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. Author manuscript; available in PMC: 2014 Jan 16.
Published in final edited form as: Magn Reson Med. 2013 Jan 28;70(5):1319–1331. doi: 10.1002/mrm.24593

FIG. 6.

FIG. 6

The optimum number of echoes for fat-corrected R2* mapping is heavily dependent on the underlying R2* value. Plots shows the theoretical noise performance (standard deviation) of fat-corrected R2* mapping as a function of number of TEs, for fixed initial TE (1 ms) and echo spacing (1 ms). Except for low values of R2* (e.g., 40 s−1), there is little benefit to increasing the echo train length beyond 6. Even with 6 echoes, the noise performance of R2* estimation when R2* = 40 s−1, is very good because the signal levels are high compared with tissue with high R2*.