Non-Cartesian sampled centric scan SPRITE imaging with magnetic field gradient and B0(t) field measurements for MRI in the vicinity of metal structures

Abstract

This paper proposes the possibility of spatially resolved MRI measurements undertaken inside metallic cells. MRI has been rarely usable inside conducting vessels due to the eddy currents in the walls caused by switching magnetic field gradients, which render most advanced MRI pulse sequences impossible. We propose magnetic field gradient waveform monitoring (MFGM) for MRI of samples inside metallic cells. In this work the MFGM method was extended to measure the B(0) field temporal evolution associated with gradient waveforms. MFGM was used to observe and correct eddy current effects associated with a metallic cell. High quality centric scan SPRITE images result from such corrections. MRI of samples held under pressure, most notably rock core samples, traditionally employs cells that are non-magnetic and fabricated from polymeric materials. The natural material for high-pressure MRI is however non-ferromagnetic metal given their high tensile strengths and high thermal conductivity. MRI measurement of macroscopic samples at high pressure would be generally possible if metallic pressure vessels could be employed. This study will form the basis of new MRI compatible metallic pressure vessels, which will permit MRI of macroscopic systems at high pressure.