| Primary liver cancer ,which is a common lethal disease in our country, does great harm to health of the people. At present,surgical operation is a main procedure which is often combined with other methods in order to improve therapeutic efficacy.As we know,there are a great many cases which cannot be treated with surgical resection or radical resection in practice because of severe cirrhosis of liver,liver disfunction,deep position and approaching intrahepatic important structure.So medical workers have been studying novel therapeutic methods all the time.Radiotherpy is an effective treatment of liver cancer,but its appllication is limited because cure dosage of external irradiation is very higher than tolerance dosage of nomal liver.Interstitial implantation of radioactive seeds ,one kind of brachytherapy,is a good method which can greatly injury tumor by implanting radioactive microsources which can irradiate gammer rays with low capacity continousely wheres nomal tissue is not or slightly injuried.It has been a long history,but has rapidly developed in the near score,especially with successful manufacturing of new safe radionucides such as iodine-125,palladium-103 and aurum-198,advance in imaging technology,and computered 3-dimensioned TPS.Characterlized by small injury,high dose in target area,and so on,it will be broadly applied clinicly. Radioactive seeds act by irradiating gammer rays,which destroy the DNA chains of tumor cells so that they cannot reproduce.After permanent implantation,there will be more complete treatment,with continuous action on tumor cells.This is like surgical resection.The method can be helpful in treatment of all localized solid malignant tumors and residual tumor after operation.Compared with external irradition ,it has many advantages:low strength of radioactive source,short distance of function,strong damage on tumor,small injury to normal tissue,continous irradition,high biological effect and thorough treatment.Iodine-125 is the most common radioactive seed nowadays,with short half life(59.6 days),gammer rays of low capacity(35.5Kev),small penetrating distance(1.7cm).Its shell is sealed with titanium alloy,its diameter is 0.8cm and its longth 4.5cm.It can produced domesticlly.It has been reported that interstitial implantation of radioactive iodine-125 seeds has made significant efficacy in the treatment of malignant tumors such as prostate carcinoma. More than 400 cases of prostate carcinoma have been treated with radioactive iodine-125 seeds in Seattle in the USA every year. Nearly this technique has been applied in the several hospitals in our country.But there is no detailed report on treatment of primary liver cancer.Radio-sensibility of different tissue is different.Liver cancer is low to moderate degree sensitive to gammer ray,so radiotherapy is somewhat effective.Although the efficacy of iodine-125 seeds depends on the whole strongth and action time, it should also be considered that dosage distribution of a seed ,a fasten radioactive microsource ,is not the same.That abides by the law that the strongth reduces rapidly when the distance increases.Thus,it is of great practical value that the effective distance of iodine-125 seeds on therapy for liver cancer be known.We studied on it through animal experiment.At the same time,the mechanism of radioactive iodine-125 seeds and radiation damage was explored preliminarily.1. Establishment of nude mice animal model of human liver cancerNude mice is a kind of mice with congenital thymus deficiency.Because of its T-cell mediated immune deficiency,subcutaneous inoculation of human liver cancer cells easily brings about tumor formation.Moreover,it is easy to observe tumor generation and perform experiment.SMMC-7721,one of human liver cancer cell strain,derived from human being,with better homology.So,we selected SMMC-7721 as object.SMMC-7721 cells(3*106cells/mouse) were injected s.c. into the right flank of BALB/c nude mice.About two weeks later,tumor was seen,with diameter of 4-6mm.The rate of tumor-f...
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