Radio frequency coil assembly for magnetic resonance imaging system and method of manufacturing same

Abstract

To provide a radio frequency coil assembly (2) for an MRI system (10).SOLUTION: A support structure (6, 130) extends between a first end (86) and a second end (88) in a first direction and between an inner surface (82) and an opposite outer surface (80) in a second direction perpendicular to the first direction. The support structure (6, 130) has channels (100) that extend into the support structure (6, 130) in the second direction. An RF coil (4) is configured to transmit and / or receive RF signals. The RF coil (4) is supported by the outer surface (80) of the support structure (6, 130). The channels (100) are at least partially positioned between the support structure (6, 130) and the RF coil (4) in the first direction and are configured to convey a cooling medium to cool the support structure (6, 130) in use.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to radio frequency (RF) coil assemblies and methods of manufacture, and more particularly to RF coil assemblies for magnetic resonance imaging systems and methods of manufacture. [Background technology]

[0002] This section includes discussion intended to aid in the understanding of various aspects of the presently disclosed subject matter below. This discussion is not to be construed as an admission of prior art.

[0003] Modern magnetic resonance imaging (MRI) systems provide imaging based on the effects of introducing electromagnetic waves (e.g., radio frequency signals) and various magnetic fields into a subject, such as a patient. MRI systems can include a primary coil assembly (or primary magnet) that generates a primary magnetic field, one or more gradient coils that interact with the primary magnetic field to generate magnetic gradients, a radio frequency (RF) transmitter that outputs an RF signal into the magnetic field, and an RF receiver that receives the RF signal that passes through the primary magnetic field. The RF transmitter and RF receiver are sometimes collectively referred to as an RF transceiver, an antenna, or a body coil. MRI systems then generate image data as a visual representation of the subject based on the effects of these RF signals and magnetic fields on the subject.

[0004] It will be appreciated that components involved in generating, transmitting, and / or receiving RF signals and magnetic fields typically generate heat during use. Various regulatory and safety requirements are imposed to ensure that heat generated by these and other components does not cause patient injury or unstable equipment. Accordingly, MRI systems also include various cooling components to cool these components during use. Summary of the Invention

[0005] This Summary is provided to introduce some of the concepts that are described later in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended for use as an aid in limiting the scope of the claims.

[0006] One aspect of the present disclosure generally relates to an RF coil assembly for a magnetic resonance imaging (MRI) system. The RF coil assembly includes a support structure extending between a first end and a second end in a first direction and extending between an inner surface and an opposing outer surface in a second direction perpendicular to the first direction. The support structure has a channel extending into the support structure in the second direction. An RF coil configured to transmit and / or receive RF signals, the RF coil being supported by an outer surface of the support structure. The channel is disposed at least in part between the support structure and the RF coil in the first direction. The channel is configured to convey a cooling medium for cooling the support structure during use. The cooling medium includes a forced air flow or forced cooled-air flow. A salient aspect of the present invention relates to providing a structure capable of efficiently cooling an RF coil assembly to maintain temperature stability.

[0007] In one embodiment, the support structure is cylindrical and the channel extends radially inward from an outer surface of the support structure.

[0008] In one embodiment, the channels are separate annular channels. In yet another embodiment, the separate annular channels are formed parallel to one another.

[0009] In certain embodiments, the support structure extends a length between a first end and a second end in a first direction, and the channels together extend a distance in the first direction, the distance the channels extend being less than 50% of the length between the first and second ends of the support structure, In further embodiments, the RF coil extends a length between its first and second ends in the first direction, and the distance the channels extend is between 50% and 200% of the length of the RF coil.

[0010] In one embodiment, the support structure includes a base portion and a standoff portion, the standoff portion being located between the base portion and the RF coil, and the channel being defined at least in part by the standoff portion.

[0011] In one embodiment, the support structure includes a base portion and a standoff portion, the standoff portion being positioned between the base portion and the RF coil, and the channel being positioned between the standoff portion and the base portion, respectively.

[0012] In a particular example, the cooling medium is air and further includes a fan for circulating the air within the channel.

[0013] Another aspect according to the present disclosure generally relates to a method for manufacturing an RF coil assembly for a magnetic resonance imaging (MRI) system. The method includes providing a support structure extending between a first end and a second end in a first direction and extending between an inner surface and an opposing outer surface in a second direction perpendicular to the first direction. Channels are provided in the support structure, each of the channels being closer to the outer surface than to the inner surface in the second direction. The method further includes positioning an RF coil to be supported by the outer surface of the support structure, and positioning the RF coil such that the channels are positioned at least partially between the RF coil and the support structure in the first direction. The RF coil is configured to transmit and / or receive RF signals. The channels are configured to carry a cooling medium for cooling the support structure in use.

[0014] In one embodiment, the method further includes machining an exterior surface of the support structure to provide channels therein.

[0015] In one embodiment, the method further includes machining an exterior surface of the support structure such that each channel forms a separate, annular channel.

[0016] In one embodiment, the method further includes machining an exterior surface of the support structure such that the plurality of channels are formed by one channel spirally wound around the periphery of the support structure.

[0017] In one embodiment, the support structure extends a length between a first end and a second end in a first direction, and the method further includes providing the channels to together span a distance in the first direction that is less than 50% of the length between the first end and the second end of the support structure.

[0018] In an embodiment, the method further includes positioning the RF coil so that it is centered in a first direction relative to the channel.

[0019] In one embodiment, the method further includes forming a support structure by coupling a standoff portion to an outer surface of the base portion, and positioning the RF coil on the standoff portion when positioning the RF coil to be supported on the outer surface of the support structure.

[0020] In an embodiment, the method further includes positioning an RF coil in the standoff portion such that the RF coil at least partially forms a channel.

[0021] In some embodiments, the method further includes operatively coupling a fan to blow air as a cooling medium into the channel.

[0022] In one embodiment, the method further includes positioning one or more circular or tubes disposed within the channel, fluidly connecting a pump to the one or more tubes, and configuring the pump to circulate liquid through the one or more tubes in the channel to cool the support structure during use.

