Validation of single reference variable flip angle (SR-VFA) dynamic T₁ mapping with T₂ * correction using a novel...

Area of Science:

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

Background:

• Accurate T₁ mapping is crucial for various MRI applications, including tissue characterization and contrast agent quantification.
• Traditional T₁ mapping techniques can be time-consuming or susceptible to artifacts.
• Dynamic T₁ mapping offers the potential for improved temporal resolution in imaging.

Purpose of the Study:

• To validate single reference variable flip angle (SR-VFA) dynamic T₁ mapping against inversion recovery (IR) T₁ measurements.
• To assess the impact of T₂ * correction on the accuracy of SR-VFA T₁ mapping.
• To evaluate the performance of SR-VFA T₁ mapping under varying rotational speeds and echo times (TEs).

Main Methods:

• A custom agar phantom with a spatial gradient of T₁ relaxation rates was used.
• Inversion recovery (IR) T₁, variable flip angle (VFA) T₁, and B₁⁺ measurements were acquired.
• Multi-echo stack-of-radial dynamic images were acquired during phantom rotation, and B₁⁺-corrected SR-VFA and SR-VFA-T₂ * T₁ maps were computed and compared to IR T₁ maps.

Main Results:

• Both VFA and SR-VFA-T₂ * T₁ maps achieved accuracy within 10% of IR T₁ measurements at low rotational speeds (mean accuracy: 2.3% ± 2.6% and 2.8% ± 2.6%, respectively).
• Increasing rotational speed reduced accuracy due to temporal smoothing, particularly where T₁ slope was non-constant.
• T₂ * correction consistently improved the accuracy and precision of SR-VFA T₁ maps, especially at later echo times.

Conclusions:

• SR-VFA-T₂ * dynamic T₁ mapping demonstrates accuracy within 10% of reference IR T₁ measurements in an agar phantom.
• The method is sensitive to rotational speed and echo time, with T₂ * correction enhancing performance.
• Further validation in mixed fat-water phantoms and in vivo is warranted.