Quantitative magnetization transfer imaging using balanced SSFP.

Area of Science:

• Magnetic Resonance Imaging
• Biophysics
• Quantitative Imaging

Background:

• Balanced steady-state free precession (bSSFP) signal formation is typically modeled solely by relaxation times and flip angle.
• Magnetization transfer (MT) effects in tissues can significantly alter bSSFP signal, necessitating a revised analytical description.
• Existing models may not fully capture the complexities of bSSFP signal in biological tissues.

Purpose of the Study:

• To derive an extended bSSFP signal equation incorporating magnetization transfer (MT) effects.
• To develop a model for quantitative MT parameter estimation using bSSFP.
• To evaluate the feasibility of high-resolution quantitative MT mapping in the human brain.

Main Methods:

• Derivation of an extended bSSFP signal equation using a binary spin-bath model.
• Application of the model to derive quantitative MT parameters (fractional pool size, exchange rates, relaxation times) in the human brain.
• Assessment of factors influencing model quality, including B(1) field inhomogeneities and off-resonances.

Main Results:

• An extended bSSFP signal equation accounting for MT effects was successfully derived.
• Quantitative MT parameters were estimated in normal-appearing human brain tissue.
• The derived bSSFP model showed good correspondence with established quantitative MT models.
• bSSFP demonstrated potential for high-resolution, isotropic quantitative MT mapping in the brain.

Conclusions:

• The revised bSSFP model accurately describes signal formation in the presence of MT effects.
• Quantitative MT parameters can be reliably derived from bSSFP data.
• bSSFP is a promising technique for rapid, high-resolution quantitative MT imaging of the brain.