Abstract:
In a magnetic resonance tomograph having a continuous channel for inserting from one end a stretcher with a female patient lying thereon in a prone position during magnetic resonance mammography, the tomograph is provided with a manipulator by which instruments for the diagnosis and surgical treatment of such patients breasts can be introduced into the channel from the other end and positioned in relation to the breasts which are disposed in the isocenter of the magnetic resonance tomograph. The manipulator has a support arm with a recess for receiving the various instruments which can be installed and exchanged from the other, that is, the proximal end. The support arm with the recess can be pivoted horizontally and vertically about a fixed point located outside the recess and beyond the tip at the distal end of the manipulator adjacent to a breast of the patient.

Description:
This is a continuation-in-part application of international application PCT/EP99/02713 filed Apr. 22, 1999 and claiming the priority of German application 198 18 785.8 filed Apr. 27, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a magnetic resonance tomograph without access to the measurement area during a measurement, comprising a continuous channel for inserting from one side a stretcher for use by female patients during magnetic resonance mammography. 
     In the conventional closed magnetic resonance tomographs (MRT), the MRT mammography with the resulting additional treatment steps such as biopsy and, if necessary, subsequent therapy is performed in a multitude of steps during which the patient needs to be moved several times into, and out of, the channel of the apparatus. Any surgery on the patient can be performed with such a closed magnetic resonance tomograph only outside the apparatus. The procedure is therefore time consuming and results in high physical and psychological stresses of the patient and involves the risk that the position of the patient&#39;s breasts changes during the long period of the procedure. The long time required for the procedure also results in high costs for the therapy. 
     EP-A-0 534 607 discloses a magnetic resonance tomograph with two annular magnets within which the patient rests and between which a mechanical device for the heat treatment of tumors of the patient by laser energy is arranged at one side of the patient. A preceding biopsy is not provided with the MRT according to this publication. It would have to be performed outside the apparatus in some other way. There is no suggestion offered in EPA-0534607 how this situation could be improved. 
     U.S. Pat. No. 5 443 068 discloses a system for a non-invasive treatment of tumors by local magnetic resonance tomography-supported ultrasonic heating. The system includes a magnetic resonance tomograph (MRT) with a continuous channel into which a stretcher can be introduced from one end thereof. The stretcher includes a manipulator with an ultrasound transducer arranged directly below the support surface of the stretcher. The manipulator has a tub-like support arm, that is, a semi-circular support arm supporting the ultrasonic transducer such that it is movable in all three spatial directions. At the same time, the ultrasonic transducer remains so oriented that it always radiates upwardly. The tub-like support arm also includes a coupling medium, which is necessary for the transmission of the ultrasound waves. For the transmission of the ultrasound waves to a patients body a membrane is disposed on the coupling medium on which membrane the patient is disposed and which conforms to the body of the patient. Lateral movement of the ultrasound transducer in the coupling medium is achieved for each of the spatial axes separately by individual cardanic drive shafts by electric motors, which are arranged outside the MR magnetic field so that they have no influence on the field. 
     It is the object of the present invention to improve a magnetic resonance tomograph of the type as initially described in such a way that the various diagnosis and treatment steps of the MR mammography can be performed in the apparatus while the patients position remains essentially unchanged and to perform such procedures within a short period of time. The positions of the patient relative to the support and the MR apparatus should remain the same as set up before the start of the procedure for the whole duration of the procedure. 
     SUMMARY OF THE INVENTION 
     In a magnetic resonance tomograph comprising a continuous channel for inserting from one end a stretcher with a female patient lying thereon in a prone position during magnetic resonance mammography, the tomograph comprises a manipulator by which instruments for the diagnosis and surgical treatment of such patients breasts can be introduced into the channel from the other end and positioned in relation to the breasts which are disposed in the isocenter of the magnetic resonance tomograph. The manipulator comprises a support arm, which has a recess for receiving the various instruments which can be installed and exchanged from the other, that is, the proximal end. The support arm with the recess can be pivoted horizontally and vertically about a fixed point located outside the recess and beyond the tip at the distal end of the manipulator adjacent to a breast of the patient. 
     The invention will be described in detail below on the basis of the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a manipulator for use in a closed magnetic resonance tomograph (MRT) with a continuous channel. 
