Abstract:
An examination system including a magnetic resonance scanner having a solenoid for generating a magnetic field, the solenoid surrounding an examination chamber is provided. In addition, a first X-ray source and a first X-ray detector are provided in the examination chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to PCT Application No. PCT/EP2012/068596, having a filing date of Sep. 21, 2012, the entire contents of which are hereby incorporated by reference. 
     
    
     FIELD OF TECHNOLOGY 
       [0002]    The following relates to an examination system and to a method for producing an angiogram. 
       BACKGROUND 
       [0003]    Magnetic resonance tomographs for imaging diagnostics for medical purposes are known from the prior art. Magnetic resonance imaging uses the dependence of the relaxation times of excited nuclear spins on the environment of the atomic nuclei in order to obtain information relating to a spatial arrangement of different tissue types in a body of a patient. Magnetic resonance tomographs are suitable, in particular, for high contrast imaging of soft tissues. 
         [0004]    X-ray units for imaging diagnostics for medical purposes are likewise known from the prior art. Radiography uses the different permeability of different tissue types for X-radiation to produce a view through a body part of a patient. It is possible in this case to produce moving images in real time. 
         [0005]    US 2008/0171931 A1 describes a hybrid system comprising a magnetic resonance tomograph and an X-ray unit which makes it possible to record an image of a body part of a patient by means of the magnetic resonance tomograph, and subsequently to undertake an intervention on the body of the patient, optical control being performed by means of the X-ray unit. 
       SUMMARY 
       [0006]    An aspect relates to an improved examination system. A further aspect relates to providing a method for producing an angiogram. 
         [0007]    An examination system comprises a magnetic resonance tomograph with a cylindrical coil for generating a magnetic field. Here, the cylindrical coil surrounds an examination space. Arranged in said examination space are a first X-ray source and a first X-ray detector. Said examination system advantageously permits images to be obtained with high spatial resolution and good soft tissue contrast by using the methods of magnetic resonance imaging. Moreover, X-ray images with high temporal resolution can be prepared by means of the first X-ray source and the first X-ray detector. The integration of the magnetic resonance tomograph with the X-ray system formed from the X-ray source and X-ray detector ensures that anatomical information obtained by using the two methods is temporally and spatially consistent. The combination of the two imaging methods supplies sets of anatomical information which complement one another, thus increasing the amount of information that can be obtained overall. There is an advantageous improvement in the clinical effectiveness of the overall system as a result. 
         [0008]    In one embodiment of the examination system, the first X-ray source and the first X-ray detector are rotatable about a rotation axis arranged in a longitudinal direction of the examination space. It is then advantageously possible to use the X-ray system formed from the X-ray source and X-ray detector to prepare X-ray images from different directions of view. 
         [0009]    In one embodiment of the examination system, the first X-ray source and the first X-ray detector are rigidly interconnected. It is thereby advantageously ensured that, given a rotation of the X-ray source and X-ray detector about the rotation axis, the X-ray detector is arranged such that it can detect X radiation emitted by the X-ray source. 
         [0010]    In one embodiment of the examination system, a gradient coil with a first gradient coil portion and a second gradient coil portion is arranged in the examination space. Here, the first gradient coil portion and the second gradient coil portion are spaced apart in an axial direction. Furthermore, the first X-ray source and the first X-ray detector are arranged between the first gradient coil portion and the second gradient coil portion. Given said arrangement, there is advantageously formed in the interspace between the first gradient coil portion and the second gradient coil portion a gradient field which permits a spatially resolved examination by means of magnetic resonance imaging. At the same time, the X-ray system formed from the X-ray source and X-ray detector is arranged in said interspace and thereby permits preparation of X-ray images of the same region, which is also displayed by means of magnetic resonance imaging. Optical obstruction or shading of the X radiation by the gradient coil is avoided by the arrangement of the X-ray system in the interspace between the gradient coil portions of the gradient coil. 
         [0011]    In one embodiment of the examination system, a radiofrequency coil is arranged in the examination space. In one embodiment, said coil is arranged between the first gradient coil portion and the second gradient coil portion. The radiofrequency coil can advantageously serve to emit radiofrequency magnetic pulses and to receive signals emitted by relaxing nuclear spins. The arrangement of the radiofrequency coil in the interspace between the first gradient coil portion and the second gradient coil portion of the gradient coil makes it possible to examine by images the same part, arranged in the examination space, of a patient&#39;s body which is also detected by the X-ray system formed from the X-ray source and X-ray detector. 
