Influence of radiofrequency amplifier nonlinearities on nuclear magnetic resonance image quality.
The quality of nuclear magnetic resonance (NMR) image is degraded by a number of disturbing influences. In this article the influence of a nonlinear radiofrequency receiving amplifier is investigated. The effect of a cubic nonlinearity on the NMR signal is analyzed. Finally, the influence on the NMR image is studied for Fourier reconstruction techniques. As a result, the images are degraded by an additional term which is proportional to a parameter characterizing the nonlinearity. The additional term causes homogeneous objects to appear inhomogeneous and gives rise to image intensity outside the object. Under normal conditions the image degradation is negligible.
D000669:Amplifiers, Electronic; D005374:Filtration / Q000295:instrumentation; D005583:Fourier Analysis; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D008961:Models, Structural