Abstract:
A railroad car for the accommodation and operation of a magnetic resonance tomography is provided. The railroad car includes a magnetic shielding of a volume for accommodation of the magnetic resonance tomograph. The magnetic shielding is designed to limit a magnetic scatter field outside a volume surrounded by the magnetic shielding to a value which is not hazardous to the environment, when a magnetic resonance tomograph is performing an examination in the interior of the volume.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to German application No. 10 2012 215366.7 DE filed Aug. 30, 2012, the entire content of which is hereby incorporated herein by reference. 
       FIELD OF INVENTION 
       [0002]    The invention relates to a railroad car for the accommodation and operation of a magnetic resonance tomograph, and a railroad car of this kind with a magnetic resonance tomograph. 
       BACKGROUND OF INVENTION 
       [0003]    In recent years, magnetic resonance tomographs have become an important mainstay in the diagnosis of a multiplicity of illnesses. This relates in particular to organs and tissue, which during imaging by means of X-rays are difficult to map due to poor differences of contrast, such as the brain, for example. 
         [0004]    On the other hand, due to the necessary magnetic fields and the magnets and supply apparatuses required to generate them, magnetic resonance tomographs have large dimensions and considerable weight by comparison with X-ray machines. 
         [0005]    In addition, the sensitivity of the measuring procedures used to magnetic field interference from external sources requires extensive shielding measures and a careful preparation of the site. Conversely, the guidelines on the protection of the environment against interference and hazards arising from the magnetic fields generated by the magnetic resonance tomograph call for corresponding protective measures for the environment. 
         [0006]    Both of these factors mean that it is not possible to provide a magnetic resonance tomograph at all locations where a requirement for magnetic resonance tomography examinations exists. This applies in particular to countries with a health system which is only under development. It would be advantageous in these cases if mobile magnetic resonance tomography installations were to be available. 
         [0007]    An ambulance with a mobile X-ray computed tomography device is, for example, known from unexamined publication DE 102 35 618 A1. Due to the cited reasons such as size, weight and shielding, the X-ray computed tomograph cannot be replaced by a magnetic resonance tomograph. 
         [0008]    Truck trailers with magnetic shieldings for the magnetic resonance tomographs installed therein, as well as containers with corresponding installations, are also known from unexamined publication US2006/0186884 A1. Here the units, which can be moved by road, are bound in terms of dimensions and weight by the statutory limitations prescribed for road traffic. 
       SUMMARY OF INVENTION 
       [0009]    The problem to be solved by the present invention thus consists of providing a mobile magnetic resonance tomography device, which is not subject to the cited restrictions. 
         [0010]    The problem is solved according to the invention by the subject matter of the claims. 
         [0011]    An inventive railroad car for the accommodation and operation of a magnetic resonance tomograph comprises a magnetic shielding of a volume for accommodation of the magnetic resonance tomograph, wherein the magnetic shielding is designed to limit a magnetic scatter field outside a volume surrounded by the magnetic shielding to a value which is harmful to the environment. The invention further provides for the arrangement of a magnetic resonance tomograph in the magnetically shielded volume of the inventive railroad car. 
         [0012]    The inventive railroad car has a series of advantages. It may be employed on all rail routes, as are also available in developing countries. The permissible weight for railroad cars exceeds that for truck trailers or containers transportable thereby. The possibility also exists of setting up the inventive railroad car at central locations with good access for patients, such as for example at railroad stations. These also frequently offer appropriate infrastructure such as platforms, in order to facilitate access for patients on stretchers. By means of the magnetic shielding it is possible to arrange a magnetic resonance tomograph in the inventive railroad car wherein the magnetic resonance tomograph is advantageously protected against external interference affecting the magnetic field by means of the magnetic shielding. In addition the magnetic field caused in the environment by the magnetic resonance tomograph is reduced to a level harmless to the environment, whereby disadvantageous effects on the environment are minimized. 
         [0013]    Advantageous developments of the invention are specified in the subsidiary claims. 
         [0014]    In a preferred embodiment the value of the magnetic scatter field which is harmless to the environment amounts to 0.5 mT. 
         [0015]    This is advantageously the legally permissible limit value in various countries. However it would also be conceivable for the shielding to be designed to reduce the scatter field in the environment to a value of 1 mT, 5 mT or 10 mT. 
         [0016]    In a preferred embodiment the magnetic shielding is designed for a maximum magnetic field strength of a magnetic resonance tomograph in the volume of 1.5 T or more. In this way it is also possible to employ magnetic resonance tomographs with a static magnetic field B0 of 1.5 T or more in a mobile manner, which results in improved resolution during the examination. In this way it is also conceivable to use systems which are already commercially available in a mobile context with 3 T. 
         [0017]    In a preferred embodiment the clear width of the volume surrounded by a magnetic shielding is greater than 2.5 meters. Clear widths in excess of 3 m are also conceivable here. Width is here in particular designated as the dimension in the direction of the width of the railroad car. In the case of railroad car it is here advantageously possible to make use of the permissible car width of 3 m and more, without compromising mobility. This width, which exceeds the values for road traffic and containers which can be transported on trucks, and can for example be up to 3.15 m, makes it possible to locate the shielding at a greater distance from the magnetic resonance tomograph. This means on the one hand that due to the dipole field rapidly falling off as the distance increases, the magnetic shielding can ultimately be thinner and thus lighter. On the other hand too, the influence of the magnetic shielding on the magnetic field in the interior of the magnetic resonance tomograph diminishes, so that for example artifacts from an image recorded with a magnetic resonance tomograph in the shielded volume of the inventive railroad car are smaller than in the case of magnetic shielding which is less wide. 
