Imaging method for obtaining spatial distribution of nanoparticles in the body

A method for imaging a region of interest in an object, a living organism or part thereof comprising:

• administering magnetic nanoparticles (MNPs) to the object, living organism or part thereof so that a portion of the MNPs are distributed within a region of interest (ROI) or a plurality of ROIs therein;
• placing the object, living organism or part thereof in a selection magnetic field generated by a drive coil assembly comprising three pairs of orthogonally arranged drive coils;
• supplying currents to the drive coils to form a zero field voxel (ZFV);
• positioning the ZFV at one or more of the ROIs;
• magnetizing the MNPs in the one or more ROIs with a magnetic field pulse generated by a magnetizing coil;
• switching the selection magnetic field off, and
• detecting magnetization decay rates of the MNPs via a sensitive magnetic field sensor assembly capable of distinguishing between bound and unbound MNPs within the ROIs,
• where the magnetic field pulse has a duration of between about 0.1 seconds and 5 seconds, where MNPs located inside or positioned in the ZFV produce an observable response due to their longer relaxation times, where MNPs located outside the ZFV have relaxation times of milliseconds (ms) and make no measurable contribution to the observable response, and where the relaxations are due to Néel and Brownian relaxations.