An apparatus for detecting magnetic particles in a field of view, which apparatus comprises: - selection means comprising a selection field signal generator unit and selection field elements for generating a magnetic selection field having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength where the magnetization of the magnetic particles is not saturated and a second sub-zone having a higher magnetic field strength where the magnetization of the magnetic particles is saturated are formed in the field of view, - drive means comprising a drive field signal generator unit and drive field coils (124; 125, 126, 127) for changing the position in space of the two sub-zones (52, 54) in the field of view by means of a magnetic drive field so that the magnetization of the magnetic material changes locally, - receiving means comprising at least one signal receiving unit and at least one receiving coil for acquiring detection signals, which detection signals depend on the magnetization in the field of view, which magnetization is influenced by the change in the position in space of the first and second sub-zone (52, 54), and - reconstruction means for reconstructing an image of the field of view from detection signals, wherein said reconstruction means is adapted to - identify in the detection signals one or more background time periods (tb1, tb2, tb3, tb4) at which no magnetic particles were present in the field of view, wherein signal time periods (ts1, ts2, ts1) at which magnetic particles were present in the field of view are interspersed with at least one (tb2, tb3) of said one or more background time periods (tb1, tb2, tb3, tb4), - using the detection signals obtained at said background time periods (tb1, tb2, tb3, tb4) to correct detection signals obtained at said signal time periods (ts1, ts2, ts1), and - reconstructing the image from said corrected detection signals obtained at said signal time periods (ts1, ts2, ts1). - selection means comprising a selection field signal generator unit and selection field elements for generating a magnetic selection field having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength where the magnetization of the magnetic particles is not saturated and a second sub-zone having a higher magnetic field strength where the magnetization of the magnetic particles is saturated are formed in the field of view, - drive means comprising a drive field signal generator unit and drive field coils (124; 125, 126, 127) for changing the position in space of the two sub-zones (52, 54) in the field of view by means of a magnetic drive field so that the magnetization of the magnetic material changes locally, - receiving means comprising at least one signal receiving unit and at least one receiving coil for acquiring detection signals, which detection signals depend on the magnetization in the field of view, which magnetization is influenced by the change in the position in space of the first and second sub-zone (52, 54), and - reconstruction means for reconstructing an image of the field of view from detection signals, wherein said reconstruction means is adapted to - identify in the detection signals one or more background time periods (tb1, tb2, tb3, tb4) at which no magnetic particles were present in the field of view, wherein signal time periods (ts1, ts2, ts1) at which magnetic particles were present in the field of view are interspersed with at least one (tb2, tb3) of said one or more background time periods (tb1, tb2, tb3, tb4), - using the detection signals obtained at said background time periods (tb1, tb2, tb3, tb4) to correct detection signals obtained at said signal time periods (ts1, ts2, ts1), and - reconstructing the image from said corrected detection signals obtained at said signal time periods (ts1, ts2, ts1). - identify in the detection signals one or more background time periods (tb1, tb2, tb3, tb4) at which no magnetic particles were present in the field of view, wherein signal time periods (ts1, ts2, ts1) at which magnetic particles were present in the field of view are interspersed with at least one (tb2, tb3) of said one or more background time periods (tb1, tb2, tb3, tb4), - using the detection signals obtained at said background time periods (tb1, tb2, tb3, tb4) to correct detection signals obtained at said signal time periods (ts1, ts2, ts1), and - reconstructing the image from said corrected detection signals obtained at said signal time periods (ts1, ts2, ts1).