title: Design of a 3T preamplifier which stability is insensitive to coil loading.
abstract: In MRI (magnetic resonance imaging), preamplifiers are needed to amplify signals obtained from MRI receiver coils. Under various loading conditions of the corresponding receiver coils, preamplifiers see different source impedance at their input and may become unstable. Therefore preamplifiers which stability is not sensitive to coil loading are desirable. In this article, a coil-loading-insensitive preamplifier for MRI is presented, derived from an unstable preamplifier. Different approaches to improve stability were used during this derivation. Since a very low noise factor is essential for MRI preamplifiers, noise contributions from passive components in the MRI preamplifier have to be considered during the stabilization process. As a result, the initially unstable preamplifier became stable with regard to coil loading, while other MRI requirements, as the extremely low noise factor, were still fulfilled. The newly designed preamplifier was manufactured, characterized and tested in the MRI spectrometer. Compared to a commercially available preamplifier, the newly designed preamplifier has similar imaging performance but other advantages like smaller size and better stability. Furthermore, presented stabilization approaches can be generalized to stabilize other unstable low-noise amplifiers.
authors.affiliation: Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany. Electronic address: xueming.cao@uniklinik-freiburg.de.
authors.forename: Xueming
authors.initials: X
authors.lastname: Cao
authors.affiliation: Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Elmar
authors.initials: E
authors.lastname: Fischer
authors.affiliation: Institute of Microstructure Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany.
authors.forename: Jan G
authors.initials: JG
authors.lastname: Korvink
authors.affiliation: Institute of Microstructure Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Gruschke
authors.affiliation: Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hennig
authors.affiliation: Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Maxim
authors.initials: M
authors.lastname: Zaitsev
keywords: High gain; Low noise; Preamplifier; Small size; Stability