Abstract:
An apparatus for medical imaging has a first detector system with a first radiation source for emission of first detection radiation, a first acquisition device for acquisition of the first detection radiation, and a first detection region that transversely penetrates an open space in the apparatus that opens at one side of the apparatus. The first detector system can be moved in the circumferential direction of the open space by a movement device. In order to enlarge the usable region of the apparatus, the apparatus has a second detector system with a second detection region that is offset in the longitudinal direction of the axis of the open space relative to the first detection region.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns a medical imaging apparatus of the type having two detector systems. 
     2. Description of the Prior Art 
     X-ray imaging is a proven examination modality in medical diagnostics, wherein a detector system is used for organ examination. A known example is a computed tomography apparatus (CT apparatus), which has a detector system (comprising a radiation source for emission of a detection radiation and an acquisition device) can be moved around an axis that proceeds through an open space between the radiation source and the acquisition device, in which a patient can be positioned. 
     An apparatus of this type enables a scanning of the organ of the patient and a representation of an image on a film or a display. 
     In order to achieve scan times in the sub-second range with a CT apparatus, it is known to provide two detector systems that each emit and detect radiation in the same geometric plane. This enabled graphically presentation of moving organs (for example a beating heart). For this purpose, the apparatus is designed with an acquisition device with 64 lines that covers only a z-depth of approximately 4 cm. Acquisition devices with fewer lines cover even smaller dimensions in the z-direction. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to enlarge the usable region in an apparatus of the types described above. This allows graphical depiction a larger region so that different or larger body parts or organs can be graphically represented. An increase of the capability of the apparatus is also achieved. 
     In a first embodiment of the invention, the above object is achieved by an apparatus for medical imaging having a first detector system with a first radiation source that emits first detection radiation and a first acquisition device that detects the first detection radiation, the first detector system having a first detection region that transversely penetrates an open space in the apparatus that is open at one side of the apparatus, the first detector system being movable in a circumferential direction of the open space by a movement device, and wherein the apparatus further has a second detector system having a second radiation source that emits second detection radiation and a second acquisition device that detects the second detection radiation, and having a second detection region that transversely penetrates the open space, the second detector system also being movable in the circumferential direction of the open space by a movement device, and wherein the second detection region is offset in the longitudinal direction of a longitudinal axis of the open space relative to the first detection region. 
     The above object is also is achieved in accordance with the present invention in a further embodiment of the apparatus that corresponds to the above-described embodiment but, instead of the second detection region being offset in the longitudinal direction of the longitudinal axis of the open space relative to the first detection region, the first and second detector systems are offset in the longitudinal direction by a displacement device, and can each be fixed at respective displaced positions along the longitudinal axis. 
     Both embodiments have in common the use of two detector systems whose detection region that extends transversely in the longitudinal region of the examination space for the patient. The detector systems and/or their detection regions can be offset relative to one another in the longitudinal direction of the axis of the open space or can be adjustable in the longitudinal direction of the axis by a displacement device interacts with at least one of the detector systems, and can be lockable in the offset position. 
     Both inventive embodiments enable offset or larger regions of the body to be detected so as to be graphically represented in the longitudinal direction of the axis of the open space. The detection regions can exhibit an axial separation from one another, or can overlap one another. It is also possible to axially offset the axially-adjustable detection systems in selected regions, and such a displacement is also possible with the regions completely overlapping one another, so that such a displacement can be considered as transverse to the axis. 
     The design is simplified when the detector systems can be displaced around the axis of the open space into a position in which they enclose between them an angle of approximately 90°. When offset or rotated in the circumferential direction, the radiation sources and acquisition devices of the detector systems can be arranged next to one another (parallel) to each other and such that they can also be moved in the longitudinal direction of the axis of the open space in the second embodiment case. 
     For movement in the displacement region, a drive motor can operate the displacement device to make the displacement wholly automatic or semi-automatic. The drive motor can be controlled or regulated with an associated control or regulation device. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an inventive apparatus for medical imaging in a schematic front view. 
         FIG. 2  shows the apparatus in side view. 
         FIG. 3  shows an inventive apparatus for medical imaging in front view in a further embodiment. 
         FIG. 4  shows the apparatus according to  FIG. 3  in side view. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The apparatus (designated in its entirety with  1 ) is advantageously a computed tomography apparatus (CT apparatus) that has a frame  2  or housing having a middle region with an open space  3  that is open toward the front side  4  of the apparatus  1  and thus is accessible from the front side  4 . A patient can be inserted into the open space  3  by a support table  5  (on which the patient lies) that can be displaced along the center axis of the open space  3 . The open space  3  can be, for example, hollow-cylindrical or hollow-elliptical in terms of its vertical cross-section). A drive (not shown) for the support table  5  can serve for the insertion of the support table  5  into the open space  3 . 
     Two detector systems  6 ,  7  are arranged in the frame  2  (for example in its center region) that each have (outside of the open space  3 ) a radiation source  6   a ,  7   a  and an acquisition device  6   b ,  7   b  opposite said radiation source  6   a ,  7   a  and on the opposite side of the open space  3 . The acquisition devices  6   b ,  7   b  respectively serve for acquisition of the detection radiation indicated by the arrows  6   c ,  7   c . Both detector systems  6 ,  7  are arranged in the same transversal plane E. 
     The radiation sources  6   a ,  7   a , for example, can be formed by a tube with a radiation region  6   d ,  7   d  directed toward the associated acquisition device  6   b ,  7   b . Radiation beams proceeding from the radiation regions  6   d ,  7   d  transversely through the open space  3  respectively form detection regions  8 ,  9 . The middle axes of the detection regions  8 ,  9  are directed transversely (in particular at right angles) to one another. This means that the detection regions  8 ,  9  intersect one another in a common section area. 