         [0012]    In one embodiment of the examination system, the radiofrequency coil is rigidly connected to the first X-ray source. The mutual orientation of the radiofrequency coil and X-ray source then advantageously remains constant even given a rotation of the X-ray system, formed from the X-ray source and X-ray detector, about the rotation axis. Influences on the X-ray system owing to the radiofrequency coil are thereby minimized. An absorption, effected by the radiofrequency coil, of X-radiation emitted by the X-ray source is temporally invariable. This advantageously enables artifacts effected by the radiofrequency coil to be minimized or removed in images prepared by the X-ray system. 
         [0013]    In one embodiment of the examination system, a second X-ray source and a second X-ray detector are arranged in the examination space. Provision of two X-ray systems advantageously enables X-ray images to be recorded at a higher rate, renders it possible to reduce an X-ray dose and provides the possibility of simultaneously using X-rays of different energies. It is possible thereby to obtain additional information relating to perfusion behavior and a type and a composition of a tissue being examined. 
         [0014]    In one embodiment of the examination system, the first X-ray source and the second X-ray source are rigidly interconnected. A viewing angle difference between the first X-ray source and the second X-ray source is then advantageously temporally constant. 
         [0015]    In one embodiment of the examination system, the second X-ray source is offset from the first X-ray source by an angle with reference to a rotation about a rotation axis arranged in a longitudinal direction of the examination space. A body part of a patient which is to be examined can then advantageously be irradiated simultaneously from two directions by means of the two X-ray systems. 
         [0016]    In one embodiment of the examination system, the angle is 90 degrees. It is then advantageously possible for the X-ray images generated by means of the two X-ray systems to be particularly easily correlated with one another. 
         [0017]    An examination system of the above-named type is used in a method for producing an angiogram. The angiogram can then advantageously include information obtained by means of examination by magnetic resonance imaging and information obtained by means of an X-ray examination, as a result of which the angiogram produced by said method has a particularly high information content. 
     
    
     
       BRIEF DESCRIPTION 
         [0018]    Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein: 
           [0019]      FIG. 1  shows a sectional perspective illustration of an examination system in accordance with a first embodiment; 
           [0020]      FIG. 2  shows a sectional perspective illustration of an examination system in accordance with a second embodiment; 
           [0021]      FIG. 3  shows a sectional perspective illustration of an examination system in accordance with a third embodiment; and 
           [0022]      FIG. 4  shows a further sectional illustration of the examination system in accordance with the third embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]      FIG. 1  shows a schematically sectional perspective illustration of an examination system  10  in accordance with a first embodiment. The examination system  10  can serve the purpose of medical diagnostics. In particular, the examination system  10  can serve for treatment by angiography. The examination system  10  comprises a magnetic resonance tomograph  100 . The magnetic resonance tomograph  100  has a cylindrical coil  120  which surrounds a tubular examination space  110 . The cylindrical coil  120  is designed as an elongated hollow cylinder. The cylindrical examination space  110  serves for recording a schematically illustrated patient  111 . In the example illustrated, a body part  116  (here, the head) of the patient  111  is arranged in a field of view  115  in the examination space  110  of the examination system  10  in order, with the aid of the examination system  10 , to obtain images of the body part  116  of the patient  111  which are suitable for the purpose of medical diagnostics. 
         [0024]    The cylindrical coil  120  of the magnetic resonance tomograph  100  serves to generate a strong static magnetic field in the examination space  110  by means of which a decay of energy between different alignments of the magnetic moments of the atomic nuclei of the body of the patient  111  is canceled out. By way of example, the cylindrical coil  120  can be designed as a superconducting magnet. The cylindrical coil  120  can, for example, be designed so as to generate a static magnetic field with a strength of between 0.2 tesla and 3 tesla or more. The magnetic field generated by the cylindrical coil  120  is preferably designed to be rather homogeneous, at least in the field of view  115  of the examination space  110 . Under the influence of the static magnetic field generated by the cylindrical coil  120 , the nuclear spins of the atomic nuclei of the body of the patient  111  precess about the axis prescribed by the magnetic field (Larmor precession). 
         [0025]    In order to produce slice images of the body part  116 , arranged in the field of view  115  of the examination space  110 , of the patient  111 , it is necessary to modify the homogeneous magnetic field generated by the cylindrical coil  120  as a function of position. The magnetic resonance tomograph  100  has a gradient coil  130  for this purpose. The gradient coil  130  is provided for the purpose of generating a magnetic gradient field for selective slice excitation and for spatial coding of a measurement signal during a measurement carried out by the magnetic resonance tomograph  100 . 
