Spin images

As an analogy to an electron cloud, imagine the spinning blades of a fan. You know that each blade can be found within the spinning image that you see. However, you cannot tell exactly where any one blade is at a particular moment. 

Fig. 2. Residual spin density at the Ni 211 surface. Dark isosurfaces represent regions of net majority spin light isosimfeces show regions of net minority spin. Image taken fix>m Karmazyn et al [34].

Spin-imaging methods proposed Lauterbur, Nature 2A2 190 Mansfield and Grannell, J. Phys. C6 L422 Damadian, NMR in Medicine, Springer-N rlag... 

Spin-imaging of human limbs and organs Wehrli, Prog. NMR Specdrosc. 28 87... 

Use of polarized rare gases in spin-imaging Albert etal. Nature370 199... 

One further application of measurements is of growing importance. NMR spin-imaging methods can be adapted to detect the spatial variation of and T2, typically that of protons, throughout a body. In this way one can detect objects such as tumors which otherwise merge with their surroundings. 

Figure Bl.14.1. Spin warp spin-echo imaging pulse sequence. A spin echo is refocused by a non-selective 180° pulse. A slice is selected perpendicular to the z-direction. To frequency-encode the v-coordinate the echo SE is acquired in the presence of the readout gradient. Phase-encoding of the > -dimension is achieved by incrementmg the gradient pulse G...

The magnetization profile in the y-direction is recovered by Fourier transfonnation with respect to G. B1.14.2.4 2D SPIN-ECHO FT IMAGING AND K-SPACE... 

Figure Bl.14.5. J2-weighted images of the propagation of chemical waves in an Mn catalysed Belousov-Zhabotinsky reaction. The images were acquired in 40 s intervals (a) to (1) using a standard spin echo pulse sequence. The slice thickness is 2 nun. The diameter of the imaged pill box is 39 nun. The bright bands...

Figure Bl.14.6. J -maps of a sandstone reservoir eore whieh was soaked in brine, (a), (b) and (e), (d) represent two different positions in the eore. For J -eontrast a saturation pulse train was applied before a standard spin-eeho imaging pulse sequenee. A full -relaxation reeovery eiirve for eaeh voxel was obtained by inerementing the delay between pulse train and imaging sequenee. M - ((a) and (e)) and r -maps ((b) and (d)) were ealeulated from stretehed exponentials whieh are fitted to the magnetization reeovery eurves. The maps show the layered stnieture of the sample. Presumably -relaxation varies spatially due to inliomogeneous size distribution as well as surfaee relaxivity of the pores. (From [21].)...

The third alternative is a more robust, sensitive and specialized fonn of the first, in that only hydrogen nuclei indirectly spin-spin coupled to in a specific molecular configuration are imaged. In achieving selectivity, the technique exploits the much wider chemical shift dispersion of compared to H. The metliod involves cyclic transfer from selected H nuclei to indirectly spin-spin coupled C nuclei and back according to the sequence... 

Figure Bl.14.9. Imaging pulse sequence including flow and/or diflfiision encoding. Gradient pulses before and after the inversion pulse are supplemented in any of the spatial dimensions of the standard spin-echo imaging sequence. Motion weighting is achieved by switching a strong gradient pulse pair G, (see solid black line). The steady-state distribution of flow (coherent motion) as well as diffusion (spatially...

Edelstein W A, Hutchison J M S, Johnson G and Redpath T W 1980 Spin warp NMR imaging and appiications to human whoie-body imaging B 25 751-6... 

Mansfieid P 1977 Muiti-pianar image formation using NMR spin echoes J. Rhys. C Solid State Rhys. 10 L55-L58... 

Attard J J, Doran S J, Flerrod N J, Carpenter T A and Flail L D 1992 Quantitative NMR spin-lattice-relaxation imaging of brine in sandstone reservoir cores J. Magn. Reson. 96 514-25... 

Figure Bl.19.30. Height and friction images of a spin-cast polystyrene-poly(methyl methacrylate) blend obtained with (a) gold and (b) silica probes under perfluorodecalin. Note the reversal of frictional contrast and the high spatial resolution. (Taken from [142], figure 7.)...

Once the job is completed, the UniChem GUI can be used to visualize results. It can be used to visualize common three-dimensional properties, such as electron density, orbital densities, electrostatic potentials, and spin density. It supports both the visualization of three-dimensional surfaces and colorized or contoured two-dimensional planes. There is a lot of control over colors, rendering quality, and the like. The final image can be printed or saved in several file formats. 

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