Abstract:
A support structure for medical diagnostic equipment provides entirely independent motions on all axes of the detector and very precise and reproducible motions while allowing for static, linear and rotational imaging such as by a rotatable scintillation detector. The support structure includes a rotor or ring on which there are two arms on which the detector is mounted and a counterweight attached by links to the opposite end of the arms and on the opposite side of the rotor. The arms, on which the detector is rotatably mounted, are attached to the rotor by means of short, double pivoted links which allow the arms to move towards or away from the rotor and pivot with respect to the rotor. Two secondary arms are connected to the pivot point of the detector and to a track mounted on the rotor. The counterweight end of the primary arms, and hence the scintillation detector may be vertically displaced to a desired position without change in the distance from the rotor and without angular displacement of the plane of view.

Description:
FIELD OF INVENTION 
     The present invention relates to a support structure for medical diagnostic equipment. More particularly, the present invention relates to a support structure for supporting and controlling the relative positions of a patient and a scintillation camera. 
     BACKGROUND OF THE INVENTION 
     In the human body, increased metabolic activity is associated with an increase in emitted radiation. In the field of nuclear medicine, increased metabolic activity within a patient is detected using a radiation detector such as a scintillation camera. 
     Scintillation cameras are well known in the art, and are used for medical diagnostics. A patient ingests, or inhales or is injected with a small quantity of a radioactive isotope. The radioactive isotope emits photons that are detected by a scintillation medium in the scintillation camera. The scintillation medium is commonly a sodium iodide crystal, BGO or other. The scintillation medium emits a small flash or scintillation of light, in response to stimulating radiation, such as from a patient. The intensity of the scintillation of light is proportional to the energy of the stimulating photon, such as a gamma photon. Note that the relationship between the intensity of the scintillation of light and the gamma photon is not entirely linear. 
     A conventional scintillation camera such as a gamma camera includes a detector which converts into electrical signals gamma rays emitted from a patient after radioisotope has been administered to the patient. The detector includes a scintillator and photomultiplier tubes. The gamma rays are directed to the scintillator which absorbs the radiation and produces, in response, a very small flash of light. An array of photodetectors, which are placed in optical communication with the scintillation crystal, converts these flashes into electrical signals which are subsequently processed. The processing enables the camera to produce an image of the distribution of the radioisotope within the patient. 
     Gamma radiation is emitted in all directions and it is necessary to collimate the radiation before the radiation impinges on the crystal scintillator. This is accomplished by a collimator which is a sheet of absorbing material, usually lead, perforated by relatively narrow channels. The collimator is detachably secured to the detector head, allowing the collimator to be changed to enable the detector head to be used with the different energies of isotope to suit particular characteristics of the patient study. A collimator may vary considerably in weight to match the isotope or study type. 
     Scintillation cameras are used to take four basic types of pictures: spot views, whole body views, partial whole body views, SPECT views, and whole body SPECT views. 
     A spot view is an image of a part of a patient. The area of the spot view is less than or equal to the size of the field of view of the gamma camera. In order to be able to achieve a full range of spot views, a gamma camera must be positionable at any location relative to a patient. 
     One type of whole body view is a series of spot views fitted together such that the whole body of the patient may be viewed at one time. Another type of whole body view is a continuous scan of the whole body of the patient. A partial whole body view is simply a whole body view that covers only part of the body of the patient. In order to be able to achieve a whole body view, a gamma camera must be positionable at any location relative to a patient in an automated sequence of views. 
     The acronym “SPECT” stands for single photon emission computerized tomography. A SPECT view is a series of slice-like images of the patient. The slice-like images are often, but not necessarily, transversely oriented with respect to the patient. Each slice-like image is made up of multiple views taken at different angles around the patient, the data from the various views being combined to form the slice-like image. In order to be able to achieve a SPECT view, a scintillation camera must be rotatable around a patient, with the direction of the detector head of the scintillation camera pointing in a series of known and precise directions such that reprojection of the data can be accurately undertaken. 
