Abstract:
The present invention relates to a magnetic resonance imaging system that includes a stationary electromagnet, a patient support for maintaining a patient in a standing or seated position, and an actuator for raising and lowering the patient relative to a magnetic field of the electromagnet such that the patient is located within the magnetic field.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation of application Ser. No. 09/118,665, filed Jul. 17, 1998. The aforementioned application Ser. No. 09/118,665 is itself a divisional of application Ser. No. 08/455,074, filed May 31, 1995. The aforementioned application Ser. No. 08/455,074 is a divisional of application Ser. No. 08/221,848, filed Apr. 1, 1994, now U.S. Pat. No. 5,577,503. The aforementioned application Ser. No. 08/221,848 is itself a divisional of application Ser. No. 07/802,358, filed Dec. 4, 1991, now U.S. Pat. No. 5,349,956. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to an apparatus and method for use in medical imaging. More particularly, the present invention relates to apparatus and method for positioning a patient and/or a secondary imaging coil inside a primary imaging coil.  
           [0003]    In magnetic resonance imaging, a patient is placed inside a coil (the “primary” coil) which is large enough in diameter to receive the patient while he is lying prone on a table slidable into and out of the coil. A selected portion of the patient is then imaged by the use of electromagnetic radiation from the primary coil.  
           [0004]    It is known to place smaller coils, called surface or volume coils, in close proximity to the specific part of the patient to be imaged, such as the neck, spine, or knee. These coils, referred to herein as secondary coils, are used to increase resolution by having a coil closer to the part to be imaged. It is essential to place the secondary coil in a particular orientation relative to the electromagnetic field generated by the primary coil.  
           [0005]    Current imaging systems can only take images while a patient is in one particular position. One known device allows the patient to move his knee joint to different selected positions while the patient is in the primary coil. This device requires the patient to lie face down in the primary coil, which is extremely uncomfortable for the extended period of time required to image properly, especially in the close, almost claustrophobic confines of a primary MRI coil.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is an apparatus and method for use in medical imaging. The present invention provides a system to simulate within an imaging coil normal movements of body parts such as joints, and to improve imaging of soft tissue and bony parts as compared to a static system in which images are taken of a joint in only one position.  
           [0007]    In accordance with a first aspect of the present invention, there is provided controlled motion of an extremity, while in an imaging coil, either patient directed or operator directed. A joint or body part is moved into various positions in multiple planes within its range of motion while a series of images are taken of the joint in the different positions. These individual images may then be collated into a cine format to effectively show the joint in motion. Thus, the present invention allows for studying a joint in motion and also allows for studying a joint or other body part at any positions within its range of motion allowable within the confines of the primary coil.  
           [0008]    In accordance with a second aspect of the present invention, a surface or volume coil (referred to herein as a secondary coil) is coupled for movement with the joint or body part. The secondary coil is maintained in the proper spatial relationship with the primary coil&#39;s electromagnetic field. Keeping the secondary coil as close as possible to the joint or tissue being imaged, while moving the joint or body part, provides greatly enhanced resolution and more detail in the final image.  
           [0009]    Thus, to illustrate these first two aspects of the invention in knee imaging, the knee is fixed by holding the upper and lower legs with cuffs and a secondary coil is placed around the knee itself. The knee is then imaged at 0 degrees by using the primary and secondary coils. The knee is then flexed (either by the patient or the operator), and the secondary coil moves with the knee. The knee is progressively moved through various positions within its range of motion as limited only by the size of the primary coil. Images are taken at each position. The images may then be collated and shown in sequence to visualize the movement of the knee joint, or may be studied individually to study the joint at each position.  
           [0010]    Similar systems are available for other joints, the back, neck, etc. These systems all are preferably provided as mechanisms usable with existing imaging tables to reduce cost. Alternatively, some of these may be built into a new imaging table.  
           [0011]    Coupling a surface coil for movement with the extremity provides the necessary detail in the images, even with a larger primary coil, which is not available with present systems. Accordingly, it is possible to use a larger diameter primary coil, allowing this increased range of movement, without the degradation in image quality which would be expected from the increased coil size. For example, the knee could be flexed through its entire range of motion to allow optimum imaging of the knee joint. This is currently impossible with the known small primary coils which only allow about 50 degrees of flexion.  
           [0012]    In accordance with another aspect of the present invention, traction is applied to a joint being imaged, in order to load the joint. This can simulate normal loading of a joint. Distracting a joint can also allow a better view of the parts of the joint and thus an increased imaging benefit. It can also allow simulation of normal loading of a joint, such as when carrying a heavy object or performing an athletic or work-related task. This feature is not available with present imaging apparatus. Traction can also be applied to a joint being imaged when the joint is in various positions, to simulate normal loading of a joint within its range of motion. Again, this feature is not available with present imaging apparatus. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The foregoing and other features of the present invention will become apparent to one skilled in the art upon a consideration of the following description of the invention with reference to the accompanying drawings, wherein:  
         [0014]    [0014]FIG. 1A is a perspective view of a magnetic resonance imaging installation including a patient support table constructed in accordance with the present invention;  
         [0015]    [0015]FIG. 1B is a view of the table of FIG. 1A in another condition;  
         [0016]    [0016]FIG. 1C is a view of the table of FIG. 1A in yet another condition;  
