Magnetic Particle Imaging: A New Imaging Modality

“MPI is the most promising emerging imaging technology in the last 20 years and is expected to change the landscape of modern medical imaging and in vivo translational research.”
– IWMPI 2014

Magnetic Particle Imaging (MPI) is a new imaging modality that directly detects iron oxide nanoparticle tracers using time varying magnetic fields. Because the tracer is not normally found in the body, MPI images have exceptional contrast and high sensitivity. The MPI technique is straight forward and can be described classically with three key concepts:

Magnetic Particle Imaging uses a unique geometry of magnetics to create a field free area, line or point. This is something you may have experienced when pointing two magnets at each other. That sensitive point controls the direction of a nanoparticle.


Two strong magnets pointing at each other produce a magnetic field gradient with an FFP or FFL at the center. The FFP or FFL is then rapidly moved across the sample to produce an image.

Rapidly Moving the sensitive point (FFL) causes a “flip” in the magnetic direction of an SPIO nanoparticle which induces a signal in a receive coil. Since we know where the sensitive point is at all times, we can assign the signal to the known position to produce a quantitative MPI image.