| BackgroundThe treatments of liver cancer (primary hepatocellular carcinoma and metastatic liver cancer) including surgical resection, liver transplantation and local ablation therapy. Surgical resection has a high local recurrence rate, while the strict indication and donor shortage limited the large scale development, only a few thousand patients received liver transplantation each year. Local ablation has been one of the basic therapy for small hepatocellular carcinoma with surgery and liver transplantation. Local treatment including temperature ablation and chemical ablation. The former is importing electricity, light, sound and other energy into the tumor tissue to make thermal or cold field within the manufacturing field, and thus inactivation of tumor cells in situ, including microwave, radiofrequency, laser ablation, high intensity focused ultrasound (HIFU) and cryoablation. Percutaneous ethanol ablation is a typical representative of chemical ablation, leading cytoplasm dehydration, protein denaturation and vascular thrombosis, and thus making tumor cells necrosis. For the difficult parts of the liver, such as closing to the liver capsule, gallbladder or large blood vessels, have high risk of local ablation. Therefore, urgent development of a variety of local therapy was needed.HCC tend to invade the portal vein, the incidence of portal vein tumor thrombus as high as62.12%～90.12%, most died in the diagnosis of3to4months if not treated. Although HCC combined with portal vein tumor thrombus is a sign of poor prognosis, but if liver function and general permit, a variety of treatment can be tried to improve the survival rate. It was treated by surgical treatment, but most patients had lost the chance to completely resect the lesions, so the non-surgical treatments such as hepatic artery embolization or chemoembolization, liver ultrasound-guided interventional treatment of portal vein tumor thrombus treatment have a good prospect. Percutaneous ethanol injection treatment of portal vein thrombosis has been applied in clinical practice. There are some limitations because of multiple injections needed and alcohol not easy to stay in the portal vein tumor thrombus. The ablation of radiofrequency is generally spherical and the needle is thick, that has high risk of bleeding. HIFU need to reduce the influence of highly reflective body tissue (such as bone, lung and intestinal gas, etc.) and to avoid normal liver tissue damage while breathing movement.Laser treatment was widely used in clinical practice, including pulsed dye laser, ruby laser, alexandrite laser, C021aser, Nd:YAG laser. Laser applied to different fields according to the characteristics of various laser wavelengths, mainly in ophthalmology, dermatology, plastic surgery and vascular surgery and other departments, like the complexity of glaucoma, retinopathy, facial plastic surgery, varicose veins, resection of the prostate, head and neck hemangioma, metastatic spinal disease, tennis elbow, vitiligo and melanoma and other diseases.Nd:YAG laser output wavelength of1064nm near-infrared light, has good penetration in the organization, as deep as3-5nm. US-guided laser (Nd:YAG) ablation has become a new treatment for hepatocellular carcinoma in situ inactivation.Laser treatment of portal vein thrombus reported mainly in China, mostly with the semiconductor laser. Nd:YAG laser was widely used for medical treatment, but less reported of liver tumors.Local inactivation tumor treatment developed well but still difficult for the lesions located in complicated area, such as subcapsular, next to the gallbladder or the large blood vessels, and the treatment of portal vein thrombus is always worth studying. This research aims to explore the ablation shapes, stability and security of Nd:YAG laser and to predict the value of Nd:YAG laser on the tumors subcapsular, near the gallbladder or blood vessels and the therapeutic value of portal vein tumor thrombus.Materials and methodsExperimental equipment and drugs:Mylab90ultrasonic diagnostic apparatus (Esaote, Italy)Echolaser laser system (Esaotte.Italy)SEQUIOA-512ultrasonic diagnostic apparatus (Siemens, Germany)linear array probe (10MHZ) and intraoperative probeCool-tip radiofrequency ablation device (Radionics Co. U.S)Microwave machine (Nanjing Sanle Electrical Co., Ltd. China)anesthesia machine21G PTC needlesSonoVue (Bracco.Co. Italy)valium, vecuronium, propofol, fentanyl, ketamine and other anestheticExperimental subjects:Isolated parts:fresh isolated livers slaughtered less than8hoursIn vivo parts:two Chinese experimental miniature pigsInstitutional animal care and use committee approval was obtained for the use of an animal model for the in vivo portion of this study. All the pigs and isolated livers were treated