Abstract:
An assembly for mounting and unmounting a surface coil of a magnetic resonance tomography apparatus includes an upper part, a lower part, a locking element to fix the upper part and the lower part to one another, and contact elements at the upper part and at the lower part. The contact elements at the upper part can be brought into an electrically conductive connection with contact elements at the lower part and the upper part and the lower part can be fixed to one another by a movement of the locking element.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention concerns a surface coil for a magnetic resonance tomography apparatus. 
         [0003]    2. Description of the Prior Art 
         [0004]    Magnetic resonance apparatuses, in particular for the examination of patients via magnetic resonance tomography, are generally known from DE10314215B4, for example. 
         [0005]    Modern magnetic resonance systems (also called MR or MRT) normally operate with multiple different antennas (also called coils in the following) to emit radio-frequency pulses for nuclear magnetic resonance and/or to acquire induced magnetic resonance signals. A magnetic resonance system frequently possesses a larger coil (what is known as a whole-body coil, also called a body coil or BC) that is normally permanently installed in the apparatus, as well as multiple small surface coils (also called local coils). In contrast to the whole-body coil, surface coils serve to acquire detailed images of body parts or, respectively, organs of a patient that are located relatively near to the surface of the body. For this purpose surface coils are applied at the point of the patient at which a region to be examined is located. 
         [0006]    Surface coils for magnetic resonance tomography often are composed of multiple coil parts. For example, head coils or knee coils are typically divided into a lower part and an upper part for a facilitated entrance for the patient. These parts are attached during an MRT measurement to fix their position. Locking elements are, for example, latch levers that are borne such that can be displaced or rotated. The coil parts can additionally also possess electrical connections (realized by plug contacts, for example). In order to release these plug contacts upon opening the coil, ejection mechanisms are integrated into the coils. The operation of these movable coil parts is performed by the user of the MRT. 
       SUMMARY OF THE INVENTION 
       [0007]    An object of the present invention to optimize the design of a surface coil. 
         [0008]    A surface coil for a magnetic resonance tomography apparatus in accordance with the invention has an upper part, a lower part, a locking element to fix the upper part and the lower part to one another, and contact elements at the upper part and at the lower part, the contact elements at the upper part being configured to be brought into an electrically conductive connection with contact elements at the lower part, and the upper part and the lower part can be fixed to one another by movement of the locking element (in particular an arm). 
         [0009]    A particularly simple locking is enabled when the contact elements at the upper part and at the lower part can be brought into electrically conductive connection with one another and the upper part and the lower part can be fixed to one another with only one movement of the locking element. 
         [0010]    A particularly simple removal of the upper part and lower part from one another is likewise enabled when the contact elements at the upper part and at the lower part can be separated from one another and the upper part and lower part can be unlocked from one another with a movement of the locking element or arm. 
         [0011]    Contact bushings at the upper part and contact pins at the lower part (or vice versa) can advantageously be provided as contact elements. 
         [0012]    A mounting or separation of the upper part and lower part without tools is supported if the locking element is an arm with a translation of force applied to it into a force separating the upper part from the lower part and/or the contact elements from one another, in particular with a conversion of approximately one to four. 
         [0013]    According to an embodiment of the invention, a latch element and the locking element can only be disengaged if the latch element is located in a position that is displaced against a force of a spring. 
         [0014]    According to another embodiment of the invention, the latch element and the locking element advantageously interlock when they are mutually engaged with one another counter to an unwanted disengagement. 
         [0015]    Guide pins are advantageously provided in order to assist in the engagement of contact elements at the upper part and at the lower part in one another given an engagement of the upper part and the lower part. Guide pins that are asymmetrical relative to one another enable a coding of upper parts and lower parts in order to avoid confusions of upper parts and lower parts that do not belong together. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  schematically illustrates an MRT with coils as an overview representation. 
           [0017]      FIG. 2  shows a head coil in plan view. 
           [0018]      FIG. 3  shows the head coil in a lateral view with an upper head coil part and lower head coil part. 
           [0019]      FIG. 4  shows the upper part of the head coil in a lateral view with lower head coil part removed from the upper head coil part. 
