<P> When "yellow" fatty marrow becomes replaced by tissue with more cellular composition, this change is apparent as decreased brightness on T1 - weighted sequences . Both normal "red" marrow and pathologic marrow lesions (such as cancer) are darker than "yellow" marrow on T1 - weight sequences, although can often be distinguished by comparison with the MR signal intensity of adjacent soft tissues . Normal "red" marrow is typically equivalent or brighter than skeletal muscle or intervertebral disc on T1 - weighted sequences . </P> <P> Fatty marrow change, the inverse of red marrow hyperplasia, can occur with normal aging, though it can also be seen with certain treatments such as radiation therapy . Diffuse marrow T1 hypointensity without contrast enhancement or cortical discontinuity suggests red marrow conversion or myelofibrosis . Falsely normal marrow on T1 can be seen with diffuse multiple myeloma or leukemic infiltration when the water to fat ratio is not sufficiently altered, as may be seen with lower grade tumors or earlier in the disease process . </P> <P> Bone marrow examination is the pathologic analysis of samples of bone marrow obtained via biopsy and bone marrow aspiration . Bone marrow examination is used in the diagnosis of a number of conditions, including leukemia, multiple myeloma, anemia, and pancytopenia . The bone marrow produces the cellular elements of the blood, including platelets, red blood cells and white blood cells . While much information can be gleaned by testing the blood itself (drawn from a vein by phlebotomy), it is sometimes necessary to examine the source of the blood cells in the bone marrow to obtain more information on hematopoiesis; this is the role of bone marrow aspiration and biopsy . </P> <P> The ratio between myeloid series and erythroid cells is relevant to bone marrow function, and also to diseases of the bone marrow and peripheral blood, such as leukemia and anemia . The normal myeloid - to - erythroid ratio is around 3: 1; this ratio may increase in myelogenous leukemias, decrease in polycythemias, and reverse in cases of thalassemia . </P>

What bones produce red blood cells in adults