[0023] Various other features, objects and advantages of the present disclosure will become apparent from the following description taken in conjunction with the drawings.

[0024] The present disclosure will be described with reference to the following drawings. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram of an MRI system according to the present disclosure. [Diagram 2] FIG. 1 is a cross-sectional side view of an MRI system according to the present disclosure. [Diagram 3] This is a temperature map of the inner surface of a coilform for an MRI scanner. [Figure 4] FIG. 2 is an isometric bottom view of an RF coil assembly according to the present disclosure. [Diagram 5] FIG. 2 is a close-up side view of an RF coil assembly according to the present disclosure. [Figure 6] 1 is a close-up side view of another RF coil assembly according to the present disclosure. [Figure 7] FIG. 2 is an isometric side view of another RF coil assembly according to the present disclosure. [Figure 8] 1 is a close-up side view of another RF coil assembly according to the present disclosure. [Figure 9] 1 is a close-up side view of another RF coil assembly according to the present disclosure. [Figure 10] 4 is a process flow diagram of a method for manufacturing an RF coil assembly according to the present disclosure. [Figure 11] FIG. 5 is a close-up bottom view of the coilform of FIG. [Figure 12] FIG. 5 is an isometric top view of the bottom inner surface of the coilform of FIG. [Figure 13] FIG. 5 is a top view of the coilform of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The present disclosure relates generally to radio frequency (RF) coil assemblies and methods of manufacture thereof, and more particularly to RF coil assemblies for magnetic resonance imaging (MRI) systems, which, as described further below, may be incorporated into MRI systems similar to those currently known in the art, such as, for example, the 3.0T SIGNA™ MR manufactured by GE Healthcare.

[0027] 1 illustrates an MRI system 10 incorporating an RF coil assembly 2 according to the present disclosure. The MRI system 10 includes an imaging portion 12 and a processing portion 14 configured to process data received from the imaging portion 12 in a manner currently known in the art. The imaging portion 12 of the MRI system 10 is generally supported within a housing 16. The components of the imaging portion 12 are supported within the housing 16 to generally surround a bore 18 of the MRI system 10. The bore 18 is configured such that an object for imaging may be placed therein, such as a human patient 19 lying on a patient table 20.

[0028] The magnet system 22 in the imaging portion 12 is supported within the housing 16 and includes a primary coil assembly 30 and an EMI shielding coil assembly 40. The primary coil assembly 30 has one or more coiled sections of conductive material (e.g., metal wire) wound around a supporting structure, referred to as a coilform, in a manner known in the art. The primary coil assembly 30 is configured to generate a static, stable, spatially uniform magnetic field (also referred to as the B0 field) across the bore 18 in a manner known in the art.

[0029] Additionally, the EMI shielding coil assembly 40 is comprised of one or more coil sections formed of conductive material (e.g., metal wire) that is wound into a coil form in a manner known in the art. The EMI shielding coil assembly 40 is configured to shield or protect the B0 magnetic field generated by the primary coil assembly 30 from low frequency electromagnetic interference (EMI). By way of example, sources of low frequency EMI include nearby traffic, parking lots, or moving metal objects that generate magnetic fluxes in the vicinity of the MRI system that, if not mitigated, disrupt the uniformity of the B0 magnetic field. The conductive materials of both the primary coil assembly 30 and the EMI shielding coil assembly 40 are configured to become superconducting when in use. When superconducting, these coils have near zero resistance and therefore can carry very large currents. This generates a strong magnetic field to provide high quality images.

[0030] As shown in FIG. 1, the primary coil assembly 30 and the EMI shielding coil assembly 40 are enclosed in a cryostat vessel 32, which is filled with liquid helium under vacuum. The liquid helium is used to maintain temperatures within the primary coil assembly 30 and the EMI shielding coil assembly 40 near absolute zero. These low temperatures enable superconducting capability through the primary coil assembly 30, as well as through the EMI shielding coil assembly 40. The exterior of the cryostat vessel 32 is surrounded by insulation 34 in a manner known in the art to maximize cooling of the primary coil assembly 30 and the EMI shielding coil assembly 40. Additional insulation may also be provided between the primary coil assembly 30 and the EMI shielding coil assembly 40 to generally prevent heat transfer therebetween, with important exceptions discussed below.

[0031] The MRI system 10 of Figure 1 includes additional coil assemblies 50 supported within the housing 16 and which provide various functions currently known in the art. These additional coil assemblies 50 can include active shims, passive shims, and step-down coils as well as gradient magnet coils 52. These additional coil assemblies 50 include one or more coil sections that collectively generate magnetic gradients in the B0 magnetic field generated by the primary coil assembly 30 along any of the three X, Y, and Z axes.

[0032] The MRI system 10 of FIG. 1 further includes an RF coil assembly 2 according to the present disclosure. In a particular embodiment, the RF coil assembly 2 includes one or more RF coils 4 and a support structure for supporting the RF coil 4, such as a coil-form 6 around which the RF coil 4 is wound. The RF coil 4 may be configured in a manner currently known in the art, also referred to as a "bird-cage" configuration. The RF coil assembly 2 of this embodiment is configured to transmit and receive radio frequency (RF) signals. In particular, the RF signals are transmitted from the coil 4 to a bore 18, and the RF signals are received from the bore 18 via the RF coil 4. In other embodiments, separate coils may be used to transmit and receive RF signals. The RF signals received by the RF coil 4 are then processed by a processor 14 to generate image data representative of an object within the bore 18 of the MRI system 10, in a manner known in the art.

