields generated by superconducting magnets, permanent magnets, electromagnets or combinations of these means. 
     System control circuitry  16  may include a wide range of devices for facilitating interface between an operator or radiologist and scanner  12  via scanner control circuitry  14 . In the illustrated embodiment, for example, an operator controller  46  is provided in the form of a computer workstation employing a general purpose or application-specific computer. The station also typically includes memory circuitry for storing examination pulse sequence descriptions, examination protocols, user and patient data, image data, both raw and processed, and so forth. The station may further include various interface and peripheral drivers for receiving and exchanging data with local and remote devices. In the illustrated embodiment, such devices include a conventional computer keyboard  50  and an alternative input device such as a mouse  52 . A printer  54  is provided for generating hard copy output of documents and images reconstructed from the acquired data. A computer monitor  48  is provided for facilitating operator interface. In addition, system  10  may include various local and remote image access and examination control devices, represented generally by reference numeral  56  in  FIG.  1   . Such devices may include picture archiving and communication systems, teleradiology systems, and the like. 
       FIG.  2    is schematic view of an embodiment of a cooling system  58  (e.g., thermal management system) coupled to a gradient coil assembly  60  (e.g., having the gradient coils  26 ,  28 ,  30  of  FIG.  1   ) of the MRI system  10  of  FIG.  1   . The cooling system  58  includes a cooling cabinet  62  coupled to a manifold assembly  64  (e.g., flexible gradient coil cooling manifold assembly). The cooling cabinet  62  provides liquid coolant (e.g., de-ionized water, ethylene glycol, etc.) to the manifold assembly  64 . The manifold assembly  64  (via supply lines) provides the liquid coolant to cooling circuits  65  (e.g., jackets, tubes, channels, etc.) disposed within the gradient coil assembly  60  to manage the temperature of the gradient coils (e.g., cool the gradient coils). The structure of the cooling circuits  65  may vary based on the gradient structure of the gradient coil assembly  60  and associated gradient coils. After flowing through the cooling circuits  65 , the liquid coolant is returned to the cooling cabinet  62  via the manifold assembly  64 . The cooling cabinet  62  may include a heat exchanger to regulate a temperature of the liquid coolant. As described in greater detail below, the manifold assembly  64  includes one or more additively manufactured manifolds or manifold modules. 
       FIGS.  3  and  4    are perspective views of the gradient coil cooling manifold assembly  64  coupled to the gradient coil assembly  60  (shown in dashed outline). The manifold assembly  64  includes a plurality of additively manufactured manifold modules or manifolds  66  (e.g., manifolds  68 ,  70 ,  72 ,  74 ) plumbed together by flexible rubber hoses  76  and secured by clamps  77 . Although 4 manifolds  66  are depicted as part of the manifold assembly  64 , the number of manifolds  66  may vary (e.g., 1, 2, 3, 4, 5, etc.). 
     The rubber hoses  76  include a main supply line  78  and a main return line  80  for the liquid coolant. Each manifold  66  includes a main or primary fluid passage  79  coupled to either the main supply line  78  or the main return line  80 . In certain embodiments, one or more modules  66  may include two separate main or primary fluid passages  79  coupled to the main supply line  78  and the main return line  80 , respectively. For example, the manifolds  68  and  70  each include two main fluid passages  79  coupled to the main supply line  78  and the main return line  80 , respectively. The manifold  72  includes a single main fluid passage  79  coupled to the main return line  80 . The manifold  74  includes a single main fluid passage  79  coupled to the main supply line  78 . The integration of two main fluid passages  79  (e.g., supply and return passages) within a single module for both of the manifolds  68  and  70  simplifies the design, reduces leak paths, and saves space. In addition, the respective walls defining two main fluid passages  79  for each of the manifolds  68  and  70  may be coupled together via one or more structural ribs extending between the walls, thus, imparting more strength into the individual modules to enable them to act as mounting features between the gradient coil assembly  60  and the gradient coil cooling manifold assembly  64 . 
     Each manifold  66  includes at least one set of secondary fluid passages  82  coupled to the main fluid passage  79 . In certain embodiments, one or more modules  66  may include at least one set of secondary fluid passages  82  coupled to each of the two separate main or primary fluid passages  79  of the module  66 . The number of secondary fluid passages  82  in each set may vary (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.). The secondary fluid passages  82  are coupled to secondary hoses  84  of the rubber hoses  76 . The secondary hoses  84  are coupled to either inlets or outlets of cooling circuits of the gradient coil assembly  60 . For example the manifolds  68  and  70  include two or more sets of secondary fluid passages  82 . The manifolds  72  and  74  include a single set of secondary fluid passages  82 . An inner diameter of the respective wall of each main fluid passage  79  is greater than respective diameters of the respective walls of each secondary fluid passage  82  coupled to the respective main fluid passage  79 . 
