Magnetic Particle Imaging in Human Subjects.

Magnetic Particle Imaging (MPI) is a tracer-based medical imaging modality that detects magnetic nanoparticles with no background tissue signal. MPI acquires quantitative, high-sensitivity tomographic images of shelf-stable magnetic tracers that safely produce signals in vivo for weeks or even months. These features can fill capability gaps in medical imaging for applications benefiting from tracer specificity with an extended imaging window. Despite two decades of preclinical validation and multiple published human-scale imagers, MPI has not previously been demonstrated in human subjects. Here we report MPI imaging in two subjects following subcutaneous administration of magnetic tracer in the scalp and foot. Our results showed quantitative and longitudinal visualization of lymphatic drainage for up to six months, with supporting validation in a mouse model. Imaging in human subjects required the development and verification of a novel clinical imager, including magnetostimulation threshold testing of all magnetic fields used in imaging sequences. To understand MPI in the context of existing medical imaging technologies, we benchmarked MPI imaging performance against SPECT using lymphatic system phantom models. These findings demonstrate that MPI can translate from animals to human subjects, and establish MPI as a new tool for longitudinal tracer imaging in medicine. The addition of MPI to the clinical imaging toolbox could enable new approaches and capabilities for diagnosis, real-time interventions, and treatment monitoring across a broad range of clinical applications.