Focused ultrasound for bone mets

Radiology has a small case series about using MRI-guided focused ultrasound to treat painful bone metastases.  It works exactly how it sounds.  It requires conscious sedation and was done on an outpatient/same-day basis.  This study is a small case series (n=11) of patients with persistently painful bone mets who had failed routine treatments, including external beam radiotherapy.  Average pain decreased from ~6/10 at baseline to ~4/10 at day 2 and 2/10 two weeks out.  Of course this is an uncontrolled case series and patients were presumably being treated with other modalities.  

The authors note that the mechanism of analgesia with this is unclear but people speculate it's due to destruction of periosteal innervation.  That said, they heated the tumors up to 65 degrees celsius and noted many patients had obvious necrosis on MRI afterwards so presumably there is an analgesic effect from tumor control as well.  The potential advantages of this over other ablative procedures (e.g. cryoablation, radiofrequency ablation) is that it's non-invasive.  One hopes larger/controlled trials are in the works.  While I have access to cryo and RFA for my patients, this is not yet available at my institution:  anyone have any experience with this?