Abstract: Objective To explore the fluoro-18-deoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) features of bone marrow necrosis and improve the understanding of the disease. Methods  The PET/CT and clinical data of 9 patients with bone marrow necrosis diagnosed by magnetic resonance imaging (MRI) were retrospectively analyzed. Compared to MRI,the distribution of lesions was summarized. The ¹⁸F-FDG metabolic and CT features of the selected largest lesion were analyzed.  Results  There were 6 males and 3 females with a median age of 28.0 years. All patients were diagnosed with lymphoma. MRI scans of the hip,spine and knee were performed in 6,2,and 1 case respectively. The iliac lesions in 6 cases showed internal high signal intensity on T1-weighted images (T1WI),low signal intensity on T2-fat suppressed images (T2FSI),and peripheral linear hypointensity on T1WI. The iliac lesions in 5 cases demonstrated internal decreased ¹⁸F-FDG metabolism,peripheral linear increased ¹⁸F-FDG uptake and density on PET/CT. The iliac lesion in one case did not show abnormal ¹⁸F-FDG metabolism and density on PET/CT,the lesion was narrow and long on MRI. The vertebral lesions in two cases showed isointensity to hypointensity on T1WI and hyperintensity on T2FSI. On PET/CT,one vertebral lesion was isometabolic with slightly higher density,the other vertebral lesion showed reduced ¹⁸F-FDG metabolism with normal density. One femoral lesion showed high signal intensity on T1WI and low signal intensity on T2FSI,with increased ¹⁸F-FDG metabolism and density on PET/CT. PET/CT revealed more lesions beyond the scan range of MRI in 8 cases. In 8 cases,abnormal signs were demonstrated on much earlier PET/CT scans performed at a median time about 13.5 (8.25,32.75) months before the MRI scan,but no one complained of any related discomfort at that time. The iliac lesions in 5 cases had decreased ¹⁸F-FDG uptake,of which 3 lesions showed peripheral linear high-density,and 2 lesions showed no abnormal density. The iliac lesion in one case did not show abnorma^{l 18}F-FDG metabolism and density. One vertebral lesion showed reduced metabolism and isodensity. In the case with knee MRI,the earlier PET/CT showed multiple linear increased ¹⁸F-FDG uptake in the bilateral femoral heads and the humerus heads,without abnormal density. During follow up PET/CT scans,the femoral head lesions in 3 cases showed cortical fracture and collapse,the vertebral lesions 2 cases demonstrated multiple Schmorl's nodules or compression fracture. Conclusion  Decreased ¹⁸F-FDG uptake,with probably subsequent peripheral linear increased metabolism and density,is a common PET/CT feature of bone marrow necrosis. PET/CT is helpful to detect bone marrow necrosis and find multiple skeletal lesions.

Key words: bone marrow necrosis, osteonecrosis, ¹⁸F-fluorodeoxyglucose, positron emission tomography/computed tomography