Update on musculoskeletal applications of magnetic resonance-guided focused ultrasound

Abstract

Magnetic resonance-guided focused ultrasound (MRgFUS) is a noninvasive, incisionless, radiation-free technology used to ablate tissue deep within the body. This technique has gained increased popularity following FDA approval for treatment of pain related to bone metastases and limited approval for treatment of osteoid osteoma. MRgFUS delivers superior visualization of soft tissue targets in unlimited imaging planes and precision in targeting and delivery of thermal dose which is all provided during real-time monitoring using MR thermometry. This paper provides an overview of the common musculoskeletal applications of MRgFUS along with updates on clinical outcomes and discussion of future applications.

Keywords: Bone metastases; Desmoid tumor; Facet arthropathy; High-intensity focused ultrasound; Magnetic resonance-guided focused ultrasound; Osteoid osteoma; Thermal ablation.

Fig. 1

Osseous metastasis. A Axial fused pre-treatment FDG PET/CT of the left iliac bone in a patient with metastatic clear cell sarcoma demonstrating hypermetabolism (white arrows) within the bone and adjacent soft tissue. B Post-treatment axial T1 post-contrast images demonstrate relative hypoenhancement within the ablation area with minimal rim enhancement

Fig. 2

Osteoid osteoma. A Axial CT image in a patient who developed recurrent night pain relieved with NSAIDS approximately 10 months after initially successful CTgRFA for osteoid osteoma. The circle demonstrates an area of persistent subcortical lucency consistent with recurrent or residual nidus. B Pre-treatment axial T1-weighted FSPGR image demonstrates slight hyperintensity at the location of the nidus, highlighted by the circle. C Pre-treatment axial T2 FS image demonstrates subtle bone marrow edema pattern and overlying soft tissue edema at the site of the nidus, highlighted by the circle. D Post-treatment axial T1-weighted FSPGR post-contrast image demonstrates mild hypoenhancement at the treated nidus and mild hyperenhancement of the overlying soft tissues, highlighted by the circle. The patient’s pain completely resolved the day following the treatment

Fig. 3

Desmoid tumor. A Pre-treatment axial T1-weighted fat-saturated post-contrast sequence obtained prior to MRgFUS demonstrates a homogeneously enhancing mass in the lateral hip superior to the greater trochanter, compatible with a biopsy-proven desmoid tumor (white arrow). B Post-treatment axial T1-weighted fat-saturated post-contrast sequence performed immediately following MRgFUS exhibits 85% ablation area with minimal residual rim enhancement (white arrows). Water bags (asterisks) are positioned anterior and lateral to the right hip to minimize the risk of skin injury