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.
Highlights
INTRODUCTIONMagnetic hyperthermia in MRI coils with high B1 field homogeneity and sensitivity cancer therapy (Di Barba et al, 2010), Magnetic are built with multiple radiating elements
Design and testing of a prototype probe with high B1 magnetic field homogeneity that can be used for MRI is presented
A complete electrical model of the four-coil system taking into account all the coupling effects will enable us to carry out the conditions of a correct operation in co-current mode which will be the mode of interest for the proposed application
Summary
Magnetic hyperthermia in MRI coils with high B1 field homogeneity and sensitivity cancer therapy (Di Barba et al, 2010), Magnetic are built with multiple radiating elements. It Resonance Imaging (MRI) (Pulyer and Hrovat, 2002), is already known that the addition of further coaxial plasma physics experiments (Anderson, 1999), rings in a Helmholtz-type design can improve calibration of magnetic fields (Bongiraud et al, 1999) homogeneity (Hoult and Deslauriers, 1990). A complete electrical model of the four-coil system taking into account all the coupling effects will enable us to carry out the conditions of a correct operation in co-current mode which will be the mode of interest for the proposed application
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