1. T2 lesions are the white spots observed on MRI using the typical imaging sequences acquired to diagnose and monitor Multiple Sclerosis. The most popular of these sequences is a FLAIR image (this stands for Fluid Attenuated Inversion Recovery).
FLAIR images are used to subtract away the white appearance of water in and around the brain (mostly Cerebrospinal fluid) that interferes with visualization of brain tissue. When the area or “lesion” in the brain is white on T2 weighted images, this could mean the area is undergoing a temporary process like inflammation and will recover completely or the area has undergone permanent scaring. We are not able to differentiate these very different outcomes within the tissue by this imaging sequence alone .
2. T1 lesions are black spots or “holes” observed within the white matter of the brain. The T1 lesions or “black holes” within the brain can be caused by temporary process like acute inflammation or permanent scaring and tissue damage. The way to determine if a “black hole” is a permanent scar is to determine if it persists over a period usually greater than 3 months. Usually, the blacker the lesion the more you can be sure that the tissue in the region has been destroyed. Eventually, the tissue is replaced entirely by water and appears totally black on T1 weighted sequences and FLAIR sequences.
-Rip Kinkel, MD