     The respective walls (outer surfaces of the walls) of the one or more main fluid passages  79  and the secondary fluid passages  82  form barbed connectors or fittings. Each barb connector enables interface with the rubber hose  76  and the ability to retain pressurized fluid (e.g. water) via leak-tight connection. A combination of the orientation of the barbs on the outer surface of the barbed connectors and post-processing (e.g., via a vibratory finisher) after additive manufacturing enables the outer surface of the barbed connectors to be leak tight up to pressures of at least approximately 450 psi (3102 kPa) (which is 3× burst pressure of a pressure of approximately 150 psi (1034 kPa)). 
     As noted above, the manifolds  66  are additively manufactured. In particular, the manifolds  66  may be formed as single piece modules via direct metal laser sintering. The manifolds  66  may be made of a non-ferrous metal (non-magnetized metal) that can hold the necessary pressure (e.g., 450 psi (3102 kPa)). In certain embodiments, the manifolds  66  are made of stainless steel. In other embodiments, the manifolds  66  are made of aluminum. After being additively manufactured, the modules may be subject to post-processing. For example, a vibratory finisher may be utilized to optimize the outer surface of barb connectors on walls defining the secondary fluid passages  82 . 
     The modular design of the gradient coil cooling manifold assembly  64  provides many options in both manufacturing and service. For example, failures (e.g., mechanical failures) can be addressed at a module or assembly level. The gradient coil cooling manifold assembly  64  is flexible and the manifolds  66  can be removed or pushed aside to provide access to the gradient coil assembly  60 . The flexible nature of the gradient coil cooling assembly  64  also provides decoupling between the gradient&#39;s high frequency vibration and the manifold  66 . Critical space (e.g., axial space  86  (see  FIG.  3   ) between the manifold assembly  64  and the gradient coil assembly  60 ) is saved by matching the module&#39;s mainline geometry to that of the gradient coil assembly&#39;s circular shape and targeting the branches (e.g., secondary fluid passages  82 ) to their destination. In particular, as depicted in  FIG.  4   , the main fluid passage  79  of each manifold  66  is oriented to extend in a direction that is parallel with and aligned with the annular shape of the gradient coil assembly  60 . 
       FIGS.  5  and  6    are perspective views of an embodiment of the manifold  68  of the gradient coil cooling manifold assembly  64  of  FIG.  3   . The manifold  68  includes a first main or primary fluid passage  88  defined by a wall  90  and a second main or primary fluid passage  92  defined by a wall  94 . Each main fluid passage  88 ,  92  is open on both ends  95 . The walls  90  are coupled via structural ribs  96 . As depicted, two structural ribs  96  extend between and connect the walls  90 ,  94 . The number of structural ribs  96  may vary (e.g., 1, 2, 3, 4, etc.). The first main fluid passage  88  is configured to couple to the main supply line (e.g., main supply line  78  in  FIG.  3   ). The second main fluid passage  92  is configured to couple to the main return line (e.g., main return line  80  in  FIG.  3   ). The first main fluid passage  88  is fluidly coupled to a set  98  of secondary fluid passages  82  (which serve as secondary fluid supply lines coupled to the cooling chambers  65  within gradient coil assembly  60  in  FIG.  2   ). An inner diameter of the wall  90  of the first main fluid passage  88  is greater than respective diameters of the respective walls  104  of the set  98  of secondary fluid passages  82 . The second main fluid passage  90  is fluidly coupled to a first set  100  of secondary fluid passages  82  and a second set  102  of secondary fluid passages  82  (each of which serve as secondary fluid return lines coupled to the cooling chambers  65  within the gradient coil assembly  60  in  FIG.  2   ). An inner diameter of the wall  94  of the second main fluid passage  92  is greater than respective diameters of the respective walls  104  of each secondary fluid passage  82  of the first set  100  and second set  102  of secondary fluid passages  82 . As depicted, each set  98 ,  100 ,  102  of secondary fluid passages  82  includes 4 secondary fluid passages  82 . Each set  98 ,  100 ,  102  on opposite sides includes 2 secondary fluid passages  82  that initially extend away from the main fluid passage  88  or  92  and then toward one of the ends  95  of the main fluid passage  88  or  92 . Each set  98 ,  100 ,  102  includes 2 secondary fluid passages  82  branching towards one end  95  and 2 secondary passages  82  branching towards the opposite end  95 . 