[0033] The processing unit 14 of the MRI system 10 also includes a controller 60, a primary magnetic field controller 62, an EMI shielding coil controller 64, a gradient field control 65, an RF transmitter 66, an RF transmit-receive (TR) switch 68, an RF receiver 70, a memory system 72, and a display device 74. The controller 60, particularly via the primary magnetic field controller 62, controls the flow of current through the primary coil assembly 30, thereby controlling the strength of the electromagnetic B0 field within the bore 18. Similarly, the controller 60 controls the flow of current through the EMI shielding coil assembly 40 via the EMI shielding coil controller 64, and the flow of current through the magnetic gradient coil 52 via the gradient field controller 65. The specific mechanisms for controlling the primary coil assembly 30, the EMI shielding coil assembly 40, and the other components described above are generally known in the art.

[0034] The TR switch 68 selectively electrically couples the RF coil 4 to the RF transmitter 66 and the RF receiver 70 for transmitting and receiving RF signals. The controller 60, via the TR switch 68, causes the RF transmitter 66 to generate radio frequency (RF) magnetic field pulses. These RF pulses cause the magnetic field to excite magnetic resonance in the object within the bore 18. In a particular embodiment, the RF transmitter 66 generates signals at resonant frequencies centered on the Larmor frequencies of protons (hydrogen nuclei, 1H) and / or carbon (e.g., 13C nuclei). The RF receiver 70 is disconnected by the TR switch 68 while these RF excitation pulses are being generated. The TR switch 128 disconnects the RF coil 4 from the RF transmitter 66 and connects the RF receiver 70 to the RF coil 4. This allows the RF receiver 70 to receive magnetic resonance signals resulting from nuclei in the object excited by the RF excitation pulses. These magnetic resonance signals are received by the controller 60 and used to generate an image of the object by processing techniques currently known in the art.

[0035] 2 is a cross-sectional view of an MRI system 10 illustrating an RF coil assembly 2 according to the present disclosure. In this example, the RF coil assembly 2 includes one or more RF coils 4 of electrically conductive material wrapped directly around a coilform 6. The coilform 6, also referred to as a support structure, is generally cylindrical and extends along a length 87 in a first direction between a first end 86 and a second end 88. The coilform 6 has an outer surface 80 and an inner surface 82 defining a thickness 84 therebetween in a second direction perpendicular to the first direction. The coilform 6 may be formed of fiber reinforced glass epoxy and / or other composite materials currently known in the art.

[0036] FIG. 3 illustrates experimental data collected by the inventors that indicates heat generated within the MRI system 10 by operating the RF coil 4 in transmitting and receiving RF signals during imaging. In particular, FIG. 3 illustrates a temperature map 7 of the inner surface 82 of the coilform 6 at different locations along a length 87 between a first end 86 and a second end 88. A partial cross-sectional view of the RF coil 4 is also shown superimposed next to the temperature map 7. The RF coil 4 extends from between a first end 90 and a second end 92 to the end rings 91, 94. Thus, FIG. 3 illustrates the location of the end rings 91, 94 relative to the coilform 6. The temperature map 7 illustrates that the regions 96, 98 of the inner surface 82 that are axially aligned with the end rings 91, 94 of the RF coil 4 are at a higher temperature than the remainder of the coilform 6. By way of example, there are several sources of heat that may affect the inner surface 82 of the support structure. The end rings 91, 94 may generate heat via RF or eddy currents, as may the gradient coils themselves. The RF of the end rings 91, 94 can generate the highest peak temperatures for the support structure. The inventors have determined that cooling the coilform 6 from the outside as currently known in the art is not efficient. In particular, to reach those peak temperature locations from the ends of the support structure, the exterior surface along the entire length of the support structure must be cooled. Additionally, the air will draw heat away from the inner diameter of the gradient coil.

[0037] 2 and 3, the inventors have determined that the end rings 91, 94 of the RF coil 4 generate significant heat from the transmission of RF signals and from eddy currents caused by rapid changes in the magnetic field generated by operating the RF coil 4, or the gradient coil 52. As an example, the input power to the end rings 91, 94 to transmit these RF signals may be 200 W, acting as a substantial heat source. Eddy currents generated by rapid switching of linear magnetic field gradients induced in the RF coil structure, including the end rings 91, 94, may also contribute to substantial heating and temperature rise.

[0038] As mentioned above, the coilform 6 is one of the components of the MRI system 10 closest to the patient 19 within the bore 18. Thus, the temperature at the inner surface 82 of the coilform 6, both peak and average temperatures, is of great importance for patient safety and regulatory compliance. If the peak or average temperature rises above acceptable threshold limits, MRI systems currently known in the art will de-rate (reduce power to the coil) to reduce this temperature. However, this also reduces the system's ability to provide high image quality. As an example, these threshold limits may be a peak temperature of 41° C. and an average temperature of 25° C. Similarly, to minimize the rise in peak or average temperature, the magnetic field gradient amplitude and slew rate may need to be reduced. Both of these will reduce the performance of the MRI system and impair image quality.

[0039] MRI systems currently known in the art attempt to control temperature by providing cooling to the coilform, specifically by cooling the annular space between the RF coil and the gradient coil, and / or the annular space between the coilform and the patient. This cooling can be provided as airflow from a fan either within the MRI system or external to the MRI system using ducts or other conduits to direct the airflow into the MRI system. Similarly, cooling can be achieved by circulating a liquid coolant through conduits located in this annular space. Examples of liquid coolants include deionized water, deionized water with a mild algaecide, or glycol.

[0040] In certain embodiments, these conduits are placed in contact with the exterior surface of the coilform to maximize cooling of the exterior surface with the goal of also indirectly cooling the interior surface of the coilform. Whether by airflow or circulation of liquid coolant, MRI systems currently known in the art provide cooling along the entire length of the coilform, starting at one end of the MRI assembly to the opposite end. Conventional cooling is not specific to cooling the localized areas of elevated temperature, which can result in reduced efficiency.

[0041] Through experimentation and development, the inventors have discovered that cooling techniques currently known in the art are inefficient and ineffective in achieving the goal of managing the temperature of the coilform. In particular, significant airflow (or liquid cooling conduits) is required to cover the entire exterior surface of the coilform. As shown in the MRI system 10 of FIG. 3, the exterior surface of the coilform 6 is not heated uniformly, but rather concentrated at portions aligned with the end rings 91, 94. With this in mind, the systems and methods disclosed herein improve the cooling of the coilform 6 in part by providing cooling specifically at the heat source, the end rings 91, 94 of the RF coil 4.