     A whole body SPECT view is a series of parallel slice-like images of a patient. Typically, a whole body SPECT view consists of equally spaced cross sections or vertical or horizontal longitudinal sections. A whole body SPECT view results from the simultaneous generation of whole body and SPECT image data. In order to be able to achieve a whole body SPECT view, a scintillation camera must be rotatable around a patient, with the direction of the detector head of the scintillation camera pointing in a series of known and precise directions such that reprojection of the data can be accurately undertaken. 
     Therefore, in order that the radiation detector be capable of achieving the above four basic views, the support structure for the radiation detector must be capable of positioning the radiation detector in any position relative to the patient. Furthermore, the support structure must be capable of moving the radiation detector relative to the patient in a controlled manner along any path. 
     In prior scintillation cameras, the vertical travel of a detector has been achieved by either counter-balancing the detector about a pivot or by a motor driven screw jack. This results in compromises in various areas of normal clinical operation including the possibility of varying the total weight of the detector, raising or lowering the detector and maintaining the focus of the collimator at the same point, the ability to perform complex motions around the patient and view the constant ‘slice’ of the patient and the precision and reproducibility of the motions. 
     While such scintillation camera systems have existed for about two decades now, performing to a greater or lesser degree satisfactorily, the advances in resolution in newer systems have created greater requirements in precision alignment between the detector and the patient or the patient support apparatus. One alternative system attempted to address this problem at the cost of great complexity. This has been particularly noticeable as nuclear camera systems have been used more and more for generating tomographic images by rotation of the detector about the patient, in addition to the more conventional static imaging. One such nuclear camera system capable of both whole body static imaging as well as emission computed tomography or ECT, is the Gemini system available from General Electric Corporation, Milwaukee, Wis., and described in U.S. Pat. No. 4,651,007 to Perusek et al. 
     In general, prior nuclear camera systems, regardless of whether they include ECT capability, feature a counter-balanced detector, with an inherent variable viewing point in the patient due to the radius from the pivot to the detector, a toe or forward projecting structure to stabilize the medical diagnostic positioner or the patient bed supported between two supports with the detector head mounted on a translatable support to traverse the patient length. The loss of resolution and contrast of the imaging device, the scintillation camera detector head, arises from variable viewing point in the patient due to the radius from the pivot to the detector and from a lack of precision alignment between the bed and detector head, particularly during rotation of the camera head. 
     Among the objects of the present invention are to provide: an improved support structure for medical diagnostic equipment, such as a nuclear camera; a support structure capable of supporting and positioning a nuclear camera in any position relative to a patient; a support structure capable of positioning a nuclear camera for spot views, whole body views, SPECT views, and whole body SPECT views; a support structure for a nuclear camera capable of accommodating a range of collimator weights; a support structure for a nuclear camera that is relatively inexpensive to manufacture. 
     SUMMARY OF THE INVENTION 
     The support structure of the present invention is designed to support and position a nuclear camera or other medical diagnostic equipment. The invention includes a stable base upon which an annular support rotates, advantageously in a vertical plane. An elongate support extends through the annular support. Attached to one end of the elongate support is a nuclear camera or other medical diagnostic device. Attached to the other end of the elongate support is a counter balance. A guide attaches the elongate support to the annular support, such that pivoting of the elongate support relative annular support results in movement of the camera end of the elongate support in a plane parallel to the plane of the annular support. 
     According to the invention, there is therefore provided a support structure for supporting and positioning a device relative to a patient, the support structure comprising: (a) a base; (b) a rotating support rotatable in a first plane relative to the base; (c) an elongate support pivotally attached to the rotating support at an angle to the first plane, the elongate support comprising a device end for supporting a device; and (d) a guide for restricting movement of the device end of the elongate support to a first plane fixed relative to the base. 
