Spiral 3DREAM sequence for fast whole-brain B1 mapping.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Quantitative MRI
• Neuroimaging

Background:

• Accurate whole-brain proton density (PD) mapping is crucial for quantitative MRI.
• Traditional methods like Cartesian 3DREAM suffer from blurring due to long echo trains, especially with decreasing signal.
• Reducing echo train length is key to overcoming signal decay and image degradation.

Purpose of the Study:

• To introduce a novel variant of the 3DREAM sequence using a 3D stack-of-spirals readout for whole-brain PD mapping.
• To evaluate the performance of the spiral 3DREAM sequence in reducing blurring and improving image quality compared to existing methods.

Main Methods:

• Developed a spiral 3DREAM sequence replacing the Cartesian readout with an accelerated 3D stack-of-spirals readout and CAIPIRINHA sampling.
• Acquired two contrasts rapidly to calculate whole-brain flip angle maps.
• Validated the sequence through phantom experiments comparing it to Cartesian 3DREAM, AFI, dual-angle, and Bloch-Siegert methods, followed by in vivo validation in five subjects.

Main Results:

• The spiral 3DREAM sequence demonstrated high agreement with reference methods in both phantom and in vivo experiments.
• Significantly reduced blurring in STE* images and flip angle maps compared to the Cartesian 3DREAM sequence.
• Achieved faster acquisition and increased effective resolution for PD maps.

Conclusions:

• The spiral 3DREAM sequence effectively minimizes echo train length via a fast readout, reducing STE* image blurring.
• This advancement leads to shorter total acquisition times and enhanced effective resolution for quantitative PD mapping.
• The spiral 3DREAM sequence offers a promising alternative for efficient and high-quality whole-brain mapping.