[en] Ten patients with avascular femoral head necrosis and four normal adults were examined by magnetic resonance imaging (MRI). In addition, the relationship between MRI and pathophysiology of three operated-on avascular femoral heads was evaluated. The medullary cavities of the normal femoral heads had a strong signal intensity on the saturation recovery (SR) image due to fat marrow, and the T₁ relaxation time was 160 ± 11 msec. In avascular femoral head necrosis, the necrotic area had a low signal intensity on the SR image and a prolonged T₁ relaxation time, while the reactive fibrous area had more prolonged T₁ relaxation time. For these reasons, MRI was found to show the pathological changes of avascular femoral head necrosis and can be expected to be useful for making early diagnoses and operation planning. (author)