     According to the invention, there is therefore further provided a support structure for supporting and positioning a scintillation camera detector relative to a patient, the support structure comprising: (a) a base positionable on a ground surface and comprising a pair of spaced apart lower rollers; (b) a vertically oriented annular rotating support defining an orifice and a first vertical plane and being rotatable in the first vertical plane, the rotating support comprising: (i) an outside surface in rolling contact with the lower rollers; (ii) an inside surface for supporting a patient support; (iii) a front surface; and (iv) a rear surface; (c) an elongate support comprising a pair of spaced apart arms extending through the rotating support, the elongate support comprising: (i) a camera end for supporting a scintillation camera detector at a distance from the front surface of the rotating support; and (ii) a counter weight end for supporting a counter weight at a distance from the rear surface of the rotating support; (d) a guiding linkage connecting the rotating support to the elongate support such that pivotal movement of the elongate support relative to the rotating support results in movement of the camera end of the elongate support in a second vertical plane, the vertical plane being parallel to the first vertical plane; (e) a counter weight depending from the counter weight end of the elongate support; (f) an actuator for pivoting the elongate member relative to the annular support; and (g) a drive unit for rotating the annular support relative to the base. 
     Advantageously, the present invention provides: an improved support structure for medical diagnostic equipment, and particularly for imaging equipment, such as a nuclear camera; a support structure capable of supporting and positioning a nuclear camera in any position relative to a patient; a support structure capable of positioning a nuclear camera for spot views, whole body views, SPECT views, and whole body SPECT views; a support structure for a nuclear camera capable of accommodating a wide range of collimator weights; a support structure for a nuclear camera that is relatively inexpensive to manufacture. 
    
    
     Other advantages, objects and features of the present invention will be readily apparent to those skilled in the art from a review of the following detailed descriptions of preferred embodiments in conjunction with the accompanying drawings and claims. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The embodiments of the invention will now be described with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a scintillation camera showing only certain aspects of the invention, and specifically not illustrating the guide of the present invention; 
     FIG. 2 is a partial perspective view of an embodiment of the invention, specifically illustrating the guide apparatus; 
     FIG. 3 is a front elevation view of an embodiment of the invention; 
     FIG. 4 is a side elevation view of an embodiment of the invention; 
     FIG. 5 is a side elevation view of an embodiment of the invention; 
     FIG. 6 is a front elevation view of an embodiment of the invention; 
     FIG. 7 is a top plan view of an embodiment of the invention; 
     FIG. 8 is a perspective view of the scintillation camera of FIG. 1 but including a patient support apparatus with the stretcher removed; and 
     FIG. 9 is a side view of a portion of the patient support apparatus. 
     Similar references are used in different figures to denote similar components. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 to  9 , a nuclear camera detector  5  is supported and positioned relative to a patient by a support structure  10 . Nuclear camera detectors are heavy, usually weighing approximately three to four thousand pounds. Thus, the support structure  10  should be strong and stable in order to be able to position the camera detector  5  safely and accurately. The support structure  10  includes a base  15 , an annular support  20 , an elongate support  25 , and a guide  30 . 
     The base  15  includes a frame  35 . The frame  35  includes twelve lengths of square steel tubing welded together in the shape of a rectangular parallelepiped. The frame  35  has a front square section  37  and a rear square section  38 . In the illustrated embodiment, the frame  35  is approximately five feet wide, five feet high, and two feet deep (e.g., approximately 1.5 m wide, 1.5 m high and 0.6 m deep). The frame  35  also includes eight triangular comer braces  40  welded to the front square section  37 , that is, each comer of the front square section  37  has two comer braces  40 , one towards the front of the front square section  37 , and one towards the rear of the front square section  37 . In the illustrated embodiment, the comer braces  40  are in the shape of equilateral right angle triangles. 
     Attached to the underside of the frame  35  are two horizontal legs  45 . Attached to each leg  45  are two feet  50 . An alternative to the use of feet  50  is to attach the base  15  to a floor by way of bolts set into the floor. The legs  45  extend beyond the frame  35  so as to position the feet  50  wider apart to increase the stability of the base  15 . The feet  50  are adjustable so that the base  15  may be levelled. Thus constructed, the base  15  is strong, stable, rigid, and capable of supporting heavy loads. 
