Investigation of the radio frequency magnetic field inside a hollow cylinder used for nuclear magnetic resonance imaging

The homogeneity of the radio frequency (rf) axial magnetic field inside a s olenoid composed of a set of current-carrying coils can be improved by impo sing appropriate current densities in the various loops that constitute the structure. In the case of a hollow cylinder made from a single sheet of co pper foil, the rf field so generated can also attain a similar degree of ho mogeneity without current compensation provided the copper foil is five to six times thicker than the skin depth and the cylinder's form factor (diame ter/length) is of the order or less than 0.5. Numerical calculations based on some basic equations allow us to predict the rf field pattern of a cylin der of given dimensions. Experimental results obtained from a 32 MHz transm ission line resonator show good agreement between theory and practice. The filling factor of this type of cylinder can also be evaluated from these ca lculations. (C) 1999 American Institute of Physics. [S0034-6748(99)03204-9] .