[MR images of bone marrow in aplastic anemia and correlation between MR findings and age]

We observed 125 lumbar vertebrae in 25 patients with aplastic anemia using a 0.5-T MR imager. Bone marrow patterns of aplastic anemia on STIR images were classified into five types: 1) homogeneously low intensity fatty marrow, 2) fatty marrow with scattered hematopoietic nodules, 3) fatty marrow with marginal hematopoietic regions, 4) fatty marrow surrounded by bandlike hematopoietic regions, and 5) homogeneously high-signal-intensity hematopoietic marrow. STIR images defined the fatty marrow as a markedly hypointense region and the hematopoietic marrow as a high signal intense area. Many cases included the homogeneously fatty marrow and fatty marrow with marginal hematopoietic areas, whereas marrow with a broad range of hematopoiesis was detected in patients younger than 40 years. MR images also demonstrated that fatty marrow could shift to hematopoietic marrow following therapy. MR images were useful for detection of the bone marrow distribution of aplastic anemia, related to aging and treatment.