MR-HIFU Treatment of Painful Osteoid Osteoma

Inclusion Criteria: * Age ≤30 years. * Diagnosis of OO: All patients diagnosed with painful OO based on characteristic clinical history of pain relieved with NSAID medications AND confirmatory imaging findings characteristic of OO on CT and/or MRI scans. * Location of OO: eligible lesions must be located in a bone with acoustic accessibility and within the normal safety margins of MR-HIFU, as specified in the instructions for use. * Prior therapy: Patients with prior unsuccessful treatments including CT-RFA and/or surgical resection are eligible for enrollment. * Patients \< 18 years old must be accompanied by a legal guardian at the time of recruitment. * Laboratory: * Complete Blood Count (CBC) values within acceptable range for safe administration of anesthesia. Hemoglobin \> 9 g/dL. * PT, PTT and INR \< 1.5 x ULN (including patients on prophylactic anticoagulation) * Basic metabolic panel (BMP) and/or Complete metabolic panel (CMP) values within acceptable range for safe administration of anesthesia. * Adequate renal function: Age-adjusted normal serum creatinine (see table below) OR a creatinine clearance ≥60 mL/min/1.73 m2 for safe contrast administration * Adequate pulmonary function: Defined as no dyspnea at rest, and a pulse oximetry \>94% on room air. Exclusion Criteria: * Diagnosis of bone lesion other than OO in the judgement of the Principal Investigator. * Clinically significant unrelated systemic illness, such as serious infections, hepatic, renal or other organ dysfunction, which would compromise the patient's ability to tolerate the general anesthetic required for the procedure in the judgment of the Principal Investigator. * Implant, prosthesis or scar tissue that would interfere with a safe completion of MR-HIFU. ablation in the judgement of the Principal Investigator. * Treatment area nidus \<1 cm from a major nerve, spinal canal, bladder, or bowel. * Target \<1 cm of growth plate (physis). * Lesion in the skull. * Lesion in the vertebral body. * Inability to undergo MRI and/or contraindication for MRI. * Inability to tolerate stationary position during MR-HIFU. * Patients currently receiving any investigational agents.