Real-Time Imaging of Granular Dynamics with Advanced MRI Methods

Probing non-intrusively the dynamics of 3D granular systems is a challenging task for which only a few techniques can be applied including positron emission tomography, X-ray tomography and magnetic resonance imaging (MRI). A remarkable advantage of MRI is its versatility since not only voidage but also velocity, acceleration and chemical reactions can be probed by implementing dedicated MR pulse sequences and image reconstruction algorithms. However, the largest systems studied with MRI so far have a diameter of 60 mm. In such systems wall effects cannot be neglected. Additionally only single-channel detection has been applied, limiting the maximal temporal resolution achievable

Here, we report methodological advances to substantially boost temporal resolution of MRI in large granular systems (diameter 194 mm), i.e. the simulation and construction of tailored, 16-channels detection hardware to acquire data in parallel, and the implementation of efficient single-shot echo-planar imaging (EPI) MR pulse sequences featuring phase contrast encoding, allowing us to probe particle velocity in highly dynamic systems in real-time.