In Vivo Measurement of Cerebral SPIO Concentration in Nonhuman Primate Using Magnetic Particle Imaging Detector

The purpose of this study is to develop a magnetic particle imaging (MPI) technique to directly measure time-varied cerebral superparamagnetic iron oxide nanoparticle (SPIO) concentration in rhesus macaques. A hand-held MPI detector was developed to monitor MPI signal changes at the third harmonics of the drive frequency in resting-state nonhuman primates. Phantom experiments were first performed to determine the sensitivity limits of the detector as a function of distance from the detector and SPIO concentration. The measured sensitivity profile was then used to reveal the most sensitive region of the detector. MPI detection was continuously performed to monitor MPI signal changes after two bolus injections of SPIOs in the rhesus macaque. We successfully developed a hand-held MPI to detect cerebral SPIO concentration changes in a living nonhuman primate. The detection limit of the MPI detector is about 125 ng iron. We reported on the in vivo measurement of cerebral SPIO concentration changes in rhesus macaque using a hand-held MPI detector. In vivo experiments showed the feasibility of the detector to sensitively measure MPI signals in a nonhuman primate brain.