B1 mapping in MRI system using k-space spatial frequency domain filtering
First Claim
Patent Images
1. A method for generating a B1 map in an MRI system, said method comprising using an MRI system to:
- (a) acquire at least one set of B1 amplitude tagged MRI data signals in spatial frequency domain k-space from MR nuclei within an imaged volume of the MRI system;
(b) process said k-space data to produce at least two sub-sets of frequency-filtered k-space data;
(i) a baseline low-frequency sub-set, and (ii) at least one of a positive higher frequency sub-set including a harmonic version of said baseline sub-set and a negative higher frequency sub-set including a harmonic version of said baseline sub-set;
(c) separately transform each of said sub-sets to respectively corresponding spatial domain data sets;
(i) a baseline magnitude set, and (ii) at least one of a positive harmonic magnitude set and a negative harmonic magnitude set;
(d) arithmetically combine said baseline magnitude set with said at least one of the harmonic magnitude sets on a pixel-by-pixel basis to provide upper and lower magnitude data sets;
(e) process said upper and lower magnitude data set values on a pixel-by-pixel basis to generate a B1 map value based on value related to a ratio of said upper and lower pixel data values at a given pixel location in the spatial domain; and
(f) store said B1 map of values in a computer accessible and readable memory device for subsequent use by said MRI system.
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Abstract
Frequency filtering of spatially modulated or “tagged” MRI data in the spatial frequency k-space domain with subsequent 2DFT to the spatial domain and pixel-by-pixel arithmetic calculations provide robust ratio values that can be subjected to inverse trigonometric functions to derive B1 maps for an MRI system.
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Citations
25 Claims
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1. A method for generating a B1 map in an MRI system, said method comprising using an MRI system to:
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(a) acquire at least one set of B1 amplitude tagged MRI data signals in spatial frequency domain k-space from MR nuclei within an imaged volume of the MRI system; (b) process said k-space data to produce at least two sub-sets of frequency-filtered k-space data;
(i) a baseline low-frequency sub-set, and (ii) at least one of a positive higher frequency sub-set including a harmonic version of said baseline sub-set and a negative higher frequency sub-set including a harmonic version of said baseline sub-set;(c) separately transform each of said sub-sets to respectively corresponding spatial domain data sets;
(i) a baseline magnitude set, and (ii) at least one of a positive harmonic magnitude set and a negative harmonic magnitude set;(d) arithmetically combine said baseline magnitude set with said at least one of the harmonic magnitude sets on a pixel-by-pixel basis to provide upper and lower magnitude data sets; (e) process said upper and lower magnitude data set values on a pixel-by-pixel basis to generate a B1 map value based on value related to a ratio of said upper and lower pixel data values at a given pixel location in the spatial domain; and (f) store said B1 map of values in a computer accessible and readable memory device for subsequent use by said MRI system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. An MRI system comprising:
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(a) an MRI scanner configured to acquire at least one set of B1 amplitude tagged MRI data signals in spatial frequency domain k-space from MR nuclei within an imaged volume of the MRI system; at least one processor configured to; (b) process said k-space data to produce at least two sub-sets of frequency-filtered k-space data;
(i) a baseline low-frequency sub-set, and (ii) at least one of a positive higher frequency sub-set including a harmonic version of said baseline sub-set and a negative higher frequency sub-set including a harmonic version of said baseline sub-set;separately transform each of said sub-sets to respectively corresponding spatial domain data sets;
(i) a baseline magnitude set, and (ii) at least one of a positive harmonic magnitude set and a negative harmonic magnitude set;arithmetically combine said baseline magnitude set with said at least one of the harmonic magnitude sets on a pixel-by-pixel basis to provide upper and lower magnitude data sets; process said upper and lower magnitude data set values on a pixel-by-pixel basis to generate a B1 map value based on a value related to a ratio of said upper and lower pixel data values at a given pixel location in the spatial domain; and (c) a data memory configured to store said B1 map of values in a computer accessible and readable memory device for subsequent use by said MRI system.
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Specification