     FIG. 2 is a top view of the manipulator, 
     FIG. 3 is a cross-sectional view of the MRT taken along the line A—A with the manipulator disposed in a center position, that is, in its basic position, 
     FIG. 4 is a cross-sectional view similar to that of FIG. 3 with the manipulator moved and pivoted to one side, 
     FIG. 5 shows the introduction motion of a diagnostic-therapeutic instrument into the MRT housing, 
     FIG. 6 shows the coupling procedure of a trocar receiver and of an instrument adapter to a drive within the housing, and 
     FIG. 7 shows the insertion of the diagnostic-therapeutic instrument into a fixed breast of a patient. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The manipulator shown in the figures is provided for use in a closed magnetic resonance tomograph (MRT) which includes a continuous channel  1 , which is shown in FIGS. 3 and 4, and into which a stretcher (not shown) for supporting a female patient can be introduced for MR mammography and possibly further treatment. The patient is disposed on her stomach. 
     The different locations of various patient&#39;s breasts—resulting from anatomic differences—are all within the area of the windows  20  which are indicated in FIG.  4  and which define the operating area for the manipulator in a vertical plane (x/y range). The breast to be treated is fixed in longitudinal direction in that area by two compression plates so as to be positioned in the iso-center of the MRT. The manipulator is introduced into the MRT from the other end that is from the end of the channel opposite the stretcher until its front end  21  is disposed in the area of the iso-center. In, or at, the front end  21 , those instruments are supported which are needed for treatment of the patient. However they are not shown in the figures. 
     The manipulator must of course consist of materials suitable for use with a MRT. It basically comprises a bow-shaped frame  2 , which has at its sides support skids  5  on which it can be moved on tracks  3  into the channel  1  in a longitudinal direction. In the predetermined position, the manipulator can be fixed in the channel  1  by means of a clamping device  4 . The pivot arms  12 , which will be described later, are in the center position as shown in FIG.  3 . In the upper part of the frame  2 , there is a conventional bridge  7  on which a horizontally movable carriage  6  is supported and guided by a guide structure so that it is movable in the x-direction. The drive for moving the carriage  6  in the x-direction includes a cable  8  wound onto a cable drum mounted on the carriage  6  and extending around opposite guide pulleys  9  disposed at opposite ends of the bridge  7 . The cable drum is driven by a drive shaft  11  by way of a transmission  10 . 
     At the bottom part of the carriage  6 , a shaft  17  is rotatably supported and two pivot arms  12  are mounted on the opposite ends of the shaft  17  so as to be rotatable therewith. The pivot arms  12  are pivotable with the shaft  17  about the axis  13  thereof, the pivot movement being indicated as a movement in the direction y. The pivot movement is performed at a respective position of the carriage  6 , which is determined by its position in the x-direction. In a particular embodiment of the y-drive as shown in the figures, the upper end of the proximal pivot arm  12  seen in FIG. 3 is provided at its top end above the shaft  17  with a gear segment  18 , which is engaged by the worm gear  19  of a transmission  22  that is disposed at the side of the carriage  6  above the pivot arm  12 . In this way, the two pivot arms can be pivoted in the y-direction about the axis  13 . The transmission  22  includes a drive stub  23  to which a computer-controlled motor is connected, which is not shown. A computer-controlled motor is also connected to the drive shaft  11  for moving the carriage  6  in the x-direction. The movement of the pivot arm  12  in the y-direction occurs by way of the transmission  22 . 
     With the superimposed movements in the x and the y directions, any desired position of the manipulator or, respectively, its tip  21  within the area of the windows  20  can be obtained. 
     At the end of the shaft  17  opposite the pivot arm with the gear segment  18 , there is disposed adjacent the pivot arm  12 , a cable pulley  16  which is fixed with respect to the carriage  6  and in which the shaft  17  is rotatable. The cable pulley  16  therefore remains in its position with respect to the carriage  6  when the pivot arms  12  are pivoted. At the ends of the pivot arms  12 , remote from the shaft  17 , a support tube  14  is rotatably supported by the pivot arms  12 . At one end of the support tube  14  outside the pivot arm  12  the support tube carries anther cable pulley  15  in radial alignment with the cable pulley  16  such that the support tube  14  can be rotated by way of a cable  24  extending around the cable pulleys  15  and  16 . Preferably, the ends of the cable  24  are clamped to the cable pulleys so that the cable is wound onto one while it is unwound from the other of the pulleys  15  and  16  during pivot movement of the arms  12 . Since the cable pulley  16  is fixed in its angular position relative to the carriage  6  by the pin  25 , the support tube  14  maintains its angular orientation in the space during pivoting of the arm  12  in the y-direction, that is, it is guided in a horizontal parallel fashion. An orientation of the support tube for an adaptation to a right or left slant of the patient support, which is not shown, is achieved by removal of the pin  25  from a pulley bore  27  and inserting it into another bore  27 . 
