Percutaneous Spinal Ablation in a Sheep Model: Protective Capacity of an Intact Cortex, Correlation of Ablation Parameters with Ablation Zone Size, and Correlation of Postablation MRI and Pathologic Findings

Anteroposterior (A) and lateral (B) CT images of a normal lumbar vertebra. The thick black line represents the unilateral transpedicular trajectory of the ablation probe. By definition, the transverse and anteroposterior dimensions of the ablation zone are parallel and perpendicular to the ablation probe in the axial plane, respectively, and the craniocaudal dimension of the ablation zone is perpendicular to the ablation probe in the sagittal plane.

Sagittal postcontrast T1-weighted image with fat suppression (A) and a T2-weighted image (B) of the vertebral level treated with cryoablation show the ablation zone extending beyond the posterior vertebral body into the spinal canal. There is enhancement and intramedullary T2 signal hyperintensity in the ventral aspect of the edematous spinal cord (white arrowheads). There is also inflammation in the soft tissues ventral to the spine where the ablation zone extended beyond the anterior vertebral body cortex (white arrows). Sagittal postcontrast T1-weighted image (C) and axial T2-weighted image (D) of the vertebral level treated with microwave ablation similarly show extension of the ablation zone into the spinal canal (white arrowheads). E, Hematoxylin-eosin staining of the spinal cord at the level of the cryoablated vertebra at ×100 total magnification shows axonal necrosis and edema. Similar findings were seen at the microwave-ablated level (not shown). F, Sagittal postcontrast T1-weighted image with fat suppression of the radiofrequency-ablated vertebra shows the posterior margin of the ablation zone confined to the vertebral body.

MR imaging findings 7 days after RFA of an L2 vertebral body in a sheep model. A, T1-weighted oblique sagittal MR imaging (left, anterior; right, posterior) shows T1 hyperintense soft tissue within the probe tract (black asterisk) outlined by a signal void. The surrounding ablation zone is isointense to normal marrow and outlined by a thin hyperintense rim (white arrowheads). B, T2-weighted oblique sagittal MR imaging with fat suppression shows the hyperintense probe tract (black asterisk) and slightly hypointense ablation zone surrounded by a hyperintense rim (white arrowheads). C, T1-weighted, postcontrast subtraction images show enhancement along the probe tract (black asterisk) and the nonenhancing ablation zone surrounded by a rim of enhancement (white arrowheads).