Very Fast Multi Channel B1 Calibration at High Field in the Small Flip Angle Regime
نویسندگان
چکیده
Transmit SENSE. For this purpose, an ROI was drawn in the occipital lobe (white ROI Fig3) and two B1 Phase Shim solutions were calculated and applied in order to obtain an homogeneous B1 magnitude within this ROI: one based on the estimated B1 maps, another one based on the measured B1 maps. As can be seen in Fig3 (in degrees), both B1 Shim sets produced tremendous improvement in B1 efficiency and B1 homogeneity (the same RF power was used for the 3 AFI B1 maps, nominal flip angle 70°. Only B1 Phases were adjusted with B1 Shim). The mean flip angle [+/-std] rose from 40° [+/-6.9] in Fig4A (before B1Shim) to 69° [6.0] in Fig4B (B1 Shim based on measured B1 maps) and 73° [7.9] in Fig4C (B1 Shim based on estimated B1 maps). Those estimated B1 maps should be compared to those in Fig.2C, obtained with a multichannel B1 mapping technique which does involve a large flip angle acquisition[1]. Even though these maps are not identical, they share very strong similarities and an interesting question is to determine whether those Very Fast Multi Channel B1 Calibration at High Field in the Small Flip Angle Regime
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