           [0020]      FIG. 5  shows details of a latching mechanism at the upper part of the head coil. 
           [0021]      FIG. 6  shows a locking element in the form of an arm. 
           [0022]      FIG. 7  shows the arm in a position removed from the head coil. 
           [0023]      FIG. 8  illustrates an exchange of an arm. 
           [0024]      FIG. 9  shows the head coil without covering. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]      FIG. 1  shows a magnetic resonance apparatus MRT  31  with a whole-body coil  32  with a tube-shaped chamber  33  into which a patient bed  34  (for example with a patient  35  and a surface coil  41 ) can be driven in order to generate exposures of the patient  35 . Here a local coil  1  (in the form of a head coil) with which good exposures are enabled in a local region (here in the head region) is placed on the head of the patient. The local coil  1  can be connected with connector cables  38 , for example with terminals in the patient bed  34  or elsewhere on the MRT  31 . 
         [0026]    In the following a head coil  41  is described as an exemplary embodiment of a surface coil using  FIG. 2-9 . Such an embodiment can be used not only in head coils but also in all other MRT surface coils. Elements of the head coil  41  can also be exchanged by a customer on site without having to open its coil housing  1 ,  2 . 
         [0027]      FIG. 2  shows a head coil  41  that comprises an upper head coil part  1  and a lower head coil part  2 , wherein the upper part  1  and the lower part can be fixed (locked/secured etc.) to one another via a locking element (here in the form of an arm  8 ). An electrical contacting (between structural elements of the upper head coil part  1  and lower head coil part  2 ) ensues via contact elements (visible in  FIG. 3 ), namely here contact bushings  3  in the lower part  2  and contact pins  4  (visible in  FIG. 4 ) in upper part  1  (or conversely contact pins  4  in the lower part and contact bushings  3  in the lower part  1 ). Contact bushings  3  and contact pins  4  can engage with one another if the upper part and lower part are fixed (locked/clamped) to one another and establish an electrically conductive connection (for example for elements in the upper part and lower part or interfaces). 
         [0028]    A peculiarity of the head coil  41  is the combination of two functions in an operating movement upon detachment of the upper part  1  of the housing of the head coil  41  from the lower part  2 . A rotating movement “O” of an arm  8  in  FIG. 2  unlocks the upper coil housing part  1  from the lower coil housing part  2  and, given a further movement “O” of the arm  8  (horizontally in  FIG. 2 ), slides electrical plug contacts out of contact bushings of the lower coil housing part. An efficient placement of the upper part  1  on the lower part  2  with contacting of the contact elements of the upper part  1  and lower part  2  is likewise possible. In spite of the simple exchange capability, the elements (for example  5 - 17 ) provided for this are completely integrated into the coil housing  1 ,  2  and do not require any additional retention parts or bold connections. Via their interplay they prevent an unwanted detachment from the coil housing  1 ,  2 . 
         [0029]    In the plan view in  FIG. 3 , retention elements  5  on both sides of the upper part  1  ensure a positive placement (for example in the direction of arrow a) of the upper part  1  to the rear (thus to the right in  FIG. 3 ) of plug contacts (contact bushings  3 ) in the lower part  2 . By shifting (for example “vertically” in the direction of arrow b) the upper part  1  along the lower part  2  (performed by a user), contact elements (contact bushings  3  and contact pins  4  in the lower part  2  and in the upper part  1 ) are contacted with one another and retention elements  5  on the upper part  1  slide behind a projecting housing edge  14  (in  FIG. 3 ) of the lower part. 
         [0030]    Upon placement of the upper part  1  on the lower part  2  with a vertical shifting (counter to the direction of the arrow b in  FIG. 3  and  FIG. 8 ) of the upper part  1  on the lower part  2  or relative to the lower part  2 , the latch element  6  glides upward (in the direction of the arrow “−a) on a slope  9  (in  FIG. 3 ) at the lower part  2  and after this plunges into the groove  10  situated after the slope  9 . The upper part  1  is now locked (at the lower part  2 ; it does not slide down from the lower part  2  counter to the direction of arrow b). 
