• Courtesy of Steven A. Newman, MD
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    Comparison of T1-weighted and T2-weighted images can yield information about the characteristics of a lesion and can be particularly helpful in dating hemorrhages. A 61-year-old patient presented with acute onset of severe headache. A hemorrhage is apparent in the parieto-occipital region in the 3 scans originally taken: T1-weighted (A), proton density (B), and T2-weighted (C) images. The signal at the lesion periphery relates to the presence of oxyhemoglobin, whereas the core remains dark in all 3 images because of the presence of deoxyhemoglobin. When the MRI series was repeated 10 days later, the signal characteristics had changed as a result of the development of methemoglobin in the outer ring, which is bright on T1-weighted (D), proton density (E), and T2-weighted (F) images. The core remains dark.