Abstract:
In a method and an apparatus for medical imaging, the radiation source is aligned relative to a detector plate, and the alignment is controlled so that the high-energy being emitted the radiation source always strikes the detector plate with a symmetrical distribution relative to a central ray of the radiation source.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention concerns a device and an associated method for a medical diagnosis with a high-energy radiation source. High-energy photon are emitted by this high-energy radiation source and detected by a high-energy detector associated with the high-energy radiation source. A subject to be examined is arranged between high-energy radiation source and high-energy detector. 
         [0003]    2. Description of the Prior Art 
         [0004]    Devices and methods of the above type are generally known in the field of mammography for the examination of the breast. Mammography is in particular used for early detection of breast cancer. For this purpose, the breast to be examined is compressed between a compression plate and a detector plate and is irradiated with x-rays that are generated by an x-ray source. A fixing and/or an alignment or, respectively, arrangement of the subject to be examined on the detector plate or detector unit ensues by a displacement of the compression plate. 
         [0005]    A deflection of the x-ray beam through an automatic tracking of the diaphragms arranged at the x-ray aperture of the x-ray source ensues, that is coupled with the displacement of the compression plate. This deflection of the x-ray beam entails the disadvantage that—due to the deflection of central x-ray beam—a reduced irradiation and thus reduced resolution occurs in tissue parts that are situated in border regions of the detector. The reduced resolution leads to a reduced image quality. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the invention is to provide a diagnosis system of the aforementioned type achieves with an optimal image quality. 
         [0007]    In the device according to the invention and the associated method a radiation source is aligned in relation to border regions of the detector unit such that the high-energy rays of the radiation source always strike the detector unit with a symmetrical distribution relative to a central ray of the x-ray source. 
         [0008]    The invention has the advantage that individual conditions and requirements in the examination of the breast can be accommodated. 
         [0009]    The invention also has the advantage that an optimal use of the radiation emitted by the high-energy radiation source can be achieved. 
         [0010]    The invention also has the advantage that, in addition to selectable compression plates with specific device angulations, an optimal use of the radiation emitted by the high-power source can be achieved in connection with a coordination between the central, symmetrical alignment of x-ray beam relative to the detector. 
         [0011]    The invention also has the advantage that all regions of the subject to be considered can be shown in an image for a diagnosis. 
         [0012]    The invention also has the advantage that a consistent, optimized image quality is ensured even in border regions. 
         [0013]    In an embodiment, an exact positioning of the radiation source can be conducted via sensors. 
         [0014]    In an embodiment, the diagnosis unit can automatically be driven into a centered default position via a reset button. 
         [0015]    In a further embodiment the radiation source can be aligned via an activation of a light field on the subject. 
         [0016]    In another embodiment an optimized gain correction can be employed. 
         [0017]    In addition to the advantage of an easy operation via a slider button, the invention has the additional advantage that a workflow is improved through this function. 
         [0018]    The invention has the advantage that image processing operations for rectifying resolution losses, image sharpness or intensity decrease at the edge of a subject to be examined are not needed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0019]      FIG. 1  shows a schematic plan view (upper portion) and a schematic front view (lower portion) of a first embodiment of a mammography apparatus constructed and operating in accordance with the present invention. 
           [0020]      FIG. 2  shows a schematic plan view (upper portion) and a schematic front view (lower portion) of a second embodiment of a mammography apparatus constructed and operating in accordance with the present invention. 
           [0021]      FIG. 3  is a schematic front view of an embodiment of a mammography apparatus in accordance with the present invention, in a first operating state. 
           [0022]      FIG. 4  is a schematic front view of an embodiment of a mammography apparatus in accordance with the present invention, in a second operating state. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    A plan view of a schematic representation of a mammography apparatus RM is shown in the upper part of  FIG. 1 . 
         [0024]    The housing unit GE arranged on a mount H has an x-ray source RR emitting x-ray radiation. The mammography apparatus RM also comprises a detector unit or, respectively, detection plate D possessing flat panel detectors, as well as a compression plate K. A mamma OB (also called a subject in the fallowing, can be aligned or, respectively, fixed between detection plate D and compression plate K. 
