Conducting dielectric samples are often used in high-resolution unwanted signals arising from inaccurate flip angles or other experiments at high field. It is shown that significant amplitude effects. Often phase cycles are used to select particular coand phase distortions of the RF magnetic field may result from herence types. For a chemical compound exhibiting spinperturbations caused by such samples. Theoretical analyses demspin coupling, spatial heterogeneity in the RF phase will lead onstrate the spatial variation of the RF field amplitude and phase to the generation of spatially dependent coherences during across the sample, and comparisons of the effect are made for a multipulse experiments which, at the least, may degrade the variety of sample properties and operating field strengths. Alsignal-to-noise ratio (SNR) of the experiment and, at the though the effect is highly nonlinear, it tends to increase with worst, can lead to the generation of spurious coherences. If increasing field strength, permittivity, conductivity, and sample both RF amplitude and phase distortions exist across the size. There are cases, however, in which increasing the conductivity sample, then the efficacy of phase cycling may be reduced.
of the sample improves the homogeneity of the amplitude of the RF field across the sample at the expense of distorted RF phase.
The origin of the distorted B 1 field can be either inherent It is important that the perturbation effects be calculated for the inhomogeneities in the RF coil itself and/or sample-induced experimental conditions used, as they have the potential to reduce perturbations (neglecting transmitter and other spectrometerthe signal-to-noise ratio of NMR experiments and may increase based errors). Here we consider samples with a range of the generation of spurious coherences. The effect of RF-coil geomeconductivities, permittivities, sizes, and irradiation at various try on the coherences is also modeled, with the use of homogeneous frequencies as well as the use of either saddle-type RF coils resonators such as the birdcage design being preferred. Recomor birdcage resonators. We have recently shown that birdmendations are made concerning methods of reducing samplecage resonators may be effectively designed and fabricated induced perturbations. Experimental high-field imaging and highfor high-resolution applications (9).
resolution studies demonstrate the effect.