         [0017]    [0017]FIG. 2 is an enlarged view of a back imaging platform of the table of FIG. 1A;  
         [0018]    [0018]FIG. 3 illustrates the platform of FIG. 2 in a raised condition;  
         [0019]    [0019]FIG. 4 illustrates the platform of FIG. 2 in a lowered condition;  
         [0020]    [0020]FIG. 5 is a view similar to FIG. 2 showing a different actuating mechanism for the back imaging platform;  
         [0021]    [0021]FIG. 6 illustrates the platform of FIG. 5 in a raised condition;  
         [0022]    [0022]FIG. 7 illustrates the platform of FIG. 5 in a lowered condition;  
         [0023]    [0023]FIG. 8 is an enlarged view of a knee imaging platform portion of the table of FIG. 1;  
         [0024]    [0024]FIG. 9 illustrates the platform of FIG. 8 in a raised condition;  
         [0025]    [0025]FIG. 10 is a view similar to FIG. 8 and showing a different actuating mechanism for the knee platform;  
         [0026]    [0026]FIG. 11 illustrates the platform of FIG. 10 in a raised condition;  
         [0027]    [0027]FIG. 12 is an enlarged view of a neck imaging platform portion of the table of FIG. 1A;  
         [0028]    [0028]FIG. 13 illustrates the platform of FIG. 12 in a raised condition;  
         [0029]    [0029]FIG. 14 illustrates the platform of FIG. 12 in a lowered condition;  
         [0030]    [0030]FIG. 15 is a view similar to FIG. 12 illustrating a different actuating mechanism for the neck platform;  
         [0031]    [0031]FIG. 16 illustrates the platform of FIG. 15 in a raised condition;  
         [0032]    [0032]FIG. 17 illustrates the platform of FIG. 15 in a lowered condition;  
         [0033]    [0033]FIG. 18 illustrates the platform of FIG. 15 with a foot rest attached for use in ankle imaging;  
         [0034]    [0034]FIG. 19 illustrates the platform of FIG. 18 in a raised condition;  
         [0035]    [0035]FIG. 20 illustrates the platform of FIG. 18 in a lowered condition;  
         [0036]    [0036]FIG. 21 illustrates the platform of FIG. 18 with a different actuating mechanism;  
         [0037]    [0037]FIG. 22 illustrates the platform of FIG. 21 in a raised condition;  
         [0038]    [0038]FIG. 23 illustrates the platform of FIG. 21 in a lowered condition;  
         [0039]    [0039]FIG. 24 is a top plan view of a shoulder positioning apparatus in accordance with the present invention shown attached to an imaging table with a shoulder coil;  
         [0040]    [0040]FIG. 25 is a side view of the apparatus of FIG. 24;  
         [0041]    [0041]FIG. 25A is a partial end view of the positioning apparatus of FIG. 25 taken along line  25 A- 25 A of FIG. 24;  
         [0042]    [0042]FIG. 26 is an enlarged perspective view of a portion of the positioning apparatus of FIG. 24;  
         [0043]    [0043]FIG. 26A is a view similar to FIG. 26 showing an alternate indexing mechanism;  
         [0044]    [0044]FIG. 27 is a top plan view of a head and neck positioning apparatus;  
         [0045]    [0045]FIG. 28 is an end view of the apparatus of FIG. 27;  
         [0046]    [0046]FIG. 29 is a perspective view of the apparatus of FIG. 27;  
         [0047]    [0047]FIG. 30 is a top plan view of a wrist imaging apparatus embodying the present invention and including a hand cuff;  
         [0048]    [0048]FIG. 31 illustrates the apparatus of FIG. 30 in a different condition;  
         [0049]    [0049]FIG. 32 illustrates the apparatus of FIG. 30 with a different hand cuff;  
         [0050]    [0050]FIG. 33 is an end view of the apparatus of FIG. 30;  
         [0051]    [0051]FIG. 34 is an enlarged end view of the hand cuff of the apparatus of FIG. 30;  
         [0052]    [0052]FIG. 35 is a side view of the hand cuff of FIG. 34;  
         [0053]    [0053]FIG. 36 is a bottom plan view of the hand cuff of FIG. 34;  
         [0054]    [0054]FIG. 37 is a top plan view of an independent patient directed knee positioning apparatus embodying the present invention;  
         [0055]    [0055]FIG. 38 is a side view of the apparatus of FIG. 37;  
         [0056]    [0056]FIG. 39 is a view similar to FIG. 38 with the apparatus in a raised condition;  
         [0057]    [0057]FIG. 40 is a view similar to FIG. 39 with an optional distraction mechanism;  
         [0058]    [0058]FIG. 41 is a schematic view showing the dimensions of a known primary MRI coil;  
         [0059]    [0059]FIG. 42 is a schematic view showing the dimensions of a larger sized primary MRI coil embodying the present invention; and  
         [0060]    [0060]FIG. 43 is a schematic view of a vertically extending primary MRI coil in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0061]    [0061]FIG. 1A illustrates a patient support table  10  for supporting a patient (not shown) during imaging inside a primary coil  12  of a magnetic resonance imaging installation. The table  10  is supported on tracks  14  and a floor support  16  for sliding longitudinal movement into and out of the coil  12 .  
         [0062]    The table  10  has an upper major side surface  20  extending between a head end  22  and a foot end  24 . The table also has a right side  26  and a left side  28 .  
         [0063]    The table  10  includes a neck imaging platform indicated generally at  30 . The neck imaging platform  30  includes a movable head panel  32  adjacent to a recess  34  for receiving a secondary imaging coil such as a cervical spine coil.  
         [0064]    The table  10  includes a back imaging platform indicated generally at  40 . The back imaging platform  40  includes a movable upper back panel  42  and a movable lower back panel  44 . A movable center section  46  of the back imaging platform  40  includes a recessed panel  48  for receiving a secondary back imaging coil. The recessed panel  48  is located between a left side back panel  50  and a right side back panel  52 .  
         [0065]    The table  10  also includes a pair of knee imaging platforms  54  and  56 . The left knee imaging platform  54  includes a movable upper left knee panel  58 , a movable lower left knee panel  60  and, between them, a recessed panel  62  for receiving a left knee secondary imaging coil. Similarly, the right knee imaging platform  56  includes a movable upper right knee panel  64 , a movable lower right knee panel  66 , and a movable recessed panel  68  for receiving a right knee secondary imaging coil.  
         [0066]    As can be seen in FIGS. 1A, 1B and  1 C, the head panel  32  is movable between a plurality of positions relative to the upper major side surface  20  of the table  1 A. In FIG. 1A, the head panel  32  is in a position level with the upper major side surface  20  of the table  10 . In FIG. 1B, the head panel  32  is raised above the upper major side surface of the table  10 . In FIG. 1C, the head panel  32  is lowered below the upper major side surface  20  of the table  10 . With a patient&#39;s head on the head panel  32  and by moving the panel  32  in a manner as described below, a patient&#39;s cervical spine can be imaged in a variety of positions, by a coil placed on the recess panel  34 .  