     Within the support tube  14 , there is a support arm  26 , which is an essential element of the manipulator. The support arm  26  is rigidly disposed in, and extends through, the support tube  14  and is movable together therewith. The distal ends form the front end  21  of the manipulator. The end portion projecting from the support tube  14  is hollow so as to form an inner space  28  which extends from the front end  21  backwardly and widens arrow-like. The widening hollow inner space  28  forms the front part of a channel  30 , which extends through the support tube  14  up to the proximal end  31  of the support arm  26 . At the proximal end  31 , the channel  30  consists only of the two side members  29 . The channel  30  of the support arm  26  consequently extends from the proximal end  31  all the way to the distal front end  21  of the manipulator. It receives all the instruments necessary for the treatment of a patient which instruments are inserted at the proximal end  31  and extend through the channel  30  to the distal front end  21 . 
     Another important element of the manipulator is the housing  32 , which is disposed in the inner space  28  so as to be pivotable horizontally and vertically about the spherical support calotte  33  and which exchangeably receives the instruments needed for treatment. In the particular use of the MRT for mammography, the instruments are a biopsy device with a trocar for taking a sample and an applicator of a laser apparatus for possible subsequent laser surgery. Adapters are provided for accommodating the respective devices and apparatus in the housing  32 . The functions of the housing in cooperation with the instruments will be described in detail later on the basis of FIGS. 5 to  7 . The housing  32  is so supported by the cable  33 , that it pivots about a fixed point  35 , which is outside the front end  21  of the manipulator. The point  35  is in the area where the tissue of the patient is penetrated so that the penetration point remains the same no matter in which way the angular position of the respective instrument is changed. Generally, an instrument is inserted through a trocar wherein then the trocar is subject to the movement constraints. The horizontal pivotability of the housing  32  is made possible by the arrow shape of the inner space  28  in which the housing  32  is disposed. Within the inner space  28 , the housing  32  is pulled by elastic straps  34  toward the calotte  33 , that is, its pivotal support area and is held in place by sidewardly pivotable support legs  36  which are rotatable about the axis  39 . At a location remote from the pivotal support point of the housing  32 , that is, as shown in FIG. 1 in the area between the point of engagement by the support legs  36  and the point of attachment of the elastic straps  34  cables  37  are attached to the housing  32 , which cables extend, by way of several guide pulleys, to the pivot drive  38  at the proximal end  31  of the support tube  14  from where they can be operated to pivot the housing  32 . 
     For a vertical pivot movement, pins  43  extending from the proximal end of the housing  32  slide in elongated slots  40  formed in the support legs  36 . The legs are rotatably mounted on the inner side of the support arms  26  by pivot discs  41  so as to be pivotable about the axis  39  together with the pivot discs  41 ., Operating cables  42  extend from the pivot discs  41  to the drive  143  by way of several guide pulleys to provide for pivoting of the housing  32  in a vertical plane from the proximal end of the support tube  14  or the support arms  26  extending through the support tube  14 . The pivotability of the housing  32  about the insertion point  35  permits a cross-section biopsy in any desired plane and also a subsequent laser therapy, depending on the instrument used. 
     As already mentioned, the housing  32  is an important element of the manipulator; it is the central unit from which the diagnostic-therapeutic procedures are functionally instigated. It is essential that the housing is supported by way of the spherical calotte  33  so that it pivots spatially about the fixed point  35 . Within the housing  32 , a drive carriage  48  is supported for linear movement in the z-direction that is in the longitudinal direction of the MRT channel  1 . It serves for moving the instruments through the fixed point  35  into the tissue  51  to be treated. The axial movement of the drive carriage  48  can be controlled from the proximal end  31  of the arm  26  by elements, which are not shown in detail. At the distal end of the housing  32 , a sterilization sleeve  49  is installed as a protective structure, which prevents contamination of the parts of the instrument entering the tissue  51 . 
     In the housing  32 , there is disposed a movable trocar receiver  44  in whose upper part the trocar  50  is disposed in alignment with the sterilization sleeve  49 . This trocar receiver  44  is supported so as to be slideable into the housing  32 , where it can be coupled to the drive carriage  48 . In FIG. 5, the trocar receiver  44  is shown before being inserted in, that is, it is shown removed from the housing  32 . In FIGS. 6 and 7, the trocar receiver is shown in different positions in the housing  32 . At the proximal end of the trocar receiver  44 , a hollow instrument adapter  45  is disposed between the support arms  26 , which instrument adapter receives a respective instrument  46  as needed for a particular procedure. When coupled to the drive carriage  48 , the trocar receiver  44  forms the connecting element between the drive carriage  48  and the instrument adapter  45  which, as a result, is also movable in the housing  32  by the carriage  48  from the proximal end  31 . By the coupling of the three components drive carriage  48 , instrument adapter  45  and trocar  50 , the instruments  46  in the instrument adapter  45  can be moved in the z-direction. The trocar  50  acts as a guide canal and forms a shield for the protection of the healthy tissue from contamination by potential cancer cells during a change of the instruments. 
