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Fast, accurate, and precise mapping of the RF field in vivo using the 180 degrees signal null
journal contribution
posted on 2023-06-07, 14:56 authored by Nicholas DowellNicholas Dowell, Paul S. ToftsRF field B-1 nonuniformity is the largest cause of error in the quantitative measurement of many clinically relevant parameters in MR images and spectra. Knowledge of the absolute flip angles at every region will improve the accuracy and precision of such parameters. This method uses the 180 degrees signal null to construct a flip angle map of the entire brain in less than 4 min, independent of T-1, T-2, and proton density. Three spoiled gradient echo volume acquisitions of the whole brain were made with three different flip angles. The optimum choice of flip angles was determined to be 145 degrees, 180 degrees, and 215 degrees. Linear regression analysis was used to determine the nominal (system calibrated) flip angle required for a signal null at every pixel and thence determine the absolute flip angle at that location. The experiment utilizes an existing MR sequence supplied by the scanner manufacturer. The technique is validated experimentally and a theoretical investigation into the optimum experimental parameters is presented.
History
Publication status
- Published
Journal
Magnetic Resonance in MedicineISSN
0740-3194Publisher
John Wiley & SonsExternal DOI
Issue
3Volume
58Page range
622-630Department affiliated with
- Clinical and Experimental Medicine Publications
Full text available
- No
Peer reviewed?
- Yes
Legacy Posted Date
2009-02-25Usage metrics
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