         [0067]    Similarly, the back imaging platform  40  is movable between a plurality of positions relative to the upper major side surface  20  of the table  10 , to image the back in varying positions. In FIG. 1A, the back imaging platform is level or flush with the upper major side surface  20  of the table  10 . In FIG. 1B, the back imaging platform  40  is raised up above the upper major side surface  20  of the table  10 , in order to hyper-extend the spine of a patient lying on the table  10 . In FIG. 1C, the back imaging platform  40  is lowered below the upper major side surface  20  of the table  10 , in order to flex the spine. Thus, by moving the back platform  40  between these various positions, in a manner to be described below, the back can be imaged in a plurality of different positions, rather than only in the one flat position possible with a flat table.  
         [0068]    Similarly, the left and right knee imaging platforms  54  and  56 , respectively, are movable between a plurality of positions relative to the upper major side surface  20  of the table  10 . In FIGS. 1A and 1C, the platforms  54  and  56  are illustrated flush with the upper major side surface  20  of the table  10 . In FIG. 1B, the left knee imaging platform  54  is illustrated as raised up above the upper major side surface  20  of the table  10 . Both knee platforms  56  and  66  are each independently movable above or below the upper major side surface  20  of the table  10 . By thus moving a knee platform among these various positions, in a manner to be described below, a knee joint can be imaged in a plurality of positions, as opposed to the one single position available with a flat or nonmovable table.  
         [0069]    FIGS.  2 - 4  illustrate in more detail the back imaging platform  40  and a mechanism for actuating same. These are exemplary of the other platforms and their actuating mechanisms. The fixed portion  70  of the table  10  includes a track  72  receiving mounting rollers  74  and  76  for the upper back panel  42  and lower back panel  44 , respectively. The upper back panel  42  is pivotally mounted at  78  to the center back section  46 . The lower back panel  44  is similarly pivotally mounted at  80  to the center back section  46 .  
         [0070]    An inflatable bladder  82  extends between the center back section  46  and the lower panel  84  of the table  10 . The inflatable bladder  82  is supplied with fluid through a fluid supply line  86  extending along the table  10 . Fluid under pressure, preferably air, is supplied to the bladder  82  through the line  86  by means not shown such as a pump or a high pressure air line as is commonly found in hospitals, etc. Upon inflation of the bladder  82  from the condition shown in FIG. 2 to the condition shown in FIG. 3, the bladder  82  extends longitudinally, raising the center back section  46  of the table  10  upwardly from the major side surface  20  of the table  10 . The pivotal connections  74 ,  76 ,  78  and  80  allow the panels  42  and  44  to pivot upwardly, as illustrated in FIG. 3, sliding inwardly along the track  72 .  
         [0071]    Similarly, upon the reduction of pressure in the bladder  82 , the bladder  82  compresses axially in length to the condition shown in FIG. 4, lowering the center back section  46  below the major side surface  20  of the table  10 . The state of inflation of the bladder  82  is selectively controllable to position the center back section  46 , relative to the upper major side surface  20  of the table  10 , at any position between the fully extended position illustrated in FIG. 3 and the fully flexed position illustrated in FIG. 4. The bladder  82  is preferably of a bellows-type construction for increased strength and controlled movement.  
         [0072]    In FIGS.  2 - 4 , a secondary coil  90  is illustrated as positioned on the center back section  46  of the table  10 . The secondary coil  90  may be any known imaging coil designed for imaging a portion of the spine of a patient. As the center back section  46  moves up and down, the secondary coil  90  moves with the back section  46 . The secondary coil  90  is initially (FIG. 2) parallel to the upper major side surface  20  of the table  10 , and stays with the center back section  46  in that parallel orientation throughout the entire range of movement of the back section  46  and the coil  90 . It should be noted that any type of secondary coil either known or to be developed in the future—surface coil, volume coil, etc.—can be used with the present invention.  
         [0073]    With a patient (not shown) lying on the table  10 , and a secondary coil  90  positioned as shown, the patient&#39;s back can be imaged in a plurality of orientations. If the table  10  is maintained in the position shown in FIG. 2, the patient&#39;s back is imaged in a flat position. If the table  10  is moved to a raised position, as illustrated in FIG. 3, the patient&#39;s back is imaged in an extended or hyper-extended condition. If the table  10  is moved to a lowered condition, as illustrated in FIG. 4, the patient&#39;s back is imaged in a flexed or hyper-flexed condition. Because the inflation state of the bladder  82  is selectively controllable and lockable at any state of inflation, the patient&#39;s back can be imaged when in any selected orientation within the full range of motion of the back imaging platform  40 . Meanwhile, the secondary coil  90  moves with the patient&#39;s back, always staying in close proximity thereto, to maintain the high resolution sought by use of a secondary coil. Further, the secondary coil  90  always maintains its orientation parallel to the upper side surface  20  of the table  10 , as is necessary for maximum resolution and clarity. Accordingly, it is seen that the present invention provides an apparatus for imaging the back of a patient, at any selected one or group of a plurality of orientations, while the patient is maintained in the primary coil  10  (FIG. 1) of the MRI imaging apparatus, and without any extra effort on the part of the patient.  
         [0074]    FIGS.  5 - 7  illustrate an alternate actuating mechanism for the center back section  46  of the table  10 . The actuating mechanism includes a threaded rod  100  rotatably mounted in a block  102  fixed to the bottom panel  84  of the table  10 . The block  102  allows the rod  100  to rotate but prevents axial movement of the rod  100 .  
         [0075]    The rod  100  includes a first threaded portion  104  threadedly received in a floating mounting block  106  (FIG. 6). The floating block  106  has a pin  108  secured thereto. The pin  108  is received in a slot  110  of an arm  112  fixed to the upper back panel  42 .  
         [0076]    The rod  100  also includes a second threaded portion  114  which is of opposite hand from the first threaded portion  104 . The second threaded portion  114  extends through a floating mounting block  116  having a pin  118  secured thereto. The pin  118  is received in a slot  120  of an arm  122  fixed to the lower back panel  44 .  
