![Understanding Spectra of [sup(31)]P MRS and [sup(1)]H MRS](https://images.tandf.co.uk/common/jackets/crclarge/978042925/9780429257087.jpg "Understanding Spectra of [sup(31)]P MRS and [sup(1)]H MRS")
ABSTRACT
Magnetic resonance peaks are often split into
3. MAJOR PARAMETERS OF MRS multiplets, and the spin-spin coupling is responsible for this splitting. The spin-spin coupling is
The major parameters of MRS-chemical shift, caused by an interaction between spins which is spin-spin coupling and relaxation time-are ex-mediated by bonding electron^.^ The magnitude of
plained, as are the techniques of Nuclear Over-the spin-spin interaction between nuclei is called
hauser Effect (NOE), and proton decoupling. the spin-spin coupling constant U), which has the unit of Hz. As shown in Figure 3-1 of the 31P
3. l . l Chemical shift spectrum of ATP, 31P signals of a-and y-ATP are
The magnetic field experienced by a nucleus is split into doublets through the coupling to neigh-
not exactly the same as applied magnetic field B,, boring 31P nucleus of 8-ATP, and the signal of because the small field Bn6 at the nucleus is 8-ATP is split into triplet through coupling to two
neighboring 31P nuclei of r a n d y-ATP. produced by the electron cloud within the molec ~ l e . ~ The orientation of the Bob is parallel to the
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3.1 .3 Relaxation mechanisms field B, in paramagnetic effect and in the opposite direction to the field B, in the diamagnetic effect. Relaxation is a process where the spin energy
The effective magnetic field Be,, at the nucleus is reverts to equilibrium after perturbation of the spin system caused by the resonance absorption of
expressed as3 radiation. Relaxation plays an important role in
(2 ) Spin-spin (transverse) relaxation Spin-spin relaxation is a process based on
energy transfer between individual spins, via a flip-flop type me~hanism.~ In the spin-spin relaxation system, no energy is transferred from the nuclei to the lattice. Spin-spin relaxation time or transverse relaxation time (T,) is a time constant in this process. Measured T, value is shorter than true T, value because of the inhomogeneity of the magnetic field,, and T," is customarily used for showing the measured T,.