[0042] FIG. 4 shows a coilform 6 according to the present disclosure separated from an MRI system 10. An RF coil 4 as described above is superimposed next to the coilform 6 to show the axial alignment therebetween. In the illustrated example coilform 6, channels 100 are formed circumferentially and radially inward from the outer surface 8, here having a depth 102, a width 104, and a rectangular cross-section. The depth 102 is less than the thickness 84 of the coilform 6. In particular examples, the depth 102 is between 2-25 mm, 4-12 mm, or 7-10 mm. As further examples, the depth 102 may be between 25-75% of the total thickness 84 of the coilform 6 (which may have a thickness between 4-12 mm, for example). Similarly, example widths 104 are between 3-20 mm, or between 7-15 mm. The size and shape of each channel 100 may vary from that shown in FIG. 4, including, for example, a cross-section that is semicircular, square (see FIG. 5), triangular, and / or shaped. Similarly, the present disclosure contemplates configurations having different numbers and / or densities of channels 100 along the length 87 of the coilform 6.

[0043] The channels 100 are defined in first and second regions 97 and 99 along the length 87 of the coilform 6. The first and second regions 97 and 99 generally coincide with the first and second regions 96 and 98 where the most heat is generated from the first and second end rings 91, 94 of the RF coil 4, respectively. In the example of FIG. 4, which may be configured for cooling via air, the channels 100 are defined parallel to one another with the RF coil 4 acting as a top cover that surrounds each channel 100 when the RF coil 4 is placed thereon. It should be appreciated that other covers, such as films or thin materials, may be placed between the exterior surface of the coilform 6 and the RF coil 4 to surround each channel 100. Each channel 100 is supplied with cooling air via a manifold 210 and conduits 116. Additional details related to the example of FIG. 4 are provided below.

[0044] In certain embodiments, the first region 97 and the second region 99 have a combined length that is less than 80%, 75%, 66%, 50%, 33%, or 25% of the length 87 of the coilform 6. In some cases, the combined length of the first region 97 and the second region 99 is between 50% and 200% of the length 95 between the first and second ends 90, 92 of the RF coil 4. Similarly, the first region 97 and the second region 99 of the coilform 6 having the channel 100 may span the same axial length as each other and / or generally correspond to the lengths of the first region 96 and the second region 98 of increased heat in the temperature map 7 of FIG. 3. In this manner, the channel 100 is generally located where the temperature map 7 indicates increased temperature relative to the remainder of the inner surface 82 of the coilform 6.

[0045] In some embodiments, the channels 100 are formed in the outer surface 80 of the coilform 6 by machining. In other embodiments, the coilform 6 is manufactured or otherwise formed with pre-existing channels 100 extending radially inward from the outer surface 80. Similarly, in some embodiments, the channels 100 are formed as separate annular channels that are parallel to one another and aligned coaxially with the central axis of the coilform 6. In other embodiments, the channels 100 in a given region (i.e., the first region 97) are formed as a single, connected, helical formation (encircling the outer surface 80 of the coilform 6), where the channels 100 are arranged to be connected in series.

[0046] In each case, the channels 100 are configured to carry a cooling medium to cool the outer surface 80 of the coilform 6, particularly in the areas most heated by the RF coil 4. Referring to FIG. 2, the channels 100 are fluidly coupled to a cooling system 110 that carries the cooling medium to and from the channels 100 and also cools the medium through a heat exchange and extraction system. It should be appreciated that the RF coil 4 does not itself cover all of the channels 100, so the channels 100 are otherwise covered or have separate sealed conduits 116 disposed therein (as shown). The cooling system 110 may include one or more fans and associated ductwork (collectively designated by reference numeral 112), and / or a pump and reservoir system 114 for carrying air or liquid coolant, respectively, as the cooling medium. The cooling system 110 may be located inside the casing of the MRI system 10 or outside the casing (which may be inside or outside the room in which the MRI system 10 is installed). The cooling system 110 may be controlled via the controller 60 described above in connection with FIG. 1, or via another control system similar to that used for cooling the coilform 6 as currently known in the art.

[0047] In the example of FIG. 2, the cooling system 110 is far enough away from the channels 100 to require a conduit 116 extending between the cooling system 110 and the channels 100 to carry the cooling medium. The configuration of FIG. 2 is further configured such that the channels 100 are formed together as a single helical groove within each of the first and second regions 97, 99. Additionally, the channel 100 of the first region 97 closest to the second region 99 is fluidly coupled thereto via a connecting conduit 118 that provides flow between the first and second regions 97, 99. As an example, the connecting conduit 118 may be disposed within another channel within the coilform 6 or may be a tube that fluidly couples two of the channels 100 of the first and second regions 97, 99. This allows a single conduit 116 to provide inflow flow from the cooling system 110 to the coilform 6 (here via the second region 99) and a single conduit 116 to provide outflow flow from the coilform 6 back to the cooling system 110 (here exiting the coilform 6 at the last portion of the channel 100 in the first region 97).

