Experimental Study Of Radiofrequency Ablation On Rabbit Pulmonary VX2 Tumor

Objective: To make a control analysis of the CT,MRI and pathological manifestations of acute thermal damages after giving radiofrequency ablation(RFA)to rabbit pulmonary VX2 tumor,and analyze the CT-MRI-pathological connection of RFA foci of pulmonary tumor through establishing rabbit pulmonary VX2 tumor models and performing CT-guided rabbit pulmonary VX2 tumor RFA.Methods: VX2 tumor was seeded in the medial muscles of bilateral rear legs of New Zealand male rabbits,which were induced to develop cell strains for the establishment of rabbit pulmonary VX2 tumor models.12 New Zealand male rabbits were fixed on the CT scan bed after the general anesthesia,then the puncture route,direction and depth were ascertained,and under the conditions of sterility,17 G puncture needle gradually reached the rabbit lungs under the guidance of CT,where the VX2 tumor tissue block was seeded.2 to 3 weeks thereafter,the CT scan confirmed the formation of intrapulmonary nodules,and MRI scan was performed to observe the MRI manifestations of tumor foci.One experimental rabbit was sacrificed randomly and pathological verification was done.The tumor-bearing rabbits were given CT-guided RFA under the conditions of sterility,and the 17 G cool-tip radiofrequency electrode needle was entered gradually along the preset angles and depth;during the operation,multiple scans were performed to determine the relationship of tumor space;the ablation needle tip penetrated the tumor along the center of the tumor,then cool-tip was connected and the automatic ablation mode was set,the output power was set to be 40 to 80 w,and the continuous treatment lasted for 3 to 5 minutes.After RFA was completed,CT plain scan was performed to observe the ablation efficacy;in case that the peri-tumor ground glass shadows exceeded the lesions by 5 to 10 mm,the evaluation was complete ablation.In case that it was satisfying ablation,then the needle was withdrawn after the needle track ablation.In case that the ablation result was dissatisfying,supplementary ablation was needed.MRI scan was immediately performed on the ablation foci after the RFA to observe the MRI manifestations of ablation foci;after the scan was completed,the experimental rabbits were sacrificed and histopathological examinations were carried out.After the operation,the CT values of pre-RFA and post-RFA tumor foci were postoperatively measured,and the following parameters were measured: the maximal diameter of pre-RFA MRI tumor foci,the maximal diameter of post-RFA fs T2 WI central low signal regions,the maximal diameter of 3DTI-VIBE central high signal regions,and the maximal diameter of pathological coagulation necrosis.In the meantime,the following parameters were measured for control analysis: the maximal diameters of post-RFA peri-CT-tumor-foci ground glass shadows and post-RFA peripheral high signal regions on the T2 WI,the maximal diameter of the 3DTI-VIBE equisignal regions on 3DTI-VIBE and the maximal diameter of pathological thermal damage regions.Results: The seeding of rabbit pulmonary VX2 tumor into 12 experimental rabbits was successful,9 presented with intrapulmonary single circular or quasi-circular tumor foci,and the tumors had the maximal diameter of 10.0-14.5mm,with a mean diameter of about 12.5±1.8mm.One presented with multiple intrapulmonary tumors with wide pleural metastases.One tumor-bearing rabbit was sacrificed and pathological verification was done.The single pulmonary VX2 tumors in 8 rabbits successfully underwent the CT-guided RFA.8 tumors underwent 10 ablations,among which 6 underwent 1 ablation and 2 underwent 2 ablations,with a mean ablation power of about 50.5±4.5w,a impedance of about 160-350?,and a mean ablation duration of 4.3±0.6min.The CT manifestations of RFA foci were slightly decreased density in the original tumor foci when compared with before,the presence of ground glass shadows of slightly high density being wrapped by the original tumor foci,and the presence of gasification shadows;low signals were visible in the center of MRI fs T2 WI of ablation foci,and ring-shaped long T2 signals were visible in the peripheral regions;high signals were visible at the center on 3DTI-VIBE,and ring-shaped equal T1 signals were visible in the peripheral regions;the signals of the tumor foci on DWI decreased significantly.The comparison with the following parameters yielded a statistically significant difference: the maximal diameter of high signal regions at the center on 3DTI-VIBE and the maximal diameter of pathological coagulation necrosis regions after PFA,and the comparison with the maximal diameter of the peri-CT-tumor-foci ground glass shadows,the maximal diameter of peripheral high signal regions on the fs T2 WI,the maximal diameter of the 3DTI-VIBE equisignal regions on 3DTI-VIBE and the maximal diameter of pathological thermal damage regions.Pathological examinations found that,the tumors of 7 tumor foci were all deactivated after RFA,and as for 1 tumor focus,tumor residue was visible at the vascular side near the hilar.Conclusion: 1.CT-guided rabbit pulmonary VX2 tumor tissue block implantation is a minimally invasive and effective modeling method.2.CT-guided RFA treatment for rabbit pulmonary VX2 tumor is an effective and feasible minimally invasive intervention method.3.MRI scan accurately display the range of ablation foci and is good control with pathology,so it is an effective measure in evaluating the efficacy of RFA in pulmonary carcinoma.