MR-guided focused ultrasound appears to be safe and effective for treating osteoid osteoma, according to a preliminary study published online Feb. 7 in Radiology.

The technique could provide an alternative to conventional therapy options, such as surgery, pharmacologic treatment or percutaneous treatment, according to Alessandro Napoli, MD, and colleagues from the University of Rome La Sapienza.

“Unlike other ablative techniques, MR-guided focused ultrasound is totally noninvasive and can be performed relatively fast in a single session with limited amounts of energy deposition (compared with other MR-guided focused ultrasound bone applications),” wrote the authors.

While painful, osteoid osteoma is a benign lesion that usually affects patients between the ages of 10 and 20 years, explained the authors. Radiofrequency ablation is the most popular percutaneous treatment, and it has high success rates, though it still requires a small amount of intervention.

To test the effectiveness of MR-guided focused ultrasound, Napoli and colleagues conducted a prospective study involving six consecutive patients with a diagnosis of osteoid osteoma based on clinical and imaging findings.

3T MRI guidance stood to be particularly helpful thanks to its ability to provide detailed morphologic evaluation of both the target lesion and adjacent areas of the patient’s body, according to the authors. MR thermometry also enabled real-time temperature monitoring and an indirect estimation of thermal damage to the periosteum and surrounding bone.

Results showed treatment was performed with a mean of four sonications and a mean energy deposition of 866 joules. The authors reported no treatment- or anesthesia-related complications and at imaging, the edema and hyperemia associated with the condition gradually disappeared in all lesions.

Patients reported that their pain also completely disappeared. Prior to treatment, the mean visual analog scale score for pain was a 7.9, and following treatment it was 0.0.

Napoli and colleagues noted that despite the relief in pain, nidus vascularization still persisted after treatment in four of the six patients. “Thus, the complete pain relief observed after MR-guided focused ultrasound ablation may be related to periosteal neurolysis rather than nidus deactivation as a consequence of heat accumulation and partial coagulative effect,” they wrote.

The authors added that further study will be required to determine the precise mechanism of action and compare the technique directly with other ablative alternatives.