“Magic-angle” NMR imaging in solids
1986; Elsevier BV; Volume: 67; Issue: 1 Linguagem: Inglês
10.1016/0022-2364(86)90424-5
ISSN1557-8968
Autores Tópico(s)Advanced MRI Techniques and Applications
ResumoThe spatial imaging of NMR parameters (1) in solids is technically difficult because of the strong nuclear dipole-dipole interaction. The dipolar interaction actually produces a natural absorption line Atin of several kilohertz that makes it difficult to satisfy the condition yArG, $ Awn necessary to get sufficient spatial resolution Ar. Here, G, is a static linear magnetic gradient and y, as usual, the gyromagnetic ratio. One possible way to overcome this limiting condition for imaging is to reduce the line broadening by multiple-pulse line narrowing sequences (2,3). Another approach proposed the use of multiple-quantum NMR transitions to increase the effective gradient intensity experienced by the spins (4-6). In this paper we propose a new imaging method for solids, which combines line narrowing at the “magic angle” in the rotating frame (7-10) with the full rotating frame NMR imaging technique (1 I). In the frame rotating (RF) at the frequency w around the main static field Bok, parallel to the z axis, the polarized laboratory frame (LF) exciting field c therefore the effective spin Hamiltonian Ze in first-order perturbation theory in this coordinate system is (7, 8, 10)
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