A Fast 0.5T Prepolarizer Module for Preclinical Magnetic Resonance Imaging

TL;DR

This paper introduces a rapid-switching 0.5T prepolarizer module for preclinical MRI, enhancing image quality and tissue contrast, with electronics capable of switching in hundreds of microseconds for hard tissues.

Contribution

The work presents a novel high-power electronics setup enabling fast switching of the prepolarization field, suitable for imaging hard biological tissues with short T1 times.

Findings

Enhanced magnetization and image SNR demonstrated with PMRI.

Electronics can switch off the prepolarization field in tens of milliseconds.

Development of electronics capable of ~300 microsecond switching times.

Abstract

We present a magnet and high power electronics for Prepolarized Magnetic Resonance Imaging (PMRI) in a home-made, special-purpose preclinical system designed for simultaneous visualization of hard and soft biological tissues. PMRI boosts the signal-to-noise ratio (SNR) by means of a long and strong magnetic pulse which must be rapidly switched off prior to the imaging pulse sequence, in timescales shorter than the spin relaxation (or T1) time of the sample. We have operated the prepolarizer at up to 0.5 T and demonstrated enhanced magnetization, image SNR and tissue contrast with PMRI of tap water, an ex vivo mouse brain and food samples. These have T1 times ranging from hundreds of milli-seconds to single seconds, while the preliminary high-power electronics setup employed in this work can switch off the prepolarization field in tens of milli-seconds. In order to make this system suitable for solid-state matter and hard tissues, which feature T1 times as short as 10 ms, we are developing new electronics which can cut switching times to ~300 us. This does not require changes in the prepolarizer module, opening the door to the first experimental demonstration of PMRI on hard biological tissues.