Quantitative T₂ mapping using accelerated 3D stack-of-spiral gradient echo readout.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Quantitative Imaging
• Biomedical Engineering

Background:

• T2 mapping is crucial for tissue characterization in MRI.
• Existing T2 mapping protocols can be time-consuming, limiting clinical applications.
• Accelerated acquisition and reconstruction methods are needed for faster imaging.

Purpose of the Study:

• To develop a rapid T2 mapping protocol using optimized spiral acquisition.
• To accelerate image reconstruction and improve T2 estimation accuracy.
• To evaluate the proposed method's performance and its ability to mitigate partial voluming effects.

Main Methods:

• A T2-prepared stack-of-spiral gradient echo pulse sequence was employed.
• Model-based approaches combined with compressed sensing were used for accelerated reconstruction.
• A 2-parameter-weighted fitting method was compared against other models for T2 estimation, considering noise and B1 inhomogeneity.
• The technique was validated using digital phantoms and healthy volunteers, including tests for cerebrospinal fluid (CSF) partial voluming mitigation.

Main Results:

• The 2-parameter-weighted fitting demonstrated robustness to varying B1 scales and signal-to-noise ratio (SNR) levels.
• The model-based compressed sensing method achieved approximately 8% normalized errors with an in-plane acceleration factor of 5.
• T2 estimations were consistent with literature values, both with and without CSF nulling.

Conclusions:

• A feasible T2 quantification technique enabling 3D high-resolution, whole-brain coverage in 2-3 minutes was demonstrated.
• The iterative reconstruction method, integrating model consistency, data consistency, and spatial sparsity, provided reliable T2 estimation.
• The technique effectively mitigated the cerebrospinal fluid partial volume effect.