     The acquisition devices  6   b ,  7   b  can respectively be fashioned as segments (when viewed along the axis  3   a  of the open space  3 ), meaning that their length L in the circumferential direction can be greater than their breadth B in the longitudinal direction of the axis  3   a . The detection regions  8 ,  9  emanating from the associated radiation sources  6   a ,  7   a  can be divergent, corresponding to the size (L×B) of the acquisition regions  6   e ,  7   e  facing towards the associated radiation source  6   a ,  7   a.    
     The radiation sources  6   a ,  7   a  and acquisition devices  6   b ,  7   b  are supported by a movement device such that they can rotate around the axis  3   a , for example, they can be pivoted or rotated back and forth. A suitable bearing arrangement can be, for example, a disc-shaped ring  10  shown in  FIG. 2  on which the radiation sources  6   a ,  7   a  and the acquisition devices  6   b ,  7   b  can be attached so that can be moved in the circumferential direction into different positions (not shown). A drive  11  (for example an electromotor) advantageously serves for producing this movement (represented by the double arrow). 
     In operation of the apparatus  1 , the detector systems  6 ,  7  are moved in the circumferential direction, and the radiation  6   c ,  7   c  proceed into the detection regions  8 ,  9  penetrates a patient located in the open space  3  in the region of a body part to be detected, and the attenuated radiation is acquired by the respective opposite acquisition region  6   e ,  7   e  and is graphically presented, for example on a film or image surface, for example, using associated measurement electronics. 
     The size of the detection region  8 ,  9  extending in the longitudinal direction of the axis  3   a , namely known as the z-depth, is limited by the effective breadth B of the acquisition device  6   b ,  7   b.    
     In the exemplary embodiment according to  FIG. 3  and  FIG. 4  (in which the same or comparable parts are designated with the same reference characters), both detector systems  6 ,  7  are arranged offset relative to one another in longitudinal direction of the axis  3   a  or can be adjusted relative to one another in the longitudinal direction of the axis  3   a  and can be fixed in the respective adjustment position. This thus also applies for the associated detection regions  9 ,  8 . In the shown position, the detector system  6  is displaced relative to the detector system  7  along the axis  3   a  until the detection regions  8 ,  9  or irradiation regions  6   d ,  7   d  lie immediately next to one another, or abut one another along the axis  3   a.    
     In accordance with the invention, the axial separation a between the transverse center planes E 1 , E 2  of the detector systems  6 ,  7  are dimensioned such that the irradiation regions  7   d ,  6   d  overlap one another or exhibit an axial separation from one another, the size of which, for example, is determined by the separation of two body parts or organs of the patient that are to be detected. 
     Due to the axially adjustable arrangement of the one detector system (here the detector system  6 ), this can be axially displaced (for example between an end position (not shown in  FIG. 4 ) in which it is located in the transversal plane E 2  with the detector system  7 ) by the amount a, and fixed in the position shown in  FIG. 4 . In the position shown in  FIG. 4 , the axial middle distance a (which corresponds to the z-depth in the exemplary embodiment, but can also be larger or smaller exists between the detector systems  6 ,  7 . The adjustable detector system  6  can be displaced back and forth along the axis  3   a  by a displacement device  12  (indicated by a double arrow  12 ), in particular can be automatically displaced with a drive  12   a  that can be actuated in both axis directions (advantageously by an electric motor) and can be controlled or regulated via a control or regulation device (see  FIG. 4 ). 
     The detector system  6  consequently can be axially displaced (relative to the detector system  7 ) into an alternative position in which either an enlarged z-depth results, or two z-depths axially spaced from one another yield a depth Z 1  corresponding to their sum. In the exemplary embodiment according to  FIG. 4 , the z-depth Z 1  is twice as large as in the exemplary embodiment according to  FIG. 2 . 
     The displacement device  12  for displacement of the displaceable detector system  6  has a guide  13  extending parallel to the axis  3   a  in the frame  2 . The guide  13  can be formed by one or more guide rods  13   a  that can have, for example, a round cross-sectional shape. For a semi-automatic or wholly automatic displacement, a chassis  14  (for example in the form of a frame surrounding the open space  3 ) can be moved back and forth in a specific manner by the drive  12   a  on the at least one guide rod  13   a . The displaceable detector system  6  is mounted on the chassis  14  or frame (see  FIG. 4 ). 
     In accordance with the invention it is possible to mount the displaceable radiation source  6   a  and acquisition device  6   b  each on its own carrier part and to axially displace the radiation source  6   a  and acquisition device  6   b  with the carrier parts. In order to improve the alignment of the radiation source  6   a  and the acquisition device  6   b  directed toward one another and in order to simplify the bearing, it is more stable and better to mount the radiation source  6   a  and the acquisition device  6   b  on a common carrier, for example the frame-like chassis  14 . 
     For example, the disc-shaped ring  10  on which the guide rods  13   a  are attached at one end can serve for bearing the aforementioned carrier parts or of the common carrier or chassis  14  on a rotatable or pivotable bearing part. 
     A further difference of the exemplary embodiment according to  FIGS. 3 and 4  compared to that according to  FIGS. 1 and 2  is that the detector system  7  (which cannot be displaced axially) exhibits an axial separation from its carrier, for example from the ring  10 . An open space F that is advantageous for design reasons and in which, for example, electronic components can be arranged thus is formed between the detector system  7  and its carrier. 
     A mounting device for mounting of the radiation source  7   a  and acquisition device  7   b  is indicated by lines  16 . 
     In the exemplary embodiments both detector systems  6 ,  7  can be moved in the circumferential direction via a common drive  11 , for example by the ring  10 . 
     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.