Abstract:
The present invention discloses a modular MRI imaging system. The imaging system includes MRI radio-frequency antenna arrays separate from the patient support structure. The antenna arrays are affixed to a thin, flexible film such that they may be located next to the anatomical region of interest. In addition, multiple antenna arrays may be configured in various planar or three-dimensional arrangements to optimize the FOV and SNR. Separate patient support structures are provided that enhance ergonomics and patient stabilization. By removing the antenna from the housing, the support structures may be designed without the constraints of supporting the antenna or the associated electronics. The MRI imaging system further employs a preamplifier module. The preamplifier module houses the preamplifier and much of the other associated circuitry for each of the antennae. The preamplifier module operates to combine the signals from the antenna arrays and pass the signals to the MRI system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. provisional application Ser. No. 61/187,522, filed Jun. 16, 2009, the entire contents of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to magnetic resonance imaging. More specifically, the subject matter relates to a modular and separable architecture of the radio frequency antenna arrays, the amplifier and channel combination circuitry, and the patient support, or stabilization, devices. 
     As is known to those skilled in the art, a magnetic resonance image (MRI) detects the faint nuclear magnetic resonance (NMR) signals given off by protons in the presence of a strong magnetic field after excitation by a radio frequency signal. The NMR signals are detected using antennae, commonly referred to as “coils.” 
     Antennae are configured to send signals to the host MRI scanner that enable trained practitioners to make appropriate diagnoses of an anatomical region of interest. For effective imaging, the antennae and their housing take on different shapes due to the shape of the anatomical region of interest. For example, the shape of a housing to fit over a shoulder is necessarily different than the shape of a housing used to image a foot. Similarly, the antennae and housings need to adapt for variations in the size of a particular anatomical region. For example, the same housing sized to fit a pediatric torso will not fit the torso of a large adult. As a result, the antennae and their corresponding housings must be designed to accommodate a broad range of anatomical regions of varying sizes, and imaging centers are required to invest in a significant number of coils to cover all imaging applications. Therefore, it would be desirable to provide an imaging system that reduces the number of sizes and configurations of housings required while servicing the same or an increased breadth of imaging applications. 
     Patient comfort and stabilization of the anatomy are important while obtaining an MRI because the procedures may last for tens of minutes and require the patient to remain still to prevent motion induced artifacts from appearing in the images. Historically, the antenna housing has served a dual role of stabilizing the anatomical region of interest and providing a support structure for the antennae and their associated electronic components. To assist with patient immobilization, housings have been formed from a rigid plastic to conform to different anatomical regions of interest. To assist with patient comfort, the housings may also include a layer of padding, such as foam, mounted on the support structure at points where the support structure contacts the patient. 
     However, requirements for designing the housing for patient comfort and for stabilizing the region of interest are often at odds with the requirements for improving the reception of the antennae within the housing. Because the sensitivity of an antenna to the NMR signals transmitted by the body decreases as the separation between the antenna and the body increases, it is desirable to place the antennae as close as possible to the anatomical region of interest, obtaining as high of a signal to noise ratio (SNR) as possible. However, design considerations for the housing to achieve patient comfort and stability impose practical limitations on how close the antennae may be placed to the anatomical region of interest. Therefore, it would be desirable to provide an imaging system that places the antennae close to the anatomical regions of interest without comprising patient comfort and stabilization. 
     Serviceability of an antenna is another important consideration for selecting an imaging system. If one of the antenna loops or other electrical component in a housing configured for a specific anatomical region were to fail, this housing and the enclosed electrical components must typically be returned to the vendor for repair. Due to the expense of each housing, an imaging center will often have only one of any particular size or configuration of housing. As a result, the imaging center loses revenue and must reschedule patients that would otherwise require that housing during the time it is out for repair. Therefore, it would be desirable to provide an imaging system with modular components at a low enough cost that spare parts may be kept on hand and readily exchanged in the event a component fails. 
     The ability to upgrade is still another important consideration when selecting an imaging system. The technology for MRI systems is constantly evolving with a trend towards higher channel count and more simultaneous imaging channels. The increased number of channels provides benefits, such as increased parallel imaging, faster scans, and images with higher signal to noise ration. Present imaging systems may have sixteen, thirty-two, sixty-four, or even ninety-six channels, with higher numbers of channels being planned. With the existing antenna and housing structures, the housings need to be upgraded as MRI scanners with higher channel counts are introduced to fully utilize the increased capabilities of the new MRI scanner. Therefore, it would be desirable to provide an imaging system which is scalable so that extra channels may be added as the capabilities of the MRI scanner allow. 
     SUMMARY OF THE INVENTION 
     Consistent with the foregoing and in accordance with the subject matter as embodied and broadly described herein, a modular and separable architecture of radio frequency antenna arrays, amplifiers, channel combination circuitry, and patient support, or stabilization, devices for use in MRI imaging is described in suitable detail to enable one of ordinary skill in the art to make and use the invention. 
     The present invention discloses an MRI radio-frequency antenna arrangement that is separate from the patient support structure. An antenna array includes multiple antenna loops and preferably includes either eight or sixteen loops, functioning as a one of the modular blocks of the present system. The antenna arrays are affixed to a thin, flexible film such that they may be located next to the anatomical region of interest. In addition, multiple antenna arrays may be configured in various planar or three-dimensional arrangements to optimize the field-of-view (FOV) and SNR. The arrays are modular such that additional arrays are readily added to increase the useable field-of-view and to support parallel imaging. 