     The annular support  20  is vertically oriented, having an inner surface  55  defining an orifice  60 , an outer surface  65 , a front surface  70 , and a rear surface  75 . The annular support  20  is constructed of a ductile iron casting capable of supporting heavy loads. In the illustrated embodiment, the annular support  20  has an outside diameter of about fifty two inches (e.g., about 1.3 m. The annular support  20  is supported by upper rollers  80  and lower rollers  85  which are mounted on the base  15 . The upper rollers  80  and lower rollers  85  roll on the outer surface  65 , thus enabling the annular support  20  to rotate relative to the base  15  in the plane defined by the annular support  20  (e.g., alternatively referred to as a first plane). Each of the upper rollers  80  and lower rollers  85  are mounted onto a pair of comer braces  40  by way of axles with deep groove bearings. The bearings should be low friction and be able to withstand heavy loads. The axles of the upper rollers  80  are radially adjustable relative to the annular support  20 , so that the normal force exerted by the upper rollers  80  on the outer surface  65  is adjustable. The curved surfaces of the upper rollers  80  and lower rollers  85  (i.e. the surfaces that contact the outer surface  65 ) should be tough so as to be able to withstand the pressures exerted by the annular support  20 , and should have a fairly high coefficient of friction so as to roll consistently relative to the annular support  20 . 
     Attached to each pair of comer braces  40  is a stabilizing arm  90  oriented perpendicularly to the plane of the annular support  20 . A pair of small stabilizing rollers  95  are mounted onto each stabilizing arm  90 . Each pair of stabilizing rollers  95  is positioned such that one stabilizing roller  95  rolls on the front surface  70 , and the other stabilizing roller  95  rolls on the rear surface  75 . The stabilizing rollers  95  maintain the annular support  20  in the vertical plane. 
     The elongate support  25  includes a pair of support arms  100 , each of which extends through an aperture in the annular support  20 . The nuclear camera detector  5  is rotatably attached to one end of the pair of support arms  100 , such that the nuclear camera detector  5  faces the front surface  70 . A counter weight  105  is attached to the other end of the pair of support arms  100 , such that the counterweight  105  faces the rear surface  75 . 
     The counter weight  105  includes a pair of parallel counter weight members  110 , each of which is pivotally attached to one of the support arms  100 . A first weight  115  is attached to one end of the pair of counter weight members  110 , and a second weight  120  is attached to the other end of the pair of counter weight members  110 . A pair of counter weight links  121  connect the counter weight members  110  to the annular support  20 . Each counter weight link  121  is pivotally attached at one end to its corresponding counter weight member  110 . Each counter weight link  121  is pivotally attached at its other end to a counter weight bracket  122  which is rigidly attached to the annular support  20 . The counter weight links  121  are attached to the counterweight members  110  and counter weight brackets  122  using bolts and tapered roller bearings. Each counter weight link  121  is pivotable relative to the annular support  20  in a plane perpendicular to and fixed relative to the annular support  20 . 
     The guide  30  attaches the elongate support  25  to the annular support  20 , and controls the position of the elongate support  25 , and hence the scintillation camera detector  5 , relative to the annular support  20 . A pair of brackets  125  is rigidly attached to the annular support  20 . A pair of rigid links  130  is pivotally attached at support arm pivot points  135  to the support arms  100 . The pair of links  130  is also pivotally attached at bracket pivot points  140  to the brackets  125 . At the support arm pivot points  135  and bracket pivot points  140  are tapered roller bearings mounted with bolts. Each link  130  is pivotable relative to the annular support  20  in a plane perpendicular to and fixed relative to the annular support  20 . Thus, as the annular support  20  rotates relative to the base  15 , the respective planes in which each link  130  and each support arm  100  can move remain fixed relative to the annular support  20 . 
     A pair of linear tracks  145  are rigidly attached to the front surface  70  of the annular support  20 . The tracks  145  are oriented such that they are parallel to the respective planes in which each link  130  and each support arm  100  can move. A pair of rigid sliding arms  150  (not shown in FIG. 1) include camera ends  155  and straight ends  160 . Each camera end  155  is pivotally attached to one of the support arms  100  at the point of attachment of the scintillation camera detector  5 . Each straight end  160  includes a pair of spaced apart cam followers or guides  165  slidable within the corresponding track  145 . Thus, movement of the scintillation camera detector  5  relative to the annular support  20  (i.e. we are not concerned, at this point, with rotational movement of the scintillation camera detector  5  relative to the elongate support  25 ) is linear and parallel to the plane of the annular support  20 . Note that if the camera ends  155  were pivotally attached to the support arms  100  between the nuclear camera detector  5  and the annular support  20 , the movement of the nuclear camera detector  5  relative to the annular support  20  would not be linear. 
