Abstract:
An assembly for magnetic resonance imaging (MRI) of a patient and a method of magnetic resonance imaging (MRI) of a patient using different MRI scanners is disclosed. In one example, the assembly includes a plurality of RF coils, wherein the RF coils are configured to be positioned adjacent to an anatomy of interest, a patient support structure configured to support of the patient, a base removably coupled to the patient support structure, the base and the patient support being configured for receipt in the bore of an MRI scanner, and an interface coupled to the plurality of RF coils and to the MRI scanner and configured to connect the plurality of RF coils and the MRI scanner and to selectively control a first RF coil and a second RF coil included in the plurality of RF coils.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims the benefit under 35 U.S.C. §120 to U.S. application Ser. No. 12/277,061, entitled “OPEN ARCHITECTURE TABLETOP PATIENT SUPPORT AND COIL SYSTEM,” filed on Nov. 24, 2008, which is herein incorporated by reference in its entirety. This application claims the benefit of U.S. Provisional Application No. 60/989,898, filed Nov. 23, 2007, and U.S. Provisional Application No. 60/989,904, filed Nov. 23, 2007, which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to devices and methods for positioning RF coils adjacent an anatomy of interest for imaging, and for facilitating connections between a magnetic imaging scanner and local RF coils used for the imaging in the bore of the magnetic imaging scanner. 
     BACKGROUND 
     In magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR) signals given off by protons in the presence of a strong magnetic field are detected after excitation by a radio frequency (RF) signal using antennae termed “RF coils”. Generally speaking, there are two types of RF coils: whole body RF coils, which are used to image large segments of a patient, and “local” or “surface” RF coils, which are configured to image specific anatomies of interest, such as the knees, shoulders, neck, breasts, hands and head. 
     Whole body RF coils are typically provided with commercially available MRI imaging systems. These RF coils provide a large field of view to accommodate, for example, the chest and abdominal regions of a human subject, and as a result, their fields couple to large amounts of tissue outside the region of interest being imaged. Because of the large field of view, the signal to noise ratio (SNR) of the signal in the anatomy of interest is relatively high, and quality factor of the RF coil is low. 
     Local RF coils are reduced in size and designed to couple solely with tissue in the region of interest. Local RF coils, therefore, are typically positioned as close as possible to the anatomy of interest, and limit the field of view of an MRI scan to the selected region. The result is a significantly improved SNR and quality factor, and a reduced image size that provides higher resolution of the area of interest. 
     To provide high resolution images of selected anatomy at high SNR, it is increasingly common to use a number of local RF coils simultaneously in parallel imaging techniques. In these techniques, images are acquired from multiple receive channels, for example 8, 16 or 32 channels receiving signals from 8, 16 or 32 RF coils respectively. In a typical multiple coil array arrangement, for example, several adjacent coils are provided for receiving signals during imaging. Coil switching, multiplexing, or dynamic coil selection strategies are used to optimize a subset of coils for imaging of anatomies of a smaller volume, or to switch between areas of interest during the image acquisition or imaging procedure. 
     To facilitate these parallel imaging techniques, there is a need for a device that allows an operator to position various types of RF coils adjacent an anatomy of interest while in the bore of a MRI scanner. Such a device should further facilitate connections between the MRI scanner and the RF coils, and allow for circuitry to switch between the coils. The present invention addresses these issues. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention provides an assembly for magnetic resonance imaging of a patient. The assembly comprises a patient support structure for positioning a local RF coil adjacent an anatomy of interest for imaging, and base removably coupled to the patient support structure for elevating the patient support structure, and a coil connector for receiving the local RF coil. The base is configured for receipt on a table sized and dimensioned for receipt in the bore of the MRI scanner, and the coil connector is coupled to an MR connector configured for connection to the MRI scanner to receive signals from the MRI scanner for controlling local RF coil. 
     In another aspect, the patient support structure is configured for imaging of the breast, and includes an anterior ramp, a posterior ramp, and a first and a second arched structure extending laterally along the edges of the anterior ramp and the posterior ramp to define an interventional opening therebetween. 