     Each secondary fluid passage  82  is defined by a respective wall  104 . As depicted in  FIGS.  5  and  6   , an outer surface of each respective wall  104  forms a barb connector or fitting  106 . An outer surface of each of the walls  90  and  94  also form barb connectors or fittings  108  at each end  95 . Each barb connector  106 ,  108  enables interface with a respective rubber hose and the ability to retain pressurized fluid (e.g. water) via leak-tight connection. A combination of the orientation of the barbs on the outer surface of the barbed connectors  106 ,  108  and post-processing (e.g., via a vibratory finisher) after additive manufacturing enables the outer surface of the barbed connectors  106 ,  108  to be leak tight up to pressures of at least approximately 450 psi (3102 kPa) (which is 3× burst pressure of a pressure of approximately 150 psi (1034 kPa)). 
       FIG.  7    is a perspective view of an embodiment of the manifold  70  of the gradient coil cooling manifold assembly  64  of  FIG.  3   . The manifold  70  includes a first main or primary fluid passage  88  defined by a wall  90  and a second main or primary fluid passage  92  defined by a wall  94 . Each main fluid passage  88 ,  92  is open on both ends  95 . The walls  90  are coupled via structural ribs  96 . As depicted, two structural ribs  96  extend between and connect the walls  90 ,  94 . The number of structural ribs  96  may vary (e.g., 1, 2, 3, 4, etc.). The first main fluid passage  88  is configured to couple to the main supply line (e.g., main supply line  78  in  FIG.  3   ). The second main fluid passage  92  is configured to couple to the main return line (e.g., main return line  80  in  FIG.  3   ). The first main fluid passage  88  is fluidly coupled to a first set  110  of secondary fluid passages  82  and a second set  112  of secondary fluid passages  82  (each of which serve as secondary fluid supply lines coupled to the cooling chambers  65  within the gradient coil assembly  60  in  FIG.  2   ). An inner diameter of the wall  90  of the first main fluid passage  88  is greater than respective diameters of the respective walls  104  of each secondary fluid passage  82  of the first set  110  and the second set  112  of secondary fluid passages  82 . The second main fluid passage  92  is fluidly coupled to a set  114  of secondary fluid passages  82  (which serve as secondary fluid return lines coupled to the cooling chambers  65  within the gradient coil assembly  60  in  FIG.  2   ). An inner diameter of the wall  94  of the second main fluid passage  92  is greater than respective diameters of the respective walls  104  of each secondary fluid passage  82  of the set  114  of secondary fluid passages  82 . As depicted, the sets  110  and  112  of secondary fluid passages  82  includes 4 secondary fluid passages  82  and the set  114  includes 2 secondary fluid passages  82 . Each set  110  and  112  includes 2 secondary fluid passages  82  on opposite sides that initially extend away from the main fluid passage  88  and then toward one of the ends  95  of the main fluid passage  88 . Set  114  includes 2 secondary fluid passages  82  that initially extend away from the main fluid passage  92  and then toward one end  95  of the main fluid passage  92 . Each set  110  and  112  includes 2 secondary fluid passages  82  branching towards one end  95  and 2 secondary passages  82  branching towards the opposite end  95 . 
     Each secondary fluid passage  82  is defined by a respective wall  104 . As depicted in  FIG.  7   , an outer surface of each respective wall  104  forms a barb connector or fitting  106 . An outer surface of each of the walls  90  and  94  also form barb connectors or fittings  108  at each end  95 . Each barb connector  106 ,  108  enables interface with a respective rubber hose and the ability to retain pressurized fluid (e.g. water) via leak-tight connection. A combination of the orientation of the barbs on the outer surface of the barbed connectors  106 ,  108  and post-processing (e.g., via a vibratory finisher) after additive manufacturing enables the outer surface of the barbed connectors  106 ,  108  to be leak tight up to pressures of at least approximately 450 psi (3102 kPa) (which is 3× burst pressure of a pressure of approximately 150 psi (1034 kPa)). 
