A Study On Rabbit's Normal Portal Vein's Early Radiation Injury Induced By Radioactive Iodine-125 Seed

Transfer is one of the biggest characteristic of malignant tumors, the transfer of lymph node metastasis is one of main ways, it is an important factor to determine the treatment and judge the prognosis of patients. Hepatoduodenal ligament lymph nodes is the common metastatic sites of digestive system malignant tumors, especially pancreas, extrahepatic bile duct cancer, stomach cancer and so on, and because of the period in patients has been late, poor tolerance and the surrounding normal tissue constraints, surgery, chemotherapy and external radiation and other conventional treatment difficult to implement, so the treatment of lymph node metastasis in this part is the clinician′s quite difficult issues. With the appearance of radioactive seeds, and because of it′s characteristics of high local doses, dose attenuation fast, less damage to the surrounding normal tissue, 125I particles implantation becoming an effective treatment.Radioactive 125I interstitial brachytherapy refers to the implantation of radioactive sources within the tumor or the tissue invaded by tumor. Through its continuous low-energyγ-rays, the target area receive high doses of anti-tumor effect but on the surrounding normal tissue the damage is small. it is easy to protect, and other advantages, so that the greatest degree of tumor tissue by the devastating destruction, while normal tissues from damage or injury minor. Radioactive 125I interstitial brachytherapy used for genito-urinary system, head and neck, lungs and other substantive organs tumor. The latest U.S. and UK studies have shown that radioactive particles implantation has become the first choice of treatment of localized prostate cancer after surgical treatment. And the clinical application in gynecological tumors, surface soft tissue sarcoma demonstrated a good therapeutic effect, the treatment in the hollow organs such as gastrointestinal, esophagus and other parts of cancer also conducted a preliminary study, showing a gratifying effect, and greatly improve their's quality of life and prolong their's survival time. With its accurate positioning, highly conformal nature and low pollution brachytherapy is in our pursuit and become an effective treatment, however we can not ignore the radioactive complications while the positive effect. As far as prostate cancer is concerned, 125I particles is most widely used, serious complications, including rectal ulcer, fistula, urethral necrosis, sexual dysfunction, and so on. Wallner, etc. reported that the incidence of rectal ulcer is 10%. Blasko, etc. reported that 19% of patients with genito-urinary complications occur. Henderson, etc. reported that 9.3% of acute urinary retention, 5.6% present with constipation or tenesmus sense and self-limiting rectal bleeding. Raina [12] also reported the incidence of sexual dysfunction was 29%.Thus, with the extensive use of radioactive 125I particles, security issues had gain more and more people's attention. Hepatoduodenal ligament lymph nodes around the complex organizational structure , near the liver, bile duct, portal vein and other important organizations, whether it would caused radiation damage to the portal vein after the implantation of particles, there is no study in this regard.In this study, different doses of 125I seed was implanted in rabbit portal vein surface, preliminary observe the 60d of the pathological changes within the vessel wall, and explore the radiation injury to portal vein and the surrounding normal tissue by particles implanted, to explore the safety and feasibility of implantation in this part , to provide experimental basis for the clinical treatment of hepatoduodenal ligament lymph node metastasis and preventive irradiation in this part with radioactive particles implantation.Objective: Hepatoduodenal lymph node is the common sites of metastases in digestive system tumors, this area near the portal vein and other important organizations, whether it would generate radioactive injury in portal vein after the implantation of 125I particles has not been reported. In this study, the radioactive 125I seeds was implanted in rabbit portal vein surface and the early radiation injury of rabbit′s normal portal vein radiated by iodine-125 ?seeds in different dose and duration was studied.Methods: Select the same general level month-old healthy New Zealand rabbits 48, weight 2000g ~ 2500g, evenly divided male and female. Divided the rabbits into four groups of 12 with computer-generated random numbers, that is, an empty source group, A group of 80Gy (14.8×107Bq), B group 120Gy (22.2×107Bq), C group 160Gy (29.6×107Bq ). The treatment plans was developed by Prowess 3D planning system. This study set the three dosage groups of 80Gy, 120Gy, 160Gy. Three different activity 125I particles were implanted in the surface of the Rabbits portal vein of each group respectively. A group of rabbits selected 3 125I particles with radioactivity of 14.8×107Bq (80Gy), B group of rabbits selected 3 125I particles with radioactivity of 22.2×107Bq(120Gy), C group rabbits selected 3 125I particles with radioactivity 29.6×107Bq(160Gy), with 5 ~ 0-line sewing fixed on the sheath surrounding the portal vein, arranged in an equilateral triangle with a source spacing of 0.3-0.5cm. implantate with empty sources were implanted in The control group by the same method. the general state of health, leucocyte count, the change of the portal vein viewed by eyes, by light microscopy and by electron microscopy 0.5cm from the target area at 30d and 60d after the operation was observe.Results: There are not any complications of ulcer, perforation, haemorrhage and death in the treatment group. The rate of particle shedding in the control group is 5.56% (2 / 36), in the experimental group was 4.63% (5 / 108). The difference of white blood cell count 7d after and before the surgery among the 4 group′s was significantly (P <0.05), the difference of peripheral blood leucocyte at different time before and after the seeds implantation in the two groups is not statistically significant to all (P﹥0.05). The particles implanted area in each group are adhesion with surrounding liver, stomach or duodenum, and the experimental group is serious than in the control group. The injury of the vessel wall after the seeds implantation were mainly the change in endodermis, oedema of muscular layer and interstitial hemorrhage viewed by light microscope. Score every group's injury degree depend on the ?improved standard of the"Schmidt", the difference of injury degree at 30d and 60d after the operation in the treatment group at the different dose was statistically significant (P<0.05). The difference in the treatment group at the same dose is statistically significant (P<0.05). Electron microscopy, the ultrastructure of portal vein in control group at 30d and 60d after operation is normal, and experimental group of 80,120,160Gy at 30d and 60d after operation were expressed as mitochondrial cristae and membrane fusion, rough endoplasmic reticulum dilation, degranulation, the nunber of Tun Yin small bubbles reduce, in addition to the above the group of 160Gy60d also see intrauterine occlusion of vascular adventitia. Degree of injury in each group increased with the dose increased, and the 60d group is serious than 30d group in the same dose group.Conclusions: The injury of portal vein, mainly at endothelial layer and muscular layer, was light and aggravate along with the increasing of dose and time when the dose is between 80-160Gy 30d and 60d after the seeds implantation but the injury depth.