Safety and Feasibility of MR-Guided High Intensity Focused Ultrasound (MR-HIFU) Ablation of Osteoid Osteoma in Children

Inclusion Criteria:

* Diagnosis:

  * All patients with a clinical suspicion of OO based on presence of typical symptoms of localized nocturnal pain that is relieved by NSAIDs and unrelated to trauma or activity.
  * Typical imaging findings on CT and/or MRI. Plain radiographs and bone scans may be obtained by referring physicians and are helpful for confirming the clinical diagnosis but cannot be substituted for a CT or MRI.
  * Non-contrast enhanced or contrast enhanced CT studies are acceptable.
  * Contrast enhanced MRI studies should be performed.
  * Tissue biopsy is not required
* Tumor location:

  * Target lesions can be located in any peripheral bone with acoustic accessibility.
  * Target lesions may be intracortical or juxtacortical in location.
  * Target lesions must be reachable within the normal safety margins of HIFU as specified in the instructions for use.
* Prior therapy:

  ●Patients with prior unsuccessful surgical resection or RFA are eligible for enrollment.
* Laboratory :

  * Hemoglobin \> 9 g/dL
  * Platelet count ≥75,000/µL (may receive transfusions)
  * Normal PT, PTT and INR \< 1.5 x ULN (including patients on prophylactic anticoagulation)
  * Renal function: Age-adjusted normal serum creatinine (table in protocol) 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 if there is clinical indication for determination.

Exclusion Criteria:

* Clinically significant unrelated systemic illness, such as serious infections, hepatic, renal or other organ dysfunction, which in the judgment of the Principal or Associate Investigator would compromise the patient's ability to tolerate the general anesthetic required for the procedure.
* Implant or prosthesis or scar tissue within the path of the HIFU beam.
* Target \<1 cm from nerve plexus, spinal canal, bladder, bowel
* Target \<1 cm of the growth plate (physis)
* Lesion in the skull or vertebral body
* Inability to undergo MRI and/or contraindication for MRI
* Inability to tolerate stationary position during HIFU
* Patients currently receiving any investigational agents.