     Separate patient support structures are provided that enhance ergonomics and patient stabilization. By removing the antennae from the housing, the support structures may be designed without the constraints of supporting the antennae or the associated electronics. The support structures are designed to provide support and stabilization for a particular anatomical region, but may also be designed to accommodate patients in a range of sizes to minimize the number of support structures required. Providing separate antenna arrays and support structures also allow components to be designed that are typically lighter than previous systems, facilitating transport and setup for imaging. 
     The MRI imaging system disclosed herein further employs a preamplifier module. The preamplifier module can automatically detect antenna arrays connected at the input connectors and determine how to process the signals to provide outputs sent to the MRI scanner. In addition, the preamplifier module houses the electronic components for the preamplifier circuit for each antenna loop along with signal processing circuitry for processing the signals received from each antenna loop connected to the preamplifier module. Each antenna loop has an electrical conductor connected to the loop by a feed circuit. All of the electrical conductors for an antenna array are bundled together and connected to the preamplifier box. The preamplifier box processes the signals from the antenna arrays, combines the signals if necessary, and passes the signals to the MRI scanner. 
     According to one embodiment of the present invention, a MRI receiver for detecting a plurality of NMR signals and for transmitting the NMR signals to a MRI scanner includes at least one antenna array. Each antenna array has a flexible substrate and a plurality of antennae mounted on the substrate, each antenna overlapping at least one other antenna. The MRI receiver also includes a cable having a plurality of electrical conductors corresponding to one of the antennae, and a preamplifier module having at least one input connector and at least one output connector. The input connector is configured to receive the cable to connect the preamplifier module to the antenna array, and the output connector is configured to connect the preamplifier module to the MRI scanner. The antenna array may also include a pick-up circuit mounted on the substrate to transfer the NMR signal received on each antenna to the corresponding electrical conductor. 
     As another aspect of the invention, a first antenna array is connected to a first input connector on the preamplifier module and a second antenna array is connected to a second input connector on the preamplifier module. The preamplifier module combines the signals from the first and second antenna arrays into a combined output transmitted on the output connector to the MRI scanner. 
     Thus, it is a feature of this invention to provide a modular system for detecting the NMR signals generated during magnetic resonance imaging. The separate antenna arrays allow freedom of placement, such as anterior and posterior positioning of an area to be imaged, to achieve desired coverage of an anatomical region. 
     As still another aspect of this invention, the antenna array is generally rectangular and may be selectively positioned in a generally planar first state or a generally arcuate second state. A spacer block extending between a first edge and a second edge of the antenna array at a first end of the antenna array is included. The spacer block is configured to be on the outer surface of the antenna array when the antenna array is in the second state and is configured to engage the inner surface of a second end of the antenna array overlapping the first end of the antenna array such that the second end of the antenna array is positioned at an angle to the first end of sufficient magnitude to minimize coupling between overlapping antennae. 
     Thus, it is another feature of this invention that the antenna array is configured to wrap around an anatomical region to be imaged such that the ends of the antenna array overlap without increasing coupling between overlapping antennae that would result in undesirable image artifacts. 
     According to yet another aspect of the invention, the MRI receiver may include a stabilization structure. The stabilization structure includes a base plate and a support member adjustably positioned on the base plate. The stabilization structure includes a first mounting surface to which a first end of the antenna array is removably connected, and a second mounting surface to which a second end of the antenna array is removably connected. An angle formed between the first mounting surface and the second mounting surface is of sufficient magnitude to minimize coupling between overlapping antennae. 
     It is still another aspect of the invention that the MRI receiver may include a shield for radiated emissions removably connected to the stabilization structure. The shield is a radio frequency (RF) blanket, including at least one conductive layer configured to prevent RF signals from radiating therethrough, a flexible outer layer substantially covering the conductive layer, and a fastener attached to the outer layer for connecting the RF blanket to the stabilization structure. The RF blanket may further include at least one absorbing layer covering one of the conductive layers wherein the conductive layer is either a sheet or mesh material. 
