Prepolarized MRI of Hard Tissues and Solid-State Matter

TL;DR

This paper demonstrates the feasibility of prepolarized MRI for hard tissues using a specialized low-field scanner, achieving significant SNR improvements and potential clinical dental applications.

Contribution

It introduces a dedicated 0.26 T scanner with a fast-switching prepolarizer module for hard tissue imaging, addressing previous limitations due to ultra-short relaxation times.

Findings

Achieved SNR enhancement consistent with theoretical models

Demonstrated rapid prepolarizer switching within 200 microseconds

Potential for replacing X-ray systems in dental imaging

Abstract

Prepolarized Magnetic Resonance Imaging (PMRI) is a long-established technique conceived to counteract the loss in signal-to-noise ratio (SNR) inherent to low-field MRI systems. When it comes to hard biological tissues and solid-state matter, PMRI is severely restricted by their ultra-short characteristic relaxation times. Here we demonstrate that efficient hard tissue prepolarization is within reach with a special-purpose 0.26 T scanner designed for dental MRI and equipped with suitable high-power electronics. We have characterized the performance of a 0.5 T prepolarizer module which can be switched on and off in just 200 us. To that end, we have used resin, dental and bone samples, all with T1 times in the order of 20 ms at our field strength. The measured SNR enhancement is in good agreement with a simple theoretical model, and small deviations in extreme regimes can be attributed to mechanical vibrations due to the magnetic interaction between the prepolarization and main magnets. Finally, we argue that these results can be applied to clinical dental imaging, opening the door to replacing hazardous X-ray systems with low-field PMRI scanners.