Abstract:
A method for operating a computer system for supporting an insertion of a guide wire into body tissue is proposed. An interventional procedure is prepared for by the insertion of the guide wire into body tissue. The guide wire is fitted with sensors. The latter&#39;s signals are received using the proposed method, so that a comparison of actual values with target values is possible and a future target direction of movement can be derived.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of German application No. 10 2010 005 744.4 filed Jan. 26, 2010, which is incorporated by reference herein in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to a method for operating a computer system, wherein the computer system is used to support the insertion of a guide wire into body tissue. The invention also relates to an arrangement for preparing for an interventional procedure. It further relates to a method for determining the position and orientation of a tip of a guide wire in body tissue. 
       BACKGROUND OF THE INVENTION 
       [0003]    To prepare for an interventional procedure such as for example the insertion of a catheter, with the aid of which a dilatation balloon or a stent is passed into a body, a guide wire is regularly inserted into the body tissue. As its name suggests, the guide wire is used to guide the catheter, which is simply pushed over the guide wire. The guide wire is a thin, flexible wire. A guide wire is used to probe a target site in a body tissue of the patient. 
         [0004]    It is known for such a guide wire to be moved in the body tissue using electromagnetic fields. WO 2006/005013 A2 describes how this “navigation” in the body tissue can be performed semi-automatically. To this end x-rays of the body to be transported are taken. 
         [0005]    Taking these x-rays is complex. 
       SUMMARY OF THE INVENTION 
       [0006]    It is the object of the invention to demonstrate a way to support the insertion of a guide wire into body tissue in a non-complex manner. 
         [0007]    The object is achieved in one aspect by a method for operating a computer system to support the insertion of a guide wire into body tissue, in another aspect by an arrangement for preparing for an interventional procedure, and in another aspect by a method for determining the position and orientation of a tip of a guide wire in body tissue, as claimed in the claims. 
         [0008]    The inventive method for operating a computer system comprises the steps:
       receipt of signals from a sensor device on the tip of the guide wire by the computer system, via which an actual location and an actual orientation of the tip of the guide wire can be transmitted,   comparison of the actual location and the actual orientation with a target location and a target orientation and determination of a target direction of movement for a future target movement of the guide wire.       
 
         [0011]    By using one or more sensors on the tip of the guide wire, the signals of which can be and are received by the computer system, x-ray images can be dispensed with. 
         [0012]    A target location and a target orientation can be determined in advance on the basis of inputs into the computer system or can be obtained automatically by the computer system itself on the basis of other information such as e.g. image information. 
         [0013]    In a possible alternative the target direction of movement determined is communicated via an output device, so that a person giving the treatment, whose task is to insert the guide wire into the body tissue of the patient, immediately receives the details of what to do next, i.e. how the guide wire should be further inserted. 
         [0014]    In another alternative the computer system generates control commands, as a function of the target direction of movement, and outputs these to means for movement of the guide wire. These can be means which at least include a magnetic coil, so that the magnetic field effects a movement of the tip of the guide wire. 
         [0015]    In a preferred embodiment the inventive method includes the receipt of an input via a user interface to determine a size of a correction variable which is used when determining the target direction of movement. For example, the target direction of movement can have a component corresponding to the target orientation and a component perpendicular thereto, and a prefactor which determines the variable of the component perpendicular to the target orientation can be determined on the basis of an input. A user can in this way determine the slope of the correction of a deviation from the desired trajectory. 
         [0016]    The inventive arrangement for preparing for an interventional procedure has a guide wire which includes at least one sensor for determining the position and orientation of the tip of the guide wire, and which is designed to emit sensor signals. It further has means for moving the guide wire in a tissue, and it has a control unit with means for receiving and evaluating the sensor signals and for determining and emitting control commands to the means for movement. 
         [0017]    The arrangement thus reflects the concept in which the actual position and actual orientation of the tip of the guide wire are automatically sensed by at least one sensor on the guide wire itself, and in which in accordance with the inventive method a computer system evaluates these signals and in accordance with one aspect of the inventive method immediately effects the correction movement. 
         [0018]    The means for movement preferably here include at least one magnetic coil. 