     As already mentioned, the instrument adapter  45  serves for the adaptation and the handling of different instruments. At its end adjacent the trocar receiver  44 , it includes a coupling mechanism which permits its coupling to, or uncoupling from, the trocar receiver  44  and which therefore allows a change of instruments while the trocar  50  remains in place. The instruments  46  comprise various diagnostic and therapeutic instruments, for example, a biopsy apparatus as a diagnostic instrument and an adapted laser head as a therapeutic instrument. At the proximal end of the instrument adapter  45 , there is provided a handling device  47 , which is also movable between the support arms  26  in the z-direction and by which the instruments can be moved into, and out of, the housing  32 . 
     Operation of the manipulator in connection with a MR apparatus. 
     Mammography is performed as follows: 
     The breast of a patient who rests in the channel  1  on her stomach is positioned in the isocenter of the MRT in the area of the windows  20 . The manipulator is introduced into the channel  1  toward the patient such that its front end  21  is disposed adjacent the isocenter. It is fixed in place by the clamping device  4 . The planigraphs are taken in the conventional manner. The target coordinates of any possible cancer location found are recorded. If a biopsy is to be performed to examine a possible cancer formation, the drive shafts  11 ,  23  and the drives  38  and  43  are connected to a drive unit (not shown) which is controlled by a control unit on the basis of the target coordinates. The target coordinates are converted to manipulator coordinates corresponding to the windows  20  and the manipulator position is adjusted corresponding to the coordinates in the x/y plane by movement of the carriage  6  and rotation about the axis  13 . The positioning in the z-axis, that is in depth, is performed by a predetermined insertion depth movement of the trocar out of the housing  32 . Then the biopsy apparatus is placed at the proximal end  31  between the side members  29  of the support arm  26  and is moved with the handling device  47  shown in FIGS. 5 to  7  into the housing  32 . After taking the biopsy, the biopsy apparatus is again retracted. For possible further treatment, the biopsy apparatus is then replaced by a laser applicator. The laser applicator is inserted into the housing  32  in the same manner as the biopsy apparatus while the housing  32  remains positioned in accordance with the target coordinates. In this fixed position, laser energy is then applied depending on the size of a tumor detected. 
     Operation of some of the elements within and at the housing  32 : 
     First, the sterilization sleeve  49  is inserted into the housing  32  with a grasping device, which is not shown. Then the trocar  50  is inserted into the trocar receiver  44  and an instrument is positioned in the instrument adapter  45 , while the manipulator is outside the MRT channel  1 . The trocar receiver  44  and the instrument adapter are then coupled and moved into guides between the side members  29  of the manipulator at the proximal end  31  thereof. Subsequently, the handling device  47  is moved into the open end of the instrument adapter  45  and is locked therein. In the next step, the components connected to the handling device  47  are advanced into the housing  32 . During the last part of this advancement, the trocar receiver  44  moves over the drive carriage  48 . In a predetermined position, the trocar receiver  44  and the drive carriage  48  are locked together. The locking is achieved by the engagement of a locking member  52 , which is provided on the trocar receiver  44  and which extends into a recess  53  in the drive carriage  48 . After this step, the handling device  47  is unlocked from the instrument adapter  45  and is pulled out of the manipulator at the end  31  thereof. The manipulator can now move toward the x/y location of the area  54  to be treated in the manner described earlier. When that location is reached the instrument  46  is inserted into the tissue  51  by advancement of the drive carriage  48 . 
     Any change of instruments  46  occurs while the trocar  50  remains in place. For such an instrument exchange the instrument adapter  45  is uncoupled from the trocar receiver  44  and retracted by a certain distance. This is done by way of a cable, preferably a Bowden wire, from without the MRT. Now the instrument adapter  45  can be pulled out of the manipulator by the handling device  47  and can then be reinserted after installation of another instrument. At the end of the treatment, the instrument adapter  45  is not uncoupled from the trocar receiver  44 , but rather the lock between the trocar receiver  44  and the drive carriage  48  is released. With the retraction of the handling device  47 , all the components initially installed in the manipulator are then removed together.