However, when two-tail t-tests were performed on the fitted results, no significant difference was found at 5% significant level, except for the 100 mM creatine concentration at pH 6 ( Fig. 6c). This study illustrates

the differences in z-spectra obtained using continuous and pulsed saturation, and how these discrepancies can affect the quantified parameters such as ωw and Clabile using continuous and discretized model-based analysis. As suggested by Zu et al. [33], the differences are caused by the irradiation schemes used, where CW-CEST is able to saturate the protons more efficiently, leading to narrower off-resonance buy Trametinib excitation around the frequency offset of water and amine protons, as shown in the simulated ( Fig. 1) and measured ( Fig. 4a) results. It is apparent from Fig. 4b that the discretized model-based approach was able to fit better than its continuous (AP) counterpart but the smaller fitted errors of the former did not translate to significantly better quantification of ωw and Clabile, as shown in Figs. 5 and 6. Although AF is not suitable for fitting the z-spectrum, one of the reviewers suggests that the magnitude of its CESTR may be approximately equal to the CESTR calculated from AP for certain pulsed parameters and labile proton exchange rate. The quantified results of ωw verify that model-based analysis ERK inhibitor can be used to determine water center frequency shift due to

field inhomogeneity and that the additional

WASSR scan is not necessarily required when the full z-spectrum is available. When the two-tailed t-test was performed for the estimated Clabile for 100 mM creatine phantom at pH 6, the quantified parameter (Clabile) using different model-based approaches was found to be significantly different, as shown in Fig. 6c. This may be caused by the strong correlation between each of the following factors: T2w [25], FA and Mlabile, with Clabile. The influence of T2w and FA on Clabile is significant because the resonance frequency of the amine protons investigated is just 1.9 ppm away from the water protons. Mlabile was estimated from the literature and derived from the equilibrium condition which makes the absolute quantification of each of them (Clabile and Mlabile) difficult. As suggested by Sun et al. [38], performing Avelestat (AZD9668) model fitting on data measured from multiple RF saturation magnitudes may be one of the ways to achieve independent quantification of the previous two parameters because optimal RF power varies strongly with Clabile but has minimal dependence on Mlabile. However, this is not the scope of this study as only a single B1 was used to perform the saturation. When model fitting was performed on the collected CEST data, all these parameters (T2w, FA, Mlabile0 and Clabile) were allowed to vary, the strong correlation between them might have contributed to the significantly different result in the quantification of Clabile.