[0048] FIG. 5 shows an example of an RF coil assembly 2 in which the cooling medium is in direct contact with the channels 100 of the coilform 6. It should be appreciated that only a portion of the coilform 6 is currently shown, here generally corresponding to region 99 of FIG. 4. When air is used as the cooling medium, one or more fans, as described above, blow air directly across the walls 120 and floors 122 of the channels 100 to cool the coilform 6. The one or more fans or ductwork 112 may be of the same type, or indeed the same fans or fans (and associated ductwork) used in MRI systems currently known in the art. In the example of FIG. 1, the one or more fans or associated ductwork 112 are shown positioned in the annular space between the RF coil 4 and the magnet system 22 to blow air directly into the channels 100 of the coilform 6. It should be appreciated that the fan may also be physically located outside the imaging room due to potential hazards of ferro-magnetic attraction and loss of performance, providing airflow to the interior of the MRI system via ducting in a manner known in the art. In a particular embodiment, the airflow from a first fan and / or ductwork 112 is aligned with channels 100 in a first region 97 (see FIG. 4) of the coilform 6, and the airflow from a second fan and / or duct is aligned with channels 100 in a second region 99 of the coilform. As will be described below, in the presently disclosed RF coil assembly 2, a significantly smaller portion of the coilform 6 is cooled, so the fan may be smaller than that required in MRI systems currently known in the art. FIG. 5 also illustrates that end rings (here shown as end rings 94) may not be at the ends 5 of the overall packaging of the RF coil 4.

[0049] FIG. 6 illustrates another example of an RF coil assembly 2 according to the present disclosure, this time with a cooling medium moving through a conduit 124 (e.g., tube) disposed within the channel 100. The cooling medium may again be air or liquid coolant. The conduit 124 may be formed, for example, of nylon, PTFE, or other non-ferrous materials. The conduit 124 is fluidly coupled to a fan, in the case of air, and / or to a pump and reservoir system 114, in the case of liquid coolant, to circulate and cool the cooling medium. In the configuration of FIG. 6, the coilform 6 is indirectly cooled via heat transfer between the cooling medium in the conduit 124 and the coilform 6, specifically via contact with the walls 120 and floor 122 of the channel 100. The conduits 124 may be of the same type as those used for the conduits 106 extending to the cooling system 110 (see FIG. 2) and may be fluidly connected via quick-disconnect connections for ease of installation and maintenance in the field.

[0050] The conduit 124 may be secured in place within the channel 100 via an adhesive 126, such as an epoxy having a high dielectric constant (also called a "high k" epoxy). The adhesive 126 may adhere the conduit 124 to the wall 120, the floor 122, or both. The adhesive 126 may also be selected to improve heat exchange between the conduit 124 and the coilform 6.

[0051] It should be appreciated that other mechanisms for conveying the cooling medium to the channels 100 are also contemplated by the present disclosure. Similarly, as discussed above, the cooling system 110 may be located inside the housing 16, outside the housing 16, or a hybrid (combination) thereof. Alternative forms of ducts or manifolds are also contemplated by the present disclosure.

[0052] The coilform 6 may be manufactured in one piece via additive manufacturing methods known in the art. In this embodiment, the cooling channels 124 are made directly from the same material of the coilform 6 during the additive manufacturing process. This embodiment eliminates the need for additional material for the channel since the walls 122 and floor 120 of the channel 100 can directly form the cooling channels 124. The ability to manufacture or design the cooling channels by additive manufacturing is suggested for the different embodiments as an alternative method of manufacturing to achieve the same purpose.

[0053] In certain embodiments, the coolant for channel 100 is delivered from other cooling systems used to cool other components within MRI system 10. For example, the airflow or liquid coolant system used to cool gradient magnet coils 52 can be routed to also provide airflow to channel 100 in coilform 6 of RF coil assembly 2. In this manner, no additional fans or pumps are required beyond those already present in the MRI system, saving space, cost, and installation and maintenance time.

[0054] The present disclosure also contemplates configurations in which the channels 100 are not formed as circumferential rings around the outer surface 80 of the coilform 6. FIG. 7 illustrates an RF coil assembly 2 in which the channels 100 are formed as one or more serpentine grooves in the outer surface 80 of the coilform 6. In this example, the conduits 106 from the cooling system 110 (FIG. 2) include splitters to provide separate flows of cooling medium to the channels 100 in the first region 97 and the second region 99. Similarly, the cooling medium exiting the channels 100 in the first and second regions 97, 99 merge to be returned to the cooling system 110 via a shared conduit 106. Other configurations of the channels 100 and conduits 106 are also contemplated by the present disclosure.

[0055] The example of FIG. 7 further illustrates a configuration in which the cooling capacity varies in the first region 97 relative to the second region 99 in the coilform 6. In many cases, approximately the same amount of heat is generated in each end ring 91, 94. The thermal map 7 of FIG. 3 illustrates a configuration in which more heat is generated in the end ring 91 at the first end 90 of the RF coil 4 than the end ring 94 at the second end 92 of the RF coil 4. With this in mind, the RF coil assembly 2 of FIG. 7 provides that the serpentine grooves forming the channels 100 in the first region 97 cover a larger surface area of ​​the outer surface 80 than in the second region 99. This may be achieved by having a greater number of turns, a larger channel 100 (and / or tubes therein), and / or the like, as illustrated.

[0056] 8 illustrates another embodiment of an RF coil assembly 2 according to the present disclosure, in this case providing an alternative approach to machining or otherwise forming the coilform 6 to have channels 100. The RF coil assembly 2 includes a support lattice 130 supported (e.g., epoxied thereto using high-k epoxy resin) on an outer surface 80 of the coilform 6. The support lattice 130 has a base 132 extending from a first end 140 to an opposite second end 142. The base 132 further has a first surface 134 and an opposite second surface 136 having a thickness 138 therebetween. The fingers 144 are formed by walls 150 extending vertically away from the second surface 136 a distance 146 to tips 148.

[0057] Channels 152 are formed between the walls 150 of adjacent fingers 144, but may otherwise be similar to the channels 100 described above. In certain embodiments, the support grid 130 is formed of a fiber reinforced glass epoxy resin, which may be the same or different from the material of the coil form 6. The base 132 and fingers 144 may be integrally formed, formed separately and then bonded, or machined or fabricated using techniques known in the art. The fingers 144 may also be referred to as standoff portions of the support grid 130. Similarly, the base 132 may also be referred to as a base portion of the support grid 130. The base 132 and / or fingers 144 may surround the entire circumference of the coil form or may be provided at periodic radial intervals that define corners (e.g., as spokes extending from a hub) to reduce material, cost, and weight.

