Time suspension

In combination with multi-pulse excitation, rotating-frame imaging can also be used for imaging of solids [Choi]. A time-suspension multi-pulse sequence (cf. Table 3.1) is applied to the sample by use of an rf coil with a homogeneous B field so that both... 

Multi-pulse sequences for line narrowing based on magic echoes represent another possibility to realize time-suspension. Such sequences are less difficult to implement than pulse sequences based on solid echoes and consequently, appear to be more popular for use in imaging. Therefore, they are treated separately in Section 8.8. 

Fig. 8.7.3 Proton images (bottom) of a phantom made from poly (acetal) (Delrin) acquired with the time-suspension pulse sequence of Fig. 8.6.2, The field of view is (5.9 mm). The sample (top) has been imaged in three dimensions at 400 MHz with a voxel size of 92 x 92 x 625(pLtti). Adapted from [Corl2] with permission from Flsevier Science.

In order to preserve the effect of the gradients on the evolution of magnetization in a time-suspension sequence, the gradient pulses must be applied with alternating polarity in successive free-evolution windows of the magic-echo sequence. In this case, the evolution of the density operator can be expressed similar to (8.8.2),... 

FIGURE 10.1 The volume of suspension for a pigment (Isol Benzidine Yellow, GA-PR, 9500). Primes are used to distinguish surface properties. (O) = long time suspension ( ) = suspension for shorter times ( ) = reaction. 

Figure 24. A schematic of the apparatus used to measure the specific resistance to filtration. This is a useful empirical method for comparing suspensions. With a defined pressure for filtration, coupled with the quantification of the filtrate produced as a function of time, suspension characteristics can he compared.

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