Using the ERETIC Method^1,2 (Electric Reference To access In vivo Concentrations) an electromotive force (emf) is directly generated in the receiving coil via a small induction loop. This emf translates into a detectable signal depending on the loading of the coil in the same manner as the emf generated by the excited spins of metabolites present in the tissue. And therefore the ratio of the ERETIC signal ($$$S_{ERETIC}$$$) and the metabolite signal is independent of the coil loading condition. This allows to reference the in vivo metabolite signal to a signal measured in a phantom while directly correcting for differences in loading between the in vivo and in vitro measurement. Therefore metabolite concentrations can be determined without the need of assumptions about concentrations of internal references as for example the tissue water. However in contrast to the signal generated by excited spins the ERETIC signal contains no information about the $$$B_1$$$-field during transmission or reception. When $$$S_{ERETIC}$$$ is used as reference, changes in $$$B_1^+$$$ or $$$B_1^-$$$ between the in vivo and in vitro measurement or at different positions will be consequently misinterpreted as changes of the metabolite concentration. In this work, we demonstrate the impact of this problem and propose a 2-step solution to correct for changes in the reception sensitivity and the use of a volume based power optimization to avoid differences during transmission. The obtained in vivo concentrations are compared to values obtained using the internal water as reference³ (IWR).A modified version of the 3T ERETIC setup attached to a commercial T/R head coil presented by Heinzer-Schweizer² was used. To demonstrate its ability to correct for the loading of the coil a series of measurements were performed in a spherical phantom filled with water while an additional plastic bottle containing a NaCl solution was stepwise inserted into the coil. At every position of the bottle $$$S_{ERETIC}$$$ and the water signal $$$S_{H2O}$$$ were recorded. In 21 healthy volunteers always three VOI arranged in one plane were measured. One VOI was placed at the center position (M) in the longitudinal cerebral fissure just above the corpus callosum containing mostly gray matter and the other two were shifted by 20 mm respectively to the left (position L) and to the right (position R) into cerebral white matter. Water-suppressed inner-volume saturated PRESS-localized spectra (TE:30 ms, TR:1800 ms, 256 averages) were recorded with an effective voxel size of 5 ml. For IWR a water unsuppressed scan (TR:6000 ms, 16 averages) was carried out at each position. Prior to each scan a volume selective RF power optimization⁴ was performed. Based on the assumption that the reception sensitivity varies similar in vivo and in vitro, the reception sensitivity changes along the FH direction were taken into account by carrying out the calibration measurement in a phantom at the average VOI position along the FH direction used in vivo ($$$c^{E+}$$$). In a second step reception sensitivity differences within the plane containing the three VOIs along AP and RL direction ($$$c^{E++}$$$) were corrected. For this purpose contrast minimized images were acquired and corrected for $$$B_1^+$$$ using Bloch-Siegert shift maps⁵, revealing the in plane reception sensitivity⁶ changes for each subject. To verify these reception sensitivity corrections Internal water concentrations obtained with ERETIC are compared with values predicted based on the individual voxel composition ($$$f$$$: volume fraction) and the relative water densities α (Tab.1):$$c ^{seg}=55.126\cdot(f_{CSF}\cdot\alpha_{CSF}+f_{GM}\cdot\alpha_{GM}+f_{WM}\cdot\alpha_{WM}) \qquad\text{[Eq.1]}$$ Metabolite concentrations obtained with IWR and ERETIC include relaxation attenuation correction [Table1] and partial volume correction. All signals were fitted using LCModel including the ERETIC signal¹³.The ERETIC setup is capable of correcting for the different loading conditions [Figure1]. With all proposed corrections of the reception sensitivity [Figure2] the agreement between ERETIC based water concentrations and values predicted by segmentation ($$$c^{seg }$$$) is improved and inequalities between the left and right hemisphere are corrected. But nevertheless also with $$$c^{E++}$$$ only an averaged effect of the receptions sensitivity changes along the FH direction is corrected. 3D reception sensitivity maps could therefore improve the correction for the cost of additional scan time⁵. Mean metabolite concentrations estimated in vivo with IWR ($$$c^{IWR}$$$) and ERETIC ($$$c^{E++}$$$) agree [Figure3]. The deviations between the reference methods in some subjects [Figure4] could potentially be reduced by using 3D reception sensitivity maps for correction, but to some extent also subject dependent variations from the assumed water relaxation times and relative water densities can cause these deviations. In conclusion, the ERETIC method is a reliable quantification method if $$$B_1$$$-field variations during transmission and reception are considered carefully.