MC BTS: Simultaneously Resolving Magnetization Transfer Effect and Relaxation for Multiple Components

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysical Modeling
• Quantitative Tissue Analysis

Background:

• Accurate multi-component tissue quantification is crucial for understanding tissue properties.
• Existing MRI methods often struggle with simultaneous assessment of relaxation, magnetization transfer (MT), and transmit field (B1+) inhomogeneity.
• Developing a unified framework is essential for comprehensive tissue characterization.

Purpose of the Study:

• To propose a novel signal acquisition and modeling framework for multi-component tissue quantification.
• To simultaneously account for transmit field inhomogeneity, multi-component relaxation, and magnetization transfer (MT) effects.
• To validate the proposed framework through simulations and in vivo experiments.

Main Methods:

• An RF-spoiled gradient-echo sequence with off-resonance irradiation and multiple echo times was employed.
• A three-pool model was developed to describe spin dynamics, including relaxation and spin exchange.
• Analytical signal equations were derived and validated using Bloch simulations and Monte Carlo analyses.
• The method's feasibility was tested in vivo on human brain and knee tissues.

Main Results:

• Simulations demonstrated excellent agreement between the analytical signal equation and numerical models.
• Monte Carlo simulations confirmed the robustness of the three-pool parameter estimation pipeline across various signal-to-noise ratios.
• In vivo multi-parameter fitting in brain and knee yielded results consistent with existing literature.
• The method effectively compensated for B1+ inhomogeneity.

Conclusions:

• A validated signal acquisition and modeling framework for multi-component tissue quantification has been developed.
• The framework effectively incorporates magnetization transfer effects and B1+ inhomogeneity.
• Both simulation and experimental data confirm the method's robustness and applicability to diverse tissues.