Arrangement and method for determining the spatial distribution of magnetic particles

Abstract

The invention relates to an arrangement and a method for determining the spatial distribution of magnetic particles in an examination area. Magnetic field means are used to generate a spatially inhomogeneous gradient magnetic field with at least one region with a low field strength, in which the magnetization of the particles is in a state of non- saturation, whereas they are in a state of saturation in the remaining region. By using change means to shift the area with a low field strength within the examination area, a change in the magnetization of the magnetic particles is brought about which can be detected from outside by detection means and contains information about the spatial distribution of the magnetic particles in the examination area. The magnetic field means or the change means or the detection means or a combination of these means are arranged at least partially on a medical instrument.

1 . An arrangement for determining the spatial distribution of magnetic particles in an examination area, comprising
 a) magnetic field means ( 13   a,    13   b,    25 ,  30 ,  31 ) for generating a magnetic field with a spatial course of the magnetic field strength such that there is in the examination area a first part-region ( 27 ) with a low magnetic field strength and a second part-region with a higher magnetic field strength,   b) change means ( 14 ,  15   a,    15   b,    16   a,    16   b ) for changing the spatial position of the two part-regions in the examination area, so that the magnetization of the particles changes locally,   c) detection means ( 17 ) for detecting signals which depend on the magnetization in the examination area that is affected by the change in spatial position,   d) evaluation means for evaluating the signals in order to obtain information about the spatial distribution of the magnetic particles in the examination area,   
     wherein the magnetic field means or the change means or the detection means or a combination of these means are arranged at least partially on a medical instrument ( 8 ,  8   a ). 
   
   
       2 . An arrangement as claimed in  claim 1 , wherein the magnetic field means arranged on the medical instrument comprise a coil arrangement ( 13   a,    13   b,    30 ,  31 ) and/or a permanent magnet ( 25 ). 
   
   
       3 . An arrangement as claimed in  claim 1 , wherein the magnetic field means arranged on the medical instrument comprise at least two coils ( 13   a,    13   b ) arranged one inside the other, which coils in the operating state are flowed through by currents in opposite directions. 
   
   
       4 . An arrangement as claimed in  claim 1 , wherein the change means arranged on the medical instrument comprise a coil arrangement with a soft-magnetic core. 
   
   
       5 . An arrangement as claimed in  claim 1 , wherein the detection means arranged on the medical instrument comprise a number of coils or coil arrangements, the directions of action of which are at an angle to one another. 
   
   
       6 . An arrangement as claimed in  claim 1 , comprising an invasive medical instrument. 
   
   
       7 . An arrangement as claimed in  claim 1 , wherein the medical instrument is a catheter and the means arranged thereon are arranged on or at least in the vicinity of the catheter tip. 
   
   
       8 . An arrangement as claimed in  claim 1 , comprising a marker ( 20 ) on the medical instrument. 
   
   
       9 . An arrangement as claimed in  claim 1 , wherein the change means are designed such that the spatial position of the two part-regions in a target area can be changed for as long as and with such a frequency that the target area heats up in a targeted manner. 
   
   
       10 . The use of a medical instrument in an arrangement as claimed in  claim 1 , wherein magnetic field means or change means or detection means or a combination of these means are at least partially arranged on the medical instrument. 
   
   
       11 . The use of a catheter as claimed in  claim 10 . 
   
   
       12 . A medical instrument suitable for the use as claimed in  claim 1 , on which the detection means and the magnetic field means and/or the change means are at least partially arranged. 
   
   
       13 . A catheter as claimed in  claim 12 . 
   
   
       14 . A method of determining the spatial distribution of magnetic particles in an examination area, comprising the steps
 a) introducing a medical instrument ( 8 ,  8   a ) as claimed in any of the preceding claims into the examination area,   b) generating a magnetic field with a spatial course of the magnetic field strength such that there is in the examination area a first part-region with a low magnetic field strength and a second part-region with a higher magnetic field strength,   c) changing the spatial position of the two part-regions in the examination area, so that the magnetization of the particles changes locally,   d) detecting signals which depend on the magnetization in the examination area that is affected by this change,   e) evaluating the signals in order to obtain information about the spatial distribution of the magnetic particles in the examination area.