Monitoring the movement of a bolus of magnetic nanoparticles by magnetorelaxometry imaging

<i>Objective</i>. Magnetic nanoparticles (MNPs) are an exciting tool in various biomedical applications. In particular, monitoring the movement and distribution of MNPs in body organs, especially in the brain, can help diagnose some life-threatening conditions such as cerebral aneurysms.<i>Approach</i>. In this study, we explore the potential of magnetorelaxometry imaging (MRXI) to monitor the movement of a fluid MNP bolus within a phantom model with different flow rates ranging from 0.6 to 1.7 ml min^-1. To carry out this experiment, we developed an MRXI setup comprising a 72-channel low-<i>T</i>_ccurrent sensing SQUID system, six excitation coils and a tube phantom, mimicking a vessel. The sensitivity of our setup was evaluated with different iron concentrations in the range of 25-100 mmol l-1.<i>Main result</i>. For all concentrations and flow rates, the localization of the MNP bolus aligns well with the ground truth. Moreover, the MRXI setup allowed the observation of the bolus movement over a specific coil to reveal details of the flow.<i>Significance</i>. These results demonstrate the ability of MRXI to monitor a MNP bolus, while passing through the tube phantom, with a temporal resolution of 1.4 sand an image resolution of approximately (6.3 × 6.3 × 2.1) mm3.