     In still another aspect, the base comprises a first platform corresponding to the anterior ramp and a second platform corresponding to the posterior ramp. When the patient support structure is aligned on the base, the portion of the ramp between the first platform and the second platform is aligned below and increases the interventional opening. 
     In another aspect of the invention, at least one of the patient support structure and the base include a plurality of slots and the other of the patient support structure and the base includes a corresponding plurality of tabs, wherein the patient support structure is selectively coupled to the base to minimize the possibility of tipping. 
     In still another aspect of the invention, the patient support structure includes a receptacle for receiving a tray including the coil connector. The patient support structure can also include an integrated RF coil. The tray can include circuitry for switching between a first RF coil connected to the connector in the tray and a second RF coil integrated in the patient support structure. The tray can also include the tray includes a moveable cover for accessing one or more connectors. 
     In yet another aspect of the invention, the base includes a raised rim that extends along the edges of the base between the first platform and the second platform. The bottom surface of the base can also include alignment feature for aligning the base with a corresponding alignment feature in a table configured for receipt in an MRI scanner. The alignment feature can, for example, be a tab or a slot. 
     The foregoing and other aspects of the invention will be described in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a patient supported on a patient support structure constructed in accordance with the present invention. 
         FIG. 2  is a perspective view of the patient support as supported on a base. 
         FIG. 3  is an alternate perspective view of the patient support and base configuration. 
         FIG. 4  is an exploded view illustrating the patient support, the base, and an underlying tabletop. 
         FIG. 5  is a bottom exploded view of the patient support structure  14  and associated base  16 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures and more particularly to  FIG. 1 , a patient is shown as supported on a patient support structure  14 . The patient support structure  14  is coupled to a base  16 , on the MRFs patient table  34  ( FIG. 5 ). The patient can be moved into the bore of the MRI scanner  10  for imaging. 
     Referring still to  FIG. 2 , the patient support structure  14  is the main structural component for supporting the patient and, as shown here, allows the patient to lie face down with the breasts hanging pendant, while positioned adjacent local RF coils for imaging. Specifically, the patient support structure  14  consists of a head support area or anterior support  9  and a lower support area or posterior support  7 , with an interventional opening  27  defined between, and positioned to receive the breasts of the patient. Two arches  11  extend laterally along the opening  27 , connecting the head support  9  to the lower patient support  7 , providing structure while maximizing the ability of medical personnel to access the breasts of a patient supported on the support member. The arches  11  preferably have a cross section of less than three square inches each. To increase the structural capacity of the patient support, a third cross member  96  ( FIG. 4 ) may be incorporated. The third cross member can be arched or straight and can be, for example, a thin, slender support adjacent to the patient&#39;s sternum, or a thin, slender support disposed along the patient&#39;s midline (left-right). When a third cross-member is used, it is preferably positioned as far anterior as possible relative to the patient. 
     Referring still to  FIG. 2 , the patient support structure  14  further includes a ramp  13  extending upward from the head support  9  and towards the interventional opening  27 , and a ramp  15  extending from the opening  27  toward the lower patient support  7 . This configuration allow physicians and technicians access to the breast from lateral, medial, superior, inferior and anterior approaches through the interventional opening. The general construction of the patient support structure is  14  described more fully in U.S. Pat. No. 7,379,769, issued on May 27, 2008, which is hereby incorporated by reference for its description of this device. Additional aspects of this invention are also described in the co-pending patent application Ser. No. 12/777,035 entitled “MICROCONTROLLER SYSTEM FOR IDENTIFYING RF COILS IN THE BORE OF A MAGNETIC RESONANCE IMAGING SYSTEM”, filed on May 10, 2010, which is hereby incorporated by reference. 
