Osteoid Osteoma: Magnetic Resonance guided Focused Ultrasound for Entirely Non-Invasive Treatment

Purpose To determine the preliminary feasibility, safety and clinical efficacy of Magnetic Resonance guided Focused Ultrasound (MRgFUS) for the treatment of painful osteoid osteoma. Materials and Methods This prospective, institutional review board-approved study involved 6 consecutive patients (5 males; 1 female; mean age of 21) with a diagnosis of osteoid osteoma, based on clinical and imaging findings. All patients underwent MRgFUS ablation after providing informed consent. Lesions located in the vertebral body were excluded. The number of sonications and the energy deposition were recorded. Treatment success was determined at 1, 3, and 6 months post-treatment. A Visual Analog pain Score (VAS) was used to assess changes in symptoms. MR imaging features of osteoid osteoma (edema, hyperemia and nidus vascularization) were considered at baseline and at imaging follow-up. Results Treatment was performed using an average of 4 ± 1.8 sonications, with a mean energy deposition of 866 ± 211 J. There were no treatment- or anesthesia-related complications. There was a statistically significant difference (p=0.001) between the pre- and post-treatment mean VAS scores (7.9 ± 1.4 and 0.0 ± 0.0, respectively). At imaging, the edema and hyperemia associated with osteoid osteoma gradually disappeared in all lesions. However, nidus vascularization was still persistent after treatment in 4 of 6 patients. Conclusion In this limited series we demonstrated that MRgFUS treatment of osteoid osteoma can be performed safely with a high rate of success and without apparent treatment-related morbidity.