Homospoil gradient

Fig. 7 A chemical shift imaging pulse sequence. The MR signal is spatially encoded prior to acquiring the spectral signal in the absence of any applied magnetic field gradients. The shaded gradient pulses applied along z either side of the n refocusing pulse are homospoil gradients.

Pulse schemes similar to that of the offset-saturation method, often with a homospoil gradient pulse to destroy any x-y magnetization, have been utilized in off-resonance Tip experiments to study intermediate molecular motions in biological systems [107-111] and inorganic compounds [112] from... 

Neuhaus et al. first introduced FLIPSY (flip angle adjustable one-dimensional NOESY) in 1996 and re-evaluated the pulse sequence in 2008 for use with meta-bonomics projects. The modified FLIPSY is similar to the original (Figure 6C) with the exception of a small homospoil gradient prior to the flip-angle controlled pulse and just after the presaturation period. 

Even though it is amusing to form echoes practically at will, these echoes are not always a blessing. For many of the T pulse sequences to be described in III.D.2., the steady state sequence, for example, the echoes must be suppressed before the application of the following pulse. This is usually accomplished by a weak pulsed field gradient called the homospoil pulse applied between the rf pulses (and after the FID has been recorded) or by reversing the phases... 

This problem was noticed in the earliest experiments in partially relaxed multiline spectra (Void, et al. 1968). A simple solution is to alternate the phase of the n/2 pulse between sequences and appropriately add or subtract the FID s from memory (Demco, et al., 1974 Levy and Peat, 1975 Cutnell, et al., 1976). Circuits for alternating the phase are described in the above references. An alternative approach is to destroy these components precessing in the x -y plane following the n pulse with a "homospoil pulse. For example, a 50 ma dc pulse applied for 5 to 10 ms to the z gradient coils with an additional wait of 50 to 100 ms before the n pulse for recovery of the homogeneity suffices (Demco, et al. 1974). 

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