Towards Picogram Detection of Superparamagnetic Iron-Oxide Particles Using a Gradiometric Receive Coil

TLDR

Superparamagnetic iron‑oxide nanoparticles are used for medical imaging, and magnetic particle imaging offers high temporal resolution and sensitivity, but the lowest achievable detection limit remains unknown. The study aims to present a highly sensitive gradiometric receive‑coil with a noise‑matching network for mouse imaging and to propose guidelines for comparing MPI detection limits. A gradiometric receive‑coil unit with a custom noise‑matching network was designed for mouse imaging. The system detected 5 ng of iron in vitro, 156 μg/L in concentration, and produced in‑vivo images of a 512 ng bolus within 21.5 ms, representing the lowest detection limit reported for an MPI scanner.

Abstract

Abstract Superparamagnetic iron-oxide nanoparticles can be used in medical applications like vascular or targeted imaging. Magnetic particle imaging (MPI) is a promising tomographic imaging technique that allows visualizing the 3D nanoparticle distribution concentration in a non-invasive manner. The two main strengths of MPI are high temporal resolution and high sensitivity. While the first has been proven in the assessment of dynamic processes like cardiac imaging, it is unknown how far the detection limit of MPI can be lowered. Within this work, we will present a highly sensitive gradiometric receive-coil unit combined with a noise-matching network tailored for the imaging of mice. The setup is capable of detecting 5 ng of iron in-vitro with an acquisition time of 2.14 sec. In terms of iron concentration we are able to detect 156 μg/L marking the lowest value that has been reported for an MPI scanner so far. In-vivo MPI mouse images of a 512 ng bolus and a 21.5 ms acquisition time allow for capturing the flow of an intravenously injected tracer through the heart of a mouse. Since it has been rather difficult to compare detection limits across MPI publications we propose guidelines to improve the comparability of future MPI studies.