         [0026]    The gradient coil  130  comprises a first gradient coil portion  131  and a second gradient coil portion  132 . The first gradient coil portion  131  and the second gradient coil portion  132  are each designed as a hollow cylinder and arranged coaxially with the cylindrical coil  120  in the examination space  110  surrounded by the cylindrical coil  120 . In this case, the first gradient coil portion  131  and the second gradient coil portion  132  of the gradient coil  130  are spaced apart from one another in an axial direction so that an interspace  133  is formed between the first gradient coil portion  131  and the second gradient coil portion  132 . The field of view  115  is located in the region of said interspace  132 . In the example illustrated, the first gradient coil portion  131  has a smaller diameter than the second gradient coil portion  132 . However, this is not absolutely necessary. 
         [0027]    By irradiating an alternating magnetic field oriented perpendicular to the static magnetic field generated by the cylindrical coil  120  at a resonant frequency, it is possible, under conditions of phase synchronism, to deflect (excite) the nuclear spins, precessing about the axis of the static magnetic field, of the atoms of the body of the patient  111 . The magnetic resonance tomograph  100  has a radiofrequency coil  140  for this purpose. The radiofrequency coil  140  is arranged in the interspace  133  between the first gradient coil portion  131  and the second gradient coil portion  132  of the gradient coil  130 . The radiofrequency coil  140  surrounds two rings, arranged coaxially with the cylindrical coil  120 , which are interconnected via a plurality of crossbars  141 . The radiofrequency coil  140  is rotatable about a rotation axis  175  which corresponds to a longitudinal axis of the cylindrical coil  120  and of the examination space  110 . The field of view  115  of the examination space  110  is arranged inside the radiofrequency coil  140 . The radiofrequency coil  140  is suitable for irradiating radiofrequency magnetic pulses. Once an alternating magnetic field irradiated by the radiofrequency coil  140  has been switched off, the nuclear spins excited by the alternating magnetic field relax after a characteristic relaxation time and in doing so emit signals which are received by the radiofrequency coil  140 . An image of the body part  116 , arranged in the field of view  115 , of the patient  111  can be reconstructed by mathematical methods from the signal data received by the radiofrequency coil  140 . 
         [0028]    The examination system  10  further comprises an X-ray system with an X-ray source  150  and an X-ray detector  160 . The X-ray source  150  and the X-ray detector  160  are arranged in the interspace  133  between the first gradient coil portion  131  and the second gradient coil portion  132  of the gradient coil  130  in the examination space  110 . The X-ray source  150  is designed to emit an X-ray beam  155  which passes through the field of view  115  and strikes the X-ray detector  160  after traversing the field of view  115 . The X-ray system formed from the X-ray source  150  and X-ray detector  160  permits a rapid preparation of X-ray images of the body part  116 , arranged in the field of view  115 , of the patient  111  with a high temporal resolution. 
         [0029]    The X-ray source  150  and the X-ray detector  160  are supported rotatably, by means of a bearing  170 , about the rotation axis  175  and are rigidly interconnected. In this case, there is a phase difference of approximately 180 degrees between the X-ray source  150  and the X-ray detector  160  with reference to a rotation about the rotation axis  175 . Arranging the X-ray system formed from the X-ray source  150  and X-ray detector  160  to be rotatable about the rotation axis  175  permits the body part  116 , arranged in the field of view  115  of the examination space  110 , of the patient  111  to be irradiated from different directions of view, and thus permits views to be prepared through the body part  116  from different directions of view. The common arrangement of the radiofrequency coil  140  of the magnetic resonance tomograph  100  and of the X-ray system, formed from the X-ray source  150  and X-ray detector  160 , in the interspace  133  about the field of view  115  ensures that the anatomical information obtained by using the methods of magnetic resonance imaging with the magnetic resonance tomograph  100  and by using the methods of X-ray examination by the X-ray system is temporally and spatially consistent. The sets of information obtained by using the two modes of examination complement one another in this case. 
         [0030]      FIG. 2  shows a schematic perspective sectional illustration of an examination system  20  in accordance with a second embodiment. The examination system  20  exhibits marked similarities with the examination system  10  of  FIG. 1 . For this reason, corresponding components are provided with the same reference symbols and are not described anew below. 
         [0031]    In the examination system  20 , instead of the radiofrequency coil  140  a radiofrequency coil  240  is provided, and is arranged in the examination space  110  around the field of view  115  in the interspace  133  between the first gradient coil portion  131  and the gradient coil portion  132  of the gradient coil  130 . The radiofrequency coil  240 , in turn, has two rings which are arranged coaxially with the cylindrical coil  120  and are interconnected by means of a plurality of crossbars. 