     According to another embodiment of the invention, a MRI receiver for receiving a plurality of NMR signals and for transmitting the NMR signals to a MRI scanner includes a stabilization structure which has a base plate and a support member adjustably positioned on the base plate. At least one antenna array is removably connected to the stabilization structure. Each antenna array includes a flexible substrate and a plurality of antennae mounted on the substrate, each antenna overlapping at least one other antenna. A preamplifier module has at least one input connector and at least one output connector. The input connector is configured to connect the preamplifier module to the antenna array, and the output connector is configured to connect the preamplifier module to the MRI scanner. A cable electrically connects the antenna array to the preamplifier module and has a plurality of electrical conductors corresponding to one of the antennae. The MRI receiver may also include a second stabilization structure adjustably positioned on the base plate 
     These and other objects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
       Preferred exemplary embodiments of the subject matter disclosed herein are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which: 
         FIG. 1  is an isometric view of one embodiment of the present invention configured to scan a leg of a patient; 
         FIG. 2  is a side view of the embodiment of the present invention in  FIG. 1 ; 
         FIG. 3  is a end view of the embodiment of the present invention in  FIG. 1 ; 
         FIG. 4  is an isometric view of another embodiment of the present invention configured to scan a leg of a patient; 
         FIG. 5  is an exploded isometric view of the embodiment of the present invention in  FIG. 4 ; 
         FIG. 6  is an isometric view of the antenna array in  FIG. 4 ; 
         FIG. 7  is a side elevation view of the antenna array in  FIG. 4 ; 
         FIG. 8  is a top plan view of the patient stabilization device of  FIG. 4 ; 
         FIG. 9  is a side elevation view of the patient stabilization device of  FIG. 4 ; 
         FIG. 10  is a bottom plan view of the patient stabilization device of  FIG. 4 ; 
         FIG. 11  is an isometric view of the preamplifier module of  FIG. 4 ; 
         FIG. 12  is an isometric view of another embodiment of the present invention configured to scan an arm of a patient; 
         FIG. 13  is a top view of the embodiment of the present invention in  FIG. 12 ; 
         FIG. 14  is an isometric view of the coil array and patient stabilization device in  FIG. 12 ; 
         FIG. 15  is an isometric view of another embodiment of the present invention configured to scan an arm of a patient; 
         FIG. 16  is an isometric view of another embodiment of the present invention configured for a smaller anatomical region or a pediatric head, neck, and spine; 
         FIG. 17  is an top view of the coil array shown in  FIG. 16  and laid flat; 
         FIG. 18  is an isometric view of another embodiment of the present invention configured to scan breast tissue of a patient; 
         FIG. 19  is a side view of one of the coil arrays in  FIG. 18 ; 
         FIG. 20  is an isometric view of the connector between the cable and the preamplifier box in  FIG. 18 ; 
         FIG. 21  is an exemplary embodiment of an antenna array according to the present invention; and 
         FIG. 22  is a flowchart showing the steps performed by the preamplifier module for auto detection of an antenna array at the input connector. 
     
    
    
     In describing the preferred embodiments of the invention which are illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the word “connected,” “attached,” or terms similar thereto are often used. They are not limited to direct connection but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The various features and advantageous details of the subject matter disclosed herein are explained more fully with reference to the non-limiting embodiments described in detail in the following description. 
     Referring to  FIGS. 1-3 , a first embodiment of an MM imaging receiver  10  according to the present invention is illustrated. In this embodiment, the imaging receiver  10  is configured to obtain images of a patient&#39;s leg and, specifically, the knee. The imaging receiver  10  preferably includes three fundamental components: the antenna arrays  20 , the patient stabilization structure  40 , and the preamplifier module  60 . Each antenna array  20  is a modular structure including multiple antenna loops  22 . The antenna arrays  20  preferably include eight, sixteen, or twenty-four individual antenna loops  22  arranged in one or more rows. Each row, for example, may contain eight antenna loops  22 . The antenna loops  22  are further arranged such that adjacent loops  22  overlap to reduce mutual coupling between the adjacent loops  22 , according to techniques known in the art. The antenna arrays  20  are mounted to a flexible, thin film substrate  28 , for example KAPTON®, such that the substrate  28  may be flexed in an arcuate manner positioning the antenna loops  22  around and close to an anatomical region to be imaged. At least one cable  32  is connected to the antenna array  20 . Each cable  32  includes at least one conductor  26  carrying the signals from each antenna loop  22 . The cables  32  are preferably pre-terminated to a single connector  30  (see, for example,  FIG. 4 ), such that each antenna array  20  may be quickly connected or disconnected as a single unit in the imaging receiver  10 . The modular nature of the antenna arrays  20  further allows multiple antenna arrays  20  to be used according to, for example, the requirements of a particular anatomical region to be imaged or the number of channels required by the MRI scanner. 
     The embodiment shown in  FIGS. 1-3 , uses two, sixteen-loop arrays  20 . A first array  20  is positioned on the anterior side of the knee and a second array  20  is positioned on the posterior side of the knee. Each antenna array  20  is curved around the respective surface of the knee such that the array  20  is positioned in close proximity to the area to be scanned. The conductors  26  are gathered together into a cable  32  and pass through an opening  46  in the stabilization structure  40 . The opening  46  may be a hole sized to permit a connector  30  attached to the antenna array  20  to pass through. Optionally, the opening  46  may be a slot, extending to one edge of the lower housing  42 , in which the cable  32  may be inserted. The cables  32  extend through a cavity within a lower housing  42  on the stabilization structure  40  to a connector portion of the stabilization structure  40 . The connector portion may have the cables  32  from the antenna array  20  plug into a mating connector on the stabilization structure  40 , which, in turn, plugs into the preamplifier module  60 . Alternately, the connector portion on the stabilization structure  40  may provide a means by which the connectors  30  on the cables  32  from the antenna array  20  are held in place by the stabilization structure  40 , for example by a clip, tab, pin, or other retaining means, such that the connector  30  may be directly connected to the preamplifier module  60 . As still another option, the connector  30  may pass through the lower housing  42  without being secured to the lower housing  42  and connect directly to the preamplifier module  60 . 
     The patient stabilization structure  40  shown in  FIGS. 1-3 , is configured to both provide support to the leg and to help prevent movement of the leg, and particularly the knee, during imaging. The stabilization structure  40  includes a lower housing  42  configured to rest on the MRI table. A base plate  44  is secured to the upper surface of the lower housing  42 . Alternately, the base plate  44  may be integrally formed with the lower housing  42 . The base plate  44  includes the opening  46  through which the cabling from the antenna arrays  20  may be passed. The base plate  44  may further include an array of mounting holes  58 , as seen in  FIG. 12 . The patient stabilization structure  40  is removably connected to the preamplifier module  60  by aligning and inserting the connector portion of the patient stabilization structure  40  with the input connectors  64  on the preamplifier module  60 . 
