Experimental Study Of MRI-guided Radiofrequency Ablation For Treatment Of VX2 Tumor Adjacent To Major Blood Vessels In Rabbit Liver

Object: To study the feasibility and curative effect of MRI-guided radiofrequency ablation for treatment of VX2 tumor adjacent to major blood vessels in rabbit liver, and evaluate the MRI findings and pathological features of the ablation lesions.Methods: 2 New Zealand rabbits were inoculated VX2 tumor in bilateral thigh muscle, the tumor formating, as the cell lines to establish the rabbit model bearing VX2 tumor near blood vessel in liver. The 11 New Zealand rabbits were anesthesia by 1ml/kg of ketamine and 0.5ml/kg of chlorpromazine injected, fixed in MRI scanning bed, using a specific liver scan sequence, determine the path, direction and depth of puncture. Under sterile conditions and the guidance of 1.5 T MRI, with 14 G magnetic resonance compatible puncture needle, the VX2 tumor was implanted near the large blood vessel in rabbit liver. The liver examination of MRI was performed 2 weeks after the implantation and 1 rabbit were executed radomly for Pathological examination.Under sterile conditions,the remaining 10 rabbits received 1.5 T MRI-guided percutaneous radiofrequency ablation(RFA) treatment. Vitamin E pills positioning, determined the puncture point and angle of needle, with 14 G magnetic resonance compatible puncture needle puncture along the set point, repeated 3D-VIBE scan to determine the direction of the puncture needle,and then gradually put the RITA RF needle to penetrate the tumor along sheath of puncture needle. The scanning bed was moved back to its original position, and then RF needles and skin electrode wires were connected with the extension cable; the power was set to 35 w, and the target temperature was set to 103℃, and ablation time was set to 12 min. After completion of the ablation, the radiofrequency generator power was switched off and the wire was unplugged. Routine MRI was performed to assess the therapeutic effect. The scope of ablation was generally 0.5–1.0 cm beyond the lesion edge where the ablation was complete. In case of residual lesions,additional ablation was performed. The 10 rabbits were sacrificed immediately after MRI scan and examinated the pathological to confirm whether the tumor rimainded.Results:1. All of the VX2 liver tumor of rabbits were established successfully, there were a total of 12 lesions each tumor diameter of 1-1.5cm(average1.35cm), 11 lesions adjacent to major blood vessels without vascular invasion and 1 lesion appeared metastases along the needle track. The tumor MRI expression: the lesions showed slightly low intensity signal on 3D-VIBE and part of the tumor necrosis in the center showed lower signal; the lesions showed slightly high intensity signal on T2 WI and part of the tumor in the center was higher, and the blood vessels was presented empety signal. Histopathological examination confirmed VX2 tumor tissue.2. All of the VX2 liver tumor of rabbits were treated successful of RFA. 11 lesions were melted in 20 times, with twice per lesion in average. Among the 11 lesions, 4 were melted once respectively, 5 were melted twice respectively and 2 were melted three times respectively. Postoperative imaging of the lesion melt completely showed a low-intensity signal on T2WI; the ablation lesions showed a concentric pattern on 3D-vibe: the central area of the original lesion continued to show a low-intensity signal and was surrounded by a clear ring with high-intensity signal that had a clear boundary,and for pathological examination, there were no tumor cells founded. Postoperative imaging of the lesion melt incompletely showed a high signal ring of ablation lesions was not completely around the low signal lesions on 3D-VIBE, and Histopathological examination revealed that the tumor was VX2.Conclusion:1. The implanting VX2 tumor near blood vessel in rabbit liver under the guidance of MRI is a minimally invasive and effective modeling method. 2. MRI scan can accurately show the ablation range, is the effective method to evaluate the efficacy of radiofrequency ablation of small hepatocellular carcinoma. 3.The MRI-guided radiofrequency ablation for treatment of VX2 tumor adjacent to major blood vessels in rabbit liver is an effective and feasible technology.