Which tissue is bright on T1 and less bright on T2?

Which tissue is bright on T1 and less bright on T2?

• A. Fat
• B. Water
• C. Calcium
• D. Gas

Answer: (A)

On MRI, image contrast comes from how fast tissue protons recover in the longitudinal direction (T1) and how fast they lose coherence in the transverse plane (T2). Fat has a short T1 relaxation time, so after the RF pulse its protons realign quickly and emit a strong signal, making fat look bright on T1-weighted images. On T2-weighted images, fat’s transverse signal decays relatively quickly, so it appears less bright or darker compared with fluids like water, which have longer T2 and stay bright. Calcium and gas, lacking mobile protons, appear dark on both T1 and T2. So the tissue that is bright on T1 and less bright on T2 is fat.

On MRI, image contrast comes from how fast tissue protons recover in the longitudinal direction (T1) and how fast they lose coherence in the transverse plane (T2). Fat has a short T1 relaxation time, so after the RF pulse its protons realign quickly and emit a strong signal, making fat look bright on T1-weighted images. On T2-weighted images, fat’s transverse signal decays relatively quickly, so it appears less bright or darker compared with fluids like water, which have longer T2 and stay bright. Calcium and gas, lacking mobile protons, appear dark on both T1 and T2. So the tissue that is bright on T1 and less bright on T2 is fat.