Magnetic Particle Imaging

The use of contrast agents in medical imaging has a long history, but a real time tomographic procedure without patient exposure was first introduced in 2005 by Gleich and Weizenecker. The new tomographic imaging modality magnetic particle imaging (MPI) is able to combine high spatial and temporal resolution with excellent sensitivity. The feasibility of these three critical qualities was illustrated in 2007, when a bolus of nanoparticles in a beating mouse heart could be tracked in real time. The imaging of a beating heart in real time, would open many new opportunities in clinical applications. The minimally invasive cardiac surgery would play a significant role. Thus, this technique is promising in terms of diagnostic and intraoperative imaging in humans.

The principle of the recording technique is based on the nonlinear magnetization curve of super-paramagnetic nanoparticles (super-paramagnetic iron oxide SPIO) and does not stress the patient with harmful radiation. The particles, which are already used in clinical MRI, are degraded after image acquisition in the liver. The signal generation works with periodically varying external magnetic fields, the spatial coding is done via external magnetic gradient fields. With optimized scanner topologies and advanced tracers a spatial resolution in the order of 1 mm is possible.