     The patient stabilization structure  40  further includes at least one and preferably two support members  48 . The bottom surface of the support members  48  is generally flat such that it rests on the upper surface of the base plate  44  and further includes mounting pegs (not shown) extending from the bottom surface of the support member  48 . The mounting pegs on the support members  48  may be inserted into the array of mounting holes  58  on the base plate  44  such that the support members  48  may be positioned on the base plate  44  in a configuration to best support the anatomical region of interest, for example the leg of the patient. The support member  48  further includes a pair of sides generally opposed to each other and extending away from the base plate  44 . A curved upper surface connects the two side surfaces with the curve of the upper surface extending downward into the support member  48 . The support member  48  may be produced in varying sizes to accommodate different sized patients as well as different portions of the anatomical region of interest.  FIGS. 1-3  illustrate two such sizes, configured to support the upper and the lower portion of a leg. Each of the support members  48  preferably includes a pad  50  inserted within the curved upper surface. The pad  50  provides support and comfort to the patient. Pads  50  of varying thicknesses may be provided to adjust the inner radius of the curved surface to better accommodate patients of varying sizes. 
     The support member  48  additionally includes a patient securing portion. For example a strap  52  connected to the support member  48  extends over the leg to secure the leg within the support member  48 . The strap  52  may be removably connected from one or both sides of the support member  48  to assist entry and exit of the patient. The strap  52  may be fastened by any means known in the art to provide an adjustable length, for example using a hook and loop fastener, such that the strap  52  securely contacts the patient and generally restricts motion of the leg with respect to the support member  48 . 
     One or more preamplifier modules  60  are used in the imaging receiver  10  to transfer the signals from the antenna arrays  20  to the MRI scanner. The preamplifier module  60  may rest on and optionally be secured to either the MRI table or the patient stabilization structure  40 . The preamplifier module  60  may further be covered by or enclosed within an outer layer for further patient support and/or comfort. For example, a foam pad (not shown) may be placed on the upper surface of the preamplifier module  60  to support a portion of the patient&#39;s body, such as the foot. Alternately, the preamplifier module  60  may be enclosed within a portion of the housing configured to support a portion of the patient, for example the patient&#39;s legs. The preamplifier module  60  includes at least one input connector  64 . Each input connector  64  is configured to receive the input signals from an antenna array  20 . The preamplifier module  60  further includes one or more output connectors  66 . Each output connector  66  is configured to provide signals to the MRI scanner. The preamplifier module  60  may further be configured to combine the input channels into a lower number of output channels. For example, multiple antenna arrays  20  may be used to provide sixty-four channels of input to the preamplifier module  60 . However, the MRI scanner may be designed to receive only thirty-two channels of input. The preamplifier module  60  can convert the higher number of input channels to the appropriate number of output channels. In addition, the preamplifier module  60  may auto-detect which input connector  64  has a connector  30  from an antenna array  20  plugged into it and may also read an antenna array identification (ID) from the connector  30 . The preamplifier module  60  may similarly auto-detect which physical stabilization structure  40  is connected. The preamplifier module  60  performs processing on the input signals according to which type of antenna array  20 , patient stabilization structure  40 , or combination thereof is connected to the preamplifier module  60 . 
     Referring next to  FIGS. 4-11 , another embodiment of an MRI imaging receiver  10  according to the present invention is illustrated. In this embodiment, the imaging receiver  10  is again configured to obtain images of a patient&#39;s leg and, specifically, the knee. The imaging receiver  10  includes an antenna array  20  and a preamplifier module  60 . The antenna array  20  and preamplifier module  60  may each be removably connected to a patient stabilization structure  40 . 
     In this embodiment, a single antenna array  20  is used and wraps around the anatomical region to be imaged. The antenna array  20  may be, but is not limited to, a sixteen-loop array. The antenna loops  22  are arranged such that adjacent loops  22  overlap to reduce mutual coupling. Any suitable arrangement of rows, and numbers of loops  22  per row, may be used to form the antenna array  20 . For example, the antenna array  20  may have three rows of antenna loops  22  including five loops  22  in the first and third rows with six loops  22  in the second row. Referring also to  FIG. 21 , each antenna loop  22  is mounted to a flexible, thin film substrate  28 . Pick-up circuits  24  are similarly mounted on the substrate  28  and connected to each antenna loop  22 . Preferably, one pick-up circuit  24  exists for each antenna loop  22 . However, it is contemplated that a single circuit may include multiple channels, receiving signals from multiple antenna loops  22 . A conductor  26  is connected to each pick-up circuit  24  to transmit the NMR signals received by each loop  22  from each pick-up circuit  24  to the preamplifier module  60 . All of the conductors  26  are bundled into a cable  32  that is pre-terminated to one or more connectors  30  and removably connected to one or more input connectors  64  on the preamplifier module  60 . 
     The antenna array  20  may also include a protective cover  25  for each of the pick-up circuits  24 . As illustrated in  FIG. 6 , the protective cover  25  is preferably elongated and may be configured to extend between a first side  27  and a second side  29  of the antenna array  20 . The pick-up circuits  24  and the corresponding protective covers  25  are spatially separated along the length of the array  20  to interface with each antenna loop  22 . The protective covers are preferably constructed of a rigid material to provide lateral stability in the antenna array  20 . As a result, the protective covers  25  restrict side-to-side flexing of the array  20  while permitting the array  20  to be flexed along the length of the array  20 , curving a first end  21  of the array back to a second end  23  of the array in an overlapping manner. It is contemplated that the protective covers  25  may be arranged in other suitable shapes or configurations, and, optionally, separate protective covers and lateral support members may be provided in the array  20 . 