         [0077]    An end portion  124  of the rod  100  projects axially from the foot end  24  of the table  10 . A drive means indicated schematically at  126  is attached to the rod  100 . The drive means  126  may be a hand crank for rotating the rod  100  relative to the table  10 . The drive means  126  may also be an electric motor or fluid drive mechanism for rotating the rod  100 . The drive means  126  is selectively controllable to rotate the rod  100  to any given extent permitted by the actuating mechanism.  
         [0078]    Upon actuation of the drive means  126 , the rod  100  rotates relative to the fixed mounting block  102  and the table  10 . Because the threaded rod portions  104  and  114  are of opposite hand, upon rotation of the rod  100  in one direction, the floating blocks  106  and  116  are moved inwardly toward each other as illustrated in FIG. 6; and upon rotation of the rod  100  in the opposite direction, the blocks  106  and  116  move axially outwardly away from each other, as illustrated in FIG. 7.  
         [0079]    Upon movement of the blocks  106  and  116  toward each other as illustrated in FIG. 6, the pins  108  and  118  pull the arms  112  and  122 , respectively, from the position shown in FIG. 5 to the position shown in FIG. 6. This causes the upper and lower back panels  42  and  44 , respectively, to pivot and move inwardly along the track  72 . This raises the center back section  46  of the table  10  upwardly away from the major side surface  20  of the table  10 . The surface coil  90 , as before, moves with the center back section  46  and maintains its alignment parallel to the upper major side surface  20  of the table  10 .  
         [0080]    Upon rotation of the rod  100  in the opposite direction, the blocks  106  and  116  (FIG. 7) move axially outwardly away from each other, thus causing the panels  42  and  44  to pivot to the position shown in FIG. 7. This drops the center back section  46  downwardly below the upper major side surface  20  of the table  10 , taking with it the secondary coil  90 .  
         [0081]    Accordingly, it is seen from FIGS.  5 - 7  that an alternate mechanism for positioning the center back section  46  of the table  10 , relative to the upper major side surface  20  of the table  10 , is provided. With a patient lying on the upper major side surface  20  of the table  10 , the patient&#39;s back may thus be imaged in any selected one of a plurality of positions between flexion and extension. Meanwhile, the secondary coil  90 , if used, moves with the patient&#39;s back to maintain high resolution, while maintaining its planar orientation relative to the upper major side surface  20  of the table  10 .  
         [0082]    [0082]FIGS. 8 and 9 illustrate operation of the right knee imaging platform  56  of table  10 . In this case, a knee secondary coil  130  is fixed by suitable means such as straps or VELCRO.RTM. to the central panel  68  of the imaging platform  56 . The central panel  68  is pivotally mounted between the upper right knee panel  64  and the lower right knee panel  66 . A threaded rod  132 , having oppositely threaded portions  134  and  136 , is rotatably mounted in a fixed mounting block  138  to block axial movement of the rod  132 . Connection means  140  (similar to the block  106 , pin  108 , and arm  112 ) movably connects the upper right knee panel  64  to the threaded rod portion  134 . Similar connection means  142  movably connects the lower right knee panel  66  to the rod threaded portion  136 .  
         [0083]    Upon rotation of the rod  132  by suitable drive means  144 , in one direction, the connection means  140  and  142  cause the panels  64  and  66 , respectively, to pivot and lift the central panel  68  upwardly away from the upper major side surface  20  of the table  10 . The knee coil  130  moves with the panel  68  and stays in the correct planar orientation relative to the primary coil. The patient&#39;s knee (not shown) also moves upwardly away from the major side surface  20 , into a different orientation than when the patient&#39;s knee is on the platform  56  when in the position shown in FIG. 8. Rotation of the rod  132  in the opposite direction causes the central panel  68  and knee coil  130  to drop below the upper major side surface  20  of the table  10 , in a manner similar to that illustrated in FIG. 7 with the back section  46 .  
         [0084]    In the structure illustrated in FIGS. 10 and 11, the rod  132  and associated actuating mechanism are replaced by an inflatable bladder  150 . The bladder  150  is supplied with fluid under pressure through suitable means (not shown). Upon inflation of the bladder  150  from the normal state illustrated in FIG. 10 to the extended state illustrated in FIG. 11, the panel  68  and the knee coil  130  are again raised above the upper major side surface  20  of the table  10 . Upon the reduction of pressure in the bladder  150 , the bladder  150  collapses axially to lower the panel  68  below the major side surface  20  of the table  10 . Thus, the knee joint can also be imaged in a hyper-extended condition.  
         [0085]    FIGS.  12 - 14  illustrate operation of the neck imaging platform  30  of the table  10 . A cervical spine coil  152  is set in the recessed panel portion  34  of the table  10 , below the upper major side surface  20 . Attached to the head panel  32  is a pivot mechanism  154 . A rod  156  has a threaded portion  158  extending through the mechanism  154 . Upon rotation of the rod  156  by a suitable drive means  160 , the actuating mechanism  154  causes the head panel  32  to pivot upwardly out of the plane of the major side surface  20  of the table  10 , from the position shown in FIG. 12 to the position shown in FIG. 13. As shown in FIG. 14 the panel  32  can be lowered below the major side surface  20  of the table  10  by rotation of the rod  156  in the opposite direction.  
         [0086]    With a patient&#39;s head lying on the panel  32  and the patient lying on the surface  20  of the table  10 , movement of the panel  32  relative to the upper major side surface  20  of the table  10  causes flexion and extension of the patient&#39;s cervical spine. With the cervical spine coil  152  disposed about the cervical spine of the patient, the patient&#39;s cervical spine can be imaged in any selected one of a plurality of positions throughout the range of movement of the panel  32 . Thus, rather than being limited to one image of the cervical spine while the patient is lying flat on an imaging table, the physician can obtain multiple images of the cervical spine at various positions throughout its range of motion. This is possible with any of the moving parts of the body which can be imaged. For example, movement can be measured and controlled in degrees—move a joint 5 degrees, image, move the joint 5 degrees further, image again, etc. Motion can also be measured in distances such as centimeters between positions.  
