T1-weighted MRI scans show old lesions. The scans show areas of permanent damage that appear as dark spots. Dark spots are called hypointense lesions. T1-weighted MRI scans show more anatomical detail than gadolinium-enchanced and T2-weighted MRIs.
T2-weighted MRI scans show the total number of lesions, both new and old. These appear as bright spots on the MRI scan and are called hyperintense lesions.
Gadolinium is a dye that can be injected in your veins during an MRI scan. It highlights areas in your brain and spinal cord with lesions that have been active in the past 4 to 6 weeks. Gadolinium allows the doctor to tell which lesions are new or active and which ones are older. This provides information on recent disease activity and whether you may be experiencing a relapse.