From the reference below: An MRI is capable of evaluating the hydration within the discs based on increased signal on the T2-weighted images. Increased disc signal on T2-weighted images is associated with dehydration of the lumbar discs. Change in the disc signal, or darkening of the signal, is associated with dehydration or loss of hydrogen ions within the disc. This is often associated with lumbar disc degeneration. Decreased hydration leads to a loss of signal intensity on the T2 images which leads to darkening of the disc on the image ...