CI of study retired on 6.10.2020 and there will be no further efforts to apply for an extension in order to recruit to this study.

The primary objective of this study is to determine whether intra- and post-procedural MR changes are indicative of reduction in pain symptom scores. The trial will recruit a cohort of patients with painful bone metastases, who wish to consider MRgHIFU treatment. These patients will be identified in conjunction with the pain and palliative care teams, as well as clinical and medical oncologists. Patients will undergo MRgHIFU treatment using scanning and treatment planning methods that have been established in the patients treated within the multi-centre study. The treatment response rate for the cohort will be recorded. Intra- and post-procedural imaging metrics will be evaluated for their ability to detect tissue changes, which may be indicative of response. Patients will be followed-up for up to 90 days after treatment, and will attend for repeat imaging and pain review at days 30, 60 and 90 after treatment. Any changes in imaging metrics will be compared between responders and non-responders.

The primary aim of this study is to investigate whether the ablated tissue volume indicated by immediate post-treatment Gd-T1W imaging is indicative of reduction in pain scores (response) 30 days after treatment.

The secondary aims of this study are:

• To record the proportion of patients responding to MRgHIFU treatment at Days 7, 14, 30, 60 and 90 after treatment
• To investigate whether intra-procedural PRFS metrics (thermal dose volume, temperature) are indicative of subsequent treatment response
• To investigate whether intra- or post-procedural changes in ADC or T2 are indicative of subsequent treatment response
• To record adverse events arising as a result of MRgHIFU treatment
• To evaluate the effect of MRgHIFU treatment on patients' quality of life
• To record the time to pain progression and the duration of pain response for patients in this cohort
• To estimate the costs of MRgHIFU treatment

This is an exploratory study, which will recruit n=15 patients into one single cohort. Enrolment of the target population for the study is expected to take approximately 2 years. Patients will be eligible for the study if they wish to consider MRgHIFU treatment for pain palliation of a region of bony metastatic disease that is accessible to the MRgHIFU device. After providing their written informed consent to participate in the study, patients' suitability for treatment will be determined by a combined assessment of clinical review by a pain specialist, and an MR screening investigation to establish lesion targetability. Baseline clinical and imaging metrics will be recorded. Patients who fulfill all inclusion criteria, have none of the exclusion criteria, and who give informed consent, will be scheduled for MRgHIFU treatment to the target lesion. Treatment will be delivered under sedation on a day-case basis, according to protocols already established in our prior study. During treatment delivery, the investigators will assess imaging metrics of tissue change, which may be indicative of subsequent treatment response. Treatment would be expected to take approximately 1-2 hours, and after an observation period of approximately 2-4 hours, the patient will be discharged. Before discharge, follow-up instructions will be given to the patient. Patients' clinical and imaging responses to treatment will then be assessed at follow-up appointments up to 3 months after treatment.

Inclusion Criteria:

• Patients with painful bony metastatic disease
• Target bony metastatic lesion is painful (NRS≥4)
• Intended target region accessible for MRgHIFU treatment (usually not skull or spinal metastases above the sacrum)
• Intended target region visible on non-contrast MR imaging

Exclusion Criteria:

• MRI contra-indicated (e.g. by incompatible metal implants, claustrophobia, or because BMI precludes accommodation in the MR scanner)
• Pregnancy
• Sedation contra-indicated
• Critical anatomical structure cannot be avoided along the beam path or the at the target (can be assessed at screening)
• Internal or external fixation device along the beam path or at the target