according to regulations after the experiments.Part one:Laser ablation of animal experiments1Isolated liver experimentsNd:YAG laser launched by Echolaser system, fiber diameter of about300μm, wavelength of1064nm, adjustable power parameter.1.1single-fiber with single-ablation:using a single fiber, parameter set to3w3min,5w3min,5w6min respectively, ablated isolated liver.1.2single-fiber with6times ablation:a single fiber repeatedly ablated the isolated liver with5backwards. Forecast the value in the treatment of portal vein tumor thrombus and the appropriate treating power and time.1.3multi-fibers ablation:multiple fibers (2,3,4) ablated the isolated liver in different shapes, studying the conformal.2In vivo experimental study2.1General anesthesia was induced initially with an intravenous injection of katamine and vecuronium, and maintained with4-12mg/kg propofol and0.1mg fentanyl, add2mg vecuronium intermittent if necessary. The anesthetized pigs were placed in a supine position and the liver exposed through a midline incision. Above work was completed by the anesthetist and surgeons. Single fiber ablation was carried out close to the gallbladder, under liver capsule, and between two big vessels. The needle was0.4cm near the gallbladder wall and liver capsule, the shortest distance between two vessels is0.85cm. Laser output was set to5W, ablated6minutes. After the laser ablation (about15-25minutes later), pigs were took Contrast-Enhanced Ultrasound (CEUS).2.2two-fiber with4times ablation:two fibers inserted into the pig’s liver parallel, repeatedly ablated with4backwards. Forecast the value in the treatment of portal vein tumor thrombus in big vessels and the appropriate treating power and time.Part two:Radiofrequency and Microwave ablation of animal experiments1Radiofrequency:A14G Cool-tip RF needle (type15-10) punctured into the isolated liver guided by ultrasound, power range0-200W, frequency of480KHz, ablated lmin,3min,5min, respectively, recorded the scope of ablation.2Microwave:A microwave needle electrode punctured into liver tissue under ultrasound guided, microwave apparatus set to50W8min and100Wlmin. Measured and recorded the ablation area and central charring zone.The data were analyzed by statistical software (SPSS16.0, Chicago, IL, USA).ResultsLaser ablation lesions were layering, from the inside central cavity out was the gasification zone, carbonized zone, necrosis and inflammatory edema. About parameters5W6min, the ablation lesions were about (2.17±0.32) cm×(1.35±0.23) cm. The lesions of pork liver treated with soaking were larger than non-treated fresh ones, the difference was statistically significant.Single-fiber laser ablation lesions in vivo liver was (1.73±0.20) cm×(1.14±0.16) cm, the areas were much smaller than in isolated liver, the difference was statistically significant. Single fiber ablation areas next to the gallbladder, blood vessels, and under capsular parts were also oval shape, like the structure of ablation lesions in vitro. CDFI showed no blood supply in the ablated zone, and the vessels beside it were not affected. CEUS showed no enhancement in the ablated lesions except gasification zone in the center, and no damage of the liver capsule, gallbladder wall and the vessel walls.The ablation shape of single-fiber ablation with6times backwards was a long and narrow strip, parameters7wlmin and5w6min got similar ablation areas, but the latter wasted significantly more energy. Laser ablation lesions of two-fiber were significantly larger than single-fiber ablation, which may be used for main vessel thrombus.The shape of two-fiber ablation area was an oval, three-fiber was nearly circular, and four-fiber was approximate square.Radiofrequency ablation was stable, the tip and tail of the RF needle first to be hyperechoic, then to the central part, till the whole into an oval-shaped hyperechoic area. The effects of RF of ablation time3min and5min were close.Microwave ablated area was long oval, without obvious central carbonization zone. It was significantly greater than the range of single laser fiber ablation. P<0.05. Single laser fiber with many backwards was also smaller than microwave ablation lesions, P <0.05.ConclusionIn this study, we studied the stability, security and shapes of Nd:YAG laser ablation. With different multi-fibers, we can get different ablation lesions. The safety with a single fiber ablation in difficult parts of the liver has been validated. Compared with radiofrequency, the stability of laser ablation yet to be improved. In addition, one or two fibers ablation with several times which gave us a strip ablation shape also provides us an experimental basis for the future using of laser at the treatment of thrombosis. |
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