Microwave Ablation of Osteoid Osteomas Using Dynamic MR Imaging for Early Treatment Assessment: Preliminary Experience

Purpose: To evaluate, the efficacy of microwave ablation for osteoid osteomas by using dynamic contrast-enhanced magnetic resonance (MR) imaging in early treatment assessment. Materials and Methods: Ten patients (two female, eight male; paean age, 28 y; range, 16-47 y) presenting with osteoid osteomas were treated between June 2010 and December 2012 with the use of computed tomography (CT)-guided microwave. ablation. Osteoid osteomas were found at the femoral neck (n = 4), tibia (n = 3), calcaneus (n = 1), navicular bone (n = 1), and dorsal rib (n = 1). Dynamic contrast enhanced MR imaging at 3 0 T was performed 1 day before microwave ablation and again after ablation. The procedure Was considered successful if the signal intensity (SI) of the lesion on MR imaging decreased by at least 50% and the patient was pain-free within 1 week of intervention. Results: All patients were pain-free within 1 week after microwave ablation and remained so during the 6 months of follow-up: :NO major or minor complications developed. On average, SI of the lesions decreased by 75% (range, 55.5%49.1%) after, treatment The difference in lesion SI before versus after ablation was significant by t test (P < .0001; confidence interval, 120.26-174.96) and Wilcoxon test (P = .0020). Conclusions: Microwave ablation treatment of osteoid osteoma was highly successful, without any complications observed. Dynamic contrast enhanced MR imaging is a useful tool for diagnosing osteoid osteoma and evaluating treatment.