         [0087]    FIGS.  15 - 17  illustrate an alternate mechanism for raising and lowering the panel  32 . An inflatable bladder  162  is fixed between the head panel  32  and the bottom panel  84  of the table  10 . When the bladder  162  is in its neutral condition, the panel  32  is flush with the upper major side surface  20  of the table  10 . When the bladder  162  is inflated, the panel  32  is raised upwardly, out of the upper major side surface  20 , to the elevated position illustrated in FIG. 16. When the bladder  162  is deflated, the panel  32  is lowered below the upper major side surface  20  to the depressed position illustrated in FIG. 17. Again, by controlling the pressure in the bladder  162 , the MRI operator can fix the head panel at any given position within its range of motion, in order to image the cervical spine at a selected degree or flexion of extension.  
         [0088]    FIGS.  18 - 20  illustrate the use of the neck imaging platform as modified for imaging an ankle of a patient (not shown). The head panel  32  is modified by the addition of a foot rest  170 . The foot rest  170  is secured to the panel  32  by suitable means. The patient lies on the table  10  with, instead of his head at the head end  22 , his feet toward that end. The bottom of the patient&#39;s foot is positioned against the foot rest  170 , with the ankle over the recessed panel  34 . An ankle imaging coil  172  is placed over the ankle. A strap  174  secures the patient&#39;s foot to the foot rest  170 .  
         [0089]    When the bladder  162  is in the neutral condition illustrated in FIG. 18, the patient&#39;s ankle is in a normal position and may be imaged. Upon further inflation of the bladder  162 , the panel  32  raises upwardly away from the major side surface  20  of the table  10 . The footrest  170  bends the patient&#39;s ankle and the ankle may then be imaged with the coil  172  in that bent condition. Upon the application of suction or lowering of pressure to the bladder  162  (FIG. 20), the panel  32  is pivoted doom below the major side surface  20  of the table  10 , thus bending the ankle in the opposite direction. The ankle may be imaged in that opposite direction with the secondary coil  172 .  
         [0090]    FIGS.  21 - 23  illustrate an alternate actuating mechanism for the ankle imaging platform of FIGS.  18 - 20 . The actuating mechanism is like the actuating mechanism illustrated in FIGS. 12 and 13 for use of the panel  32  in cervical spine imaging. Upon rotation of the rod  156  in one direction or the other, the panel  32  and footrest  170  are pivoted either above the major side surface  20  of the table  10 , or below the surface  20 , to position the ankle for imaging at any selected position within its range of motion. It should be understood that a separate movable portion of the table  10  could be provided for use in ankle imaging, rather than using the neck imaging platform.  
         [0091]    It should also be understood that a table in accordance with the present invention need not include every specific movable platform as shown herein. Rather, such a table may include only one movable platform, or any combination of various movable platforms. It should further be understood that suitable control means is provided for moving the several platforms, in a known manner, in order to provide repeatable movement of the various platforms through their respective ranges of motion, in order to provide repeatable imaging at known positions. The table can also be used, of course, for other types of imaging such as ultrasound or CAT scans. It should further be understood that any of the platforms may be provided as separate devices which can be placed atop a known imaging table, rather than being built into a new table as shown.  
         [0092]    Accordingly, it is seen that the present invention provides an imaging table for positioning a body part so as to control the position or orientation of the body part. This positioning is independently controllable by the operator from a location external to the primary coil. This positioning requires no physical support effort by the patient during the time period of the imaging to maintain the selected position, as the table fully supports the weight of the body part connected therewith. Accordingly, a plurality of sequential images may be taken of a joint, for example, in differing positions, without undue effort on the part of the patient.  
         [0093]    In another embodiment of the invention, FIGS.  24 - 26  illustrate an apparatus  200  for positioning a body part within a primary imaging coil. The apparatus  200  is mounted to an imaging table  202  which may be the imaging table  10  or may be a known imaging table. A known secondary imaging coil  204  is secured to the table  202  by suitable means. The coil is located in a position for imaging a particular body part. As illustrated in FIGS. 24 and 25, the coil  204  is positioned to image a shoulder of a patient who is lying on the table  202  with his head adjacent the end  206  of the table  202 .  
         [0094]    The apparatus  200  includes a support rod  210  extending longitudinally along the table  202  from a position over the table  202  (inside the primary coil) to a position off the end of the table  202  (outside the coil). The rod  210  has an inner end portion  212  to which is fixed an attachment member  214 . The member  214  may be any suitable structure such as a cuff for attachment to a body part such as a forearm, for example, and may include means (such as the straps  215 ) for securing the cuff to the body part for movement therewith. The rod  210  also has an outward end portion  216  to which is attached a handle  218  for rotational and longitudinal movement of the rod  210  by a person other than the patient (not shown).  
         [0095]    The rod  210  extends through and is positioned by an index mechanism  220 , better seen in FIG. 26. The index mechanism  220  includes a base  222  having a first leg portion  224  and a second leg portion  226 . The leg portion  224  is fixed to the table  202 . The leg portion  226  has an upper major side surface  228  to which are attached support blocks  230  and  232 . The support block  230  has an opening  234  through which the rod  210  extends and is movable. The support block  232  has an opening  236 , aligned with the opening  234 , through which the rod  210  also extends and is movable. The blocks  230  and  232  support the rod  210 , and thus the cuff  214 . The block  232  also has a plurality of index openings  238 . The index openings  238  are spaced regularly in a circle around the rod  210 .  
         [0096]    An index block  240  is disposed on the rod  210  outside the block  232 . The rod  210  extends through an opening  246  in the index block  240 . The index block  240  includes a split clamp portion  242  and a clamping bolt  244 . When the split clamp  242  is loosened, the index block  240  is rotatable on and movable longitudinally on the rod  210 . When the split clamp  242  is tightened, the block  240  is fixed for movement with the rod  210 .  
