[Bone infarction and fat island appearing as local defects in radionuclide bone marrow imaging]

Parallel studies of radionuclide bone marrow imaging and bone scanning are helpful in the early diagnosis of skeletal metastasis. In bone marrow imaging, most lesions are observed as a local defect. We had two cases of nonmetastatic lesions which appeared as local defects in bone marrow imaging. The first case was a male Hodgkin's disease patient, aged 48, who had been treated with frequent chemotherapy, including the administration of a large quantities of steroids. He complained of slight pain in the left shoulder. Without increased uptake in bone scanning, abnormal accumulation of 67Ga-citrate and a local defect in bone marrow imaging appeared, corresponding to localization of the pain. Suspecting bone marrow metastasis, we performed magnetic resonance imaging (MRI). An area of slightly decreased intensity in T1-weighted spin-echo images and lower intensity than fat tissue in T2-weighted images were observed, although it was slightly enhanced by Gd-DTPA. This lesion was diagnosed by biopsy as a bone infarction. The second case was that of a 69-year-old male lung cancer patient. Though no abnormality was revealed by bone scanning or 67Ga-citrate scintigraphy, an apparent defect at the 10th thoracic vertebra was observed in bone marrow imaging. It was not accompanied by pain. MRI was also performed in this case. This was depicted as a clearly defined high intensity area. This was diagnosed as a fat island, and no change has been seen in the seven months of follow up. In conclusion, it is necessary to consider the possibility of nonmetastatic lesions, when local defects appear in bone marrow imaging performed on cancer patients.