         [0025]    The front view of the schematic representation of the mammography apparatus RM is shown in the lower part of  FIG. 1 . The radiation region of the x-rays RS emitted by the x-ray tube RR as well as the course of the central x-ray RZS are shown. The region in which the x-ray RS strikes the detector plate D is likewise indicated. 
         [0026]    Another embodiment of a mammography apparatus RM according to the invention is shown in  FIG. 2 . In the plan view in the upper part of  FIG. 2 , the x-ray tube RR and the compression plate D are viewed as a unit. A collimator for filtering the x-ray radiation RS can be associated with this unit. A housing unit GE incorporating the x-ray tube RR is connected with the mount H such that it can be fixed. This housing unit GE can be horizontally displaced. A vertical shift of the housing unit GE can likewise be conducted. 
         [0027]    A front view of the mammography apparatus RM is shown in the lower part of  FIG. 2 . The unit can be displaced corresponding to the indicated movement directions such that a position in which each region of the mamma that is to be examined can be reached with an undeflected x-ray beam can be adopted for the time period of the examination of the patient. 
         [0028]    By the use of differing sizes of compression plates at specific device angulations, the embodiment enables an improved patient access. The device angulation can be implemented with a C-arm typical to diagnostic apparatuses, for example. The local alignment of the housing unit GE accommodating the x-ray tube ensues by means of electrical actuating means, for example. The position of the unit can be shifted either continuously or to positioning points by means of a shift button. A fixing of the housing unit GE in connection with the compression unit ensues via releasing the slider button. A fixing can also ensue in the manner of a grid, wherein the position can also be acoustically indicated. An automatic activation of a light field can ensue at the collimator simultaneously with the shifting of the unit E, such that a visual presentation of the selected examination region or, respectively, image region is immediately provided. 
         [0029]    An embodiment of a mammography apparatus RM with the unit E (already desorbed) is schematically shown in a front view in  FIGS. 3 and 4 . This unit E consists of, among other things, the housing unit GE, the x-ray source RR integrated into the housing unit and the compression plate K. The position elements PE bounding the deflection of the unit E are drawn in, for example.  FIG. 3  shows the mammography apparatus RM with the unit E in a starting or rest position. The unit E is displaced to the right in  FIG. 6 . A positioning of the unit E can ensue via a stepper SP arranged in the housing GE. This can exactly determine the positioning of the x-ray tube RR or, respectively, that of x-ray radiation emanating from this to the detector D. A fine control of the unit E in or out of an operating position can thereby be conducted with the assistance of laser technology or via reflection measurement. An alignment can likewise ensue by means of memory function. A mechanically implementable positioning is also possible in addition to the electrical and electronic positioning. 
         [0030]    A calibration can be conducted at least in the central, left-of-center and right-of-center positions. A linear interpolation by means of a gain mapping is additionally possible for possible intermediate positions. 
         [0031]    In an alternative embodiment the slider function ensues continuously, limited only by a left-side and right-side end position. The left-side and right-side end position can be predetermined by the border region of the x-ray beam at the detector edge. The position detection can ensue by means of laser technology. A central position of the x-ray tube can be taken up again via a reset function. The position of the unit E can be stored by the operating system of the diagnostic unit and be retrieved for new examinations. 
         [0032]    In an additional embodiment, the information from a positioning can be used in order to focus on a preselected detector region and to save time for the data read out, data transfer and data processing. 
         [0033]    In an additional embodiment, tube and diaphragm unit are shifted synchronously. The operating system of the diagnostic unit RM has an automatic position detection and a reset function with which the tube and diaphragm unit BE, including the compression plate K, can be respectively driven into the central starting position. The focusing by means of the stepper SP can ensue either via laser diode or via reflection measurement, or mechanically by means of a memory function. 
         [0034]    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 heron all changes and modifications as reasonably and properly come within the scope of his contribution to the art.