     The antenna array  20  further includes a protective outer layer  31 . The outer layer  31  preferably covers the substrate and antenna loops  22 . Optionally, the outer layer may also cover the protective covers  25 . The outer layer  31  may be a foam layer to provide additional comfort to the patient during imaging. 
     Because the antenna array  20  wraps around the region being imaged, the antenna array  20  preferably includes a fastener  19 , including but not limited to a hook and loop fastener, to secure the first end  21  of the array to the second end  23  of the array. The outer surface of the first end  21  includes one of the hook or loop portions  19   a  of the fastener and the inner surface of the second end  23  includes the other of the hook or loop portions  19   b . The second end  23  of the array may also include a tab  33  extending longitudinally from the array  20  across at least a portion of the width of the array  20 . The hook or loop portion  19   b  of the second end  23  may similarly be placed along the inner surface of the tab  33  such that the array  20  may be overlapped by a varying amount, resulting in a varying diameter curvature to the array  20 . Optionally, any suitable fastening means for use in conjunction with an MRI scanner may be used. 
     The antenna array  20  further includes at least one spacer block  34 . As seen in  FIG. 7 , the spacer block  34  is preferably located at the first end  21  of the array, and the hook and loop fastener  19   a  may be placed on the outer surface of the spacer block  34 . The spacer block  34  has a generally trapezoidal cross-section. The cross-section is narrowest along a first edge  35  of the spacer block  34 , positioned nearest the first end  21  of the array  20 , with a gradually increasing thickness to a second edge  36  of the spacer block  34 . The thickness of the spacer block  34  is selected to minimize coupling between overlapping antenna loops  22 , increasing as the size of the antenna loops  22  increases. 
     The patient stabilization structure  40  includes a base plate  44  and at least one support member  48 . The support member  48  positions and provides stability to the anatomical region to be imaged. The support member  48  is preferably curved such that the anatomical region being imaged, for example a leg or an arm, is supported within the curved surface. A pad  47  may also be provided on the curved surface to increase the comfort of the patient. 
     As previously discussed, the antenna array  20  may include a fastener  19  to secure the first end  21  of the array to the second end  23  of the array. When the antenna array  20  is used in cooperation with the patient stabilization structure  40 , a first mating portion  51 , corresponding to the hook or loop portion  19   a  on the antenna array  20 , is positioned on the inner curved surface of the support member  48 . The first end  21  of the antenna array  20  may then be removably connected to the support member  48  by attaching the hook or loop portion  19   a  to the first mating portion  51 . The support member  48  also includes a mounting plate  49  which may either be connected to or integrally formed with the support member  48 . A second mating portion  53 , corresponding to the hook or loop portion  19   b  on the antenna array  20 , is positioned on the mounting plate  49  of the support member  48 . The second end  23  of the antenna array  20  may then be removably connected to the mounting plate  49  by attaching the hook or loop portion  19   b  to the second mating portion  53 . The mounting plate  49  is further oriented at a sufficient angle to the curved surface of the support member  48 , providing sufficient separation between overlapping antenna loops  22  to prevent coupling between the loops  22  in a manner similar to the spacer block  34  discussed above. 
     The support member  48  may also be variably positioned on the base plate  44 . A hub  54  extends away from the support member  48  and engages an elongated opening  43  in the base plate  44  such that the support member  48  is slidably positioned along the opening  43 . The hub  54  may be spring-biased, such that a force applied to the support member  48  in the direction of the base plate  44  permits the support member to slide along the opening  43 . Removing the force permits the spring to bias the outer edges of the hub  54  against the base plate  44  at the edges of the opening  43 , positively retaining the support member  48  in position along the opening  43 . Optionally, any other securing means may be used to secure the support member  48  along the opening  43 , including, but not limited to, a threaded portion on the hub and a nut. The hub  54  further permits the support member  48  to rotate about the hub with respect to the base plate  44 , providing an additional degree of alignment with a patient&#39;s body for increased patient comfort. 
     The patient stabilization structure  40  may further include a second support member  48 . The second support member  48  slidably engages the base plate  44  along one or more openings  43  and may be used, for example to support the leg of the patient which is not being imaged. The second support member  48  may further be configured to accept optional accessories to be mounted thereto including, but not limited to, additional padding for patient comfort or a shield for radiated emissions such as a radio frequency (RF) blanket  55  to prevent image wrap around from occurring. Image wrap around occurs when the antenna array  20  detects NMR signals generated from an area outside of the desired field of view (FOV), for example, a leg not being imaged. The RF blanket  55  prevents transmission of radiated emissions between the area covered by the blanket and the antenna array  20 . The RF blanket  55  may include, for example, one or more conductive layers, such as copper, which may be either a solid surface or fine mesh, and one or more absorptive layers. The RF blanket  55  also includes a flexible outer layer substantially covering the conductive and absorptive layers and a fastener attached to the outer layer. The fastener may be a hook and loop fastener and removable connect the RF blanket  55  to the second support member  48 . Optionally, the RF blanket  55  may be integrally formed with the patient stabilization structure  40 . 
