The Effect of Magnetic Field Inhomogeneity on the Transverse Relaxation of Quadrupolar Nuclei Measured by Multiple Quantum Filtered NMR
✍ Scribed by U. Eliav; T. Kushnir; T. Knubovets; Y. Itzchak; G. Navon
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 153 KB
- Volume
- 128
- Category
- Article
- ISSN
- 1090-7807
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✦ Synopsis
The effects of magnetic fields B 0 and B 1 inhomogeneities on either by a 180Њ pulse in the middle of the creation time in techniques which are commonly used for the measurements of the standard TQF sequence (Fig. 1a) (6) or by selecting a triple-quantum-filtered (TQF) NMR spectroscopy of 23 Na in biopathway (Fig. 1e) in which equal time evolution of p Å 1 logical tissues are analyzed. The results of measurements by pulse and p Å 01 coherences results in an echo (5). sequences with and without refocusing of B 0 inhomogeneities are We have compared the values obtained by the use of the compared. It is shown that without refocusing the errors in the TQF pulse sequence (Fig. 1a) with the full phase cycling of measurement of the transverse relaxation times by TQF NMR 192 steps (7, 8) to those determined from the TQF sequence spectroscopy may be as large as 100%, and thus, refocusing of without the 180Њ pulse and with various pathways (Figs. magnetic field inhomogeneity is mandatory. Theoretical calcula-1b-1e). tions demonstrate that without refocusing B 0 inhomogeneities the For pulse sequences a-d (Fig. 1) the dependence of the spectral width and phase depend on the interpulse time intervals, thus, leading to errors in the measured relaxation times. It is shown TQF spectra intensities on the creation time, t, were anathat pulse sequences that were used for the refocusing of the maglyzed in terms of a difference of two exponentials netic field (B 0 ) inhomogeneity also reduce the sensitivity of the experimental results to radiofrequency (B 1 ) magnetic field inhomo-82