         [0031]    Contact pins  17  on two sides (left and right in  FIG. 4 ) of the plug contacts (the contact elements  4  of the upper part  1 ) that lead the contact elements  4  in the upper part  1  (upon displacement of the upper part  1  on the lower part  2  in the direction of arrow b) optimize the insertion precision (upon insertion of plug elements  3 ,  4  into one another during the sliding b of the upper part  1  over the lower part  2 ). In order to prevent lifting (counter to arrow a) of the upper head coil part  1  during the insertion process (of plug elements  3  and  4  into one another), the length of the guide pins  17  is designed so that they already dip into bushings (into plug elements on the lower part) before the slope  9  (in the form of a displacement of the latch element  6 ) is effective. 
         [0032]    An asymmetrical shaping of the guide pins  17  and/or a rotation capability of a complete plug module  15  (comprising contact elements  4  and contact pins in the event that they are present) and an entire bushing module  16  (comprising contact elements  4  and, in the event that they are present, guide bushings to receive guide pins) achieve the capability of a coding in the manner that only specific upper coil parts can be plugged into specific lower coil parts. For example, this coding can be used as a frequency coding—and therefore as a differentiation between 1.5 T and 3 T coils (for example such that a 3 T upper coil part can only be plugged into a 3 T lower coil part)—in order to avoid errors to the effect that an upper part and a lower part that do not belong together are plugged into one another. 
         [0033]    The arm  8  is moved (rotated) by approximately 60° in a rotation movement “O” to open the local coil arrangement  41  (thus to remove the upper part  1  from the lower part  2 ). The rotation movement “O” of the arm  8  produces a shifting movement (counter to the direction of arrow a) of the latch element  6  by approximately 20 mm. The first 5 mm of the shifting movement unlock the coil  41  (a cross-web  18  of the latch element  6  emerges from the groove  19  at arm  8 ). An additional 15 mm of the sliding movement shift the upper part  1  counter to the direction of arrow b via slope  11  at the latch element  6  and slope  12  at the lower coil part  2  and thus separate the contact elements  3 ,  4  of the upper part and lower part from one another. The mechanism requires little expenditure of force given a translation of approximately 4:1 (for example the lever arms H 1 , H 2  of the arm  8  for manual force application and at the cross-web  18  of the latch element  6 ). Even coil parts with a large number of plug contacts (such as high-channel coils) can thus be moved or unlocked with little force. 
         [0034]    A latch element  6  can be moved vertically into the upper part  1 . It is pressed in the direction of the lower part  2  by springs  7  (not visible in  FIG. 5 ). The vertical displacement path of the latch element  6  in and opposite the direction of the lower part  2  is limited by an arm  8  (upward and downward in  FIG. 7 ). Upon insertion of an arm  8  into the upper part  1  according to  FIG. 7 , the latch element  6  is shifted as far as possible from the lower part (or upward in  FIG. 7 ); the springs  7  can thereby be maximally compressed. Given a closed head coil housing ( 1 ,  2 ), a region below the cross-web  18  of the latch element  6  is cleared into which the arm  8  can dip horizontally. By releasing (detensioning) the springs  7 —and therefore releasing the latch element  6 —a cross-web  18  of the latch element engages in a groove  19  of the arm  8 . Both head coil housing parts  1 ,  2  thus interlock themselves and presumably will not be accidentally unlocked from one another in typical operation of the coil. As  FIG. 8  shows, to exchange a defective latch element  6  or arm  8  the latch element  6  is maximally [sic?] pressed upward (for example with fingers, thus without a tool) counter to an elastic force of the spring  7  in the direction of arrow “−a” and the arm  8  is drawn out vertically (in the direction of arrow “−b”) from a keyhole with rotation of approximately 15° in  FIG. 8 . The rotation by 15° disengages the securing edge  13  (from the upper part  1 ). Given an unwanted upward slide of the latch element  6  (in the direction of arrow “−a”), the securing edge  13  prevents the arm  8  from falling out of the upper part  1  whose center of gravity is located on this shown side. By releasing the elastic force of the springs  7 , the latch element  6  is slid out of the upper housing part  1  and can likewise be exchanged (depending on the degree of wear). 
         [0035]    Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.