     Referring still to  FIG. 2  and now also to  FIG. 3 . The patient support structure  14  including apertures  31  and  33  for receiving local RF coils at locations selected to provide clinically relevant imaging, particularly to provide lateral imaging of the breast. In addition, RF coils  29   a ,  29   b ,  29   c ,  29   d  can be integrated into the patient support structure  14  to allow imaging with a higher signal to noise ratio, and in regions outside of the breast. Relevant positions are adjacent to the groin region ( 29   a ), neck ( 29   b ), underarm ( 29   c ,  29   d ) and adjacent to the back. These RF coils can be either fixed or removable. In addition to the coils shown, other coils, such as chest wall coils for improved imaging of the chest and auxiliary region, and interventional coils for imaging and providing interventional access points can also be used, as well as scout coils for imaging regions associated with breast cancer including: coils located in armpit region for imaging local lymph nodes; coils located in neck region for imaging local lymph nodes; coils located in the groin region; and coils wrapping around the back for coverage of the spine. 
     Referring still to  FIGS. 2 and 3 , and now also to  FIG. 4 , the base  16  can be a removable structure that can be selectively coupled to the patient support  14  to elevate the patient support  14 , and to provide additional support. Referring now specifically to  FIG. 4 , and also to  FIG. 5 , in one embodiment, the base structure  16  includes a plurality of slots  64 ,  66 ,  68 , and  70  that receive mating tabs  84 ,  86 , and  88  formed in a bottom surface at the patient support structure  14  and mechanically link the patient support structure  14  and base  16 . The base  16  preferably includes platforms  20  and  22  at the front and back end, and a non-elevated portion  24  connecting the platforms  20  and  22 . The elevated platforms  20  and  22  are preferably aligned with the anterior  9  area and posterior  7  portions of the patient support structure and enable additional access to the breast by elevating the patient and patient support  14  (posterior direction) above the underlying tabletop thereby increasing the size of the interventional opening  27  beneath the patient. The non-elevated portion  24  advantageously incorporates a raised rim  26  and  28  for entrapment of blood during biopsy procedures. 
     The removable base  16  further allows for the use of the same patient support structure  14  with various MRI systems  10 . For example, a patient support structure  14  can be selectively positioned on a base  16  that is specifically configured for a particular MRI system  10 . The base  16 , moreover, can be constructed at a height that is selected for a particular bore diameter of an MRI scanner. For example, the patient support structure  14  could be placed on the MRI table  34  without the base  16  when the MRI scanner has a 60 cm bore, but could be used in combination with the removable base  16  when the MRI scanner has a 70 cm bore, in order to provide better interventional access to the breasts, and to bring the breast tissues closer to the MRI&#39;s isocenter for better imaging. 
     Referring now to  FIG. 5 , mirrors or prisms  41  and lighting elements  43  to facilitate site lines to the breast for imaging or intervention can be integrated into the base  16 . An exemplary position for a mirror  41  is located at the superior line of the breast. Alternatively, the mirror  41  can be configured to be manually adjustable by the user. A low power array of lights can be powered, for example, through a connection to the MRI scanner  10  (not shown). Such lights illuminate the open region of the patient support  14 , in order to aid in positioning the patient, coil arrays, and needles. RF coils, such as a loop coil  94  located centrally on each breast, can also be integrated into the base  16 . In this application, a connector similar to the connector  17  described above can be provided to allow connection either directly to the MRI scanner  10  or to the cable tray  60 , described below. Connectors for connecting RF coils and devices for coupling interventional devices such as compression grids, or needle alignment devices can also be provided in the base  16 . 
     Although the base  16  is shown here as a separate component, the base  16  can also be embodied by legs that retractably extend from a bottom surface of the patient support  14  to raise or lower the patient support  14 . The configuration at the base  16  would be done by the operator before the patient is positioned on the patient support  14 , particularly to adapt the patient support  14  to the diameter of the bore of the MRI scanner  10  being used, and to create optimal space for the breasts and for physician access to the breasts. 
     Referring again to  FIG. 5 , the bottom surface of the base  16  can also include alignment features  40 ,  42 , such as the tabs shown here, to align the base  16  with corresponding apertures  44 ,  46  in the table  34 , and to mechanically couple the base  16  to the table  34  without the need for tools. The alignment features  40  and  42  can be used to guide the base  16  into position on the table  34 , and also to position the patient support  14  correctly. Support structures in the base  16  that receive tabs  72 ,  74  incorporated in the patient support  14  add rigidity to the patient support structure  14  and resist flex. Although a tab and slot connection is shown here, it will be apparent that mechanical fastening devices such as clips, pegs, clamps or straps can be coupled to slots  44  positioned along the edges of the table  34 . As shown here, the bottom surface of the patient support surface  14  preferably includes a similar tab structure to allow direct connection of the patient support structure  14  to the table  34 . 
