Magnetic assembly and method for defining a magnetic field for an imaging volume

A method of defining a magnetic field for a target volume, the method comprising:

• generating an initial model of a magnet assembly comprising at least two magnets arranged in a fixed spaced relationship having an axis extending generally from a center of the first magnet to a center of the second magnet;
• and one or more objects capable of disturbing the magnetic field in the target volume to be unacceptably inhomogeneous;
• estimating a magnetic field for the target volume based on the model;
• calculating deviation between the estimated magnetic field and the target magnetic field for the target volume;
• and
• updating the model to reduce the deviation by non-axisymmetrically modifying one or more parameters representing the magnet assembly to produce a variety of magnetic field strengths that, in combination, produce substantially the target magnetic field in the imaging volume.

A non-transitory computer readable medium embodying a computer program for defining a magnetic field for a target volume, the computer program comprising:

• computer program code generating an initial model of a magnet assembly comprising at least two magnets arranged in a fixed spaced relationship having an axis extending generally from a center of the first magnet to a center of the second magnet;
• and one or more objects capable of disturbing the magnetic field in the target volume to be unacceptably inhomogeneous;
• computer program code estimating a magnetic field for the target volume based on the model;
• computer program code calculating deviation between the estimated magnetic field and the target magnetic field for the target volume;
• and
• computer program code updating the model to reduce the deviation by non-axisymmetrically modifying one or more parameters representing the magnet assembly to produce a variety of magnetic field strengths that, in combination, produce substantially the target magnetic field in the target volume.