Part 2
FLAIR is the best sequence to determine whether the high signal on T2WI is due to fluid or something else. We can see on our FLAIR study that in case 3.1 the area in the left frontal region completely saturates out on FLAIR. However, in case 3.2 the lesion does not completely saturate out.
Which lesion contains purely fluid?
Case 3.2
Sorry, on FLAIR the lesion does not completely lose its signal, which it should do if it contains purely fluid (hint: look at the CSF signal).
Case 3.1
Correct! The lesion has completely lost its signal and is similar in signal to the CSF indicating it is fluid.