     Movement of the scintillation camera detector  5  relative to the annular support  20  is effected by an actuator  170 . The actuator  170  includes a fixed end  175  pivotally attached to the annular support  20 , and a movable end  180  pivotally attached to the elongate support  25 . The actuator  170  is extendable and retractable, and is thus able to move the elongate support  25  relative to the annular support  20 . 
     Movement of the annular support  20  relative to the base  15  is effected by a drive unit  185 . The drive unit  185  includes a quarter horsepower permanent magnet DC motor and a gearbox to reduce the speed of the output shaft of the drive unit  185 . Alternatively, other types of motors could be used, such as hydraulic or pneumatic motors. The output shaft of the drive unit  185  is coupled, by means of a toothed timing belt  195  and two pulley wheels  200 , to the axle of a drive roller  190 , which is simply one of the lower rollers  85 , thus driving the drive roller  190 . Power is then transferred from the drive roller  190  to the annular support  20  by friction between the drive roller  190  and the outer surface  65  of the annular support  20 . 
     The support structure  10  of the illustrated embodiment is designed to operate with an apparatus for supporting and positioning a patient, such apparatus including a detached patient support  205 , an engaged patient support  210 , and a cylinder  245 . 
     The detached patient support  205  includes rigid patient frame  215  supported by four casters  220 . Mounted near the top of the patient frame  215  are first support wheels  225  for supporting a stretcher  227  upon which a patient is lying. Two parallel, spaced apart side rails  230  are rigidly attached to the patient frame  215 . The first support wheels  225  and the side rails  230  are arranged to enable the stretcher  227  to roll lengthwise on the detached patient support  205 . Thus, if the patient support  205  faces the front surface  70  such that the patient support is central and perpendicular relative to the annular support  20 , the stretcher  227  is movable on the first patient support wheels  225  substantially along the axis of the annular support  20 . A gear box and motor unit  237  driving at least one of the first patient support wheels  225  moves the stretcher  227  as described. A 0.125 horsepower permanent magnet DC motor has been found to be adequate. 
     The detached patient support  205  can be used both for transporting a patient to and from the scintillation camera detector  5  and support structure  10  therefor, and for supporting and positioning a patient relative to the base  15  during operation of the scintillation camera detector  5  and support structure  10 . To ensure that the detached patient support  205  remains stationary during operation of the scintillation camera detector  5 , four stabilizers  233  can be lowered. Thus lowered, the stabilizers  233  ensure that the detached patient support remains stationary relative to the floor. 
     The engaged patient support  210  includes second support wheels  235 . The second support wheels  235  are positioned such that the stretcher  227  rolled along the first support wheels  225  can roll onto the second support wheels  235  until the stretcher  227  is either fully or partially supported by the second support wheels  235 . The engaged patient support  210  also includes four transverse wheels  240 . 
     The cylinder  245  is rigidly mounted to the annular support  20 . The cylinder  215  is aligned with the orifice  60  of the annular support  20  such that the cylinder is coaxial with the annular support  20 . The cylinder  245  includes a smooth inner surface  246  upon which rest the transverse wheels  240  of the engaged patient support  210 . Thus, the arrangement is such that the patient remains stationary substantially along the axis of the annular support  20  as the annular support  20  rotates relative to the base  15 , regardless of whether the board or stretcher is supported by the first support wheels  225 , the second support wheels  235 , or both. 
     The engaged patient support  210  also includes a stabilizer  250 . The stabilizer  250  includes outside wheels  255  to maintain the engaged patient support  210  horizontal, that is, to stop the engaged patient support from tipping relative to the cylinder  245 . The outside wheels  255  roll on the outside surface  243  of the cylinder  245 . The stabilizer  250  also includes end wheels  256  to prevent the engaged patient support  210  from moving in a direction parallel to the axis of the cylinder  245 . The end wheels  256  roll on the ends  244  of the cylinder  245 . 
     Numerous modifications, variations and adaptations may be made to the particular embodiments of the invention described above without departing from the scope of the invention, which is defined in the claims.