A human-scale magnetic particle imaging system for functional neuroimaging

Non-invasive neuroimaging techniques have enabled a paradigm shift in the way neuroscientists study the human brain. However, the sensitivity limitations of existing methods are a barrier to the identification of differences in brain function in disease states in individuals, as required for clinical use. In contrast, conventional neuroscience studies can average across large cohorts (up to 100s of subjects) to discern significant differences. Magnetic Particle Imaging is naturally sensitive to changes in hemodynmaic blood volume associated with brain activation and may overcome the sensitivity barrier to clinical use. The sensitivity of MPI stems from the strong magnetic moment that induces the signal paired with an elimination of biological background signals and their associated biological nuisance fluctuations ("physiological noise"). However, MPI instrumentation is not widely available at the human scale, especially for the time-series imaging required for functional studies. Here, we demonstrate the sensitivity of a human-scale field-free line MPI system capable of long-term time series imaging at a 5 second temporal resolution and a spatial resolution of 6 mm, with a detection limit of 150 ng Fe (at SNR = 1). We hope this step toward human fMPI provides the sensitivity to enable new directions in neuroimaging, particularly permitting diagnostic functional neuroimaging of diseases states.