     Referring still to  FIGS. 2  though  5 , both the patient support structure  14  and the base  16  include a number of features which can aid in reducing the tendency of the patient support  14  to tip. Particularly, the base  16  is designed to be weight-bearing, and is configured to be substantially as wide as the top surface of the patient support structure  14  extending as wide as possible in the left-right direction and to use substantially all of the cross-sectional area in the base. Therefore, when a patient is positioned on the patient support structure  14 , the patient does not overbalance the edge of the structure. The load, moreover, is supported along the raised edges  30  and  32  of the table  34  corresponding to the MRI system  10 . As discussed above, the base  16  includes slots  64 ,  66 ,  68 ,  70  ( FIG. 4 ) for receiving matching tabs  84 ,  86 ,  88  ( FIG. 5 ) in the patient support structure  14 . In addition to limiting the tendency to tip, these connectors ensure centering of the patient support structure  14  upon entry to the MRI scanner  10 . The corresponding slots and tabs, moreover, can provide an electrical connection to power, for example, RF coil elements  94  ( FIG. 5 ) in the base  16 . 
     Referring now to  FIGS. 2 and 3 , a receptacle  18  is provided in the patient support structure  14  for receiving a cable tray  60 , which simplifies connections between the local RF coils and the MRI scanner  10  through the connector  62 , as discussed below. Referring now also to  FIG. 5 , the cable tray  60  is shown received in the cable tray receptacle  18  of the patient support  14 . The cable tray  60  provides an electrical connection point for connecting local RF coils to the patient support, and is linked to connector  62  which is configured to be connected to the control system of the MRI scanner  10  for driving the RF coils. To limit noise, coaxial cables and signal lines are routed through the cable tray  60  and to the MRI system  10 . Local RF coils that are coupled to the patient support structure  14  or to the base  16  can be routed or connected to the cable tray  60  states indicator lights  80   a ,  80   b ,  80   c , can be provided to indicate that the RF coils connected to the cable tray  60  are a valid coil combination. An indicator  82  is activated by circuitry in the cable tray  60  when the connector  62  is fully connected to the MRI scanner  10 . 
     The housing of the cable tray may, as shown, enclose the connection points, and the electrical connections made by opening or removing a panel or panels  19  in the anterior end  9  of the patient support  14 , so that RF coils can be connected to receptacles in the cable tray  60 . In order to facilitate access to the connections of the cable tray  60  by the user, and to limit access by the patient, the panel  19  can be a folding, sliding or like covering that is integrated into the housing. Alternatively, the housing of the cable tray  60  can directly incorporate connectors (plugs or receptacles) which permit electrically connecting detachable RF coil arrays directly to the housing at cable tray  60 . The cable tray  60  is removably attached to the patient support  14  in receptacle  18  to allow a user to interchange the cable tray  60  for a system upgrade, transfer between magnets, or other reasons. Suitable connectors include, for example, latches, sliders, hook and loop fasteners, threaded fasteners, quarter-turn fasteners, and other mechanical coupling devices. 
     Internally, the cable tray  60  can include RF circuits for signal filtering, signal combination, shield current traps and baluns. Circuitry for determining the appropriate combination of RF coils can also be provided, and may include, for example, a microprocessor, or multiplexing or switching circuitry that provides intelligent selection of the RF coil arrays for imaging. Visual indicators such as light emitting diodes can be located in the cable tray  60  to provide coil status and configuration indicators to the user. 
