On T2-weighted MRI, which tissue is bright?

On T2-weighted MRI, which tissue is bright?

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

Answer: (A)

In T2-weighted imaging, brightness reflects how long tissues retain transverse magnetization after excitation. Tissues with long T2 relaxation times stay bright, while those with short T2 fade quickly and appear darker. Water has a very long T2, so free water, CSF, edema fluid, and other fluid-rich areas light up strongly on T2 images. In contrast, calcium and gas do not produce MR signal well and show up as dark voids. Fat has a shorter T2 than pure water, so it is not as bright as water on a standard T2 image, though it can be relatively bright compared to many other tissues.

In T2-weighted imaging, brightness reflects how long tissues retain transverse magnetization after excitation. Tissues with long T2 relaxation times stay bright, while those with short T2 fade quickly and appear darker.

Water has a very long T2, so free water, CSF, edema fluid, and other fluid-rich areas light up strongly on T2 images. In contrast, calcium and gas do not produce MR signal well and show up as dark voids. Fat has a shorter T2 than pure water, so it is not as bright as water on a standard T2 image, though it can be relatively bright compared to many other tissues.