How do T1, T2, and FLAIR MRI sequences differ in signal characteristics for brain tissue?

How do T1, T2, and FLAIR MRI sequences differ in signal characteristics for brain tissue?

• A. T1 shows fluids bright and fat dark; T2 shows fluids bright; FLAIR suppresses CSF to reveal edema and gliosis.
• B. T1 shows fluids bright; T2 shows fats bright; FLAIR suppresses fats.
• C. T1 shows fats dark; T2 shows fluids dark; FLAIR enhances CSF.
• D. T1 shows fluids dark; T2 shows fluids bright; FLAIR suppresses brain tissue.

Answer: (A)

Think about how each MRI sequence uses relaxation times to create contrast. On T1-weighted images, fat-rich tissues appear bright while water-based structures like cerebrospinal fluid are dark, so anatomy with fat stands out and fluid-filled spaces look subdued. On T2-weighted images, fluids dominate the signal, so CSF and edema shine as bright areas because water has a long T2. FLAIR is like a T2 sequence but with CSF signal suppressed by an inversion pulse, so CSF becomes dark. This suppression makes periventricular and other edema or gliotic lesions more conspicuous against the dark CSF. So, the common, correct outline is: T1—fat bright, fluids dark; T2—fluids bright; FLAIR—CSF suppressed to reveal edema and gliosis.

Think about how each MRI sequence uses relaxation times to create contrast. On T1-weighted images, fat-rich tissues appear bright while water-based structures like cerebrospinal fluid are dark, so anatomy with fat stands out and fluid-filled spaces look subdued. On T2-weighted images, fluids dominate the signal, so CSF and edema shine as bright areas because water has a long T2. FLAIR is like a T2 sequence but with CSF signal suppressed by an inversion pulse, so CSF becomes dark. This suppression makes periventricular and other edema or gliotic lesions more conspicuous against the dark CSF. So, the common, correct outline is: T1—fat bright, fluids dark; T2—fluids bright; FLAIR—CSF suppressed to reveal edema and gliosis.