Abstract:
A bite device for the correct positioning of a patient when a panoramic x-ray is taken, comprising a holder part ( 42 ) which can be placed in a fixed direction in relation to the x-ray device, a plate ( 46 ) which can pivot against the holder and which is provided with a bite part ( 50 ) into which a patient bites, and means ( 58, 60 ) for detecting the pivoting angle A between the plate ( 46 ) and the holder part ( 42 ).

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to a system for correct positioning of a patient when the latter is X-rayed with a medical panoramic X-ray device.  
       PRIOR ART  
       [0002]     When recording a panoramic X-ray image, the tomography zone ideally runs through the alveolar ridge of the patient. In order to achieve a high degree of recording quality, it is necessary to bring these two elements, tomography zone and alveolar ridge, into the best possible spatial relationship. In the panoramic X-ray device, the tomography zone can be adjusted to the individual shape and position of the jaw of a patient within certain limits. The condition is, however, that these are known to the operator. In particular, knowledge of the following features is significant: 
        the spatial orientation of the edge-to-edge occlusal plane (bite plane) relative to a reference point on the panoramic X-ray device; and     the individual anatomic characteristics of the jaw: its size, shape, anomalies and the like.        
 
         [0005]     Traditionally, the patient&#39;s head is fixed in position relative to the device for taking a panoramic radiograph by means of a patient&#39;s head positioner comprising a forehead pad and/or ear pads, a bite block, a nasion, or a chin pad. The necessary alignment of the head is usually achieved with the aid of optical lines projected onto the patient&#39;s head and depicting the Frankfurt horizontal and median planes. The Frankfurt horizontal plane runs through the right and left porion, the highest point of the meatus acusticus externus, and the orbital, which represents the lowest point of the osseous edge of the orbita. The projected median plane runs as a sagittal plane from the crown of the head through the center of the nose to the chin. It assists symmetrical positioning of the head.  
         [0006]     The position of the occlusal plane is not directly registered but only indirectly by way of the Frankfurt horizontal plane. To this end, the Frankfurt horizontal plane projected onto the patient&#39;s head by the panoramic X-ray device and the incisal teeth in the edge-to-edge bite are used to derive the position of the occlusal plane. The correlation between the occlusal plane and the Frankfurt horizontal plane is generally acknowledged from an anatomical standpoint, but positioning errors relative to the Frankfurt horizontal plane of the patient cannot be excluded.  
         [0007]     In order to determine the individual size of the patient&#39;s jaw, a frontal diameter measurement may be carried out, if necessary. Derivation of the jaw size is not, however, sufficiently reliable.  
         [0008]     Neither has any reliable system been as yet developed for determining the shape of the alveolar arch or any anomalies of the jaw.  
         [0009]     Present-day panoramic X-ray devices, therefore, offer only a few modification options, since the operator could not in any case make use of such adjustment options due to insufficient knowledge of the individual form of a patient&#39;s jaw.  
         [0010]     This forms the basis of the invention. It is an object of the invention, as characterized in the claims, to provide a system for correct positioning of a patient for image recording using a medical panoramic X-ray device, which allows for simple and stable measurement and/or adjustment of the inclination of the occlusal plane of a patient.  
       DESCRIPTION OF THE INVENTION  
       [0011]     This object is achieved, according to the invention, by the bite device defined in claim  1 . Advantageous embodiments of the invention are subject matter of the sub-claims.  
         [0012]     The invention improves on the prior art in that a bite device includes a holding member held in a directionally fixed position relative to the X-ray device, and a plate which is pivoted relative to the holding member and which has a bite piece on which the patient bites. The bite device also includes means for measuring the angle of deflection a between the plate and the holding member, which means for measuring the angle of deflection a are located in a zone of the bite device which is free from radiation during X-ray imaging. The zone involving X-ray irradiation can therefore be kept substantially free from metal.  
         [0013]     The invention is thus based on the idea of measuring the position of the occlusal plane of the patient relative to the device by determining the position of a plate disposed in the occlusal plane. For this purpose, the angle is measured between the plate and a holding member, which can be positioned relative to the X-ray device in fixed alignment. From this angle a signal can be derived which indicates the degree of inclination of the occlusal plane.  
         [0014]     It is advantageous for the means for measuring the angle of deflection a to contain one or more sensors located in the holding member. For example, the sensors might be in the form of a photoelectric sensor located in the holding member and adapted to register the position of an opening that is moved upwardly and downwardly in accordance with the pivotal motion of the plate.  
         [0015]     The bite device of the invention can conveniently include means for displaying the angular position of the pivoted plate.  