     A cavity  57  is integrally formed in the patient stabilization structure  40  to receive the preamplifier module  60 . Walls  59  extend upward around at least a portion of the periphery to positively retain the preamplifier module  60  within the cavity  57 . A portion of the periphery of the cavity  57  is preferably open to slidably receive the preamplifier module  60 . Optionally, walls  59  may extend upward around the entire periphery and the preamplifier module  60  may be inserted through an open top side of the cavity  57 . Openings in the walls  59  provide access to the preamplifier module  60 , for example, to connect cables to the input connector  64  and output connector  66  of the preamplifier module  60 . 
     According to yet another feature of the invention, the patient stabilization structure  40  is pivotally mounted, for example, to the table of an MRI scanner. The patient stabilization structure  40  may be rotated plus or minus one hundred eighty degrees to facilitate imaging of either the right or left anatomy. 
     Referring to  FIGS. 12-14 , another embodiment of an MRI imaging receiver  10  according to the present invention is illustrated. This embodiment of the imaging receiver  10  is configured to obtain images of a patient&#39;s arm and, specifically, the wrist. The lower housing  42  of the patient stabilization structure  40  is configured to be offset from the preamplifier box such that it may comfortably support and stabilize an arm of a patient which would be oriented along or overhanging the edge of an MRI table. A connector portion of the patient stabilization structure  40  plugs into one of the leftmost or the rightmost connectors on the preamplifier box. A first portion of the housing extends generally perpendicular to the axis of insertion  68  to the preamplifier box and towards the edge of the table. A stabilizing portion of the housing extends generally parallel to and along the side of the preamplifier box. The stabilizing portion rests on the table and contacts the preamplifier box to reduce rotational forces exerted on the connector when a patient&#39;s arm is placed on the stabilization structure  40 . The main portion of the lower housing  42  connects to the first portion of the housing and extends generally parallel to the axis of insertion  68  of to the preamplifier box and along the MRI table. The lower housing  42  encloses a cavity through which the cable  32  from the antenna array  20  may be directed to the connector portion of the patient stabilization structure  40 . 
     At least one surface of the lower housing  42  includes an array of mounting holes  58 . The mounting holes  58  may be included in a base plate  44  secured to the lower housing  42  or alternately the mounting holes  58  may be integrally molded into the lower housing  42 . Preferably both surfaces of the lower housing  42  include the array of mounting holes  58  such that one patient stabilization structure  40  may be configured to be inserted into either the leftmost or the rightmost connector on the preamplifier module  60  and have the mounting holes  58  on the upper surface of the lower housing  42 . 
     The embodiment illustrated in  FIGS. 12-14  includes two support members  48 . A first support member  48  is shown which is identical in construction to the support member  48  disclosed for the leg. The modular nature of the support members  48  permits them to support either an arm or a leg. Depending on the region of anatomical interest to be scanned, two of the first support structures may be used to stabilize the upper and the lower portion of the arm, permitting the elbow to be imaged. Alternately, as illustrated in  FIGS. 12-14 , the wrist may be the region to be scanned and a second support member  48  to support the hand may be provided. The bottom surface of the second support members  48  is generally flat such that it rests on the upper surface of the lower housing  42  or base plate  44  and further includes mounting pegs (not shown) extending from the bottom surface of the support member  48 . The mounting pegs on the second support member  48  may be inserted into the array of mounting holes  58  on the base plate  44  and positioned on the base plate  44  in a configuration to best support the arm or hand of the patient. 
     A pair of hand retaining members  56  is connected to the upper surface of the second support member  48 . The main body of each retaining member  56  is generally rectangular in shape and includes a tab portion at the distal end of the retaining member  56 . The retaining members  56  extend upward from the support member  48  and generally opposing each other. The tab portion of each retaining member  56  interlocks the tab portion of the other retaining member  56  to secure the retaining members  56  around the hand of a patient. Alternately, any means of connecting the two retaining members  56  around the hand of a patient suitable for use in an MRI scanner as is known in the art may be used. 
     Due to the modular nature of the system, the antenna array  20  described previously for imaging a patient&#39;s leg may also be used to image a patient&#39;s arm. In this embodiment, a single antenna array  20  is positioned generally around the side of the wrist oriented towards the base plate  44  of the stabilization structure  40  and extending around to the front and rear of the wrist. The conductors  26  from the antenna array  20  are gathered together to form a cable  32  and pass through an opening  46  in the lower housing  42 . The opening  46  is preferably sized to permit a connector  30  attached to the antenna array  20  to pass through. Alternately, the opening  46  may be a slot extending to one edge of the lower housing  42  and sized to permit the cable  32  to be inserted. The cables  32  extend through the cavity in the lower housing  42  to the connector portion. The cable connector  30  may alternately be joined to the preamplifier module  60  through a mating connector attached to the lower housing  42  or by securing the cable connector  30  in the lower housing  42  such that it is oriented in the connector portion to engage the preamplifier module  60 . 
     Referring next to  FIG. 15 , another embodiment of an MRI imaging receiver  10  according to the present invention is illustrated. In this embodiment, the imaging receiver  10  is again configured to obtain images of a patient&#39;s arm and, specifically, the wrist. The antenna array  20  and preamplifier module  60  as discussed previously with respect to imaging a leg may be used independent of a patient stabilization structure. Other stabilization methods as known in the art, for example sand bags placed along either side of the arm may be used in cooperation with the imaging receiver  10 . The preamplifier module  60  may be positioned next to or overhead of the patient as is convenient to provide a connection between the antenna array  20  and the MRI scanner. Optionally, one or more antenna arrays  20  may be used with one or more preamplifier modules  60 , the antenna arrays  20  curved or laid flat against the anatomical region to be imaged, as required to obtain the desired image. 
