Experimental Study Of Hepatic Ablation By Nanoknife

Purpose1、Using Nanoknife to make CT-guided percutaneous ablative lesions of liver in swine,to evaluate clinical feasibility of irreversible electroporoation(IRE) procedure, as well as to determine safety and effectiveness.2、To discuss ablative mechanism of IRE,by observing the radiological and histological characteristics of the lesions, especially specific immune cell apoptosis analysis.3、To compare advantages and limitations of an IRE device (Nanoknife) and a argon-helium cryoknife (CryoHit),by respectively ablation in a same liver parenchyma of swine, as a result, to evaluate the possibility in combination of the two ablative methods.Materials and Methods1、Ten miniature pigs underwent CT-guided NanoKnife of normal liver. The animals randomly divided into five groups, and each group contains 2 animals.Two electrode probes (diameter 19G/1.06mm, exposure 2.5cm)were positioned 1.5 cm apart. The ablation procedure was performed 90 pulses of 1500-2000V/cm(pulse length of 70μsec 10 groups with interval time of 3.5s).Ablation zones were created in liver parenchyma and hilum. Radiologic analysis, containing computed tomography(CT) and magnetic resonance image (MRI) were performed on 5 time points, that is postoperative 1 day,3days,7days,14days and 28days,which was corresponding to 5 groups. Then animals were put to death to make histological evaluations including hematoxylineosin (H-E), Von Kossa staining, von Willibrand factor (vWF) staining, and terminal deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) assay. Apoptosis index(AI) was involved in TUNEL detect, to make statistical analysis in different time points of both ablative and non-ablative zones, statistical figure was performed to describe the variation of AI.2、Four miniature pig, evenly divided into two groups, were enrolled in the contrast experiment. All experimental animals were received both Nanoknife and CryoHit ablations in the same liver. Ablation parameters of Nanoknife were the same as above. As for single-needle cryoablation, two freeze-thaw cycles were designed, containing 6 minutes of freezing and 2 minutes of thawing. CT scans were performed in intraperative and postoperative period, to compare the different characteristics and changes of the two ablation lesions. Animals in first group were put to death immediately after the operation, and the other group was done that after 30 days, then histological differences were detected.Results1、All animals survived.Their daily activities were of no difference with preoperative period. One animal were found a small amount of ascites, with yellow clear liquid. Significant bleeding, infection, organ damage and other serious complications were not encountered.A total of 24 ablation zones were created, and 16 in hepatic parenchyma and the other 8 in hilum. The ablation zones were well characterized with enhanced CT and MR imaging, which were charactered by homogeneous low density or signal without enhancement immediately after the ablation. However, changes began from postoperative 14 days. The ablation areas appeared mild to moderate enhancement from the edge, besides, the borderline gradually blurred. HE, Von Kossa and vWF staining showed cell death with a sharply demarcated treatment area, and without evidence of heat sink. Bile ducts and vessels were completely preserved. Positive effect of cell death for apoptotic markers (TUNEL) occurred in ablation areas, suggesting involvement of the apoptotic process in the pathology of cell death caused by NanoKnife. Statistical analysis of AI between ablative and non-ablative zones showed obvious difference (P<0.05). Ablative AI changed over time. AI began to ascend after ablation, and postoperative 3 days up to the highest, about 48.8±13.9%, then it descended gradually to the same level with non-ablative zones when postoperative 28 days (P>0.05).2、All animals were succeed in simultaneously Nanoknife and cryoablation. No serious complications occurred. Ablated procedures worked well. After cryoablation, hepatic cells turned out acute damage, with obvious blood stasis; and after 30 days, hyperplasia of fibrous tissue were observed. On the contrary, IRE ablation areas were gradually replaced by normal hepatic cells. Blood vessels and bile ducts were preserved well.Conclusion1、NanoKnife appears to be safe, feasible and effective for hepatic ablation in an animal model,causing cell death by means of apoptosis. The ablative zones are well characterized with enhanced CT and MRI. Vital structures proves preservation, including blood vessels and bile ducts. The ablation areas are gradually replaced by normal hepatic cells on postoperative 28 days.2、Argon-helium cryoablation destroys cells without selectivity. However, Nanoknife, avoiding the heat sink effect, does no harm to blood vessels and bile ducts. As a result, Nanoknife can be used for treatment of lesions closed to hepatic hilar and other special locations.3、Nanoknife is a new and effective approach of minimally invasive ablation whose advantages are irreplaceable, and will have a prospect future in clinical practice.