Experimental generation of an arbitrarily rotated field‐free line for the use in magnetic particle imaging

PURPOSE: The concept of a magnetic field-free line (FFL), with regard to the novel tomographic modality magnetic particle imaging (MPI), was recently introduced. Theoretical approaches predict the improvement of sensitivity of MPI by a factor of ten replacing the conventionally used field-free point (FFP) by a FFL. In this work, an experimental apparatus for generating an arbitrarily rotated and translated FFL field is described and tested. METHODS: A theoretical motivation for the implemented setup is provided and the required currents are derived in dependency of the coil sensitivities. A prototype of a FFL field generator is manufactured and the fields are measured using a Hall effect sensor. An evaluation of the generated fields is performed via comparison to simulated data. RESULTS: To utilize the FFL concept for MPI, the setup generating the fields needs to be feasible in praxis with respect to power loss. Furthermore, rotating and translating the FFL, while keeping the setup static in space, is a crucial aspect for conveying FFL imaging to clinical applications. The implemented setup copes with both of these challenges and allows for experimental generation as well as evaluation of the required fields. The generated fields agree to within 3.5% of model predictions. CONCLUSIONS: This work transfers the FFL concept from theoretical considerations to the implementation of an experimental setup generating the required fields. The high agreement of the measured fields with simulated data indicates the feasibility of magnetic field generation for the implementation of FFL imaging in MPI.