Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1999-01-27
2000-10-03
Oda, Christine K.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324309, 324322, G01V 300
Patent
active
061278262
ABSTRACT:
A method of calibrating pre-emphasis gradient pulse conditioning for long term eddy current compensation in an MRI system is provided. It includes positioning an object in the MRI system for imaging therewith. A long term eddy current generating pre-scan gradient pulse is applied, and after a delay, an EPI sequence is run such that a resulting image of the object is acquired. This process of applying the pre-scan gradient pulse followed by the EPI sequence is repeated while varying the delay therebetween. Size variations in the resulting images of the object are observed, and these size variations are fit to an exponential curve to obtain one or more time constants for the long term eddy currents. Next, a reference EPI sequence is run without applying the long term eddy current generating pre-scan gradient pulse such that a reference image of the object is acquired. The long term eddy current generating pre-scan gradient pulse is reintroduced, and after a delay which is shorter than the time constants, a test EPI sequence is run such that a test image of the object is acquired. The process of applying the pre-scan gradient pulse followed by the test EPI sequence is repeated while adjusting the pre-emphasis gradient pulse conditioning which is based upon the time constants obtained. This continues until the test images of the object have a size substantially equivalent to that of the reference image.
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Dannels Wayne R.
Loncar Mark J.
Schlitt Heidi A.
Thompson Michael R.
Oda Christine K.
Picker International Inc.
Shrivastav Brij B.
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