         [0097]    The index block  240  has an index pin opening  250  through which is extensible an index pin  252 . The opening  250  is the same distance from the center of the opening  246 , as the index openings  238  are from the center of the opening  236  in the block  232 . Thus, the index pin opening  250  is alignable with any selected one of the index openings  238  on the support block  232 . When the opening  250  is aligned with one of the index openings  238 , the index pin  252  may be inserted through the index pin opening  250  and into the selected index opening  238 , to block rotation of the index block  240  relative to the support block  232 . If the index block  240  is clamped firmly to the rod  210 , this blocks rotational movement of the rod  210  relative to the support block  232 . Since the support block  232  is fixed to the table  202 , this therefore blocks rotational movement of the rod  210  relative to the table  202 , also thus fixing the cuff  214  in position. Further, when the index pin  252  is extended through the index pin opening  250  and into one of the index locations  238 , the index assembly  220  blocks longitudinal movement of the rod  210  relative to the table  202 . Thus, the cuff  214  is completely fixed in position relative to the table  202  and the coil  204 .  
         [0098]    It should be noted that other indexing mechanisms may be provided to replace the index pin opening  250  and index pin  252 . For example, as shown in FIG. 26A, the index block  240  may have a spring loaded ball  254  on its radially outer surface facing the support block  232 , which is selectively engageable at one of a plurality of ribbed index locations  256 , thus functioning as a detent mechanism. This is suitable for a patient-directed operation. If the apparatus  200  is to be patient directed, the portion of the rod  210  extending outwardly past the index mechanism  220  may be omitted. The patient adjusts the index mechanism by moving the body part, thus moving the cuff and support rod. Other index constructions are equally feasible.  
         [0099]    In operation of the positioner apparatus  200 , the patient is first placed on the table  202  in a position as desired. The coil  204  is adjusted so as to properly image the body part in question. (It should be noted that use of a secondary coil such as the coil  204  is not essential to functioning or use of the apparatus  200 .) The cuff  214  is then attached to a portion of the patient&#39;s body at a location selected to be able to move the body part to be imaged into a plurality of different positions. For example, if a shoulder joint is to be imaged, then the cuff  214  may be attached to the patient&#39;s forearm. Movement of the patient&#39;s forearm by means of the rod  210  will then cause the shoulder joint to move between a plurality of different positions. Similarly, if the patient&#39;s hip is to be imaged, the cuff  214  may be attached to the patient&#39;s leg, for example, the lower leg. Movement of the cuff  214  will cause movement of the hip joint to a plurality of different positions in which it may be sequentially imaged.  
         [0100]    The rod  210  as noted is longitudinally movable by pulling or pushing on the handle  218 . Thus, as the imaging operator moves the handle  218  longitudinally relative to the table  202 , the cuff  214  thus moves longitudinally also. The operator can therefore control the longitudinal position of the cuff  214 , and of its attached body part, from a location exterior to the primary coil.  
         [0101]    The rod  210  is also rotatable, by means of the handle  218 . The operator rotates the handle  218  to position the cuff  214  and its attached body part in the desired orientation for imaging. This rotational position is then locked in by means of the index assembly  220 . It should be noted that any number, location, or sequence of index locations  238  may be provided. Those shown are illustrative only. In fact, an index assembly may be provided which can be locked in any rotational position within a full circle.  
         [0102]    Many joints are movable in multiple degrees of freedom. The shoulder joint, for example, is movable in four degrees of freedom (or multiple planes of movement). In order to fully understand the joint anatomy, it is desirable to be able to image a joint in all these possible positions. Accordingly, the present invention provides for movement of a positioning apparatus such as the cuff  214  not merely rotationally and longitudinally, but also up and down and sideways.  
         [0103]    Thus, as seen in FIGS.  24 - 26 , the apparatus  200  may be made movable up and down and also sideways relative to the table  202 . The index blocks  230  and  232  are movable up and down along rods  231  and  233 , respectively, which rods are fixed to the base block  222 . Thus, the support rod  210  and cuff  214  can be moved up and down to provide a third degree of movement in addition to the rotation and longitudinal movement available. Further, the index assembly  220  has a guide member  235  engaging in a slot  237 . Thus, the index assembly is movable sideways along the table  202  to carry the support rod  210  and the cuff  214  in a fourth degree of movement. With these multiple degrees of movement, in multiple planes, it is now possible to move a joint into almost any position to simulate natural joint movement, while within an imaging coil.  
         [0104]    Another feature of the present invention is that traction can be applied to a joint being imaged, in order to distract the joint. For example, in the apparatus illustrated in FIGS.  24 - 26 , traction can be applied to a joint by pulling outwardly (to the right as viewed in FIG. 24) on the rod  210 . Such force when applied to the rod  210  acts through the cuff  214  on the joint being imaged. Distracting a joint can allow a better view of the parts of the joint and thus an increased imaging benefit. This feature is not available with present imaging apparatus.  
         [0105]    It should be noted that additional body part attachments are possible in order to better control movement and positioning. For example, extra cuffs or clamps, in addition to the one cuff shown in the drawings, may be attached to the body to more carefully and tightly control its movement and positioning. Further, it should be understood that other types of cuffs may be used, such as inflatable cuffs, etc. The cuffs should further be designed so that there is no plastic in contact with the skin. Such contact causes sweating and perspiration build up which causes imaging aberrations. Accordingly, a material is preferably provided against the skin to wick the perspiration away.  
         [0106]    Accordingly, it is seen that the present invention provides an apparatus for longitudinally and rotationally positioning a body part so as to control the position or orientation of a joint connected with the body part. This positioning is independently controllable by the operator from a location external to the primary coil. This positioning requires no physical support effort by the patient during the time period of the imaging, since the rod positioning apparatus fully supports the weight of the body part connected therewith. Nor does this adjustable positioner require any effort on the part of the patient to maintain the selected position, as the apparatus  200  performs that function also. A plurality of sequential images may be taken of a joint, for example, in differing positions, without undue effort on the part of the patient. (It should be noted that patient control of any of the positioning apparatus of the present invention is possible, as well as the described operator control.)  