     Referring to  FIGS. 16-17 , another embodiment of an antenna array  20  for use in the MM imaging receiver  10  is disclosed. The antenna array  20  of  FIGS. 16-17  is preferably used for imaging the head, neck, and spine of pediatric patients. A first row comprised of multiple antennae form a spinal array configured to be placed under and extending along the spine of the patient. Alternately, the spinal array may be formed from multiple rows of antenna coils. At one end of the spinal array, the conductors  26  from each antenna loop  22  are combined to form a cable  32  extending to the preamplifier module  60 . At the other end of the spinal array, a second array of antenna coils is connected. 
     The second array of antenna coils is preferably connected to the spinal array such that the two arrays form a “T” shape. The second array of antenna loops  22  is illustrated as including two rows of eight antenna loops  22 . Alternately, the second array may include any suitable configuration, such as a single row or additional rows of antenna loops  22  of varying numbers of antenna loops  22 . The second array is configured to be curved upward around the head of a patient. It is contemplated that the pediatric antenna array  20  may be made of multiple arrays  20  integrally formed into a “T” shape or, alternately, multiple, separate antenna arrays  20  may be positioned to form a “T” shape. The pediatric antenna array  20  is used in coordination with an appropriate stabilization structure  40  to provide simultaneous images of the head, neck and spinal region of a patient. 
     Referring to  FIGS. 18-20 , another embodiment of a series of antenna arrays  20  configured for use in imaging breast tissue is disclosed. Four antenna arrays  20  are provided. The antenna arrays  20  are used along with an appropriate stabilization structure  40  such that one array  20  is placed on each side of a breast. Optionally, a single antenna array  20 , wrapped around the chest of the patient, or two antenna arrays, one positioned around each breast, may be used along with an appropriate stabilization structure  40  to image the breast tissue. In  FIG. 17 , each antenna array  20  includes two rows of antenna loops  22  although any suitable antenna array  20  may be used. A cable  32  extends from one end of antenna array  20  and may be directly connected to a preamplifier module  60 . Each array  20  may be connected to a different input connection of the preamplifier module  60  or, optionally, to an input connection of different preamplifier modules  60 . Although, each of the above-described configurations preferably permits both breasts to be simultaneously imaged, the antenna arrays  20  may also be arranged to image a single breast. 
     Referring to  FIG. 21 , an exemplary embodiment of an antenna array  20  is disclosed. The illustrated antenna array  20  includes three rows of antenna loops  22 , each row having eight antenna loops  22 . It is contemplated that the antenna array  20  may have varying numbers of rows of antenna loops  22  and varying numbers of loops  22  within each row. The antenna loops  22  are arranged such that adjacent loops  22  overlap to reduce mutual coupling between adjacent loops  22 , according to techniques known in the art. The antenna arrays  20  are mounted to a flexible, thin film substrate  28 , for example KAPTON®, such that the substrate  28  may be flexed in an arcuate manner, the curvature of the substrate  28  preferably following the rows of antenna loops  22 . A pick-up circuit  24  is joined to each antenna loop  22 , for example by soldering. A conductor  26  is also connected to the each pick-up circuit  24  for transmitting the signal received by the antenna loop  22 . Each conductor  26  is routed together to form a cable  32 . The cable  32  is preferably pre-terminated to a single connector  30 , such that each antenna array  20  may be quickly connected or disconnected as a single unit in the imaging receiver  10 . The modular nature of the antenna arrays  20  allows multiple antenna arrays  20  to be used according to, for example, the requirements of a particular anatomical region to be imaged or the number of channels required by the MRI system. 
     Referring also to  FIG. 10 , the preamplifier module  60  includes, in part, the electronic components associated with the preamplifier circuits of each antenna loop  22 , which have commonly been included within the housing used to hold the antenna coils. Dividing these electronic components into a separate module reduces the number of electronic components required to be mounted to the antenna arrays  20  and facilitates providing separate antennae arrays  20  and patient support structures. Optionally, the preamplifier circuits may be divided into sections and supplied in part on the antenna array  20  and in part within the preamplifier module  60 . Similarly, the entire preamplifier circuit may still be provided on the antenna array  20 . It is further contemplated that a portion of the circuit may be provided within the cable  32  or connector  30  as a cable assembly (not shown). Further, the preamplifier module  60  may auto-configure itself, described below, and may bypass a portion or all of the preamplifier circuitry contained within the preamplifier module if duplicate circuitry exists on the antenna array  20  or within the cable assembly. 
     The preamplifier module  60  can auto-configure itself according to the devices connected to it and perform initial processing on the signals received from the antenna arrays  20  prior to passing the signals to the MRI scanner. The preamplifier module  60  initially detects the components connected to it using a processor executing a stored program and information stored on a memory device connected to the processor. For example, each antenna array  20  may be assigned a unique identifier and provide a signal to the preamplifier module  60  indicative of this identifier. The program may then access the memory device to determine the attributes of the antenna array  20 , such as the number of loops  22 , within with the antenna array  20 . 
