Ablation of cervical facet joints is safe and feasible with two magnetic resonance-guided focused ultrasound transducers as demonstrated by thermal simulations.

Abstract

Background: Chronic neck pain due to cervical facet joint degenerative disease is a leading cause of disability. Denervation of the facet joint capsule with magnetic resonance-guided focused ultrasound (MRgFUS) ablation could provide a noninvasive treatment option. Our study investigates the safety and feasibility of targeting the cervical facet joints with two clinical transducers.

Methods: We simulated MRgFUS treatments in the cervical spine of six individuals using models from MR datasets segmented into eight tissue types. We determined the feasibility of targeting the facet joints in every cervical vertebral level at different trajectories for two 1 MHz clinical transducers. Using acoustic (hybrid angular spectrum method) and thermal (Pennes' bioheat equation) simulations, we determined the feasibility of reaching ablative temperatures at the targets while avoiding thermal damage in off-target locations.

Results: Both simulated transducers produce ablative or near-ablative temperatures at the target while maintaining tissue safety in off-target locations. We quantified the tissue temperature during a 20-second sonication at the target and in important surrounding structures including the spinal nerves, the spinal cord, surrounding CSF, and the major cervical arteries. Temperatures in critical structures demonstrated a less than 3 °C temperature rise, which is well within the level for tissue safety. Ablative thermal doses were achieved at the target (>240 CEM at 43 °C).

Conclusion: This simulation study demonstrates the feasibility and safety of targeting cervical facet joint capsules with clinically available MRgFUS transducers. Integrating these transducers into an MRgFUS device introduces a novel noninvasive modality to treat cervical neck pain.