Imaging with CPMG echoes

RARE rapid acquisition with relaxation enhancement 

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Fig. 6.2.9 [Mor2] Imaging with CPMG echoes, (a) Pulse sequence and A-space trajectories for relaxometric imaging, (b) The RARE sequence for rapid imaging. This sequence is also referred to as turbo spin-echo imaging.

Fig. 2.4.4 Profile of a sample made from two latex layers 70 pm thick separated by a 150 pm thick glass spacer. The full profile is the combination of 10 images with an FOV of 50 pm, covering a total depth of 500 pm. Each of these images is the FT of the echo signal obtained as the addition of the first 16 echoes acquired during a CPMG sequence and 512 scans with...

The T2 distribution has applications as diverse as petroleum geology and bread making. It distribution has been applied in the petroleum industry for many years to characterize rock cores to obtain pore size distributions in well-logging operations. Rock cores from oil wells are filled with water or oil. The NMR CPMG echo train is acquired in a TD-NMR instrument and the T2 distribution is obtained. This is essentially a mirror image of pore size distribution, as water in small pores is more restricted it is less mobile (short T. Water in large pores has more freedom to move (long Tj). 

Our method is demonstrated with experiments on a Bentheimer sandstone sample. The sample was prepared to be cylindrically shaped with a diameter of 2.5 cm and a length of 2.0 cm. The sample was fully saturated with de-ionized water under vacuum. We performed the CPMG imaging experiment described in the previous section to measure the magnetization intensity at 50 echoes spaced by 4.6 ms for each of 32 x 16 x 16 voxels within the field of view of 3.0 cm x 3.0 cm x 3.0 cm. The corresponding voxel size is 0.938 mm x 1.88 mm x 1.88 mm. We used 1 s of repetition time (TR) and the total imaging time was 4.3 min. 

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