[0058] The tips 148 of the fingers 144 are configured to support the RF coil 4 thereon, similar to how the outer surface 80 of the coilform 6 supports the RF coil 4 in the embodiments described above. As such, the coilform 6, the support grid 130, or a combination thereof, may be referred to as the support structure that supports the RF coil 4 in the RF coil assembly 2 disclosed herein.

[0059] The inventors have recognized that providing channels 152 in the support grid 130, rather than directly in the coilform 6, advantageously allows coilforms 6 currently known in the art to be cooled in accordance with the present disclosure. This allows for easier integration of new MRI systems and / or the opportunity for retrofit or retrofit of existing MRI systems. The support grid 130 may also provide a more cost-effective solution for machining or otherwise forming the coilform 6 such that the channels 100 are formed therein.

[0060] In the example of Figure 8, the channels 152 formed between the base 132 and the fingers 144 of the support grid 130 open radially away from the bore 18 of the MRI system. In contrast, Figure 9 shows a similar support grid 130 disposed and supported on the outer surface 80 of the coilform 6 such that the channels 152 open radially inward toward the bore 18. In each case, a cooling medium is provided to flow through the channels 152, either directly, or via conduits disposed therein (as described above and shown in Figure 6).

[0061] FIG. 9 illustrates an example of a method 160 for manufacturing an RF coil assembly for an MRI system according to the present disclosure, as described above. Step 162 provides for providing a support structure extending between a first end and a second end in a first direction and extending between an inner surface and an opposing outer surface in a second direction perpendicular to the first direction. The support structure may be a coilform alone or in combination with other structures, such as a support grid, as described above. Conduits are provided within the support structure, each of the conduits being closer to the outer surface than the inner surface in the second direction. Step 164 positions the RF coil to be supported by the outer surface of the support structure, such that the conduits are positioned at least partially between the RF coil and the support structure in the first direction. The RF coil is configured to transmit and / or receive RF signals. The conduits are configured to carry a cooling medium for cooling an inner surface of the RF coil in use.

[0062] With further reference now to Figures 11-13, additional details will be provided regarding the embodiment of Figure 4. As discussed above, the coilform of Figure 4 is configured to be cooled via air. Openings 200 are provided through the coilform 6, with a first opening 200 aligned with the channels 100 of the first region 97 and a second opening 200 aligned with the channels of the second region 99. Each opening 200 extends along a length between a first end 202 and a second end 204 and extends along a width between a third end 206 and a fourth end 208. Two manifolds 210 are coupled to the inner surface 82 of the coilform 6 via fasteners (e.g., screws, rivets, or other fasteners known in the art) in the openings 211. Each manifold 210 extends along a length between a first end 212 and a second end 214, along a width between a third end 216 and a fourth end 218, and along a length between a top end 220 and a bottom end 222. The length of the manifold 210 corresponds to the length of the openings 200. In certain embodiments, the openings 200 are located at the bottom of the coilform 6, allowing the manifold 210 (which is internal to the coilform 6) to be hidden from view below the patient table 20, as shown in FIG. 1.

[0063] With continued reference to Figures 4 and 13, air enters the manifold through ports 224 connected to conduits (discussed above) and is directed perpendicularly across the channels 100 in the coilform 6. The air then circulates independently through each channel 100 before exiting through an outlet channel 230, here on the opposite side of the coilform 6 (e.g., above the patient and hidden from view under the patient cover). Figure 13 shows an example of an outlet channel 230 extending from a first end 232 to a second end 234 within the outer surface 80 of the coilform 6, specifically running perpendicular to the channels 100. In this manner, all of the channels 100 in a given region (first region 97 and second region 99) are interconnected such that all air flowing through that region is combined and exits together via the corresponding outlet channel 230.

[0064] It should be appreciated that the second ends 234 of the outlet channels 230 extend closer to the ends of the coilform (i.e., the first and second ends 86 and 88, as the case may be) than the outermost channels 100. This is necessary to ensure that the second ends 234 are not covered by the RF coil 4 or other covering device surrounding the channels 100. Thus, air enters the coilform 6 via the manifold 210 on the inner surface of the coilform 6 and exits via the outlet channels 234 on the outer surface of the coilform 6. It should be further appreciated that other positions and configurations of the manifolds and outlets are contemplated by this disclosure.

[0065] Through experimentation and calculation, the inventors have discovered that by cooling only those areas of the coilform 6 where the RF coil 4 generates heat that is transferred to the coilform 6 (primarily those areas aligned with the end rings 91, 94), less cooling is required compared to configurations currently known in the art. For example, a typical system currently known in the art may require a flow rate of 2-2.5 cubic meters per minute to cool the coilform 6. In contrast, the inventors have discovered that cooling only the first and second areas 97, 99 (see FIG. 4) of the coilform 6 can be accomplished with only one eighth (1 / 8th) of this flow rate. This allows for the use of smaller fans (or pumps and reservoirs in the case of liquid coolants), saving space within the MRI system 10 (or its external cooling system). It also reduces the noise level when operating the fans and pumps, saving costs. Variable speed fans can also be used for flexibility, such as to balance sound levels and cooling demands at a given time.

[0066] Similarly, the improved cooling provided by the presently disclosed systems and methods results in a lower operating temperature of the inner surface 82 of the coilform 6 during use, thereby avoiding the need to de-rate operation of the RF coil 4, primary coil assembly, EMI shielding coil assembly, gradient magnets, and / or shim coils to reduce heating, and improving safety and regulatory compliance in operating the MRI system 10.

[0067] Although the present disclosure generally focuses on MRI systems and the use of such systems for imaging patients, it should be appreciated that other uses are contemplated. For example, MRI systems can be combined with other types of medical imaging techniques, such as computed tomography (CT), positron emission tomography (PET), single photon emission computed tomography (SPECT), ultrasound, or any other system for generating images. Furthermore, the systems disclosed herein need not be limited to systems for imaging patients (human or animal), but can also be used for security or other purposes (e.g., airport baggage scanners).

