PET/CT > Normal Activity > Musculoskeletal > Bone
Normal bone marrow
Normally mild to moderate activity, similar in intensity to liver activity, can be seen within the bone marrow. It is typically relatively more prominent within the axial (spine, pelvis, sternum, ribs) and proximal appendicular (proximal femurs, proximal humeri) skeleton. This distribution can change with any process that changes normal marrow distribution or marrow metabolism. Diffusely increased marrow activity might be the result of anemia and resultant activation of hematopoiesis, common following many chemotherapy regimens. Increased marrow activity can also be seen following various bone marrow stimulatory agents including granulocyte-colony stimulating factor (G-CSF) and erythropoietin. Marrow activity is often decreased geographically after radiation therapy in the portion of marrow included in the radiation field. Of course in the setting of cancer, focal increased marrow activity correlating with CT evidence of lytic or sclerotic changes in the same bone would be considered worrisome for osseous metastatic disease.