NMR flow imaging

Rombaoh K, Laukemper-Ostendorf and Blumler P 1998 Applioations of NMR flow imaging in materials soienoe Spatially Resolved Magnetic Resonance, Proc. 4th Int. Cent, on Magnetic Resonance Microscopy and Macroscopy ed P Blumler, B Blumioh, R E Botto and E Fukushima (Weinheim Wiley-VCFI) pp 517-29... 

We would like to thank Peter Blunder and Simone Laukemper-Ostendorf who initially established the collaboration between the company Membrana and the RWTH. They started NMR flow imaging studies to characterize filtration in hemodialyzer modules, and Volker Gobbels measured the first 2D VEXSY data of counterflow in such applications. All experimental work has been accomplished in the Magnetic Resonance Center (MARC) directed by Bernhard Bliimich, whose support and leadership is greatly acknowledged. 

K. Rombach, S. Laukemper-Ostendorf, P. Bluemler 1998, (Applications of NMR flow imaging in materials science), in Spatially Resolved Magnetic Resonance, eds. P. Bluemler, B. Bluemich, R. Botto, E. Fukushima, Wiley-VCH, New York. 

Figure 13.. Comparison of theoretical analysis and empirical NMR imaging of fluid flow during extrusion. Limiting cases for theoretical analysis (a), the velocity profile as a function of position with no pressure gradient in the z-direction (b), the velocity profile as a function of position with no net flow through the extruder. Limiting cases for empirical analysis by NMR flow imaging (c), no pressure gradient in the z-direction (die open) (d), no net flow through the extruder (die closed).[Reproduced with permission from Ref.61].

Integration of biaxial planar gradient coils and an RF microcoil for NMR flow imaging, Meas. Sci. Technol. 2005,16, 505-512. 

NMR Methods. Altobelli et al. (82) and Sinton and Chow (83) studied solid velocity and concentration profiles of flowing slurries using NMR flow imaging techniques. These profiles were obtained from the displacement of a tagged slice oriented perpendicular to the flow direction using fast Fourier reconstruction algorithms (83). 

Fig. 2.6.5 Hardware for high field NMR remote probe in (c) contains a relatively large saddle-detection. Photographs (a) and (b) show la- coil and is used for (flow) imaging. The detec-boratory-built remote detection probes with tor probe in (d) contains a microsolenoid coil both rf coils built into the same body (c), (d) for optimized mass sensitivity, which is parti-and (e) are detector-only remote probes that cularly useful for microfluidic NMR applica-can be inserted from the top or bottom into the tions. The same probe is shown in (e) with a NMR imaging assembly, so that the well mounted holder for a microfluidic chip that is...

In summary, we have commented briefly on the microscopic applications of NMR velocity imaging in complex polymer flows in complex geometries, where these applications have been termed Rheo-NMR [23]. As some of these complex geometries can be easily established in small scales, NMR velocimetry and visc-ometry at microscopic resolution can provide an effective means to image the entire Eulerian velocity field experimentally and to measure extensional properties in elastic liquids non-invasively. 

The key challenge for the successful use of NMR velocity-imaging techniques to characterize fluid flow properties is the interpretation of the measured parameters. Different experimental strategies provide information about flow processes at different spatial and dynamic scales in porous media. In principle, the flow velocity can be probed either as a local quantity with an image resolution below the pore level,2425 or as a macroscopic flow property corresponding to local volume and temporal averages of fluid molecular displacements.26 One must develop a suitable methodology to correctly determine the parameters that best describe the properties of interest. 

Instead of polarized noble gases, thermally polarized NMR microimaging was used to study of liquid and gas flow in monolithic catalysts. Two-dimensional spatial maps of flow velocity distributions for acetylene, propane, and butane flowing along the transport channels of shaped monolithic alumina catalysts were obtained at 7 T by NMR, with true in-plane resolution of 400 xm and reasonable detection times. The flow maps reveal the highly nonuniform spatial distribution of shear rates within the monolith channels of square cross-section, the kind of information essential for evaluation and improvement of the efficiency of mass transfer in shaped catalysts. The water flow imaging, for comparison, demonstrates the transformation of a transient flow pattern observed closer to the inflow edge of a monolith into a fully developed one further downstream. 

Figure 5 NMR microscopy images of tablet dissolution. The images show the behavior of an erodible matrix containing an internal scaffold, within a flow-through dissolution cell. Images A-D were obtained under static conditions, images E-H and I-L were obtained at 4 and 16 mL/min flow, respectively. The rows represent images taken at 0.5, 3, 6, and 10.5 hours. The full width of the image is equivalent to 16 mm in the sample. Source From Ref. 92.

U. TaDarek, E. Rapp, H. van As, E. Bayer, Using NMR displacement imaging to characterize electroosmotic flow in porous media. Magn. Reson. Imaging, 2001, 19, 453 56. 

---