Effects of T₂ * on accuracy and precision of dynamic T₁ measurements using the single reference variable flip angle...

Area of Science:

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

Background:

• Accurate T1 quantification is crucial for various MRI applications.
• Dynamic T1 measurements are sensitive to confounding factors like T2* variations.
• Existing single-reference variable flip angle (SR-VFA) methods can introduce bias.

Purpose of the Study:

• To evaluate the accuracy and precision of dynamic T1 measurements using SR-VFA.
• To investigate the impact of dynamic T2* changes on SR-VFA T1 calculations.
• To develop and validate a corrected SR-VFA method (SR-VFA-T2*) for improved T1 mapping.

Main Methods:

• Monte Carlo simulations (1000 iterations) were performed for VFA, SR-VFA, and SR-VFA-T2* methods.
• Analytical calculations modeled signals using the steady-state spoiled gradient echo equation.
• Parameters varied included repetition time (TR), T1, T2*, flip angles, and echo time (TE).

Main Results:

• SR-VFA method exhibited significant bias (approx. 1% for 0.01 T2* deviation) due to dynamic T2* changes.
• SR-VFA-T2* method, using multiecho measurements for T2* correction, demonstrated comparable or superior bias and precision to VFA.
• An analytical variance equation for SR-VFA-T2* accurately predicted simulation results, enabling inverse-variance weighted T1 mapping.

Conclusions:

• Multiecho SR-VFA-T2* T1 mapping offers a promising alternative to conventional VFA methods.
• This technique maintains the speed of SR-VFA while achieving accuracy and precision similar to VFA.
• The SR-VFA-T2* method effectively corrects for dynamic T2* variations, enhancing T1 quantification reliability.