Multiple spin echoes

R. A. Marion, S. M. Klainer, Multiple Spin Echos in Pure Quadrupole Resonance, Journal of Chemical Physics, 67 (1977) 3388. 

As in the case of the single spin-echo detection, the multiple spin-echoes method attenuates magnetization components with short 72(5 ) values and the magnitude of the attenuation increases with increasing echo... 

The excitation schemes, or pulse sequences, that optimize the SNR depend on the relaxation times and frequencies inherent to the quadrupolar nuclei under observation and on the characteristics of the excitation/detection hardware. Focusing first on relaxation times, we define two broad categories (i) 7 , 1 and (ii) 7 2 Tl. Most materials fall in the former category, and the pulse sequences discussed in Sector 4.1.1. all involve the creation and detection of multiple spin echoes, which generally requires that r2e be at least several tens of milliseconds. The most notable exception is RDX, which is in the second category under ambient conditions. For materials with very short 7 ,s such as RDX at elevated temperatures, a single echo pulse sequence, or even a single-pulse FID acquisition, may be required. 

Fig. 11.4. Fast spectroscopic imaging of stroke. SI maps of lactate and NAA. Metabolite intensities are plotted as color-coded overlay on diffusion-weighted images. Intensities were obtained by numerical integration of the peak areas defined in the two spectra below. Data were acquired with the multiple spin echo SI sequence (7 min acquisition time), thus signal resolution is considerably reduced compared to single voxel spectra in Fig. 11.2 or conventional CSI in Fig. 11.3. (Data courtesy of A. Stengel)...

Duyn JH, Frank JA, Moonen CT (1995) Incorporation of lactate measurement in multi-spin-echo proton spectroscopic imaging. Magn Reson Med 33 101-107 Duyn JH, Moonen CT (1993) Fast proton spectroscopic imaging of human brain using multiple spin-echoes. Magn Reson Med 30 409-414... 

Measurement of T2 Values Using Multiple Spin Echoes CPMG... 

Postprocessing suppression methods (see Postprocessing and selective detection-based methods, p. 325) have particular relevance to imaging since insufficient apodization and truncation can result in ringing over a large portion of the spectrum. This is often the case in spectroscopic imaging using multiple spin-echoes. ... 

Williams W D, Seymour E F W and Cotts R M 1978 A pulsed-gradient multiple-spin-echo NMR technique for measuring diffusion in the presence of background magnetic field gradients 1978 J. Magn. Reson. 31 271-82... 

E. D. Ostroff and J. S. Waugh, "Multiple spin echoes and spin locking in solids," Phys. Rev. Letters 16, 1097 (1966). 

Ostroff, E.D. and Waugh, J.S. 1966. Multiple spin echoes and spin blocking in solids. Phys. Rev. Lett. 16 1097-1098. 

---