Thermal effect of percutaneous radiofrequency ablation with a clustered electrode for vertebral tumors: in vitro and vivo experiments and clinical application
To investigate the effect and heat distribution of radiofrequency ablation (RFA) on vertebral tumors in swine experiments in vitro and in vivo and its clinical application.
Materials and methods
RFA was performed on the swine spine in vitro and in vivo for 20 minutes at 90 °C at the electrode tip, and the temperature at the electrode tip and surrounding tissues were recorded before and after ablation. Clinical application of ablation combined with vertebroplasty was subsequently performed in 4 patients with spinal tumors.
In the in vitro study, the mean temperature at the front and ventral wall of the spinal canal was 50.8 °C and 43.6°C, respectively at 20 mm significantly greater than 37.7 °C and 33.7±1.7 °C, respectively, at 10 mm ablation depth. The coagulative necrosis area was significantly (P<0.0001) greater at 20 mm depth than at 10 mm depth (mean 17.0×20.7 mm2 vs. 14.2×16.6mm2). In the in vivo experiment, the local temperature increased significantly (P<0.05) from around 36 °C before ablation to over 41 °C at 20 minutes after ablation, with the temperature at the electrode tip (90.4°C) and withint the vertebral body (67.0°C) significantly (P<0.05) greater than at the posterior (41.9°C) and lateral wall (41.8°C). Immediately and one week after RFA, coagulative necrosis was present in the ablation site. From 2 to 5 weeks, bone remodeling began with proliferatin of granulation, fibrous tissues, callus, and normal bone trabecula. Clinically, all four patients had successful RFA and vertebroplasty, with no neurological deficits. The pain scores were significanlty (P<0.05) improved before (4.5-10, mean 8.0) compared with at four weeks (0-1.8, mean 1.8). Radiological examination revealed good filling of the bone cement in all the osteolytic area except for one patient who had cement leakage. The vertebral bodies remained intact in the rest three patients.
The clustered electrode can be efficiently and safely applied in the treatment of spinal tumors without damaging the spinal cord and adjacent nerves by heat distribution.
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