Optimization of Scan Parameters for T1-FLAIR Imaging at 1.5 and 3T using Computer Simulation

Abstract

We attempted to optimize scan parameters for T₁-weighted fluid-attenuated inversion recovery (T₁-FLAIR) sequence at 3 and 1.5 tesla (T) using computer simulation. We measured the T₁ and T₂ relaxation time values (T₁v and T₂v) of gray (GM) and white matter (WM) at 3 and 1.5T, generated computer-simulated T₁-FLAIR (CS-T₁-FLAIR) images using those values, and compared the simulated and actual T₁-FLAIR images to verify the contrast reliability of our computer simulation. We mathematically and visually evaluated CS-T₁-FLAIR images at various repetition times (TR) and echo times (TE). At 3T, the measured relaxation values for GM were T₁v, 1524 ms, and T₂v, 85 ms, and for WM, T₁v, 750 ms, and T₂v, 65 ms. At 1.5T, the measured relaxation values for GM were T₁v, 1251 ms, and T₂v, 99 ms, and for WM, T₁v, 623 ms, and T₂v, 75 ms. Contrast of CS-T₁-FLAIR and actual T₁-FLAIR images was identical. An optimal TR of 3140 ms was determined for T₁-FLAIR at 3T and 2440 ms at 1.5T based on mathematical evaluation. The optimal TR ranges were 2400 to 3900 ms at 3T and 1800 to 3200 ms at 1.5T based on visual assessment of CS-T₁-FLAIR. A shorter TE provided better T₁ contrast. We optimized T₁-FLAIR by focusing on its most important scan parameters using computer simulations and determined that a longer TR was suitable at 3T than at 1.5T. Our computer simulation was useful for determining the optimal scan parameters.