Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1988-11-23
1989-08-29
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324322, G01R 3320
Patent
active
048620815
ABSTRACT:
In the absence of signals supplied to gradient field coils (14), radio frequency signals, or magnetic resonance signals received by coil (18), analog-to-digital converters (44, 46) indicate background noise and DC offset. An attenuator (26) attenuates signals from the receiving coil in the absence of magnetic resonance signals. A phase sensitive detector (38) produces real and imaginary signal components both in the absence of magnetic resonance signals during calibration and subsequently during the processing of magnetic resonance signals. The analog-to-digital converters, low pass filters (40, 42), and the phase sensitive detectors inject an undesirable DC offset into the signals. In the absence of a magnetic resonance signal, the digitized output of the analog-to-digital converters is substantially the DC offset plus noise. A statistical analysis routine (64) analyzes the sampled analog-to-digital data in the absence of a magnetic resonance signal. Based on the variation among the samples, the desired level of confidence and accuracy, the statistical analysis means determines how many samples must be averaged to determine the DC noise with the desired confidence. An averaging circuit (66) averages at least the selected number of samplings. DC correction circuits (50, 52) subtract the determined DC offset values for the real and imaginary channels from the real and imaginary magnetic resonance signals in subsequent scans before the magnetic resonance data is reconstructed (54) into an image representations.
REFERENCES:
patent: 4604580 (1986-08-01), Sugiura
patent: 4612504 (1986-09-01), Pelc
patent: 4616133 (1986-10-01), Glover et al.
patent: 4616182 (1986-10-01), Kramer
patent: 4694250 (1987-09-01), Iwaoka
patent: 4766400 (1988-08-01), Fox
Picker International Inc.
Tokar Michael J.
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