         [0018]    In one embodiment it is further possible that the railroad car comprises a refrigeration (cooling) device for cooling of a magnetic resonance tomograph, including the supplier systems (amplifier, gradient coil). As a result of the great permissible length of a railroad car of, for example, 22 m, it is possible to provide refrigeration devices for dissipation of the waste heat generated in the inventive railroad car by the magnetic resonance tomograph, so that prior to operation it is unnecessary first to connect up corresponding supply devices. 
         [0019]    In one embodiment of the railroad car it is also provided for the railroad car to comprise a power supply device for the magnetic resonance tomograph. The great permissible length of a railroad car also enables the provision of a power supply device for the magnetic resonance tomograph, so that prior to operation it is unnecessary first to connect up corresponding supply devices. 
         [0020]    In one embodiment it is here provided for the power supply device to be designed to draw energy from an electrical catenary. No additional energy source or power line is thus necessary for operation. 
         [0021]    In a further embodiment it is conceivable for the power supply device to be designed to draw energy from an external low voltage source. This can for example be a supply line from a locomotive carrying low voltage 350 to 480 V or from another generator unit. The magnetic resonance tomograph in the inventive railroad car is thus independent of the electrification of the relevant section of track. Neither is it necessary for costly high-voltage technology and a pantograph to be provided on the railroad car. 
         [0022]    It would however also be conceivable for the inventive railroad car to comprise an energy source, for example a generator, for supplying the magnetic resonance tomograph. Thanks to the great permissible length of a railroad car it is possible to provide an energy source in the railroad car itself, so that prior to operation it is unnecessary first to connect up corresponding supply devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The above-described properties, features and advantages of this invention and the manner in which these are achieved are more clearly and readily understandable in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings wherein: 
           [0024]      FIG. 1  shows a longitudinal section through an inventive railroad car. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0025]      FIG. 1  shows in diagrammatic form a longitudinal section through an inventive railroad car  1 . In the embodiment shown an examination room  10  is arranged centrally in the railroad car  1  with a magnetic resonance tomograph  20  located therein. This central arrangement has the advantage that the technical supply units  30 ,  40 ,  50  can be arranged at a side of the examination room  10  away from the preparation room  70  for a patient and a control room  60 , and the patient need not pass these equipment units in order to reach the examination room  10 . The safety requirements for separate technology rooms of this kind are less stringent than for rooms to which the public has access. Also, the patient and operator can thus be more easily protected against the development of noise and heat from the supply units  30 ,  40 ,  50 . 
         [0026]    The magnetic resonance tomograph  20  is surrounded by a magnetic shielding  11 , which has the task of reducing the scatter field generated by a static magnet of the magnetic resonance tomograph  20  to a limit value which depending on the legal circumstances generally lies below 0.5 mT. At the same time the magnetic shielding  11  reduces interference caused by the effects of external magnetic fields on the magnetic resonance tomograph  20 . 
         [0027]    The static magnetic field rapidly reduces with the distance from the source. It is thus advantageous if the magnetic shielding  11  is arranged at the greatest possible distance from the magnetic resonance tomograph  20 . It is thus advantageous if the magnetic shielding  11 , as shown in  FIG. 1 , is part of the outer wall of the railroad car or also provides the supporting structure. In this way the distance to the magnetic resonance tomograph can be maximized and the material thickness of the shielding can turn out to be less. It is here particularly advantageous that the permissible width of a railroad car exceeds the width which is customarily permissible for road traffic. 
         [0028]    All materials which demonstrate high magnetic permeability and thus concentrate the field lines of the scatter field in their interior may be considered as material for the shielding  11 . On cost grounds, iron is here the preferred material, as it can also be processed using the customary procedures such as welding, riveting or the like. Due to the requisite material thickness and the associated weight it is once again advantageous that relatively high axle loading in the case of rail traffic is permitted. 
         [0029]    In principle, all types of construction which correspond to the maximum dimensions of the railroad car may be considered for the magnetic resonance tomograph  20 . On grounds of weight, magnetic resonance tomographs  20  with superconducting magnets are preferred, as these have lower space requirements and lower weight for comparable field strength. Due to the better shielding options in a railroad car  1 , as previously explained, it is even possible to employ systems with stronger static magnetic fields in a mobile manner Systems with up to 3 Tesla are commercially available. 
         [0030]    In one embodiment of the railroad car on one side of the magnetic resonance tomograph  11 , the examination room is abutted by technology rooms, in which are accommodated supply units  30 ,  40 ,  50 . These are on the one hand the supply units  50  for activating gradient coils and high-frequency coils, which are located in the immediate vicinity of the magnetic resonance tomograph  11 , in order to ensure the shortest possible cable lengths and losses. Arranged at increasing distances in the railroad car  1  are supply units such as the cooling units  30  or power supply  40 , which themselves generate electromagnetic fields and would disrupt operation of the magnetic resonance tomograph  11 . Further shown in  FIG. 1  is a power line  41 , which connects the railroad car to an external power supply. This can be a link to a public grid or to the power supply of a locomotive. It is also conceivable, however, to supply the railroad car from a catenary wire via its own pantograph or by means of a power unit in the railroad car itself. 
         [0031]    Located on the side of the magnetic resonance tomograph  11  away from the supply units  30 ,  40 ,  50  in the embodiment shown is a control room, in which are located a console and a workstation for an operator of the magnetic resonance tomograph  11 . The examination can be controlled and monitored from here. This can be connected to a preparation room  70 , in which a patient is prepared for an examination. Patient access to the preparation room  70  is facilitated by means of a ramp  80 , which is arranged at an access of the railroad car and overcomes the height difference between the railroad car and a station platform or ground level. 
         [0032]    Although the invention has been illustrated and described in greater detail by means of the preferred exemplary embodiment, the invention is not restricted by the disclosed examples, and other variations can be derived by the person skilled in the art, without departing from the protective scope of the invention.