Shimming with MRI gradient
First Claim
Patent Images
1. A magnetic resonance imaging device calibrated by shimming, comprising:
- i. a magnetic circuit constructed from strong permanent magnets;
ii. an adjustable shimming mechanism;
iii. at least one gradient coil (3b);
iv. at least one shimming coil (2a-f);
v. a contained cavity into which at least one sample is introduced and measured;
vi. at least one magnetic resonance RF coil; and
,vii. a plurality of a predetermined distinct N sub measurement volumes,viii. a processing means, wherein said processing means generates a correction table for adjusting said shimming coils by calculating a line shape deviation between a standard reference and a magnetic resonance measured sample at each of said N sub measurement volumes.
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Abstract
A method of correcting active shimming element of a magnetic resonance device, including providing a set of correction values for each shimming element for a given N sub volumes, wherein N is an integer number greater than or equal to 1, detecting irregularities in the magnetic field of the sample regions, optimizing all the shimming elements according to the set of correction values, assessing the regularity of the corrected magnetic field, and reiterating the process until field uniformity is achieved, such that an accurate magnetic resonance measurement of the sample is achieved after a minimum number of iterations.
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Citations
17 Claims
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1. A magnetic resonance imaging device calibrated by shimming, comprising:
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i. a magnetic circuit constructed from strong permanent magnets; ii. an adjustable shimming mechanism; iii. at least one gradient coil (3b); iv. at least one shimming coil (2a-f); v. a contained cavity into which at least one sample is introduced and measured; vi. at least one magnetic resonance RF coil; and
,vii. a plurality of a predetermined distinct N sub measurement volumes, viii. a processing means, wherein said processing means generates a correction table for adjusting said shimming coils by calculating a line shape deviation between a standard reference and a magnetic resonance measured sample at each of said N sub measurement volumes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A calibration method for enhancing the uniformity of the magnetic field of a magnetic resonance imaging (MRI) device within a sample measurement volume by shimming, the method comprising:
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i. creating a set of correction values for each shimming coil in a MRI device having an MRI magnet by; (a) measuring the line shape of a reference standard sample in N sub volumes within said measurement volume; and (b) recording this line shape as a calibration reference; ii. conducting a magnetic resonance measurement of a sample in at least one of said N sub volumes; iii. shimming the magnetic field of said MRI device by disposing a plurality of shimming elements proximate to said MRI magnet and iteratively adjusting the magnetic field of said shimming elements until a line shape of the measurement sample of said sub volume represents a substantially homogeneous magnetic field within said measurement sub volume; and iv. calculating and recording a shimming correction table used for changing said correction values of said shimming coils; wherein said calculating of said shimming correction table is functionally dependent on a deviation between said line shape of said standard sample and the line shape of the measurement sample of said sub volumes. - View Dependent Claims (15, 16, 17)
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Specification