SQUID-based microtesla MRI for in vivo relaxometry of the human brain

TL;DR

This paper demonstrates in vivo measurement of brain tissue relaxation times using SQUID-based microtesla MRI, revealing that T1 and T2 relaxation times are similar at this ultra-low magnetic field, which could impact imaging contrast strategies.

Contribution

First in vivo measurement of T1 relaxation times in the human brain at microtesla magnetic fields using a specialized SQUID system.

Findings

T1 values are within 5% of T2 values at 46 microtesla.

Successful application of SQUID-based MRI for in vivo relaxometry.

Implications for imaging contrast in microtesla MRI.

Abstract

SQUID-based MRI (magnetic resonance imaging) at microtesla fields has developed significantly over the past few years. Here we describe application of this method for magnetic relaxation measurements in the living human brain. We report values of the longitudinal relaxation time T1 for brain tissues, measured in vivo for the first time at microtesla fields. The experiments were performed at 46 microtesla field using a seven-channel SQUID system designed for microtesla MRI and MEG. Values of T1, measured for different tissues at this field, are found to be close (within 5%) to the corresponding values of the transverse relaxation time T2 at the same field. Implications of this result for imaging contrast in microtesla MRI are discussed.