         [0032]    However, in contrast to the radiofrequency coil  140 , the radiofrequency coil  240  is rigidly connected by means of a rigid connection  245  to the X-ray system formed by the X-ray source  150  and X-ray detector  160 . The radiofrequency coil  240  is therefore supported rotatably about the rotation axis  175  in common with the X-ray system by means of the bearing  170 . The radiofrequency coil  240  is thereby rotatable about the rotation axis  175  under conditions of phase synchronism in relation to the X-ray system formed from the X-ray source  150  and X-ray detector  160 . During a rotation of the radio-frequency coil  240  and of the X-ray system about the rotation axis  175 , the relative arrangement between the radiofrequency coil  240 , the X-ray source  150  and the X-ray detector  160  remains constant. 
         [0033]    This offers the advantage that influences caused by the radiofrequency coil  240  and exerted on X-ray images recorded by means of the X-ray system are temporally constant and can be minimized. Since the X-ray source  150 , the X-ray detector  160  and the radiofrequency coil  240  are rigidly interconnected, an absorption, caused by the radiofrequency coil  240 , of the X-ray beam  155  is temporally invariant. This enables any possible artifacts in X-ray images prepared by means of the X-ray system, for example artifacts effected by the crossbars  241  of the radiofrequency coil  240 , to be minimized or to be removed. For example, the radiofrequency coil  240 , the X-ray source  150  and the X-ray detector  160  can be mutually oriented so that the X-ray beam  155  does not strike one of the crossbars  241  of the radiofrequency coil  240 . It is likewise possible for artifacts occurring unchanged over time to be eliminated by computation by using the methods of digital image processing. 
         [0034]      FIG. 3  shows a schematic perspective sectional illustration of an examination system  30  in accordance with a third embodiment.  FIG. 4  shows a further sectional illustration of the examination system  30 . The section runs vertically to the rotation axis  175  in the illustration of  FIG. 4 . The examination system  30  has similarities with the examination system  10  of  FIG. 1 . Mutually corresponding components are therefore provided with the same reference symbols and are not described anew in more detail below. 
         [0035]    In addition to the components of the examination system  10 , a second X-ray source  350  and a second X-ray detector  360  are present in the examination system  30 . The second X-ray source  350  and the second X-ray detector  360  form a second X-ray system. The second X-ray source  350  and the second X-ray detector  360  are likewise arranged in the interspace  133  between the first gradient coil portion  131  and the second gradient coil portion  132  of the gradient coil  130  and are oriented so that a second X-ray beam  355  emitted by the second X-ray source  350  passes through the field of view  115  before it strikes the second X-ray detector  360 . 
         [0036]    The second X-ray source  350  and the second X-ray detector  360  are likewise supported rotatably about the rotation axis  375  by means of the bearing  170 . The second X-ray source  350  and the second X-ray detector  360  are rigidly interconnected in such a way that a constant angular relationship of preferably approximately  180  degrees exists between the second X-ray source  350  and the second X-ray detector  360  with reference to a rotation about the rotation axis  175 . 
         [0037]    In a preferred embodiment, the X-ray source  150  and the second X-ray source  350  are also rigidly interconnected in such a way that a constant angle  351  always exists between the X-ray source  150  and the second X-ray source  350  with reference to a rotation about the rotation axis  175 . The angle  351  can be between 0 degrees and 180 degrees. In a preferred design, the angle  351  is approximately 90 degrees. X-ray images recorded by means of the X-ray system formed from the X-ray source  150  and the X-ray detector  160 , and X-ray images recorded by means of the second X-ray system formed by the second X-ray source  350  and the second X-ray detector  360  then show the body part  116 , arranged in the field of view  115 , of the patient  111  from mutually perpendicular directions of view. 
         [0038]    The presence of two X-ray systems in the examination system  30  offers the advantage that it is possible to record X-ray images at an even higher rate and image repetition frequency. Moreover, this opens up the possibility of reducing an X-ray dose. The two X-ray systems can also be operated at different wavelengths or energy levels. It is thereby possible to obtain additional information relating to the body part  116 , arranged in the field of view  115 , of the patient  111 . For example, it is possible thereby to obtain additional information relating to the perfusion behavior or to tissue types of the body part  116 . 
         [0039]    In the examination systems  10 ,  20 ,  30 , the magnetic resonance tomograph  100  and the X-ray systems are preferably operated simultaneously in each case. However, it is also possible to operate only either the magnetic resonance tomograph or the X-ray system for individual examinations. The two modes of examination can also be performed sequentially in time. 
         [0040]    Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. 
         [0041]    For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements. The mention of a “unit” or a “module” does not preclude the use of more than one unit or module.