Reducing Inhomogeneous MT (ihMT) Acquisition Time Using Frequency Alternation at Low Duty Cycle for Single Offset...

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysics
• Neuroimaging

Background:

• Inhomogeneous Magnetization Transfer (ihMT) MRI is crucial for myelin imaging.
• Current ihMT protocols can be time-consuming, limiting clinical applications.
• Faster acquisition methods are needed to improve the utility of ihMT in neurological studies.

Purpose of the Study:

• To evaluate Frequency Alternation at Low duty cycle for Single Offset (FALSO) MT as a novel preparation scheme.
• To assess FALSO MT's potential to increase speed and spatial resolution of ihMT MRI.
• To determine if FALSO MT reduces the number of required acquisition volumes.

Main Methods:

• Compared FALSO MT to standard single frequency MT preparations.
• Utilized signal simulations and ihMT data from rat and human brains at 3T and 9.4T.
• Acquired high-resolution ihMT data (down to 1.4 mm isotropic) using FALSO MT with optimized Variable Flip Angle (VFA) MPRAGE readouts.

Main Results:

• No statistically significant difference in ihMT ratios between FALSO MT and standard ihMT methods.
• VFA readouts enabled high-resolution ihMT imaging with fewer volumes and reduced variance.
• FALSO MT effectively controls for MT asymmetry, similar to standard ihMT.

Conclusions:

• FALSO MT preparations reduce acquisition requirements for ihMT while managing MT asymmetry.
• VFA readouts combined with FALSO MT enhance spatial and/or temporal resolution.
• This combination facilitates clinical translation and improves ihMT's utility in myelin-related neurological research.