Patent ID: 7778681

Claim:
A method of determining the spatial distribution of magnetic particles in an examination zone, which method comprises the acts of a) generating a magnetic field having a magnetic field strength which varies in space wherein a first sub-zone having a low magnetic field strength and a second sub-zone having a high magnetic field strength are formed in the examination zone, wherein the act of generating comprises acts of: providing a first substantially constant current in a first coil of a coil pair; and providing a second substantially constant current in a second coil of the coil pair, wherein the first current and the second current are substantially equal and oppositely directed currents, wherein but for other magnetic forces, the coil pair produces a temporally constant magnetic field, b) changing the position in space of the two sub-zones in the examination zone wherein the magnetization of the particles changes locally by inducing a spatially variable magnetic field into the magnetic field, c) acquiring signals which are dependent on the magnetization in the examination zone which has been influenced by the changing of the position in space, and d) evaluating the signals in order to extract information concerning the spatial distribution of the magnetic particles in the examination zone.