| Purpose: By establishing a rabbit liver VX2 tumor model and MRI-guided microwave ablation of rabbit liver VX2 tumor,MRI(magnetic resonance imaging)and pathological findings of rabbit liver VX2 tumor after MWA(microwave ablation)were compared,and the correlations between the microwave ablation site MRI and pathology of liver tumor were also analyzed.Methods: The VX2 tumor strain was inoculated into the muscles of both hind legs of two New Zealand white rabbits to make the tumor passaged after establishing the tumor of the rabbit liver VX2 tumor model.12 New Zealand white rabbits were implanted with MRI-guided percutaneous transhepatic puncture.The rabbits were fixed on MRI scans after general anesthesia.Body surface positioning by using vitamin E pills,determine the puncture path,direction and depth.In aseptic conditions,with 16 G magnetic-compatible puncture needle under the guidance of MRI gradually into the rabbit liver and planting VX2 tumor mass.After 2-3 weeks,MRI scans confirmed tumor growth and diameter ? 1.5 cm.MRI findings of the tumor foci were performed on MRI scans.Two experimental rabbit was sacrificed randomly and pathological verification was done.Under general anesthesia and aseptic conditions,the rest of the 10 tumor-bearing rabbits underwent MRI-guided microwave ablation.A disposable,magnetic-compatible,water-cooled circulating microwave antenna was used to gradually advance the needle along the set angle,direction and depth.Multiple intraoperative scans confirmed the positional relationship between the microwave antenna and the tumor.The microwave antenna penetrated the tumor foci along the center of the tumor,connected the water cycle and microwave connection cable,set the output power 40-60 w,continuous treatment 3-5min.After MWA,MRI scanning was performed to evaluate the ablation efficacy.Completely wrap around the ablation zone and exceed the primary tumor 0.5-1cm for the complete ablation of the tumor.If the ablation effect is unsatisfactory,supplementary ablation.Immediately after microwave ablation,MRI scans were performed to observe appearance of ablation lesions.The rabbits were sacrificed after MRI scan and the liver was removed for histopathological examination.Measure the maximum diameter of preoperative tumor on MRI.Measure the maximum diameter of central low signal area,surrounding ring high signal area and the outermost low signal ring on the 3D-Vibe-T1 WI sequence after ablation,the maximum diameter of the periphery's low signal ring,the maximum diameter of the low signal zone and the surrounding annular high signal zone on the fs-tse-T2 WI sequence after ablation,the maximum diameter of the coagulation necrosis area and the thermal injury edema congestion area in the pathological gross specimen.In the meantime,The above diameter were measured for paired sample analysis.Results: 12 rabbits successfully completed tumor modeling after percutaneous transhepatic inoculation of the tumor.All the tumors were inoculated into the left liver,forming a total of 12 lesions with an average diameter of about 1.84 ± 0.29 cm.Two tumor-bearing rabbits were sacrificed and pathologically confirmed.Ten liver VX2 tumors in 10 experimental rabbits were successfully performed MRI-guided MWA.Ten tumors were ablated 12 times,of which 8 tumors were ablated only once,and 2 lesions were supplementary ablation due to incomplete ablation.The average ablation power was about(50.5 ± 4.5)W and the average ablation time was(4.3 ± 0.6)min.Forthwith MRI imaging of rabbit liver VX2 tumor after MWA showed "target sign" in the sequence of 3D-Vibe-T1 WI after ablation,low signal needle trace in ablation zone,low signal in tumor zone and high signal completely surround the tumor.Fs-tse-T2 WI sequence in the middle of the ablation zone to see the high signal needle trace,the tumor signal was reduced compared with preoperative,in the surrounding area,there was a low signal ablation area,and a circular high signal appeared in the periphery.DWI showed a low signal around the ring to see the high signal.High signal on ADC.MRI scanning of two rabbits after MWA see a small amount of short T1 and long T2 hemorrhage under the liver capsule.Measurement of ADC value in tumor area before and after operation in 10 rabbits.The average ADC value of preoperative tumor was(0.82 ± 0.12)×10-3 mm2/s and ADC value of tumor area after operation was(1.43 ± 0.24)×10-3 mm2/s,using SPSS22.0 t test,P <0.05,with significant statistical differences.The pathological examination showed 10 lesions after MWA complete tumor ablation,gross specimen were seen in the center of the lesion area of needle tract is Black carbonized fissure.,the tumor tissue showed gray coagulation necrosis,and the hepatic parenchyma around the tumor showed coagulative necrosis of grayish yellow,and hyperemia and edema band surrounded the lesion between the lesion and the normal liver parenchyma.Optical microscope observation(hematoxylin-eosin staining)ablation zone from the inside to the outside were: tumor coagulative necrosis,hepatic parenchyma coagulative necrosis and hemorrhage edema zone.In the area of coagulation necrosis of the tumor,a large number of large nuclei and deep dyed cells(ghost cell),which are similar to normal tumors cell.In the coagulative necrosis area of the liver,the hepatic lobule structure disappeared,the liver cell cord ruptured,the hepatocytes atrophied,the nuclei contracted,the hepatic sinusoids expanded,and a large number of ghost red cell were seen.The most peripheral congestion,edema,inflammatory area and normal liver parenchyma were not clear.Near the ablation area,liver tissue was obviously congested and edema,peripheral vascular dilatation,the hepatic sinusoids expanded Infiltration of neutrophils,macrophages,and lymphocytes in peripheral areas of edema.There was no significant difference between(P>0.05)the maximum diameter of the 3D-Vibe-T1 WI high signal ring(4.96±0.90)and the maximum diameter of the fs-tse-T2 WI low signal zone(4.97±0.86),the maximum diameter of the 3D-Vibe-T1 WI high signal ring(4.96±0.90)and the maximum diameter of solidification necrosis area in the gross specimen(4.97±0.89),the maximum diameter of the peripheral low signal area in the 3D-Vibe-T1WI(5.24±0.86)and the maximum diameter of the peripheral high signal loop in the fs-tse-T2WI(5.27±0.85),The maximum diameter of the central low signal zone in the fs-tse-T2WI(4.97±0.86)and the maximum diameter of the coagulation and necrosis zone of the gross specimen(4.97±0.89),the maximum diameter of the peripheral high signal ring of the fs-tse-T2WI(5.27±0.85)and the maximum diameter of congestion area in gross specimen(5.30±0.86).The remaining data were statistically significant(P<0.02).Conclusion: 1.MRI-guided MWA treatment of rabbit liver VX2 tumor is an effective and feasible method of minimally invasive intervention.2.MRI imaging can clearly distinguish the post-ablation tissue changes,and is well-matched with pathological zoning,and is an effective means to evaluate the efficacy of liver cancer MWA. |
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