A probe for detecting magnetic particles. In one embodiment, the probe includes: a cylindrical probe core having a first end and a second end, the cylindrical probe core defining two channels for containing coils of wire, one of the channels being adjacent the first end of the cylindrical probe core; two sense coils, one each of the sense coils being located in a respective one of the channels; and two drive coils, one each of the drive coils being co-located with the respective sense coil in a respective one of the channels.