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Normal changes in the MR appearance of the spleen during early childhood.

OBJECTIVE
During the first year of life, the spleen undergoes histologic changes as the lymphoproliferative system matures. The purposes of this study were to describe the normal MR appearance of the spleen during infancy and early childhood and to correlate imaging findings with age-related histologic changes.


MATERIALS AND METHODS
The spleen was evaluated on 28 abdominal MR studies obtained during the first 23 months of life. Splenic signal intensity was compared to that of the liver. Selected autopsy specimens were compared with the imaging results.


RESULTS
The T2-weighted signal intensity of the spleen gradually increased from isointense to hypointense relative to the liver during the first week of life to moderately hyperintense to the liver by 8 months of age. T1-weighted splenic signal intensity gradually decreased. These findings corresponded to histological increases in white-pulp-red-pulp ratios.


CONCLUSION
Before the lymphoid system completely matures, the T2-weighted signal intensity of the normal neonatal spleen appears decreased compared with the moderately hyperintense splenic signal seen in older children and adults. This finding should not be mistaken for disease.