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. Author manuscript; available in PMC: 2013 Jan 1.
Published in final edited form as: Magn Reson Med. 2012 Mar 12;69(1):127–136. doi: 10.1002/mrm.24241

Figure 4. Constrained Cramér-Rao bounds as coefficients of variation.

Figure 4

Parameter values are listed as sets 1–5 in Table 1, and accurate constraints on T2,S,T2,F, andkFS are assumed. This study was performed at σSPGR = 1 × 10−3 M0, which corresponds to a clinically-feasible SNR for gradient echo sequences, and it should be noted that coefficients of variation scale with image SNR. The dotted lines on each plot are a reference goal for quantitative precision. There is a drastic improvement in free-parameter precision when the T2s and exchange rate are constrained. Acquiring using multiple phase cycling patterns in the SSFP images does not benefit precision as it does when parameters are left unconstrained, but still removes a source of bias; i.e., the implicit assumption of B0 homogeneity described previously (25).

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