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Rapid B1 field mapping at 3 T using the 180° signal null method with extended flip angle
Abinand C Rejimon1, Diana Y Lee1, Christopher M Bergeron1
1Laboratory of Clinical Investigation, National Institute on Aging, NIH, 251 Bayview Boulevard, Baltimore, MD 21224, USA.
Magnetic Resonance Imaging
|July 1, 2018
Summary
The extended angle-range null signal method (EA-NSM) improves B1 mapping accuracy in 3T MRI by expanding the flip angle range. This fast and accurate method is suitable for clinical settings.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Quantitative MRI
- Radiofrequency (RF) field
Background:
- The null signal method (NSM) is used for B1 mapping in MRI.
- Conventional NSM has limitations with large B1 variations common in high-field MRI (3T).
- This necessitates an extension of the NSM for accurate B1 mapping at 3T.
Purpose of the Study:
- To extend the null signal method (NSM) for B1 mapping to 3 Tesla (T) magnetic resonance imaging (MRI).
- To improve the accuracy of B1 mapping at higher magnetic field strengths.
Main Methods:
- Analyzed the effect of flip angle (FA) range on NSM B1 determination at 3T.
- Developed and validated the extended angle-range NSM (EA-NSM).
- Compared EA-NSM with conventional NSM and the double angle method (DAM).
- Investigated compatibility with acceleration techniques like half-scan and SENSE.
Main Results:
- Conventional FA range in NSM leads to significant B1 inaccuracies at 3T.
- Expanding the FA range (EA-NSM) substantially improves B1 map accuracy.
- EA-NSM B1 maps are quantitatively comparable to the time-consuming DAM.
- EA-NSM is compatible with acceleration methods, enabling whole-brain B1 mapping in ~1 minute.
Conclusions:
- The EA-NSM provides accurate, fast, and practical B1 mapping at 3T.
- This extended method is suitable for clinical MRI applications.
- EA-NSM overcomes limitations of conventional NSM in high-field settings.
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