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

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.

Multifrequency magnetic particle imaging enabled by a combined passive and active drive field feed‐through compensation approach

“…The frequency dependence results from capacitive coupling between the two coils and the frequency‐dependent nonuniform current distribution along the wire in each coil. The suppression values reported by other research groups using gradiometer coils for passive decoupling are comparable …”

“…MPI provides fast imaging with high spatial resolution and sensitivity, while no ionizing radiation is used. Currently, much effort is made to improve the performance of MPI in regard to these key parameters . They mainly depend on the hardware of the MPI system, imaging parameters, reconstruction techniques, as well as on the tracer properties .…”

Superparamagnetic iron oxides as MPI tracers: A primer and review of early applications

“…One example is to synthesize Janus iron oxide nanoparticles that are three times more effective compared to Resovist and 7 times more compared to Feraheme [25]. It has been reported that MPI can have extreme high sensitivity, in the order of <1 pg within the entire FOV [26]. Since cells labeled with SPIO for MRI cell tracking purposes have an average iron content of 5–10 pg Fe/cell, one can in theory track a single cell with MPI.…”

Magnetic particle imaging for radiation-free, sensitive and high-contrast vascular imaging and cell tracking

“…Commercial preclinical MPI scanners were only recently introduced by Bruker GmbH and Magnetic Insight Inc, and specifications are steadily improving. Theoretical work predicts that a human MPI scanner could have picogram sensitivity in a 1 second scan 9 and technical improvements have been made approaching this goal 10 . MPI has no view limitations, and it works robustly even in the lungs and bones, where MRI and Ultrasound routinely fail.…”