Fig 1.
Targeting of peripheral nerve using MR-HIFU treatment planning system.
The sciatic nerve is hyper-intense on MR neurography and iso-intense on T1 where dual-bundle structures are seen against fat. HIFU beam overlay (white) indicates 12 mm diameter target region.
Table 1.
MRI protocol for MR-HIFU for peripheral nerve ablation.
Table 2.
Characteristics of consecutive experiments.
Fig 2.
MR thermometry guidance of HIFU thermal ablation of peripheral nerves.
Temperature maps (top) indicate peak temperature of 82.5°C. Thermal dose maps (bottom) predict lesion size of 12 x 29 mm.
Fig 3.
MR neurography of pig sciatic nerve before (top) and after (bottom) MR-HIFU.
SHINKEI images reconstructed as thick-slab (15 mm) maximum intensity projections in sagittal, axial, and coronal orientations.
Fig 4.
MRI evaluation of thermal lesions in peripheral nerve.
Hyperintense region on 3D diffusion-prepared MR neurography (top) corresponds with non-enhancing region on T1 post-contrast image.
Fig 5.
Boxplot of lesion diameter and length in 12 mm treatment cells (n = 5) as measured on imaging, thermometry and macroscopy.
Fig 6.
Light microscopy images of nerves, H&E staining.
A Untreated peripheral nerve at 5x magnification. B Treated peripheral nerve (6 mm distal to center of ablation) at 5x magnification showing epineurial collagen homogenization (a), vascular congestion (b), widening of the subperineural space (arrow). C Untreated peripheral nerve 40X detail of axons and Schwann cells. D Treated peripheral nerve 40x detail showing regressive nuclear changes karyolysis (dashed arrow) and pyknosis (arrow) and vacuolization (arrowhead).
Fig 7.
Light microscopy images of peripheral nerves at 40x magnification, Masson’s trichrome staining.
A Normal appearance of myelin on Masson’s trichrome; myelin sheaths stain purple-red (black arrow). B Section of treated peripheral nerve at the center of the lesion showing absence of purple-red staining (arrow) indicating acute damage to the myelin sheaths. Asterisk (*) indicates subperineural edema.
Fig 8.
Light microscopy images at 40x magnification of semi-thin (1.5 μm) toluidine blue stained sections A Normal appearance of myelinated (arrow) nerve fibers in a cross section. B Pallor and irregularity of myelin (arrow) and vacuolization (a) in a HIFU-treated nerve segment.
Table 3.
Histological analysis of treated peripheral nerve segments.