Free-breathing simultaneous native myocardial T1, T2 and T1ρ mapping with Cartesian acquisition and dictionary...

Area of Science:

• Cardiovascular Imaging
• Magnetic Resonance Imaging
• Biomedical Engineering

Background:

• Quantitative cardiac MRI relies on T1, T2, and T1ρ parameters for myocardial tissue characterization.
• Conventional methods for simultaneous T1, T2, and T1ρ mapping involve separate or prolonged breath-hold acquisitions, leading to potential registration issues or patient intolerance.
• There is a need for efficient, free-breathing techniques to obtain co-registered multi-parametric maps for comprehensive cardiac assessment.

Purpose of the Study:

• To develop and validate a free-breathing multi-parametric mapping (FB-MultiMap) technique for simultaneous quantification of myocardial T1, T2, and T1ρ.
• To achieve co-registered parameter maps in a single, efficient acquisition, overcoming limitations of conventional methods.
• To enable comprehensive myocardial tissue characterization, including fibrosis and edema, in a patient-friendly manner.

Main Methods:

• The FB-MultiMap technique utilizes electrocardiogram-triggered, single-shot Cartesian acquisition over 16 cardiac cycles with T1, T2, and T1ρ preparations.
• Prospective through-plane motion correction via diaphragmatic navigator and retrospective in-plane motion correction using group-wise image registration were employed.
• Quantitative mapping was performed using dictionary matching with Bloch simulations, incorporating subject-specific dictionaries for T1, T2, T1ρ, and B1 inhomogeneity.

Main Results:

• Phantom studies showed FB-MultiMap T1, T2, and T1ρ values agreed well with reference measurements, independent of heart rate.
• In healthy subjects, FB-MultiMap T1 values were slightly higher than MOLLI (1218 ± 50 ms vs. 1166 ± 38 ms, p < 0.001).
• FB-MultiMap T2 and T1ρ values were comparable or lower than conventional 2D balanced steady-state free precession methods (T2: 41.2 ± 2.8 ms vs. 42.5 ± 3.1 ms, p = 0.06; T1ρ: 45.3 ± 4.4 ms vs. 50.2 ± 4.0 ms, p < 0.001), and pathological changes in patients were consistent with conventional techniques.

Conclusions:

• The proposed FB-MultiMap technique enables simultaneous, co-registered myocardial T1, T2, and T1ρ mapping in a single, efficient free-breathing acquisition.
• This method achieves comparable mapping quality to conventional breath-hold techniques.
• FB-MultiMap offers a patient-friendly approach for comprehensive myocardial tissue characterization.