         [0107]    FIGS.  27 - 29  illustrate another body part positioner having two degrees of movement. An apparatus  260  includes a saddle  262  having upstanding side portions  264  and  266  joined by a bottom portion  268 . The saddle  262  is mounted on a base block  270 . The base block  270  is mounted on a panel  272  which may be the head panel  32  of the table illustrated in FIG. 1A. The panel  272  has a plurality of index openings  274 . An index pin  276  (FIG. 27) extends through a portion  278  of the base block  270  and is receivable in a selected one of the openings  274 . The base block  270  is pivotally mounted at  280  to the panel  272 . Thus, the base block  270 , with its attached saddle  262 , may be positioned at a selected one of a plurality of rotational positions relative to the panel  272 , as shown in phantom in FIG. 27.  
         [0108]    An index plate  282  is attached to the saddle  262 . The index plate  282  and saddle  262  are pivotally mounted at  284  to the base block  270 . The index plate  282  has a plurality of index openings  286  spaced in an arc about the pivot mounting  284 . A locator opening (not shown) is located behind the index plate  282 , in the base block  270 . The saddle  262 , with its attached index plate  282 , may be pivotally rotated about the mounting  284 , as shown in phantom in FIG. 28, and secured in a position by insertion of an index pin (not shown) through the selected opening  286  into the locator opening in the base block  270 .  
         [0109]    In operation of the positioning assembly  260 , the patient&#39;s head is secured in the saddle  262 . The saddle  262  and base block  270  are then swung around the pivot axis  280  and locked in a selected position with the index openings  274 . The saddle  262  is also rotated, with the index plate  282 , about the pivot axis  284  and locked in a selected position. The patient&#39;s head or cervical spine is then imaged. The apparatus  260  is then adjusted to a different condition, moving the patient&#39;s head or spine to a new position. The patient&#39;s head or spine is then imaged again.  
         [0110]    Accordingly, it is seen that a patient&#39;s head or cervical spine, when the head is in the saddle  262 , can be selectively positioned in any one of a plurality of different orientations within two separate degrees of motion. Further, if the head panel  272  is pivotally mounted to the table  10 , the attached saddle  262  may also be moved up and down out of the plane of the table, thus moving the patient&#39;s head in the saddle  262  in yet a third degree of motion. The control of all these movements may be automated with a fluid drive or other means, may be made remotely controllable from a location outside the coil, or may be patient directed.  
         [0111]    Accordingly, it is seen that the present invention also provides apparatus for positioning a body part of a patient for imaging in a plurality of different degrees of motion. For example, the patient&#39;s cervical spine may be imaged in a sequence of images by moving the saddle  262  in the desired direction within the various degrees of motion and locking it in place at each selected position. There is no need for the patient to hold any selected position, as the positioning apparatus  260  does this for him. Accordingly, the imaging process is made significantly more stable and more comfortable for the patient.  
         [0112]    Because coil support panels such as the recessed panels  34  and  48  (FIG. 1A) are located below the upper major side surface  20  of the table  10 , a flat surface coil placed therein will not interfere with normal body positioning. Thus, it is seen that recessing the coils, itself, provides a significant benefit.  
         [0113]    Several patient directed devices are illustrated in FIGS.  30 - 40 . Such devices can be part of a new imaging table as described above, but can also be independent, that is, add-ons to an existing imaging table (as the apparatus  200  is an add-on to the table  202  in FIGS.  24 - 26 ). They are therefore less expensive and more widely usable.  
         [0114]    These patient-directed devices can be end-mounted fixtures such as a modification of those shown in FIGS.  24 - 26 . They can also be fixtures mounted to the upper surface of the table, in effect replacing the movable platforms of the table of FIG. 1A.  
         [0115]    FIGS.  30 - 36  illustrate a patient directed wrist movement apparatus  300 . The apparatus  300  includes a base  302  which may be secured to an imaging table with suitable means not shown. The base  302  supports an imaging coil  304 . The patient&#39;s forearm is placed on a forearm cuff  306  secured to the base  302 . The patient&#39;s hand is placed, thumb up as seen in FIG. 33, in a hand cuff  308 . The hand cuff  308  is pivotally mounted at  310  to the base  302 . A detent member  312  is located on a lower end portion  314  of the hand cuff  308 . The detent member  312  is engageable with a ratchet-type member  316  on the base  302 . Thus, the hand cuff  308  and the base  302  are releasably interlockable at a plurality of positions within their range of rotational movement.  
         [0116]    To adjust the apparatus  300 , the patient simply applies sufficient torque to release the interconnection between the hand cuff  308  and the base  302  and thereby flex or extend his wrist to the next desired position. The apparatus  300  then interlocks at this newly selected position for imaging by the coil  304 .  
         [0117]    A modification of the apparatus  300  is illustrated in FIG. 32 with an apparatus  320  having a different hand cuff  322 . The hand cuff  322  is designed to have the hand lie flat rather than on edge, with the thumb to the side as viewed in FIG. 32. The wrist is again movable through its range of motion, this time being imaged in a position 90.degree. from that shown in FIG. 30.  
         [0118]    FIGS.  37 - 40  illustrate a patient directed knee imaging apparatus  330 . The apparatus is similar to the knee platform of the table  10  of FIG. 1A, but is instead designed to be patient directed (actuated) rather than technician or operator directed.  
         [0119]    The apparatus  330  includes a base  332 . The base  332  rests on the upper major side surface of the table. Suitable means may be provided to secure the base  332  to the table. A lower leg cuff  334  is releasably secured to the lower leg. The cuff  334  is attached at  336  to the base  332  to maintain the same focal point of imaging as the knee is flexed. An upper leg cuff  338  is releasably secured to the upper leg. The upper leg cuff is also attached at  340  to the base  332 .  
         [0120]    A knee imaging coil  342  is fixed for movement with a movable panel or portion  344  of the base  332 . Attached to the patient&#39;s foot is a footrest  346  with a pawl member  348 . The pawl member  348  engages a ratchet portion  350  on the base  332 .  
         [0121]    To adjust the device, the patient simply bends his knee to move his foot and thus the pawl member  348  along the ratchet portion  350  from one position to the next. The panel  344  moves in a manner as described above. The patient&#39;s foot is then held in that position firmly enough to allow for accurate imaging.  
