A new approach of simultaneous imaging of magnetic nanoparticle (MNP) concentration, temperature and viscosity with a custom-built scanning magnetic particle spectrometer (SMPS) is presented. The fundamental f0 and the 3f0 and 5f0 harmonics of the MNPs dominated by Brownian relaxation are measured with the SMPS. The effects of viscosity and temperature on the harmonics are studied in ac magnetic fields with different frequencies and amplitudes. Afterwards, phantom experiments are performed on the MNP samples with different spatial distributions of viscosity and temperature, which demonstrates the feasibility of the proposed approach for simultaneous imaging of MNP concentration, temperature and viscosity imaging