         [0019]    The inventive method for determining the position and orientation of a guide wire in body tissue includes the acquisition of measuring signals by at least one sensor arranged on the guide wire, the sending of measuring signals by the sensor, the receipt of the measuring signals by a computer unit and the subsequent evaluation of said measuring signals by the computer unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    A preferred embodiment of the invention is described below, with reference to the drawing, in which 
           [0021]      FIG. 1  schematically shows the components of an inventive arrangement for preparing for an interventional procedure, 
           [0022]      FIG. 2  shows a flow diagram of two alternative embodiments of the inventive method and 
           [0023]      FIG. 3  is a graphical representation explaining the variables used in the description of the inventive method. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    An arrangement designated overall by  100  for preparing for an interventional procedure includes a guide wire  10 , on which a plurality of coils is arranged, of which two coils  12   a ,  12   b  are shown by way of example. With the aid of coils a position and an orientation of the front region  14  can be measured. 
         [0025]    One coil is normally provided for this for each component of the three-dimensional space. 
         [0026]    The guide wire  10  should be inserted into the body tissue of a patient (not shown) and should be automatically movable there. To move the guide wire, magnetic fields are generated, as a result of which the guide wire  10  consisting of ferromagnetic material is attracted or repelled. The magnetic fields are generated by a coil shown schematically by  16 , which is supplied with current by a current source  18 . The size of the current is determined by a computer unit  20 . The measured values of the sensor coils  12   a ,  12   b  are fed to the computer unit  20  via cables  24  arranged in a cavity  22  of the guide wire  10 . Inputs can be made at the computer device  20  using a computer mouse  26  or a keyboard  28 . Images  32  can be displayed on a screen  30 . 
         [0027]    It will now be shown how the inventive method is executed, said method being performed by the computer unit  20  and the technical devices linked thereto. A receiver unit of the computer unit  20  (not shown in  FIG. 1 ) receives the signals from the sensor coils  12   a ,  12   b  in accordance with step S 10 . The computer unit  20  then evaluates the incoming signals with the aid of a microprocessor  34  in accordance with step S 12  and then in step S 14  calculates the current to be applied to the coil  16 . In a first alternative a display is output on the screen  32  showing how the guide wire  10  should be further moved, in accordance with step S 16   a . In a second alternative a signal is automatically emitted by the current source  20  to the current source  18  indicating the current to be supplied to the coil  16 , in accordance with step S 16   b.    
         [0028]    In the computer unit  20  a navigation path NP is in particular laid down. This can be determined by a user for example on the basis of x-ray images of the patient taken previously; for example, the user can mark particular places in an x-ray image and in this way determine the path. Alternatively the central line of a body vessel can be automatically determined by the computer unit  20  on the basis of medical images such as x-ray images, nuclear resonance images, etc. Based on a representation of vessels, the path of least resistance through tissue can additionally be automatically determined. 
         [0029]    In accordance with  FIG. 3 , now let the guide wire be moved on a curve FD which deviates from the navigation curve NP in one region. Let an actual location r FD  deviate from the target location r NP . In the same manner, also let actual orientation S FD  deviate from a target orientation S NP . The guide wire should now subsequently be moved in accordance with the target orientation S NP  on the one hand, and on the other hand the deviation between actual location and target location should be equalized. In this way a target direction of movement S NPkorr  can be assembled from a component S NP  and a component perpendicular to the target orientation S NP , S NP     ⊥   . 
         [0030]    The length of S NP  can here be equal to the length of S NP , whereas the length of S NP     ⊥    can be proportional to the angle θ which occurs in a triangle, the sides of which pass through the points r Np  or r FD  in the directions S NP  or S FD . Alternatively the perpendicular component S NP     ⊥    can also be proportional to the sine of this angle θ, sin θ. A possible proportional factor can if necessary be input via the user interfaces  26 ,  28  by an operator. 
         [0031]    The computer unit  20  now calculates the variable S NPkorr . 
         [0032]    The role of the magnetic coil  16  is to generate such a magnetic field that is parallel to the direction arrow S Npkorr , so that the guide wire  10  can be moved in this direction and hence approximates to the normal path NP. 
         [0033]    The inventive method performed on the computer unit  20  hence enables automatic navigation of the guide wire  10  in the body tissue of a patient. To this end the computer unit  20  must interact with the guide wire  10  and the means  16 ,  18  for movement of said guide wire, and must receive and/or output signals. 
         [0034]    The method for operating a computer system, as described above, essentially functions even if sensor signals from the computer unit are merely simulated and the receipt of control signals is likewise merely simulated. The computer unit  20  can hence also essentially be operated without the guide wire  10  and the means  16 ,  18  for movement of said guide wire, although in that case there is of course no obvious perceived effect on a guide wire  10  in the patient tissue. 
         [0035]    Instead of using magnetic fields, an electromechanical guidance system in accordance with the Hansen principle can also be used.