3:54 PM Abstract No. 55 - Irreversible electroporation (IRE) ablation of the lumbar vertebrae in a porcine model: a correlation of clinical, radiologic and pathologic findings

Abstract

Purpose To evaluate the effects of IRE ablation of the lumbar vertebrae in pigs. Materials and Methods Sixteen CT-guided IRE ablations [transpedicular location, (n=8 vertebrae) and directly over the posterior cortex (n=8 vertebrae)] were performed in the lumbar vertebrae of 8 pigs. Magnetic resonance imaging (MRI) was obtained immediately prior to euthanasia at 2 or 7-days postablation. Clinical, imaging and histopathological data were analyzed. The maximum length and width of the ablation zone was measured on the T2 and T1 + contrast MRI sequences and compared with histopatholgic measurements. Miller’s low-bias back-transformation was used to construct 95% confidence intervals for the mean absolute percent difference using square root transformed data. Results IRE probe placement and ablation was successful in all cases. The mean distances from the IRE probe to the posterior wall of vertebral body or the exiting nerve root were 2.93 ± 0.77 mm and 7.87 ± 1.99 mm respectively. None of the animals had neurologic deficits or MRI findings of focal myelopathy or radiculopathy. Well delineated areas of necrosis of bone marrow and bone tissues, and acute degeneration and necrosis of skeletal muscle adjacent to the vertebral body were present. These lesions were associated with tissue repair changes in the 7-day postablation animals. Four of 8 ablations in the transpedicular group and 3 of 8 ablations in the posterior cortex group had minimal to moderate acute degenerative lesions of adjacent nerve roots that were not clinically significant. The absolute percent difference of ablation measurements between MRI sequences and histopathological lesions showed an average error range of 24.2-28.8% [95% CI: (12.2%, 47.3%)] on T2 and 26.1-33.3% [95% CI: (15.1%, 52.6%)] on T1+contrast sequences. Conclusion IRE ablation of the lumbar vertebrae in pigs is feasible, safe, and produces localized necrosis of the bone, bone marrow and muscle tissues. No neurological clinical symptoms were associated with this procedure. MRI signal changes are not accurate indicators of the ablation zone when compared with histopathologic findings.