         [0016]     In a preferred development of the bite device, there are further provided driving means for vertical adjustment of the holding member and thus for pivoting the plate into a predetermined angular position. This makes it possible to adapt to the patient&#39;s body size, and the patient can be constrained to adjust the inclination of his head to the inclination of the plate, so that a desired angular position of the patient&#39;s occlusal plane relative to the X-ray device will be achieved.  
         [0017]     It is advantageous for the plate-swinging means to move the plate to the predetermined angular position automatically and to stop when the predetermined angular position has been reached.  
         [0018]     Alternatively or additionally, provision may be made for said means to indicate that the predetermined angular position of the plate has been reached by emitting optical and/or acoustic signals.  
         [0019]     In a preferred embodiment of the bite device of the invention, the pivoted plate is connected to a rail within the holding member, which rail can be moved upwardly and downwardly and has an opening for indicating the position of the rail in the holding member.  
         [0020]     The bite piece of the bite device is preferably equipped with a replaceable protective sheath for hygienic reasons.  
         [0021]     Alternatively, the bite piece can be in the form of a replaceable bite piece. The bite piece is preferably composed of a soft material, particularly a substantially radiolucent material. It has proved to be particularly suitable to fabricate the bite piece from closed-cell ethylene foam.  
         [0022]     The bite piece preferably occupies an angular range β of the mandibular arch, which is between 20° and 40°, particularly 30°. This substantially prevents any sideways tipping or tilting of the patient&#39;s head.  
         [0023]     In an advantageous embodiment, the bite piece has on its upper surface and on its undersurface a bite groove to accommodate part of the dental arch of the patient&#39;s upper and lower jaw respectively.  
         [0024]     The bite piece is preferably a unitary piece foldable about a folding edge. It preferably has on opposite sides a wedge-shaped projection and a complementary depression for the accommodation of said projection, to enable the bite piece to be removably attached to the pivoted plate.  
         [0025]     Further advantageous embodiments, features, and details of the invention are given in the dependent claims, the description of embodiments, and the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]     The invention will now be explained in more detail with reference to an embodiment and the drawings. Only those elements are shown which are significant for comprehension of the invention.  
         [0027]     In the drawings:  
         [0028]      FIG. 1  is a diagrammatic illustration of a panoramic X-ray system;  
         [0029]      FIG. 2  is a diagrammatic representation of the system for aligning the tomography zone of the X-ray device to the alveolar arch of a patient;  
         [0030]      FIG. 3  shows a perspective view of a bite device according to one embodiment of the invention, shown diagrammatically;  
         [0031]      FIG. 4  is a cross-section through the bite device of  FIG. 3 ;  
         [0032]      FIG. 5  shows perspective views of an bite piece for a bite device according to one embodiment of the invention, shown (unfolded) diagonally from below in  FIG. 5 ( a ) and diagonally from above in  FIG. 5 ( b );  
         [0033]      FIG. 6  is a cross-section through the bite piece of  FIG. 5 , taken along line VI-VI; and  
         [0034]      FIG. 7  shows the bite piece of  FIG. 5  in the folded position, as attached to the bite device of  FIG. 3 . 
     
    
     DESCRIPTION OF EMBODIMENTS  
       [0035]      FIG. 1  is a diagrammatic representation of a panoramic X-ray system  10 , in which a rotary unit  12  carries a radiation source  14  equipped with a shutter  16 , and a diametrically opposed detector camera  18  equipped with a shutter  20 . The beam of X-rays  22  emitted from the radiation source  14  transilluminates the jaw region of the head  24  of a patient and produces an image signal in detector camera  18 . This is directed to a control unit  26  for evaluation and display in the usual manner.  
         [0036]     Rotary unit  12  is pivotally or hingedly mounted on an arm  11  which is mounted on a column  13  for vertical adjustable thereon. A drive  15  is provided to perform the vertical adjustment. In this way, the position of X-ray emitter  14  and detector camera  18  can be adjusted to the stature of the patient. It is essential, for obtaining a faultless, high-quality panoramic radiograph, for the tomography zone  30  ( FIG. 2 ) to be in line with the alveolar arch  32  of the patient.  FIG. 2  depicts perfect spatial alignment of these two elements, this ensuring the production of a qualitatively good image. Insufficient alignment can necessitate a repeat radiograph, resulting in increased X-irradiation of the patient and additional expense in terms of material and time.  
         [0037]      FIG. 3  is a perspective view of a bite device referenced as  40 , according to one embodiment of the invention, shown diagrammatically, and  FIG. 4  is a cross-section through the bite device  40  of  FIG. 3 . Bite device  40  has a holder  42  which is hinged to a thin plate  46  by means of a pivot  44 . The thin plate  46  is adjoined, at its end remote from pivot  44 , by an imaging zone  48  parallel to said thin plate.  
