Systems and methods for detecting magnetic markers for surgical guidance

A method for detecting a magnetic marker comprises generating a driving magnetic field comprising first and second frequencies and detecting a response magnetic field comprising first and second response components. The magnetic marker provides a non-linear response to the driving signal. A primary portion of the response components is generated by the magnetic marker, and a secondary portion of the response components is generated by a secondary magnetic source. The method comprises determining a driving factor representing a ratio of the frequencies in the driving signal; determining a correction factor corresponding to the secondary portion of the second response component, based on the first response component and the driving factor; determining a detection signal corresponding to the primary portion of the second response component, based on the second response component and the determined correction factor; and generating an output signal based on a strength of the detection signal.