         [0122]    As the patient moves his foot and knee, the secondary coil  342  moves with the knee and generally stays in position relative to the knee. The secondary coil  342  is constrained for movement by the panel  344  so that it stays in the proper planar orientation relative to the primary imaging coil (not shown). As the patient moves his foot and knee, the cuffs  334  and  338  are constrained for proper movement by the mechanisms which attach them to the base  332  in order to maintain the same focal point of imaging as the knee is flexed. The coil  342  stays in close proximity to the knee, moves longitudinally and up and down as the knee moves, and maintains its proper planar orientation throughout its range of motion.  
         [0123]    An optional addition to the apparatus  330  is a distraction member  352  (FIG. 40). As illustrated the distraction member  352  is an inflatable bladder having a bellows-type construction for support. The bladder  352  extends between the lower leg panel  354  and the lower leg cuff  334 . When the bladder is inflated, it applies force to push the lower leg up to stress the knee outwardly. This can be done to check ligaments in the knee for damage or weakness. This feature of distraction or stressing of a joint can be applied in other joints, on other positioning apparatus, and to move body parts in an manner needed to simulate natural loading of a joint or to enable better imaging of the joint under various conditions.  
         [0124]    Thus, it is seen that the present invention provides apparatus for use in imaging which can be attached to an existing table, allows the patient to direct the movement, controls the motion of the joint in a repeatable manner, moves a secondary coil with the joint, and holds the secondary coil in proper alignment. Of course, the movement can be operator controlled, also, by using, for example, a rod attached to the pawl device for moving the patient&#39;s foot. Similar constructions as modified can be used to provide for patient directed movement of other body parts and joints.  
         [0125]    If a joint is small enough and/or limited enough in its range of motion that imaging the joint with one fixed secondary coil provides acceptable resolution, then it may not be necessary to move the secondary coil. For example, the wrist is a relatively small joint which, even when moved through its entire range of motion, does not take a large amount of space. Thus, the wrist is imaged using flat plates on either side of the wrist or a coil extending around the wrist.  
         [0126]    An example of these features is the patient directed apparatus  300  (FIGS.  30 - 36 ) for moving the wrist through its range of motion within fixed coils. Similarly, the shoulder is a joint which does not move significantly through space when bent. Accordingly, it can usually be imaged successfully using a fixed coil. In this case, the present invention provides the fixture  200  (FIGS.  24 - 26 ) for moving the shoulder through its range of motion within the fixed coil.  
         [0127]    However, some joints are large enough and/or move through space so that it is impossible to obtain optimum resolution with a fixed secondary coil through the entire range of motion of the joint. In this case, the present invention provides fixtures for moving the secondary coil with the joint. An example is the movable knee platforms of the table of FIG. 1A. Another example is the apparatus of FIGS.  37 - 40  for imaging the knee in a patient directed manner with a moving secondary coil.  
         [0128]    It should be understood that the present invention contemplates the use of drive or actuating mechanisms other than those shown. For example, any one of the movable portions of the apparatus shown could be driven by a piston-cylinder device which is pneumatic or hydraulic. A pneumatic motor drive could be used, as well as an electric motor drive. Similarly, the pawl and ratchet or detent mechanisms illustrated in FIGS.  30 - 40  could be used in other configurations, as they are especially suitable for precise, repeatable incremental motion control.  
         [0129]    In this regard, reproducability of the movement is desirable so that the patient&#39;s progress over a period of time can be checked. Thus, indexing movement of the body part being imaged through degrees or distance is advantageous. Reproducability, as provided by the present invention, is also useful in conducting clinical studies of groups of patients.  
         [0130]    In accordance with the present invention, it is possible to use a larger diameter primary coil, allowing increased range of limb movement, without the degradation in image quality which would be expected from the increased coil size. This is possible because of total imaging available with the extensive use of secondary coils as described herein. For example, the knee could be flexed through its entire range of motion to allow optimum imaging of the knee joint. This is currently impossible with the known small primary coils which only allow about 50 degrees of flexion.  
         [0131]    Thus, as illustrated in FIG. 41, a known primary MRI coil  360  with a table  362  has a height  361  from the table to the inside of the coil of 16″. The table  362  has a width  363  of 19″. As illustrated in FIG. 42, a replacement primary MRI coil  364  in accordance with the present invention, with a table  366 , has a height  365  from the table to the inside of the coil of 21.5″. The table has a width  367  of 24″. With these dimensions and the moving secondary coils, substantially increased limb movement is possible, without degradation of image quality.  
         [0132]    In a further embodiment of the present invention, an MRI primary coil is mounted to extend vertically rather than horizontally. Thus, as illustrated in FIG. 43, a primary MRI coil  368  extends vertically rather than horizontally. A patient may be placed in a standing or seated position on a support  370  for imaging in the coil  368 . A ram  372  is operable to move the patient into and out of the coil  368 . Positioning fixtures, etc. are mounted to a support member  374 .  
         [0133]    With the patient in a vertical or in a seated position, it is possible to simulate joint positionings and joint loadings which can not readily be simulated when the patient is lying down in a known horizontal imaging coil. For example, a weight or other tractive force can be attached to the arm to simulate shoulder joint loading experienced when carrying a heavy object. The knee can be imaged with the patient standing to see how the joint appears when loaded with body weight. The spine can be imaged when standing or seated to check for disc or vertebral problems which are experienced in normal life but which disappear when the patient lies down to be imaged in a known horizontal imaging coil. The possibilities for increased usefulness of the imaging methodology are manifold.  
         [0134]    Any of the positioning apparatus disclosed herein are usable with or without a secondary coil. When used with a secondary coil, they provide the benefit of constraining movement of the secondary coil in a proper planar orientation relative to the primary coil, and also the benefit of keeping the secondary coil in close proximity to the body part being moved and imaged.  
         [0135]    If the various apparatus of the present invention are used for magnetic resonance imaging, they must be made of non-ferromagnetic materials. Plastic is preferred for the table and the positioner, while brass is suitable for mechanical drive mechanisms. Fluid drive mechanisms are also highly suitable because they can be easily constructed using plastic components. Wood is also usable.  
         [0136]    From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications in the invention. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.