MRI of bone marrow.

MRI can visualize bone marrow more clearly than X-CT or RI because the bone generates weak signals whereas the fat in the marrow gives strong signals. We described diagnosis of various bone marrow disorders by MRI technique. Hyperplasia of bone marrow decreased fatty cells and resulted in prolongation of T1, whereas hypoplasia of bone marrow replaced hematopoietic cells with fatty cells and resulted in shortening of T1. In aplastic anemia, the localized hyperplastic areas in abnormal fatty marrow can be visualized. In bone tumor and metastasis to bone marrow, T1-weighted IR image can provide the best contrast between the tumor and normal marrow, although neoplastic and inflammatory lesions can not be differentiated by MRI. In iron storage diseases, MRI can detect early changes by its higher sensitivity to iron than that of X-CT. MRI may be usefull in monitoring bone marrow damages noninvasively to patients under radiation and/or anticancer drug therapy.