Electrical permittivity imaging at 3T: a precision and accuracy study of three $$$ \it{B_1^+}$$$ mapping techniques

The feasibility of permittivity imaging relies on high precision of the underlying $$$\it{B_1^+}$$$ amplitude maps. We tested AFI, Bloch-Siegert and DREAM $$$\it{B_1^+}$$$ mapping techniques on a pelvic-sized phantom at 3T, comparing their SNR in $$$\it{B_1^+}$$$ maps and (resulting) permittivity precision. Our results indicated that the DREAM-based permittivity map was the most sensitive to sequence-related systematic errors. The commonly-used AFI technique, instead, was the least precise method. We also found that Bloch-Siegert is generally best suited for permittivity mapping compared to the other two methods, due to its higher $$$\it{B_1^+}$$$ precision and accuracy.