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This article explores the decay of transverse magnetization and the recovery of longitudinal magnetization in MRI using inversion recovery techniques. The characteristic time constants, T1 and T2, as well as different echo times (TE) and inversion times (TI) are analyzed. The article also discusses the contrast between T1-weighted (IR) and T2-weighted (SE) images in the brain.
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Exponential decay = 30 ms Inversion Recovery
T2: decay of transverse magnetization after excitation TE = 15 ms TE = 20 ms = T2= 30 ms T2= 50 ms TE = 30 ms TE = 60 ms Inversion Recovery
Inversion Recovery B0 180º Longitudinal magnetization relaxes back to equilibrium with characteristic time constant, T1 M|| Inversion Recovery
Negative magnetization looks like positive magnetization in magnitude images T1 Inversion recovery T1= 900 ms T1= 1100 ms T1= 2000 ms TI = 50 ms 100 ms 400 ms 800 ms 1600 ms 3200 ms 4800 ms Inversion Recovery
Contrast in the brain T1 (IR) T2 (SE) Inversion Recovery