       FIG.  8    is a perspective view of an embodiment of the manifold  72  of the gradient coil cooling manifold assembly  64  of  FIG.  3   . The manifold  72  includes a single main or primary fluid passage  92  defined by a wall  94 . The main fluid passage  92  is open on one end  95  and closed on the opposite end  95 . The main fluid passage  92  is configured to couple to the main return line (e.g., main return line  80  in  FIG.  3   ). The main fluid passage  92  is fluidly coupled to a first set  116  of secondary fluid passages  82  and a second set  118  of secondary fluid passages  82  (each of which serve as secondary fluid return lines coupled to the cooling chambers  65  within the gradient coil assembly  60  in  FIG.  2   ). An inner diameter of the wall  94  of the main fluid passage  92  is greater than respective diameters of the respective walls  104  of each secondary fluid passage  82  of the first set  116  and the second set  118  of secondary fluid passages  82 . As depicted, the sets  116  and  118  of secondary fluid passages  82  each include 4 secondary fluid passages  82 . Each set  116  and  118  includes 2 secondary fluid passages  82  on opposite sides that initially extend away from the main fluid passage  88  and then toward one of the ends  95  of the main fluid passage  88 . Each set  116  and  118  includes 2 secondary fluid passages  82  branching towards the open end  95  and 2 secondary passages  82  branching towards the closed end  95 . 
     Each secondary fluid passage  82  is defined by a respective wall  104 . As depicted in  FIG.  8   , an outer surface of each respective wall  104  forms a barb connector or fitting  106 . An outer surface of the wall  94  forms a barb connector or fitting  108  on the open end  95 . Each barb connector  106 ,  108  enables interface with a respective rubber hose and the ability to retain pressurized fluid (e.g. water) via leak-tight connection. A combination of the orientation of the barbs on the outer surface of the barbed connectors  106 ,  108  and post-processing (e.g., via a vibratory finisher) after additive manufacturing enables the outer surface of the barbed connectors  106 ,  108  to be leak tight up to pressures of at least approximately 450 psi (3102 kPa) (which is 3× burst pressure of a pressure of approximately 150 psi (1034 kPa)). 
       FIG.  9    is a perspective view of an embodiment of the manifold  74  of the gradient coil cooling manifold assembly  64  of  FIG.  3   . The manifold  74  includes a single main or primary fluid passage  88  defined by a wall  90 . The main fluid passage  88  is open on one end  95  and closed on the opposite end  95 . The main fluid passage  88  is configured to couple to the main supply line (e.g., main supply line  78  in  FIG.  3   ). The main fluid passage  88  is fluidly coupled to a set  120  of secondary fluid passages  82  (each of which serve as secondary fluid supply lines coupled to the cooling chambers  65  within the gradient coil assembly  60  in  FIG.  2   ). An inner diameter of the wall  90  of the main fluid passage  88  is greater than respective diameters of the respective walls  104  of each secondary fluid passage  82  of the set  120  of secondary fluid passages  82 . As depicted, the set  120  of secondary fluid passages  82  includes 6 secondary fluid passages  82  circumferentially distributed about and extending toward the closed end  95  of the main fluid passage  88 . 
     Each secondary fluid passage  82  is defined by a respective wall  104 . As depicted in  FIG.  9   , an outer surface of each respective wall  104  forms a barb connector or fitting  106 . An outer surface of the wall  90  forms a barb connector or fitting  108  on the open end  95 . Each barb connector  106 ,  108  enables interface with a respective rubber hose and the ability to retain pressurized fluid (e.g. water) via leak-tight connection. A combination of the orientation of the barbs on the outer surface of the barbed connectors  106 ,  108  and post-processing (e.g., via a vibratory finisher) after additive manufacturing enables the outer surface of the barbed connectors  106 ,  108  to be leak tight up to pressures of at least approximately 450 psi (3102 kPa) (which is 3× burst pressure of a pressure of approximately 150 psi (1034 kPa)). 
     Technical effects of the disclosed embodiments include providing a gradient coil cooling manifold assembly that includes one or more additively manufactured manifold modules. The additively manufactured manifold modules include complex geometries that enable them to be optimized to produce maximum flow with minimal volumetric space, efficient fabrication, assembly, and service ability. Critical space (e.g., axial space between the manifold assembly and the gradient coil assembly) is saved by matching the module&#39;s mainline geometry to that of the gradient coil&#39;s circular shape and targeting the branches to their destination. Fabricating this complex geometry would be substantially more difficult with traditional module fabrication techniques. Additive manufacturing allows combining otherwise separate components into a single part enable to withstand the system parameters for cooling a gradient coil assembly of a MRI system. The disclosed embodiments enable less connections in the manifold assembly, thus, lowering the risk of leaks. In addition, less braze joints/fittings enables a lower risk of mechanical failure in the manifold assembly. Further, the custom precise geometry enables better cooling with fewer failures. Even further, the disclosed embodiments enable a lower cost manifold assembly. 
     The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f). 
     This written description uses examples to disclose the present subject matter, including the best mode, and also to enable any person skilled in the art to practice the subject matter, including making and using any devices or systems and performing any incorporated 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 insubstantial differences from the literal languages of the claims.