Overview of Solid Imaging Techniques

Furthermore, they applied the initial 90° RF pulse at a zero crossing of a sinusoid, so that the RF power requirement was simply that associated with a solid. 

Imaging with multi-pulse line narrowing 

Multiple pulse (MP) sequences work on the spin part of the interaction Hamiltonian, and are based on the original ideas of Ostroff and Waugh75 and 

Mansfield and Ware76 of extending the time domain signal of dipolar coupled systems by applying a cyclic train of 90° pulses. An MP sequence typically consists of a train of several hundred RF pulses comprising repeated sets of n pulses,2 with 4 48. If the sequence is applied at a rate sufficiently rapid compared with the value of the linewidth to be narrowed, it will average to zero dipolar interactions within the sample, while the chemical-shift interaction is either scaled or eliminated, depending on the type of MP sequence used. 

An alternative approach to solid imaging is the CW-NMRI technique, which uses continuous-RF irradiation and detection in the presence of continuously applied, moderately strong gradients. This technique offers a number of advantages compared to other solid imaging techniques  

---