18F-FDG PET/CT in the evaluation of femoral head osteonecrosis in patients with lymphoma

Objective To describe the imaging features of osteonecrosis of the femoral head (ONFH) on fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT and explore the value of PET/CT in assessing ONFH in patients with lymphoma. Methods A retrospective analysis was conducted on the clinical data, PET/CT, and MRI manifestations of 17 patients with ONFH and lymphoma. The FDG uptake of ONFH was recorded, and the maximum standardized uptake value (SUV _max ) of ONFH was measured. The staging and extent of ONFH, and other bone involvements, were visually assessed. Results A total of 31 femoral heads were involved, including 2 in stage 1, 24 in stage 2, 4 in stage 3, and 1 in stage 4. The median SUV _max of ONFH in stage 3–4 (5.27) was higher than that in stage 1–2 (1.37) ( P  = 0.002). In stage 1 lesions, both density and FDG uptake were normal. For stage 2 lesions, 11 showed increased FDG uptake along the peripheral linear high-density and/or within the necrotic region, 5 had peripheral increased uptake with internal decreased uptake, 2 exhibited decreased uptake, and 6 showed normal uptake. All lesions in stages 3–4 demonstrated increased FDG uptake along the peripheral linear high-density and/or at the osteolytic area. Thirteen stage 2 lesions were confined above the epiphyseal line, while 11 stage 2 lesions and 5 stage 3–4 lesions extended below the epiphyseal line. The extent of 20 stage 2 lesions and 5 stage 3–4 lesions observed on CT matched that seen on MRI. Nine patients had osteonecrosis in other bones. The humeral heads were involved in 9 patients, with 4 showing increased FDG uptake along the linear high-densities. Bilateral ilia were involved in 6 patients, with 5 demonstrating peripheral linear high densities and internal decreased FDG uptake. One patient had multiple involvements of the vertebrae, ribs, and scapulae. Conclusions In patients with lymphoma, ONFH exhibits variable degrees of FDG uptake and may be accompanied by involvement of other bones. PET/CT is helpful in diagnosing ONFH and detecting multiple bone involvements while assessing lymphoma.