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

Abstract

Purpose: We attempted to optimize scan parameters for T 1 -weighted ‰uid-attenuated inversion recovery (T 1 -FLAIR) sequence at 3 and 1.5 tesla (T) using computer simulation.Methods: We measured the T 1 and T 2 relaxation time values (T 1 v and T 2 v) of gray (GM) and white matter (WM) at 3 and 1.5T, generated computer-simulated T 1 -FLAIR (CS-T 1 -FLAIR) images using those values, and compared the simulated and actual T 1 -FLAIR images to verify the contrast reliability of our computer simulation. We mathematically and visually evaluated CS-T 1 -FLAIR images at various repetition times (TR) and echo times (TE).Results: At 3T, the measured relaxation values for GM were T 1 v, 1524 ms, and T 2 v, 85 ms, and for WM, T 1 v, 750 ms, and T 2 v, 65 ms. At 1.5T, the measured relaxation values for GM were T 1 v, 1251 ms, and T 2 v, 99 ms, and for WM, T 1 v, 623 ms, and T 2 v, 75 ms. Contrast of CS-T 1 -FLAIR and actual T 1 -FLAIR images was identical. An optimal TR of 3140 ms was determined for T 1 -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-T 1 -FLAIR. A shorter TE provided better T 1 contrast.Conclusion: We optimized T 1 -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.

Three-dimensional Multi-parameter Mapping of Relaxation Times and Susceptibility Using Partially RF-spoiled Gradient Echo

“…T 1 and T 2 * values for WM and GM estimated using QPM were evaluated through comparison with reference values. 13 , 14 To evaluate the QSM obtained using QPM, we examined the correlation with QSM acquired at the same spatial resolution as QPM and the same imaging conditions as in the reference: FA = 15 degrees, TR = 35 ms, and TE = (7.0, 11.6, 16.2, 20.8, 25.4, and 30.0) ms. 15 …”

A prospective comparison study of fastT1weighted fluid attenuation inversion recovery andT1weighted turbo spin echo sequence at 3 T in degenerative disease of the cervical spine

“…6 For operation at 3 T, longer values of TR, TI and TE are generally employed, e.g. 2675, 2000 and 17 ms. 1 Longer TRs are acceptable for the T 1 FLAIR sequence at 3 T, and, by mathematical simulation, Oda et al 7 showed a wide but optimum range of TRs between 2400 and 3900 ms at 3 T. Although T 1 FLAIR sequences are commonly used in the spine and are said to provide excellent delineation of CSF, bone and disc bone interfaces at 3 T, [1][2][3] to date there has been little critical evaluation of their performance. Most of the articles have dealt with the role of T 1 FLAIR sequence in imaging degenerative disease of the lumbar spine, 5,8 wherein suppression of the abundant quantity of CSF within the lumbar thecal sac would allow for greater tissue contrast and improved image quality.…”