Retrograde pulses

Composite 90° pulses, which are optimized for high sensitivity towards Bi variation are called narrow-band pulses. They are also referred to as retrograde pulses. 

Subclavian steal is caused by retrograde flow in the vertebral artery. It is a common angiographic or ultrasound finding when there is stenosis or occlusion of the subclavian artery proximal to the vertebral artery origin, particularly on the left, or of the innominate artery. When the ipsilateral arm is exercised, the increased blood flow to meet the metabolic demand may be enough to steal more blood down the vertebral artery, away from the brainstem into the axillary artery. If there is poor collateral blood flow to the brainstem, then symptoms may occur, but this is very rare. The subclavian disease is almost always severe enough to be detectable by unequal radial pulses and blood pressures, and often there is a supraclavicular bruit (Cho et al. 2007). 

Fig. 5.3.11 The effect of prograde and retrograde composite pulses on the magnetization as a function of the actual flip angle with reference to a nonselective pulse P. (a) 90° pulses Bz and C2, respectively [Wiml]. (b) 180° pulses and Q, respectively [Shal],...

Originally, the concept of prograde and retrograde composite pulses was developed for inversion pulses [Shal]. For instance, a prograde inversion pulse, is obtained for (Fig. 5.3.11(b)) [Shal]... 

Various studies have been carried out on the gelatinization and retrogradation processes of starch. Starch gelatinization was followed by pulsed H NMR by... 

Pulsed NMR of rice starch during gelatinization and retrogradation... 

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