Usefulness of Functional Image Analysis Using Positron Emission Tomography for the Discrimination between Hypoplastic Myelodysplastic Syndromes and Aplastic Anemia.

Myelodysplastic syndromes (MDS) and aplastic anemia (AA) are classified bone marrow failure syndromes. Their clinical and pathological features partly overlap. It is sometimes difficult to distinguish hypoplastic MDS from AA by using current common diagnostic methods such as bone marrow biopsy and chromosome analysis. Although magnetic resonance image (MRI) is useful for diagnosis of MDS with hypercellular bone marrow, it is difficult to discriminate between hypoplastic MDS and AA using this method because the high intensity patterns on T1-enhanced images are similar in these disorders. Quantitative imaging with fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has been recognized as a useful examination for discrimination between benign and malignant regions in various conditions. Since the decrease in FDG uptake at the late phase is much slower in a malignant region than in a benign region, dual time point imaging provides more accurate information than does conventional single time point scanning. In this study, we investigated the usefulness of dual time protocol FDG-PET in differential diagnosis of hypoplastic MDS and AA. Seventeen patients (7 with typical MDS (RA), 4 with hypoplastic MDS, 6 with AA) and 30 healthy adults agreed to participate in this study. Bone marrow biopsy, FDG-PET, MRI and CT were carried out. Spine, femur and iliac lesions were detected by their increased FDG uptake at 60 and 120 min after injection of 0.12 mCi/kg of FDG. The mean lesional standardized uptake values (SUVmean) at 60 and 120 min after injection of FDG were determined. While the median SUVmean of normal lumbar regions at 60 min was 1.123 ± 0.219, that of MDS cases was 2.06 (range, 1.62–2.32). At 120 min, the median SUVmean of normal cases was 1.180 ± 0.119, whereas that of MDS cases was 2.44 (range, 2.08–2.98). It is noteworthy that the SUVmean of four hypoplastic MDS cases was also high (ranges: 1.96–2.23 at 60 min and 1.97–2.52 at 120 min), suggesting that bone marrow in hypoplastic MDS has a hyper-metabolic state of glucose like other malignant disorders. We also observed a patchy hot area, which may be a visualization of ineffective hematopoiesis, throughout the spine image of hypoplastic MDS. In contrast, the SUVmeans at both time points of four AA cases were not different from those in normal control cases. These results suggest that functional imaging analysis using an FDG-PET dual time protocol enables discrimination between hypoplastic MDS and AA, in which MR images similar intensities.