Overcoming the limitations of NMR Field Probes: A Novel Integrated Sensor Utilizing Pre-Polarization for (Ultra) Low Field MRI

TL;DR

This paper introduces a novel, low-cost NMR sensor with pre-polarization that improves magnetic field measurement for low-field MRI, aiding development and deployment in resource-limited settings.

Contribution

The paper presents a new integrated NMR sensor using pre-polarization and high-voltage silicon carbide transistors, enabling accurate field measurement without prior knowledge, suitable for low-field MRI development.

Findings

Validated from 1 mT to 45 mT magnetic fields

Achieves measurement sensitivity up to 1,000 times stronger than similar systems

Supports low-cost, modular design for global MRI access

Abstract

Access to magnetic resonance imaging (MRI) remains severely limited in low- and middle-income countries, especially in sub-Saharan Africa, despite rising rates of non-communicable diseases. Low-field MRI presents an affordable, locally developable diagnostic solution, but its performance is constrained by magnetic field instability. We present a novel NMR field probe designed to overcome these challenges using a rapid non-adiabatic switch-off of a pre-polarization field resulting in precessing spin magnetization. Achieved by first use of high-voltage silicon carbide transistors operating in controlled avalanche breakdown, it measures the Larmor frequency without prior field knowledge, unlike conventional probes. This capability is crucial during magnet development with often unknown fields, allowing early detection of magnet issues, and offering an urgently needed tool for magnet design and image-quality improvement. Validated from 1 mT to 45 mT (up to 1,000 times stronger than similar systems) its low-cost, modular design supports replication, upgrades, and enhanced field control, helping expand global MRI access.