High-sensitivity in vivo contrast for ultra-low field magnetic resonance imaging using superparamagnetic iron oxide nanoparticles.

David E J Waddington,Zdenka Kuncic,Richard Maschmeyer,Matthew S Rosen,Thomas Boele

doi:10.1126/sciadv.abb0998

Abstract

Magnetic resonance imaging (MRI) scanners operating at ultra-low magnetic fields (ULF; <10 mT) are uniquely positioned to reduce the cost and expand the clinical accessibility of MRI. A fundamental challenge for ULF MRI is obtaining high-contrast images without compromising acquisition sensitivity to the point that scan times become clinically unacceptable. Here, we demonstrate that the high magnetization of superparamagnetic iron oxide nanoparticles (SPIONs) at ULF makes possible relaxivity- and susceptibility-based effects unachievable with conventional contrast agents (CAs). We leverage these effects to acquire high-contrast images of SPIONs in a rat model with ULF MRI using short scan times. This work overcomes a key limitation of ULF MRI by enabling in vivo imaging of biocompatible CAs. These results open a new clinical translation pathway for ULF MRI and have broader implications for disease detection with low-field portable MRI scanners.

Highlights

Magnetic resonance imaging (MRI) has been unparalleled in its ability to noninvasively image soft tissue since it was introduced to the clinic over 30 years ago
We look to the future and present a susceptibility-based positive contrast technique for ultra-low field regime (ULF) MRI that is directly enabled by the high magnetization of superparamagnetic iron oxide nanoparticles (SPIONs)
The results presented here illustrate the clinical potential of SPIONs as ULF contrast agents (CAs) that give sensitive contrast with time-efficient imaging techniques

Summary

Introduction

Magnetic resonance imaging (MRI) has been unparalleled in its ability to noninvasively image soft tissue since it was introduced to the clinic over 30 years ago. Decades of technical improvements have not reduced the price of an MRI scanner, which, mostly due to superconducting magnets and siting infrastructure requirements, is nominally US$1 million per tesla of magnetic field [1]. These high costs have meant that MRI has typically been available only to relatively wealthy populations [2] in areas of high population density [3]. Using modern hardware and new acquisition techniques, this new wave of low-cost scanners can acquire far superior diagnostic information [13] to earlier generations of low-field MRI scanners [17] and could become common screening tools, at remote hospitals and medical clinics [4]

Methods

Results

Conclusion