MRI pulse sequence

Figure 5.5.8 shows the volume selective spectroscopy pulse sequence used. This pulse sequence combines elements of NMR spectroscopy and MRI pulse sequences three slice selective rf pulses are applied in three orthogonal directions to obtain 1H spectra from pre-determined local volumes within the sample [30]. In this particular application, spectra were recorded from local volumes of dimension 1.5 mm x 1.5 mm x 0.5 mm within the fixed bed the data acquisition time for each spectrum was 3 min. Figure 5.5.9(a) shows the local volumes selected within slice 3 of the bed, as identified in Figure 5.5.7. In Figure 5.5.9(b) the 1H spectra recorded from within these volumes are shown data are presented only for the range of... 

This section introduces the reader to the basic principles of MRI and the concept of the k-space raster. The basic MRI pulse sequence, the spin-echo imaging sequence, is described at this point. For more detailed discussion of the background theory of MRI the interested reader should refer to texts by Callaghan5 and Kimmich.6... 

II.2 The simplest MRI pulse sequence spin-echo imaging... 

Fig. 10 Spatially resolved 13C DEPT (or 13C DEPT-MRI) pulse sequence. This provides signal enhancement for 13C observation without need for using isotopically enriched materials. The signal is acquired under conditions of H decoupling.

Recently, Sederman and co-workers (755) used the DEPT MRI pulse sequence described in Section V.A.2 to investigate 1-octene hydrogenation occurring over a l-wt.% Pd/Al2O3 catalyst in a trickle-bed reactor. The reactor was of inner diameter... 

Temporal variation of magnetic field gradients along the X, Y, and Z axes a so-called pulse sequence for image acquisition is applied for MRI measurements. Several procedures have been developed for an effective determination of the spatial distribution of the spins. A detailed description of MRI pulse sequences is available in explanations by Callaghan,37 Blumich,38 and Kimmich.39... 

Figure 2. Example of a basic MRI pulse sequence with the spin-echo.

While the simple schematic of Fig. 4 allows us to appreciate the concept of obtaining spatial resolution in the measurement, it is almost impossible to understand and design MRI pulse sequences using this approach. Instead, the approach used is that of the so-called k-space raster, introduced by Mansfield (1977). 

Pulsed magnetic resonance experiments are represented by parallel time lines of the applied pulses and the signal (Figure 50.4A). We will introduce this formalism here to explain the spin-echo and, in the next section, the spin-echo MRI pulse sequence. The first line is the time line of the applied B pulses, also refeiTed to as radioffequency, or RF pulses because they are applied at the Larmor frequency, which are typically in the radiofrequency range. 

In this chapter, the most important 3D MRI pulse sequences commonly used in the clinical routine will be reviewed. 

Jackson EF, Ginsberg EE, Schomer DF, Leeds NE. A review of MRI pulse sequences and techniques in neuroimaging. Surg Neurol 1997 47 185-199. 

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