Magnetic Particle Imaging

Molecular imaging has been instrumental for unraveling the mystery of biological processes and for diagnosing disease with more accuracy than ever before. The existing repertoire of molecular imaging techniques has been exceedingly fruitful for both preclinical applications and clinical diagnosis, but to date, no technique combines exquisite tracer detection sensitivity with quantitativeness for longitudinal, months-long in vivo imaging deep in tissue. Magnetic Particle Imaging (MPI) is an emerging technique that directly images the strong electronic magnetization of clinically safe superparamagnetic iron oxide (SPIO) tracers. Because biological tissues do not produce signals detectable in MPI scanners, MP images have high contrast and sensitivity for SPIO tracers, comparable to nuclear medicine techniques. The MPI signal is also robust and linearly quantitative of SPIO tracers anywhere in the body. Hence, MPI may be useful in applications ranging from coronary angiography to stem cell tracking and has potential for human translation. In this chapter, we describe the differences between MPI and MRI physics, since most MRI-tailored SPIOs are not effective as MPI tracers. This chapter is designed so nanoparticle scientists can design ideal MPI-tailored SPIOs.