Analytical approach to noncircular section birdcage coil design: verification with a Cassinian oval coil.

A general analytical framework is presented for the design of birdcage radiofrequency resonators on cylindrical formers having arbitrary cross-sectional shape. The primary objective of such shapes would be to improve the sensitivity of the NMR experiment to noncircular regions of the human anatomy while maintaining field homogeneity and quadrature polarization comparable to those of standard circular birdcage coils. The shape of the corresponding radiofrequency screen, which is required to decouple the coil from the rest of the NMR system and which is key to the performance, is also provided by this methodology.

Comments on "theoretical model for an MRI radio frequency resonator".

In contrast to a previous report [Baertlein et al. (2000)], the transverse electomagnetic resonator used in magnetic resonance imaging is shown to be similar to the high-pass "birdcage" resonator in having an electric field minimum in correspondence with the maximum of the magnetic field. The noise performance of each resonator will, in consequence, be comparable, since at high frequencies patient conductive losses are predominant.