Equations describing the multiple-quantum (MQ) signal prospace . Therefore, when a shift reagent is employed duced by an MQ pulse sequence are systematically derived in both in such systems, only the sodium in the extracellular space absence and presence of refocusing RF pulses. When the RF pulses is chemically shifted. The extracellular MQ signal may then in an MQ pulse sequence satisfy certain conditions, these equations be eliminated by use of the off-resonance effects, enabling may be arranged in a factorized form. The off-resonance effects selective acquisition of the intracellular MQ signal. on the MQ signal due to chemical shift can then be analyzed In the MQ pulse sequence with nonrefocused evolution separately during the preparation and evolution times. Using the time, the amplitude of the MQ signal has been found to be reformulated equations, the dependence of the amplitude of an a cosine function of the off-resonance-induced phase shift MQ signal on the phase shift induced by the resonance offset during the evolution time. However, the off-resonance efduring the preparation and evolution times is demonstrated. By fects on the MQ signal have not yet been fully analyzed.
use of the new equations, it is shown that the off-resonance effects, occurring during both the preparation and evolution times, may Furthermore, the previously determined cosine function may be described in terms of the same physical process, i.e., interference not be sufficiently practical for elimination of the extracellubetween echo and antiecho. In applying the off-resonance effects lar signal in the presence of a shift reagent due to the narrow for the elimination of the MQ signal in the presence of chemical bandwidth for elimination. New equations that permit the shift, it is possible to suppress the MQ signal over a wider offanalysis of the off-resonance effects on the MQ signal are resonance bandwidth by use of the nonrefocused preparation and derived here. It is also shown how these effects may be evolution times than by use of a single time. Furthermore, by physically described with the help of a modified coherencetaking an alternative approach in deriving the equations, the interlevel diagram .
ference between echo and antiecho due to the resonance offset is
Recently, new equations for on-resonance double-quanshown to be insensitive to the flip angle of the creation RF pulse tum (DQ) signals with nonvanishing quadrupolar splitting (usually the second p/2 RF pulse). The theoretical findings were (v Q ) have been derived for DQ filtering (7). Compared to experimentally verified by use of a phantom containing sodium in agarose.