The present invention relates to an apparatus (100) for detecting magnetic particles in a field of view (28), which apparatus comprises selection means, drive means, receiving means for acquiring detection signals, and reconstruction means (152) for reconstructing an image of the field of view (28) from detection signals. 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 (28), wherein signal time periods (ts1, ts2, ts1) at which magnetic particles were present in the field of view (28) are interspersed with at least one (tb2, tb3) of said one or more background time periods (tb1, tb2, tb3, tb4), using the detection signals ob tained 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).
