5545999 Preamplifier circuit for magnetic resonance system

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partial coil (Cli through Cpi) has, in each case, as small a separation from the middle plane as possible generally equal to the separation of the radially inner field current pair (2a, 2b) from the middle plane and whereby each correction pair has, in each case, at least one second partial coil (Cla through Cpa) with an oppositely directed current which has a larger axial separation from the middle plane than the radially inner field coil pair (2a, 2b).

5545998

MIXING DEVICE FOR THE MIXING OF FLUIDS IN AN NMR APPARATUS INCLUDING A SPRING ATTACHED TO THE COIL AFFIXED TO A MIXING ROD Favre Patrick; Frey Urban; Marek Daniel; Metz Fran Lausanne, SWITZERLAND assigned to Spectrospin AG

A mixing device for the mixing of fluid measuring samples in an NMR measuring device, whereby the measuring device includes a rod which is arranged coaxially to the main field magnet coil of the NMR measuring device to be movable in the axial direction and, on one end, exhibits a piston projecting into the measuring sample and, with the assistance of a drive coil arranged at the end facing away from the measuring sample, is moved in the axial direction when current flows through the drive coil, wherein a spring element is provided to move the rod into a rest position when no current flows through the drive coil, is characterized by the drive coil being arranged, in an axially movable fashion, in the inhomogeneous region of the magnetic field produced by the main field magnet coil coaxial to the main field magnet coil, the drive coil, on one axial end, being rigidly connected to the rod and, on the end facing away from the rod, being connected, via the spring element, to a housing surrounding the NMR measuring apparatus. In this fashion the mixing device does not require magnetic components which would interfere with the homogeneity of the NMR magnetic field and can be arranged compactly in the vicinity of the measuring sample.

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5545999

PREAMPLIFIER CIRCUIT FOR MAGNETIC RESONANCE SYSTEM Mueller Otward M; Yakymyshyn Christopher P; Roemer Peter B; Watkins Ronald D Ballston Lake, NY, UNITED STATES assigned to General Electric Company A circuit for amplifying signals received by the receive coil of a magnetic resonance (MR) system includes a preamplifier employing an active circuit device, such as a GaAs-MESFET or HEMT. The preamplifier is located proximate to the receive coil in order to maintain as high a signal-to-noise ratio as possible for the preamplifier output signals. A capacitance is coupled to the receive coil to form an input impedance matching network for the input of the preamplifier. The preamplifier output is coupled through a fiber optic cable to remotely located MR signal processing electronics, which further processes signals received by the MR receive coil and amplified by the preamplifier.

5546000

METHOD FOR THE REDUCTION OF RADIATION DAMPING DURING SIGNAL ACQUSITION IN NMR EXPERIMENTS Maas Werner E; Cory David G; Laukien Frank H Billerica, MA, UNITED STATES assigned to Bruker Instruments Inc A method of reducing radiation damping during free induction decay in NMR measurements of samples having a narrow line width uses the active switching of the quality factor value of the coil circuit of an NMR detection probe. After application of an excitation pulse to the sample, data acquisition is accomplished in periodic samples. The Q of the coil circuit is set to a high value while each sample is being taken, but is reduced significantly in between samples by detuning the coil circuit. Minimization of the high-Q state of the coil circuit and maximization of the difference between the high Q value and the low Q value greatly decrease the detrimental effects of radiation damping on free induction decay. The coil circuit Q is modified automatically by the application of a Q switching sig-