Most bone tumors have prolonged T1 and T2 relaxation times. Even lesions that appear relatively dense on CT may have sufficient soft tissue matrix to render them hyperintense on T2-weighted images. The presence of hemorrhage or fat alters the signal characteristics. Aneurysmal bone cysts have a distinctive feature of multiple cysts with variable signal intensities related to protein content, in some cases with fluid-fluid levels. Paget's disease Paget's disease, or osteitis deformans, is an acquired disorder of unknown etiology.
Normal bone is destroyed and replaced by poorly mineralized osteoid matrix.
The bones most often involved are the pelvis, skull, femur, and spine, followed by other long bones and the mandible. Paget's disease results in enlarged, expanded bone that has a heterogeneous texture. The mineralized components, underestimated by MR, become more prominent in later stages of the disease. With aging, the bone becomes demineralized and the ratio of hematopoietic to fatty marrow changes. MR studies of patients of varying ages have revealed that the T1 relaxation time of bone marrow progressively decreases with age.