Fast magnetization transfer saturation imaging of the brain using MP2RAGE T₁ mapping

Area of Science:

• Neuroimaging
• Biophysics
• Magnetic Resonance Imaging

Background:

• Magnetization transfer saturation (MT_sat) mapping assesses brain tissue macromolecular content.
• Variable flip angle (VFA) T₁ mapping is a common, but slower, method for MT_sat imaging.

Purpose of the Study:

• Compare VFA T₁ mapping with compressed-sensing MP2RAGE (csMP2RAGE) T₁ mapping for accelerating MT_sat imaging.
• Evaluate the speed, accuracy, and repeatability of different T₁ mapping techniques for MT_sat applications.

Main Methods:

• Acquired VFA, MP2RAGE, and csMP2RAGE protocols in phantoms and 4 healthy subjects at 3 T.
• Compared T₁ and MT_sat measurements across methods.
• Used Bloch-McConnell simulations to investigate discrepancies.
• Assessed repeatability of csMP2RAGE MT_sat in 10 healthy controls.

Main Results:

• csMP2RAGE was significantly faster than VFA (32.4% acceleration).
• All methods showed good phantom repeatability and T₁ accuracy (<5% difference).
• In vivo VFA T₁ values were higher than MP2RAGE/csMP2RAGE, potentially due to magnetization transfer effects.
• csMP2RAGE demonstrated high repeatability with minimum detectable changes of 2.3% for T₁ and 7.8% for MT_sat.

Conclusions:

• MP2RAGE can replace VFA T₁ mapping in MT_sat protocols.
• csMP2RAGE offers accelerated scan times and high repeatability for MT_sat imaging.
• csMP2RAGE is a viable alternative for efficient and reliable assessment of brain tissue macromolecular content.