Quantitative mapping of chemical compositions with MRI using compressed sensing.

In this work, a magnetic resonance (MR) imaging method for accelerating the acquisition time of two dimensional concentration maps of different chemical species in mixtures by the use of compressed sensing (CS) is presented. Whilst 2D-concentration maps with a high spatial resolution are prohibitively time-consuming to acquire using full k-space sampling techniques, CS enables the reconstruction of quantitative concentration maps from sub-sampled k-space data. First, the method was tested by reconstructing simulated data.

Ultrafast magnetic-resonance-imaging velocimetry of liquid-liquid systems: overcoming chemical-shift artifacts using compressed sensing.

We present simultaneous measurement of dispersed and continuous phase flow fields for liquid-liquid systems obtained using ultrafast magnetic resonance imaging. Chemical-shift artifacts, which are otherwise highly problematic for this type of measurement, are overcome using a compressed sensing based image reconstruction algorithm that accounts for off-resonant signal components. This scheme is combined with high-temporal-resolution spiral imaging (188 frames per second), which is noted for its robustness to flow.

Exploring the origins of turbulence in multiphase flow using compressed sensing MRI.

Ultrafast magnetic resonance imaging, employing spiral reciprocal space sampling and compressed sensing image reconstruction, is used to acquire velocity maps of the liquid phase in gas-liquid multiphase flows. Velocity maps were acquired at a rate of 188 frames per second. The method enables quantitative characterization of the wake dynamics of single bubbles and bubble swarms.

Time resolved velocity measurements of unsteady systems using spiral imaging.

Spiral imaging has been assessed as a tool for the measurement of spatially and temporally resolved velocity information for unsteady flow systems. Using experiments and simulated acquisitions, we have quantified the flow artefacts associated with spiral imaging. In particular, we found that despite the adverse effect of in-plane flow on the point spread function, for many physical systems the extent of blurring associated with spiral imaging is marginal because flows represented by high spatial Fourier coefficients, which would be those most affected by the distortion of the point spread function, exist at the physical boundaries of the flow and are therefore associated with much smaller velocities than are characteristic of the bulk flow.

'Snap-shot' velocity vector mapping using echo-planar imaging.

A 'snap-shot' ultra-fast MRI velocimetry technique based upon the echo-planar imaging (EPI) pulse sequence is presented. The new technique is an extension of the GERVAIS pulse sequence previously developed by Sederman et al. (2004) and is capable of acquiring both reference and velocity encoded phase maps following a single excitation for generation of three-component velocity vectors in under 125 ms.