Magnetic Particle Imaging Emerges into Preclinical Research: Hardware, Nanoparticles, and Animal Models
Patrick W Goodwill
Magnetic Particle Imaging (MPI) is an emerging tracer imaging technique that directly detects superparamagnetic iron oxide (SPIO) nanoparticles with exceptional contrast and high sensitivity at millimeter-scale resolutions.1 MPI’s contrast is similar to nuclear medicine, but without the complex workflow, safety, and half-life limitations of a radioactive tracer. These capabilities help fill in some of the gaps of current technologies and position MPI as complementary to anatomical imaging techniques such as MRI and X-ray/CT.
The magnetic properties of the nanoparticle tracers seen by MPI define the technique’s image resolution and sensitivity. This is because the MPI signal arise from the interaction between a magnetic nanoparticle, a strong magnetic field gradient, and a time varying magnetic drive field.2,3 To improve MPI’s spatial resolution, we and others have researched SPIOs with varying core diameters, since Langevin steady-state physics predicts a cubic resolution improvement with increasing SPIO core size. This effort has already produced exciting results, effectively reducing the FWHM resolution by a factor of two and increasing sensitivity an order of magnitude.4 However, much remains unknown about the physical mechanisms and trade-offs for further improvements.
Our group and others have begun testing MPI on animal models. We have used long circulating PEG coated nanoparticles to image the brain, detect cancers,5 detect gut bleeds,6 and visualize traumatic brain injury.7 MPI’s high sensitivity also makes it well suited for cell tracking. For example, we have tracked therapeutic neural stem cells for three months8 and the biodistribution of mesenchymal stem cells post administration.9 In the future, we see opportunities for MPI tracking of immune therapies or immune cells to sites of inflammation such as cancer.
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- Date: 26 Feb 2019
- Time: 06:30 PM to 08:30 PM
- All times are (UTC-08:00) Pacific Time (US & Canada)
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