Gradient-echo imaging of bone marrow in the appendicular skeleton

This study shows that bone marrow has specific magnetic susceptibility and chemical shift characteristics that are demonstrated only by gradient- echo imaging. First, because fat contains several spectral components, yellow marrow signal displays a chemical shift- induced amplitude modulation with echo delay. Second, marrow exhibits a shortened T2 and resultant signal loss in those anatomic regions with greater trabecular bone content (i.e., epiphysis vs diaphysis). This T2 dephasing is due most likely to local field gradients resulting in inhomogeneous susceptibilities where the mineralized matrix interfaces with marrow. The clinical consequences are discussed in normal and abnormal extremities