MR imaging of normal bone marrow: evaluation of changes over time

The bone marrow is a complex organ that contains fat and nonfat cells, the proportion of which varies greatly with age and in the different bones of t he skeleton. Magnetic resonance imaging provides information on the composi tion of the medullary cavity of any given bone and on the distribution of r ed and yellow marrow in the skeleton. The wide spectrum of appearances of t he normal bone marrow at MR imaging will be reviewed. The purpose of this p aper is to determine the MR appearance of the bone marrow, to illustrate th e phenomenon of marrow conversion and to familiarize the readers with the c omplex parameters that interfere with the MR appearance of normal bone marr ow.