We had challenges related to participant recruitment due to inclusion/exclusion criteria.

The Philips Sonalleve MR-HIFU system is expected to be effective in reducing pain intensity and/or reducing analgesic use in patients with painful uncomplicated bone metastases. No serious adverse effects are expected to result from this treatment.

The objective of this study is to determine if MR-guided high intensity focused ultrasound (MR-HIFU) is an effective technique for alleviating the pain associated with bone metastases in paediatric cancer patients. This technique meant to be an adjunct therapy to the standard-of-care, which includes radiation therapy and chemotherapy. Safety of the technique will be assessed through evaluating non-targeted heating using MRI-based temperature mapping, and inspecting patients post-treatment for skin burns. or other signs of serious adverse events. Efficacy of the technique will be assessed by evaluating/recording patients observed pain, quality of life, and pain medication usage both before and up to 3 months following treatment.

Inclusion Criteria:

• able to give informed consent
• weight <140 kg (requirement to fit safely on top of the HIFU table and inside MRI
• any radiologic evidence of bone metastases from any solid tumor (neuroblastoma, osteosarcoma, soft tissue sarcoma, or any other solid tumor metastases).
• pain specifically at the site of interest (target lesion)
• pain score for target lesion >/ = 4 (indicating at least moderate pain) on an age-appropriate 0-10 point scale
• Target lesion in uncomplicated (ie no fracture / spinal cord compression /cauda equine syndrome/ soft tissue component)
• Available 3D MRI image of the target lesion (or be able to obtain one in a clinically feasible amount of time as part of the baseline investigational stage.)
• Proposed MR-HIFU treatment date >/= 2 weeks from most recent treatment of target tumour or systems chemotherapy
• Proposed MR-HIFU treatment date >/= 1 week after administration of steroids for pain flare

Exclusion Criteria:

• Unable to characterize pain specifically at the site of interest (target lesion).
• Pregnant / nursing females
• Target lesion is complicated (ie pressure of one fracture /spinal cord compression/cauda equine syndrome/soft tissue component)
• Target lesion < 1cm from nerve bundles/ bladder/bowel
• Target lesion in contact with hollow viscera
• Target lesion located in skull, spine (excluding sacrum which is allowed) or sternum.
• scar along proposed HIFU beam path.
• Orthopaedic implant along proposed HIIFU beam path or at site of target lesion.
• Active infection.
• Contradiction to general anesthesia or or gadolinium MRI contrast agent.
• Requirement for general anaesthesia for non -HIFU related MRI scans.