Untuned MPI relaxometer for nanoparticle characterization at arbitrary frequencies

MPI resolution and SNR are driven by the magnetic response of the iron oxide nanoparticles. Prior work has shown that magnetic nanoparticles respond differently to a wide range of excitation frequencies and amplitudes. Most prior work on MPI spectrometers and relaxometers have tuned the transmit coil at a single frequency.^1-3 In contrast, in this work, we have constructed an agile frequency and amplitude relaxometer capable of reaching excitation fields of 0–60 mTpp across a continuous frequency range of DC-150 kHz without requirement of capacitors for tuning to discrete frequencies.