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. Author manuscript; available in PMC: 2015 Jul 30.
Published in final edited form as: NMR Biomed. 2014 Jan 3;27(3):240–252. doi: 10.1002/nbm.3054

Figure 8.

Figure 8

Region of interest (ROI) evaluation of the three point methods: APT*, the spillover-corrected MTRRex and the spillover- and T1-compensated AREX. Similar to the phantom study, APT* shows a strong decrease with B1 for values higher than 1.5 µT, whereas MTRRex and AREX show a smaller decrease in signal for higher B1. This pattern is similar to the phantom results (cf. Fig. 5) and indicates validity of the spillover correction. However, the plateau of the full-saturation limit is not reached, probably as a result of contamination of the reference scan. It is important to note that the differences between signals in the stroke lesion and normal tissue are much more significant after spillover correction and T1 compensation. Under the assumption of equal amide concentrations in stroke and normal tissue, the signal drop reflects a change in exchange rate of about a factor of two. APT, amide proton transfer; AREX, apparent exchange-dependent relaxation; MTRRex, spillover-corrected magnetization transfer ratio yielding Rex.