Abstract: The invention relates to a method and apparatus for detecting superparamagnetic material. The method comprises applying, by an excitation coil, a magnetic field during a first period to an object to modulate a magnetization of the superparamagnetic material, the magnetic field comprising a first component with a first frequency; positioning a sensing device at a first position from the excitation coil receiving a first signal by a first detection sub-coil in the sensing device and a second signal by a second detection-sub-coil in the sensing device; determining a sensor signal from the first signal and the second signal; determining a detection signal based on the sensor signal; determining a parameter indicating an amount of superparamagnetic material by dividing the detection signal by the first signal, and repeating steps to at at least one different position in order to determine a location where the parameter has a maximal value.

Abstract: Method and apparatus for measuring an amount of superparamagnetic material in an object, the method including a) applying a magnetic field having a first component alternating with a first period to the object and a magnetic field strength lower than a magnetic field strength at which the superparamagnetic material is driven in saturation; b) measuring a first magnetic susceptibility of the object with a detection coil; c) applying a static second component to the magnetic field for a second period being equal or larger than the first period, the strength of the magnetic field during the second period is such that the superparamagnetic material is driven towards saturation; d) measuring a second magnetic susceptibility of the object with the detection coil during the application of the static second component; and e) determining the amount of superparamagnetic material from a difference between the measured first and second susceptibility of the object.

Abstract: Method and apparatus for measuring an amount of superparamagnetic material in an object, the method including a) applying a magnetic field having a first component alternating with a first period to the object and a magnetic field strength lower than a magnetic field strength at which the superparamagnetic material is driven in saturation; b) measuring a first magnetic susceptibility of the object with a detection coil; c) applying a static second component to the magnetic field for a second period being equal or larger than the first period, the strength of the magnetic field during the second period is such that the superparamagnetic material is driven towards saturation; d) measuring a second magnetic susceptibility of the object with the detection coil during the application of the static second component; and e) determining the amount of superparamagnetic material from a difference between the measured first and second susceptibility of the object.