@article {10.3844/ajassp.2014.534.540, article_type = {journal}, title = {A HIGH B1 FIELD HOMOGENEITY GENERATION USING FREE ELEMENT ELLIPTICAL FOUR-COIL SYSTEM}, author = {Ghaly, Sidi M. Ahmed and Al-Sowayan, Sulaiman S.}, volume = {11}, year = {2014}, month = {Jan}, pages = {534-540}, doi = {10.3844/ajassp.2014.534.540}, url = {https://thescipub.com/abstract/ajassp.2014.534.540}, abstract = {Design and testing of a prototype probe with high B1 magnetic field homogeneity that can be used for MRI is presented. It consists of four coaxial separately tuned rings of wire in a symmetric arrangement on an ellipsoidal surface. Compared to Helmholtz pair, which presents 2nd-order homogeneity, an improvement in field homogeneity is achieved, while preserving the simplicity of implementation. The proposed probe has an identical self-resonance frequency for all coils to allow easy tuning. The position and diameter of each ring are optimized so that the assembly produces a 6th-order homogeneous field. A complete electrical model of the four-coil system taking into account all coupling effects permits to determine the resonance frequency in the co-current mode and consequently to predict the value of the tuning capacitors. Resulted field homogeneity of the proposed four-coils are compared to that of Helmholtz coil which shows an improvement of 58% in field homogeneity profile when considering 10% profile uniformity width. Moreover, compared to the homologous Helmholtz coil, the proposed four-coil prototype possesses a better quality factor and therefore leads to an improved Nuclear Magnetic Resonance (NMR) sensitivity.}, journal = {American Journal of Applied Sciences}, publisher = {Science Publications} }