     Although shown on a specific end of the patient support  14 , the cable tray  60  can be mounted at the anterior support  9  or posterior support  7  thereby allowing the cable tray  60  to be adapted to different MRI devices or scanners  10 . The cable tray  60  can be, as shown in the figures, centered between the left and right sides of the patient support  14 , and is preferably removable for cleaning. The cables are preferably sized to be sufficiently long to allow left/right and anterior/posterior movement of an attached RF coil for breast imaging, and to take up slack and tension, but are restricted in length to prevent tangling or interference with the moving parts of the system, or interference with relative motion between the patient support structure  14  and the bore of the MRI scanner  10 . 
     The cable tray  60  can include a plurality of plugs or receptacles corresponding to cables attached to RF coil arrays and elements that are moveable in the system. Cables can be permanently attached to the RF coil, or can include a connector that mates with the coil element. Alternatively, cables can be permanently attached to the cable tray, and include connectors for receiving mating connectors associated with local RF coils and coil elements. The RF coils can, for example, be provided with cords of 20-60 cm length which permit free positioning without undue signal loss or the possibility of looping. 
     Referring now to  FIG. 5 , a slider  50  coupled to the patient support structure  14  provides an attachment point for compression devices and RF coils. The sliders  50  are rigidly attached to the patient support structure  14 , and may be attached to the patient support structure  14  on the posterior  9 , anterior  7 , or both sides of the interventional gap  27  simultaneously. Compression plates and compression plates housing RF coils can be coupled to the slider  50  with several degrees of freedom and can, for example, house coils specifically designed for improved imaging of the chest wall. The RF coils in the compression system can be coupled to the MRI system  10  through the cable tray  60 , as described above. Compression plates and other devices suitable for the application are described more fully in U.S. Pat. No. 7,379,769, issued on May 17, 2008, which is hereby incorporated by reference for its description of these devices. 
     In use, therefore, the present invention provides many advantages over the prior art, providing significantly improved access to breast tissue for imaging and intervention, particularly from beneath the breast, superior and inferior to the breast. For newer MRI types having geometries with large bore sizes (for instance 70 cm versus 60 cm in diameter), the benefit of the larger bore can be utilized for breast imaging by raising the patient support structure  14  to a higher position in the bore for greater access. Additionally, by removing the base  16 , the patient support structure  14  can be lowered to provide room for larger patients. The base  16 , for example, can ensure access for the larger magnet (i.e. 70 cm bore), while the patient support structure  14  can be used without a base  16  for a smaller magnet (i.e. 60 cm bore), while the patient is located near the same relative central point in the magnet. 
     Integrated coils at openings located at the groin region can accommodate coils allowing for survey scans of that region for signs of cancer progression. RF coils may also be provided at the neck region, allowing scanning of the lymph nodes and spine in that region. RF coils may also be attached at the back region to allow for scanning of the spine while the patient is positioned prone for breast imaging. Through the use of RF coil switching technology (i.e. the ability to sample from various combinations of coils in a dynamically switching fashion), these coil arrays can be selectively activated or deactivated during specific scanning protocols or dynamically through a protocol, i.e. scan the breast region, then selectively scan the axilla then scan the back, etc. 
     An important feature of the disclosed invention is the ability to incorporate multiple coils to provide coverage for a selected anatomy, or regions of interest. These coils can be integrated into the frame of the tabletop, the base structure, or fixably attached to the tabletop by way of compression plates or support structures. The invention also importantly provides structure for restraining a patient in an appropriate position for imaging throughout a procedure. The patient support structure  14  described above, for example, has been shown to be sufficiently strong to support a patient of between three hundred and fifty and five hundred pounds with a safety factor of four, even without additional supports or structures. 
     A preferred embodiment of the invention has been described in considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to a person of ordinary skill in the art. For example, although the invention is described here specifically for use in breast imaging, it will be apparent to those of skill in the art that many of the novel features described can be embodied in structures configured for other anatomies of interest. Although tab and slot connections have been described above in a number of applications, it will be apparent that the slots and tabs can be received and that other types of mechanical connections can also be used. Furthermore, although the cable tray  60  and receptacle  18  are shown at a specific end of the patient support structure  14 , it will be apparent to those of ordinary skill in the art that this orientation could be received. Therefore, the invention should not be limited to the embodiment described. To apprise the public of the scope of this invention, the following claims are made: