[Evaluation of bone marrow by opposed phase T1-weighted images and enhanced MR imaging]

We investigated bone marrow in a control group, cases of aplastic anemia and post-irradiation patients by examining T1-weighted (T1WI), short TI inversion recovery (STIR), opposed phase T1WI (op-T1WI) and Gd-DTPA enhanced op-T1WI images obtained by 0.5T MRI. Bone marrow was classified into four types based on MR findings. Normal marrow showed low intensity on op-T1WI and STIR images without enhancement (I). Fatty marrow, which showed high intensity on T1WI and op-T1WI images was observed in aplastic anemia and post-irradiation patients (II). Hematopoietic marrow (III) showed low intensity on op-T1WI and enhanced, while active hematopoietic marrow (IV) revealed high intensity on both STIR and op-T1WI images and was enhanced following Gd-DTPA infusion. Aplastic anemia of moderate grade included types II, III and IV. Enhanced MR was needed to differentiate between types I and III since both types showed low intensity on op-T1WI images. Furthermore, type IV was considered as hyperplastic compared with type III. Enhanced MR and op-T1WI images were useful in evaluating hematopoiesis of bone marrow.