A high T2 foci signal of the supratentorial white matter in the brain is an area of brightness in the cerebellum seen on magnetic resonance imaging scans using spin-echo pulse sequences. The bright spots are the signs of lesions, areas with increased water retention that reflect aging and disease.
Magnetic resonance imaging, or MRI, records changes to brain tissue based on the time required to return to relaxation after excitation by a magnetic field. The T2-weighted method uses pulses to spin the field and displays the time it takes for the brain tissue to reach its normal state as a level of relative brightness. The longer the brain requires, the higher the T2 value and the brighter the image. Water takes longer to return to rest than the brain tissue, yielding higher T2 values. This indicates damage to the water-adverse white matter.
Brain lesions increase with age, representing reduced or slowed blood flow caused by high blood pressure, diabetes and other common conditions. The increase of water also results from diseases such as multiple sclerosis, where the myelin around the axons in white matter is reduced along with the water-repelling attribute myelin provides. The lesions produced by this condition appear on imaging as well-defined with smooth borders, while lesions caused by encephalitis are irregular.