     Similarly, each stabilization structure  40  may be configured to provide an identifier to the preamplifier module  60 . For example, an additional connector may be included on the preamplifier module  60  which engages a corresponding connector on the stabilization structure  40 . The support structure ID may be passed using this additional connector. Alternately, a series of switches may be mounted on the preamplifier module  60 . Each stabilization structure  40  may engage the preamplifier module  60  such that a different combination of switches is engaged for each stabilization structure  40 . Alternately, any means known in the art may be used to provide a support structure ID to the processor in the preamplifier module  60 . 
     As still another step in the auto-configuration process, the preamplifier module  60  interfaces with the MRI scanner to determine the number of channels available on the MRI scanner. The preamplifier module  60  then determines how to process the signals from the antenna arrays  20  according to the number of input channels, the anatomical region being imaged, and the number of channels available on the MRI scanner. For example, the preamplifier module  60  may permit signals to simply pass through from the antenna loop  22  to the MRI scanner. Alternately, the preamplifier module  60  may configure switching and combination logic to read signals from the appropriate set of antenna arrays  20 . The preamplifier module  60  may arrange signals from multiple arrays  20  to provide a single array of signals with a higher number of channels to the MRI scanner. In this manner, the preamplifier module  60  may facilitate using multiple antenna arrays  20  to scan a FOV beyond the size of a single antenna array  20 . Alternately, the preamplifier module  60  may also be used to convert the number of channels available from the coil arrays  20  to the number of channels available on the MRI scanner. For example, the combined number of channels from each of the coil arrays  20  connected to the preamplifier module  60  may be greater than the number of channels available on the MRI scanner. The preamplifier module  60  can combine the signals input from the coil arrays  20  to output the appropriate number of channels to the MRI scanner. 
     As still another aspect of the invention, multiple preamplifier modules  60  may be used in cooperation with multiple antenna arrays  20  to provide the output signals to the MRI scanner. Each preamplifier module  60  may receive input signals from one or more antenna arrays  20  as required by the imaging applications. An output cable  72  and connector  70  may be provided to connect each preamplifier module  60  to the MRI scanner. 
     Referring to  FIG. 22 , a flowchart  100  illustrating, in part, the automatic configuration of the preamplifier module  60  is disclosed. The preamplifier module  60  is first connected  102  to the MRI scanner using a cable between at least one, and preferably each, of the output connectors  66  of the preamplifier module  60  and the MRI scanner connectors. An antenna array  20  is connected  104  to one of the input connectors  64  on the preamplifier module  60 . The preamplifier module  60  detects  106  the presence of an array  20  at each of the input connectors  64  having an antenna array  20  connected. The preamplifier module then determines  108  whether a new antenna array has been added to the system. If no new antenna array has been added, the antenna array IDs previously detected are read  110  from memory and moved to an output register. 
     If a new antenna array  20  is identified at one of the input connectors  64 , the preamplifier determines  112  whether the new array  20  has an array ID. If the antenna array  20  does not have a valid array ID or the preamplifier module  60  is unable to read the array ID, then the preamplifier module  60  indicates to the MRI scanner that it is not ready to begin imaging. If the antenna array  20  has an array ID, the preamplifier module  60  reads  114  the array ID from the new device, and that array ID is moved  110  to the output register. The preamplifier module sets  116  the number of input channels according to the array ID information and configures the combiner within the preamplifier module  60 . The combiner may be configured to parallel process multiple images, combine multiple arrays into a single image, pass channel information directly to the MRI scanner, or convert the input channels to the appropriate number of output channels for the MRI scanner. 
     The preamplifier module  60  next determines whether the new device includes a patient stabilization structure  40 . If the new device is a patient stabilization structure  40 , the array ID is updated  120  to indicate that a new patient stabilization structure  40  has been connected. After updating the array ID or if the new device was not a patient stabilization structure  40 , the preamplifier module  60  then reinitiates  122  reading all of the coil ID information. If no changes  124  have been made to the inputs to the preamplifier module  60  and no unidentified devices have been detected, the preamplifier module  60  indicates  126  to the scanner that it is ready to scan. If the number of inputs to the preamplifier module  60  changed, the process of identifying what antenna arrays  20  are connected and configuring the preamplifier module  60  is repeated. 
     Different MRI scanners have different requirements for identifying which antenna arrays  20  are connected to the preamplifier module  60  and, ultimately, to the MRI scanner. The preamplifier module  60  may be configured to communicate to different MRI scanners to properly identify the type and number of antenna arrays  20  connected to the preamplifier module  60 . For example, the memory device in the preamplifier module  60  may include a second table of coil IDs that properly identify the antenna arrays  20  for different MRI scanners. The second coil ID may subsequently be passed to the MM scanner. Alternately, the preamplifier module  60  may include one or more additional connectors to either directly provide identifying electrical signals to the MRI scanner or to pass identifying signals through from the antenna arrays  20  to the MM scanner. 
     The preamplifier module  60  may additionally be used to help configure the MRI scanner. By sending the IDs of the coil arrays  20  and the patient stabilization structures  40  to the MM scanner, the MRI scanner is able to present the proper scanning protocols to the technician according to the imaging system that is connected to the scanner. 
     The preamplifier module  60  can also be used to detect the number of times a specific antenna array  20  has been connected to the preamplifier module  60 . This function enables the pre-amplifier module  60  to detect if an antenna array  20  has been used in excess of a contracted number of uses or expected lifetime. 
     It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention