Magnetic Particle Imaging: A New Imaging Modality

Magnetic Particle Imaging (MPI) is a new imaging modality that directly detects iron oxide nanoparticle tracers at any point, space and time within the body. Because the tracer is not normally found in the body, MPI images have exceptional contrast and high sensitivity. This allows us to see tracers in cells (cell tracking), blood (perfusion) and other functional systems (targeting, drug delivery systems..) within a living organism.

Magnetic Particle Imaging uses a unique geometry of magnetics to create a field free region (FFR). This is something you may have experienced when pointing two magnets at each other. That sensitive point controls the direction of a nanoparticle. This is very different from MRI physics where an image is created from a uniform field.

Rapidly Moving the FFR 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.

The performance, resolution and sensitivity of magnetic particle imaging with the MOMENTUM system is primarily impacted by the nanoparticle. Using a better or specific SPIO can increase the resolution and/or the sensitivity.

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

MRI creates a uniform field to produce an image using weak gradients (mT) and strong field strengths (T).

Two strong magnets pointing at each other produce a magnetic field gradient with an FFR at the center. The FFR is then rapidly moved across the sample to produce an image using strong gradients (T) and weak field strengths (mT).

Generating a 2D image of a nanoparticle.

Translating MPI to In Vivo Imaging

With the MOMENTUM imaging system, a sensitive field free line (FFL) is rastered across the sample to map the distribution of nanoparticles.

Following scanning, a 3D tomographic image is produced.  MPI signal (hot iron color) is detectable in the liver and spleen. The MPI has been co-registered with a CT image for anatomical context.

Want more information?