[0068] The functional block diagrams, operational sequences, and flow diagrams provided in the figures are representative of example architectures, environments, and methodologies for implementing novel aspects of the present disclosure. For ease of explanation, the methodologies contained herein may be in the form of functional diagrams, operational sequences, or flow diagrams, and may be described as a series of acts, however, it is understood and appreciated that the methodologies are not limited by the order of acts, since some acts may occur in different orders and / or simultaneously with other acts as accordingly shown and described herein. For example, those skilled in the art will understand and appreciate that the methodologies may alternatively be expressed as a series of interrelated states or events, such as a state diagram. Moreover, not all acts illustrated in the methodologies are required for novel implementation.

[0069] This specification uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to make and use the invention. Certain terminology has been used for brevity, clarity, and understanding. Such terms are used for descriptive purposes only and are intended to be broadly interpreted, so that no unnecessary limitations should be inferred therefrom beyond the requirements of the prior art. 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 features or structural elements that do not differ from the language of the claims, or if they include equivalent features or structural elements that do not differ substantially from the language of the claims.

[0070] [Embodiment 1] An RF coil assembly (2) for a magnetic resonance imaging (MRI) system (10), comprising: a support structure (6,130) extending in a first direction between a first end (86) and a second end (88) and extending in a second direction perpendicular to the first direction between an inner surface (82) and an opposing outer surface (80), the support structure (6,130) having a channel (100) extending within the support structure (6,130) in the second direction; an RF coil (4) configured to transmit and / or receive RF signals, the RF coil (4) being supported by the outer surface (80) of the support structure (6, 130); Including, An RF coil assembly, wherein the channel (100) is disposed at least partially between the support structure (6, 130) and the RF coil (4) in the first direction, and the channel (100) is configured to transport a cooling medium for cooling the support structure (6, 130) during use. [Embodiment 2] 2. An RF coil assembly as described in embodiment 1, wherein the support structure (6, 130) is cylindrical in shape and the channel (100) extends radially inward from the outer surface (80) of the support structure (6, 130). [Embodiment 3] 3. An RF coil assembly as described in embodiment 2, wherein the channels (100) are separate annular channels. [Embodiment 4] 4. An RF coil assembly as recited in embodiment 3, wherein the separate annular channels are formed to be parallel to one another. [Embodiment 5] 2. The RF coil assembly of embodiment 1, wherein the support structure extends a length between the first end and the second end in the first direction, the plurality of channels extend together a distance in the first direction, and the distance over which the plurality of channels extend is less than 50% of the length between the first end and the second end of the support structure. [Embodiment 6] 6. The RF coil assembly of embodiment 5, wherein the RF coil extends a length between the first end and the second end in the first direction, and the distance over which the multiple channels extend is between 50% and 200% of the length of the RF coil. [Embodiment 7] 2. The RF coil assembly of embodiment 1, wherein the support structure comprises a base portion and a stand-off portion, the stand-off portion being disposed between the base portion and the RF coil, and the plurality of channels being at least partially defined by the stand-off portion. [Embodiment 8] 2. The RF coil assembly of embodiment 1, wherein the support structure comprises a base portion and a standoff portion, the standoff portion being disposed between the base portion and the RF coil, and the plurality of channels being disposed between the standoff portion and the base portion. [Embodiment 9] 2. An RF coil assembly as described in embodiment 1, wherein the cooling medium is air, and further comprising a fan for circulating air within the multiple channels. [Embodiment 10] 2. An RF coil assembly as described in embodiment 1, further comprising one or more tubes disposed within the plurality of channels, the cooling medium being a liquid conveyed within the one or more tubes in the plurality of channels to cool the support structure during use. [Embodiment 11] 1. A method of manufacturing an RF coil assembly for a magnetic resonance imaging (MRI) system, comprising: providing a support structure extending in a first direction between a first end and a second end and extending in a second direction perpendicular to the first direction between an inner surface and an opposing outer surface, wherein a plurality of channels are provided within the support structure, the plurality of channels extending within the support structure in the second direction; positioning an RF coil to be supported by the outer surface of the support structure, the plurality of channels being positioned at least partially between the RF coil and the support structure in the first direction; wherein the RF coil is configured to transmit and / or receive RF signals and the plurality of channels are configured to carry a cooling medium for cooling the support structure in use. [Embodiment 12] 12. The method of claim 11, further comprising machining the exterior surface of the support structure to provide the plurality of channels therein. [Embodiment 13] 13. The method of claim 12, further comprising machining the exterior surface of the support structure such that the plurality of channels are separate annular channels. [Embodiment 14] 13. The method of embodiment 12, further comprising machining an exterior surface of a support structure such that the plurality of channels are formed as channels wound helically around the support structure. [Embodiment 15] 12. The method of claim 11, further comprising providing the support structure to extend a length between the first end and the second end in the first direction, and the plurality of channels to extend together a distance in the first direction that is less than 50% of the length between the first end and the second end of the support structure. [Embodiment 16] 12. The method of embodiment 11, further comprising positioning the RF coil to be centered in a first direction with respect to the plurality of channels. [Embodiment 17] The method of embodiment 11, further comprising forming the support structure by coupling a stand-off portion to an outer surface of a base portion, and further comprising positioning the RF coil on the stand-off portion when positioning the RF coil to be supported by the outer surface of the support structure. [Embodiment 18] 18. The method of embodiment 17, further comprising positioning the RF coil on the standoff portion such that the RF coil at least partially forms the multiple channels. [Embodiment 19] 12. The method of embodiment 11, further comprising operatively connecting a fan to blow air as a cooling medium into the plurality of channels. [Embodiment 20] 12. The method of embodiment 11, further comprising positioning one or more tubes positioned within the plurality of channels, fluidly connecting a pump to the one or more tubes, and configuring the pump to circulate liquid through the one or more tubes in the plurality of channels to cool the support structure during use. [Explanation of symbols]

