To determine treatment safety and efficacy of MR-HIFU ablation of painful Osteoid Osteoma (OO) in children and young adults.

Osteoid Osteoma (OO) is a benign, but painful, bone tumor commonly occurring in children and young adults. Definitive treatment options are CT-guided radiofrequency ablation (RFA) and less commonly, open surgical resection. RFA is less invasive than surgery, but it still requires drilling from the skin through muscle and bone. It also exposes the patient and operator to ionizing radiation.

Magnetic Resonance guided High Intensity Focused Ultrasound (MR-HIFU) provides precise and controlled delivery of focused ultrasound energy inside a lesion using an external applicator, without any incisions or drilling. MR-HIFU has been successfully used to treat painful bone metastases in adult clinical trials. Several recent reports, including two publications from our group, show that MR-HIFU is a feasible and safe treatment for OO.

MR-HIFU ablation of OO may provide a better alternative to surgical resection or RFA as it is completely non-invasive and does not require ionizing radiation. These two qualities of MR-HIFU are especially beneficial in growing children and young adults. Furthermore, MR-HIFU OO ablation is quick, with expected total procedure time of less than two hours. Such short treatments offer additional safety benefits from reduced anesthesia / sedation requirement compared to surgery and RFA.

The investigator's group has performed the first pilot clinical trial in the U.S. to evaluate MR-HIFU treatment for painful osteoid osteoma (PI: K.V. Sharma, NCT02349971). This trial shows that MR-HIFU ablation is feasible, well tolerated, and can be safely performed in a pediatric cohort. Based on these results, the investigators propose a pivotal clinical trial designed to evaluate treatment efficacy as the next logical step required for clinical translation. The investigators hypothesize that noninvasive and radiation-free MR-HIFU ablation for osteoid osteoma will be a clinically effective treatment, with success rate comparable to that currently reported for RFA.

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.