Magnetic Particle Imaging - Promises and Challenges of an Emerging Imaging Modality

13.01.2020 von 16:00 bis 17:00

Magnetic Particle Imaging (MPI) is a recently invented three-dimensional imaging method that quantitatively measures the spatial distribution of a tracer based on magnetic nanoparticles. The modality promises a high sensitivity and high spatial as well as temporal resolution. There is a high potential of MPI to improve interventional and image-guided surgical procedures because, today, established medical imaging modalities typically excel in only one or two of these important imaging properties. MPI makes use of the non-linear magnetization characteristics of the magnetic nanoparticles.

For this purpose, two magnetic fields are created and superimposed, a static selection field and an oscillatory drive field. If, for instance, SPIONs, i.e. superparamagnetic iron-oxide nanoparticles, are subjected to the oscillatory magnetic field, the particles will react with a non-linear magnetization response, which can be measured with an appropriate pick-up coil arrangement. Due to the non-linearity of the particles' magnetization characteristics, the received signal consists of the fundamental excitation frequency as well as of harmonics, i.e. oscillations with multiples of the fundamental frequency.

After separation of the fundamental signal, the nanoparticle concentration can be estimated based on the harmonics. The spatial coding is realized with the static selection field that produces a field-free point. Essentially, reconstruction in MPI is the solution of an inverse problem, where, based on the measured induction voltages in the pick-up coils, the spatial distribution of the nanoparticles can be estimated. The relation between the measured voltages and the desired tracer distribution is established by the MPI system function.

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