[0071] 2: RF coil assembly 4: RF coil 5: End 6: Coil form 7: Temperature map 10: MRI system 12: Imaging section 14: Processing section 16: Housing 18: Bore 19: Patient 20: Patient table 22: Magnet system 30: Primary coil assembly 32: Cryostat vessel 34: Insulation 40: EMI shielding coil assembly 50: Additional coil assembly 52: Gradient magnet coil 60: Control unit 62: Primary magnetic field control unit 64: EMI shielding coil control unit 65: Gradient magnetic field control unit 66: RF transmitter 68: RF transmit / receive (TR) switch 70: RF receiver 72: Storage unit 74: Display unit 80: Exterior surface 82: Interior surface 84: Thickness 86: First end 87: Length 88: Second end 90: First end 91, 94: End rings 92: Second end 95: Length 96, 98: Area 97: First area 99: Second area 100: Channel 102: Depth 104: Width 106: Conduit 110: Cooling system 112: Duct 114: Reservoir system 116: Conduit 118: Connecting conduit 120: Wall 122: Floor 124: Conduit 126: Adhesive 128: TR switch 130: Support grid 132: Base 134: First surface 136: Second surface 140: First end 142: Second end 144: Finger 146: Distance 148: Tip 150: Wall 152: Channel 200: Opening 202: First end 204: Second end 206: Third end 208: Fourth end 210: Manifold 212: First end 214: Second end 216: Third end 218: Fourth end 220: Top 222: Bottom 224: Port 230: Outlet channel 232: First end 234: Second end

Claims

1. 1. An RF coil assembly (2) for a magnetic resonance imaging (MRI) system (10), comprising: a support structure (6, 130) extending in a first direction between a first end (86) and a second end (88) and extending in a second direction perpendicular to the first direction between an inner surface (82) and an opposing outer surface (80), the support structure (6, 130) having a channel (100) extending within the support structure (6, 130) in the second direction; an RF coil (4) configured to transmit and / or receive RF signals, the RF coil (4) being supported by the outer surface (80) of the support structure (6, 130), the RF coil (4) extending in the first direction between the first end (86) and the second end (88) centered about the RF coil; Including, the channel (100) is disposed at least partially between the support structure (6, 130) and the RF coil (4) in the first direction, the channel (100) is configured to carry a cooling medium for cooling the support structure (6, 130) in use, and the channel (100) is non-uniformly distributed in the first direction to cool the support structure (6, 130) more near the first end (86) and the second end (88) of the RF coil (4) than near a center of the RF coil (4).

2. The RF coil assembly of claim 1, wherein the support structure (6,130) is cylindrically shaped and the channel (100) extends radially inward from the outer surface (80) of the support structure (6,130).

3. The RF coil assembly of claim 2 , wherein the channels (100) are separate annular channels.

4. 2. The RF coil assembly of claim 1, wherein the support structure (6, 130) extends a length (87) between the first end (86) and the second end (88) in the first direction, the channel (100) extends the same distance in the first direction, and the distance that the channel extends is less than 50% of the length between the first end and the second end of the support structure.

5. 5. The RF coil assembly of claim 4, wherein the RF coil (4) extends in the first direction a length between the first end (86) and the second end (88), and the distance the channel extends is between 50% and 200% of the length of the RF coil (4).

6. 2. The RF coil assembly of claim 1, wherein the support structure (6, 130) comprises a base portion (132) and a stand-off portion (144), the stand-off portion (144) being disposed between the base portion (132) and the RF coil (4), and the channel (100) being at least partially defined by the stand-off portion (144).

7. 2. The RF coil assembly of claim 1, wherein the cooling medium is air, and further comprising a fan for circulating air within the channel (100).

8. A method for manufacturing an RF coil assembly (2) for a magnetic resonance imaging (MRI) system (10), comprising the steps of: providing a support structure (6, 130) extending in a first direction between a first end (86) and a second end (88) and extending in a second direction perpendicular to said first direction between an inner surface (82) and an opposing outer surface (80), wherein a channel (100) is provided in said support structure (6, 130), said channel (100) extending in said second direction within said support structure (6, 130); positioning an RF coil (4) to be supported by the outer surface (80) of the support structure (6, 130) and such that the channel (100) is at least partially disposed between the RF coil (4) and the support structure (6, 130) in the first direction; Including, The RF coil (4) extends centrally between the first end (86) and the second end (88) in the first direction; the RF coil (4) is configured to transmit and / or receive RF signals, and the channel (100) is configured to carry a cooling medium for cooling the support structure (6, 130) in use; the channel (100) is configured to cool the support structure (6, 130) more near the first end (86) and the second end (88) of the RF coil (4) than near the center of the RF coil (4).

9. The method of claim 8, further comprising machining the exterior surface of the support structure (6, 130) to provide the channel.

10. The method of claim 9, further comprising machining the outer surface (80) of the support structure (6, 130) such that the channels (100) are a plurality of separate annular channels.

11. 9. The method of claim 8, further comprising the step of: providing the support structure (6, 130) extending in the first direction a length (87) between the first end (86) and the second end (88), and providing the channels (100) so that they co-extend a distance in the first direction that is less than 50% of the length (87) between the first end (86) and the second end (88) of the support structure (6, 130).

12. 9. The method of claim 8, further comprising forming the support structure by coupling a standoff portion to an outer surface of a base portion, and further comprising positioning the RF coil on the standoff portion when positioning the RF coil to be supported by the outer surface of the support structure.

13. The method of claim 12, further comprising positioning the RF coil (4) on the stand-off portion (144) such that the RF coil (4) at least partially defines the channel.

14. The method of claim 8, further comprising operatively connecting a fan (112) to blow air as a cooling medium into the channel.

15. 9. The method of claim 8, further comprising positioning one or more tubes (124) positioned within the channel (100); and fluidly connecting a pump (114) to the one or more tubes (124) and configuring the pump (114) to circulate liquid through the one or more tubes (124) in the channel (100) for cooling the support structure (6, 130) in use.

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