Normal childhood developmental patterns in skull bone marrow by MR imaging

To establish the normal developmental pattern of skull bone marrow in children by MR imaging, sagittal T1-weighted MR skull images of 324 normal children (newborn to 18 years) were reviewed. Bone marrow intensity was assigned four gradations as compared with that of muscle and fat on the same image. Bone marrow became isointense with fat (yellow marrow) at a mean age ±S.E.M. (in years) of 8.5±0.24 in sphenoid, 9.1±0.29 in mandible, 9.3±0.28 in hard palate, 9.7±0.26 in frontal, 11.0±0.26 in squamous occiput, 11.5±0.28 in parietal, and 11.9±0.24 in basiocciput. There is a strong correlation between age and marrow intensity by Spearman analysis (p<0.001): hard palate 0.64, mandible 0.61, parietal 0.42, sphenoid 0.70, cervical spine 0.50, basi-occiput 0.58 and occiput 0.52. Two consistent overall patterns of red-yellow marrow conversion were observed. Bone marrow became isointense with fat prior to pneumatization of the paranasal sinuses. Marrow conversion in the bones of the face occurred before those of the calvarium in a specific pattern. There was no significant sex difference in the pattern or rate of marrow conversion. These normative data are necessary to evaluate the immature skull by MR imaging in disease states.