Introduction: Ablative lesions are current treatments for epilepsy and brain tumors. Interstitial MR guided focused ultrasound (iMRgFUS) may be an alternate ablation technique which limits thermal tissue charring as compared to laser therapy (LITT) and can produce larger ablation patterns nearer the surface than transcranial MR guided focused ultrasound (tcMRgFUS).
Methods: In an initial three animals, we optimized the workflow of the robot in the MR suite and made modifications to the robotic arm to allow range of motion. Then, six farm pigs (4 acute, 2 survival) underwent 7 iMRgFUS ablations using MRgRA. We altered dosing to explore differences between thermal dosing in brain as compared to other tissues. Imaging were compared to gross examination.
Results: Our work culminated in adjustments to the MRgRA, iMRgFUS probes and dosing, culminating in 2 survival surgeries; swine had ablations with no neurological sequelae at 2 weeks post-procedure. Immediately following iMRgFUS therapy, DWI and T1 weighted MR were accurate reflections of the ablation volume. T2 and FLAIR images were accurate reflections of ablation volume 1-week post procedure.
Conclusions: We successfully performed MRgRA iFUS ablation in swine and found intraoperative and post-operative imaging to correlate with histological examination. These data are useful to validate our system and to guide imaging follow-up for thermal ablation lesions in brain tissue from our therapy, tcMRgFUS, and LITT.
Patient Care: If successful, this therapy offers an alternative approach to the treatment of brain metastases that allows for both diagnosis and immediate tumor ablation.
Learning Objectives: Here we describe our experience with interstitial focused ultrasound (iFUS) ablations in swine, using MR guided robotically assisted (MRgRA) delivery.