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. 2019 May 1;84(5):1138-1148.
doi: 10.1093/neuros/nyy266.

Robotic Assisted MRI-Guided Interventional Interstitial MR-Guided Focused Ultrasound Ablation in a Swine Model

Jacquelyn MacDonell  1 , Niravkumar Patel  2 , Gregory Fischer  2 , E Clif Burdette  3 , Jiang Qian  4 , Vaibhav Chumbalkar  4 , Goutam Ghoshal  3 , Tamas Heffter  3 , Emery Williams  3 , Matthew Gounis  5 , Robert King  5 , Juliette Thibodeau  1 , Gene Bogdanov  5 , Olivia W Brooks  6 , Erin Langan  6 , Roy Hwang  1 , Julie G Pilitsis  1   7
Affiliations

Robotic Assisted MRI-Guided Interventional Interstitial MR-Guided Focused Ultrasound Ablation in a Swine Model

Jacquelyn MacDonell et al. Neurosurgery. .

Abstract

Background: Ablative lesions are current treatments for epilepsy and brain tumors. Interstitial magnetic resonance (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).

Objective: To describe our experience with interstitial focused ultrasound (iFUS) ablations in swine, using MR-guided robotically assisted (MRgRA) delivery.

Methods: In an initial 3 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, 6 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 was 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 wk postprocedure. Immediately following iMRgFUS therapy, diffusion-weighted imaging, and T1 weighted MR were accurate reflections of the ablation volume. T2 and fluid-attenuated inversion-recovery (FLAIR) images were accurate reflections of ablation volume 1-wk postprocedure.

Conclusion: We successfully performed MRgRA iFUS ablation in swine and found intraoperative and postoperative 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.

Keywords: Brain tumor; High intensity focused ultrasound; Interstitial focused ultrasound; MRI-Guided; Neural ablation; Robot assisted surgery.

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Figures

FIGURE 1.
FIGURE 1.
A, Photo of an applicator inserted into a catheter used for the experiment. B, Fabricated ultrasound applicators with 1, 2, 3, and 4 transducers. C, TheraVision™ ultrasound thermal therapy system (Acoustic Medsystems) with 1 to 4 RF output channels used to power each transducer element.
FIGURE 2.
FIGURE 2.
Registration of the robot using multiple coronal images of the fiducial frame (top left image). By attaching the fiducial frame to the robot and then acquiring a stack of coronal images, the registration transformation from the image coordinate system and the robot coordinate system is determined using software algorithms developed during this program.
FIGURE 3.
FIGURE 3.
A, Robotic manipulator and base platform without draping. B, Sterile environment for survival surgeries created by draping both the animal and robot manipulator in a sterile plastic sheet. Wires and tubing leaving the robot manipulator were wrapped in a sterile surgical cloth that was secured by zip ties.
FIGURE 4.
FIGURE 4.
MR images used throughout the procedure starting with fiducial frame robot registration (top left) and ending with MRTI (bottom).
FIGURE 5.
FIGURE 5.
Custom wire surface coil for pig brain imaging: A, CAD model; B, prototype with insulation and wires bent into the desired shape.
FIGURE 6.
FIGURE 6.
Postexplant examination revealing subarachnoid blood.
FIGURE 7.
FIGURE 7.
Comparison of MRI imaging sequence to histological section for an acute surgery where TTC staining methods were utilized. Each row represents a different MR-imaging sequence taken at tp0. Each column represents an MRI slice taken at the same location as the histological section.
FIGURE 8.
FIGURE 8.
A, Low power view (5×) of petechial hemorrhage in/near hippocampus. B, Higher power view (20×) of petechial hemorrhage in/near hippocampus, with edema and pyknotic and eosinophilic neurons visible (within rectangles).
See this image and copyright information in PMC

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