Space-encoding period

Fig. 6.2.3 [Wehl] Principle of spectroscopic Fourier imaging with slice selection. To separate spatial and spectroscopic responses, the spectroscopic evolution must be constant during the space-encoding period fj. The spectroscopic signal is acquired during the detection time tz in the absence of a gradient.

By using the density-matrix formalism for calculation of the detected signal, the evolution of the double-quantum part p2Q of the density matrix during the double-quantum space-encoding period t is needed as an intermediate result [Gun2, Gotl],... 

Fig. 5. Pulse sequence for MR detection of vibration using a radiofrequency field gradient. A binomial 1331 radiofrequency pulse (pulse length D, interpulse delay r) is applied in-phase with the mechanical wave. Thus the vibration period 7V is equal to 4(D + r). The number of cycles can be increased to ensure a better frequency selectivity. The constant RF field gradient generated by a dedicated RF coil allows space encoding without using conventional static field gradients (from Ref. 16 with permission from Elsevier).

Fig. 8.4.1 General scheme for excitation and indirect detection of multi-quantum signals. The evolution operators for generation and reconversion of multi-quantum coherences are denoted by Up and Umi respectively. The space-encoding field gradient is applied during the evolution period t to modulate the precession phases of the multi-quantum coherences.

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