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

## TL;DR

This paper demonstrates a highly sensitive magnetic particle imaging system capable of detecting picogram levels of superparamagnetic iron-oxide particles, significantly advancing MPI detection limits for medical imaging applications.

## Contribution

Introduction of a novel gradiometric receive coil and noise-matching network that achieve the lowest reported detection limit for MPI, enabling ultra-sensitive in vivo imaging.

## Key findings

- Detected 5 ng of iron in vitro at 2.14 seconds
- Achieved detection of 156 μg/L iron concentration, lowest reported for MPI
- Captured in vivo mouse blood flow with 512 ng tracer at 21.5 ms

## Abstract

Superparamagnetic iron-oxide nanoparticles can be used in a variety of 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 measurement of mice. The setup is capable of detecting 5 ng of iron in vitro at 2.14 sec acquisition time. In terms of iron concentration we are able to detect 156 {\mu}g/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 at 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 improving the comparability of future MPI studies.