         [0038]     The imaging zone  48  has an opening  62  by means of which, in a manner to be described in more detail below, a replaceable bite piece  50  can be quickly and easily attached to the thin plate. On its upper surface and on its undersurface, bite piece  50  has occlusal grooves  64  and  66  respectively, which accommodate the dental arches of the patient&#39;s upper and lower jaw respectively. This arrange-ment ensures that the thin plate  46  runs parallel to the occlusal plane of the patient when he bites on the bite piece  50  for taking the radiograph.  
         [0039]     The angle of deflection a of thin plate  46  is measured using a rail  54  capable of being moved upwardly and downwardly and connected to thin plate  46  in a region  56 , and adapted to extend vertically down the inside  52  of the holding member  42 . In its lower section, rail  54  is provided with a hole  58 . The vertical position of hole  58  is detected by two photodetectors indicated by arrows  60 . The angle of deflection of plate  46  can be deduced from said vertical position. By transferring the inclination of plate  46  to the movable rail, measurement of the angle of deflection α is carried out in a region of holder  42  which is far below plate  46  and is free from radiation. The X-irradiated region can thus be kept substantially free from metal.  
         [0040]     The bite device cooperates with a driving system  15  shown in  FIG. 1  such that rail  54  moves upwardly or downwardly and the thin plate  46  can thus be brought into any desired position. The deflection of thin plate  46  accompanying such vertical adjustment makes it possible to gently guide the patient&#39;s head until it assumes the correct degree of inclination for the panoramic radiograph.  
         [0041]     Vertical adjustment of plate  46  can be performed interactively by the operator. For example, the operator can press an adjustment button until the desired degree of inclination is attained. When a previously defined angular position, for example α=100°, which corresponds to an angle between plate  46  and the horizontal of 15°, is attained, this can be indicated by means of optical and/or acoustic signals.  
         [0042]     Alternatively, the drive can automatically move plate  46  into the predetermined angular position and stop when the desired position is reached. Additionally, the angular position of the plate can be displayed for checking by the operator.  
         [0043]     The bite piece  50  shown in  FIGS. 3 and 4  will now be described in more detail with reference to  FIGS. 5 through 7 .  FIG. 5  shows, in  FIG. 5 ( a ) and  FIG. 5 ( b ), a per-spective view of the unfolded insert, shown diagonally from below in  FIG. 5 ( a ) and diagonally from above in  FIG. 5 ( b ).  FIG. 6  shows a cross-section through the bite piece taken along line VI-VI of  FIG. 5 ( b ), and  FIG. 7  represents the bite piece in the folded position, as attached to the bite device of  FIG. 3 .  
         [0044]     In the present embodiment, bite piece  50  is fabricated as a single piece of closed-cell ethylene foam, a soft and substantially radiolucent material. On its upper surface, bite piece  50  has occlusal grooves  64  and  66  adapted to accommodate part of the dental arch of the upper and lower jaws of the patient. Bite piece  50  can be folded along a central folding edge  70 , defined by notches  72  on the undersurface and a central groove  74  on the upper surface of the insert.  
         [0045]     On its underside, bite piece  50  has a wedge-like tapered projection  76  which, when the insert is folded, slides into a complementary depression  78  located on the opposite side of the insert, this making for a stable but easily releasable connection. The flat imaging zone  48  of the bite device contains an opening  62  ( FIG. 4 ) through which the projection  76  projects when the bite insert is attached, so that insert  50  is firmly attached to the thin plate  46  of the bite device once it has been folded together. After use, however, the insert can be unfolded with no great effort and thrown away for hygienic reasons.  
         [0046]     The insert shown in the embodiment illustrated in  FIGS. 5 through 7 , has a width of  40  mm, occupies an angular region β of the dental arch of about 30°. In order to accommodate for different jaw sizes of patients, bite pieces are also fabricated and used in other widths. The different widths can be easily distinguished by the user on the basis of different color markings or other labels. With this kind of bite piece, the position of the patient can be fixed with great accuracy but without discomfort for the patient.  
       LIST OF REFERENCE NUMERALS OR CHARACTERS  
       [0000]    
       
           10  radiographic system  
           12  unit  
           14  source of radiation  
           15  driving system  
           16  shutter  
           18  detector camera  
           20  shutter  
           22  beam of X-rays  
           24  head  
           26  evaluation unit  
           30  tomography zone  
           32  alveolar arch  
           40  occlusal device  
           42  holder  
           44  pivot  
           46  plate  
           48  imaging zone  
           50  bite piece  
           52  interior of holding member  42   
           54  rail  
           56  region  
           58  hole  
           60  arrows  
           62  opening  
           64  occlusal groove  
           66  occlusal groove  
           70  folding edge  
           72  notches  
           74  central groove  
           76  projection  
           78  depression