Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1988-06-27
1989-09-26
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324307, G01R 3320
Patent
active
048703613
ABSTRACT:
An MR angiography method in which an angiogram is formed from the difference between amplitude and/or phase information contained in first and second complex images produced by different gradient waveforms in respective first and second types of excitation sequences. The gradient waveforms are chosen so that in the angiogram obtained from the first and second complex images, ideally, signals orginating from excited stationary spin nuclei are not present while the signals orginating from moving spin nuclei, due to flow in blood vessels, are present. However, stationary spin nuclei can be somewhat differently excited in the first and second sequence due to the different gradient waveforms used which cause different eddy currents to flow in metal parts of the apparatus. In the absence of correction, these eddy currents would exert their influence magnetically by causing a smoothly varying phase error in the difference between the first and second complex images resulting in erroneous signal contribution to the angiogram from stationary spin nuclei. This erroneous signal is eliminated by estimating the smoothly varying phase difference before forming the angiogram from the first and second complex images and by thus carrying out a non-linear phase correction.
REFERENCES:
patent: 4609872 (1986-09-01), O'Donnell
patent: 4683431 (1987-07-01), Pattany
patent: 4718424 (1988-01-01), Nishimara
De Graaf Rudolf G.
Groen Johannes P.
In Den Kleef Josephus J. E.
Briody Thomas A.
Haken Jack E.
Slobod Jack D.
Tokar Michael J.
U.S. Philips Corporation
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