A field free line (FFL)-based magnetic particle imaging (MPI) device comprising: a first set of elongated electromagnets having lengths greater than widths and disposed along a common first axis; a second set of elongated electromagnets having lengths greater than widths and disposed along a common second axis, the common first axis being parallel to the common second axis and displaced from the common second axis in a direction normal to the common first axis, the second set of elongated electromagnets disposed directly over and overlapping the first set of elongated electromagnets in the direction normal to the common first axis; and a current generator configured to: drive a first selection current in a first direction about the common first axis through an elongated electromagnet in the first set of elongated electromagnets; and drive a second selection current in a second direction about the common second axis through an elongated electromagnet in the second set of elongated electromagnets, the second direction being opposite to the first direction, wherein the elongated electromagnet in the second set of elongated electromagnets is disposed directly over the elongated electromagnet in the first set of elongated electromagnets in the direction normal to the common first axis, and wherein the first selection current and the second selection current create a selection magnetic field defining a field free line between the first set of elongated electromagnets and the second set of elongated electromagnets and parallel to a direction defined by the lengths of the elongated electromagnets. a first set of elongated electromagnets having lengths greater than widths and disposed along a common first axis; a second set of elongated electromagnets having lengths greater than widths and disposed along a common second axis, the common first axis being parallel to the common second axis and displaced from the common second axis in a direction normal to the common first axis, the second set of elongated electromagnets disposed directly over and overlapping the first set of elongated electromagnets in the direction normal to the common first axis; and a current generator configured to: drive a first selection current in a first direction about the common first axis through an elongated electromagnet in the first set of elongated electromagnets; and drive a second selection current in a second direction about the common second axis through an elongated electromagnet in the second set of elongated electromagnets, the second direction being opposite to the first direction, drive a first selection current in a first direction about the common first axis through an elongated electromagnet in the first set of elongated electromagnets; and drive a second selection current in a second direction about the common second axis through an elongated electromagnet in the second set of elongated electromagnets, the second direction being opposite to the first direction, wherein the elongated electromagnet in the second set of elongated electromagnets is disposed directly over the elongated electromagnet in the first set of elongated electromagnets in the direction normal to the common first axis, and wherein the first selection current and the second selection current create a selection magnetic field defining a field free line between the first set of elongated electromagnets and the second set of elongated electromagnets and parallel to a direction defined by the lengths of the elongated electromagnets. <EOS>