%0 Journal Article %J Journal of Physical Chemistry A %D 2011 %T Remotely Detected MRI Velocimetry in Microporous Bead Packs %A Halpern-Manners, N. W. %A Paulsen, J. L. %A Bajaj, V. S. %A Pines, A. %K gradients %X

Many NAIR and MRI methods probe fluid dynamics within macro- and mesoporous materials, but with few exceptions, they report on its macroscopically averaged properties. MRI methods are generally unable to localize microscopic features of flow within macroscopic samples because the fraction of the enclosing detector volume occupied by these features is so small. We have recently overcome this problem using remotely detected MRI velocimetry, a technique in which spatial, chemical, and velocity information about elements of the flow is encoded with a conventional NMR coil and detected sensitively at the sample outflow by a volume-matched microdetector. Here, we apply this method to microporous model systems, recording MRI images that correlate local velocity, spin relaxation, and time-of-flight in microscopic resolution and three spatial dimensions. Our results illustrate that remotely detected MRI is an effective approach to elucidate flow dynamics in porous materials including bead pack microreactors and chromatography columns.

%B Journal of Physical Chemistry A %V 115 %P 4023-4030 %8 Apr 28 %@ 1089-5639 %G English %U ://WOS:000289697500039 %N 16 %M WOS:000289697500039 %! Remotely Detected MRI Velocimetry in Microporous Bead Packs %R Doi 10.1021/Jp109728j %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2008 %T Volume-selective magnetic resonance imaging using an adjustable, single-sided, portable sensor %A Paulsen, J. L. %A Bouchard, L. S. %A Graziani, D. %A Blumich, B. %A Pines, A. %K xenon %X

Portable, single-sided NMR sensors can operate under conditions inaccessible to conventional NMR while featuring lower cost, portability, and the ability to analyze arbitrary-sized objects. Such sensors can nondestructively probe the interior of samples by collecting images and measuring relaxation and diffusion constants, and, given careful shimming schemes, even perform chemical analysis. The inherently strong magnetic-field gradients of single-sided sensors developed so far has prevented imaging of materials with high water content, such as biological tissues, over large volumes whereas designs with more homogeneous fields suffer from low field strength and typically cannot probe volumes larger than approximate to 10 cm(3). We present a design with a continuously adjustable sensitive volume, enabling the effective volume to be enlarged several fold. This capability allows for imaging in reasonable times of much bigger objects and opens the door to the possibility of clinical imaging with portable sensors. We demonstrate MRI in axial and sagittal planes, at different depths of the sensitive volume and T(1)-weighted contrast in a tissue sample.

%B Proceedings of the National Academy of Sciences of the United States of America %V 105 %P 20601-20604 %8 Dec 30 %@ 0027-8424 %G English %U ://WOS:000262092800008 %N 52 %M WOS:000262092800008 %! Volume-selective magnetic resonance imaging using an adjustable, single-sided, portable sensor %R Doi 10.1073/Pnas.0811222106