The Comparative Study About Protection Effect Itself After Application Of Radioactive¹²⁵I Seeds With The Shielding Materials

At present,125I implantation has become an emerging advanced malignanttumor therapy. And it has been chosen by more and more doctors and patientsbecause of characteristics its small trauma, accurate positioning， moreconformal dose distribution of the tumor size and shape, higher local dose oftumor, reaching the lethal dose radiotherapy unattainable, while smallerdamage to the surrounding normal tissue, fewer complications,quickerpostoperative recovery[1-2].With the wide application of radioactive125I seedsimplantation therapy, the safety of radiation has become one of the hottestissues and concern between the medical staff and the public[3]. And it needs toproperly evaluate and guiding the patients with postoperative radiationprotection.Objective: Within24hs after the operations, with or without covering the0.05mm lead equivalent shielding materials, to scan the dose rate of30cm and100cm from the skin of40patients with pocket-size radiometer, the effectivedose and precaution time of common adults,children andpregnant,coworkers,adults who sleep with the patients were caculatedaccording to the formula. Though our studying the protective effect of the0.05mm lead shielding material to reduce the radiation damage in closecontact withthe crowd, we can provide the preliminary clinical study ofdifferent groups and guiding individual shielding protection for people.Methods: Twenty cases of cancer patients in different parts from HebeiProvince People’s Hospital is implanted of radioactive125I seed treatment inthe CT and B super dual image-guided. Before the operation treatment ofpatients，we should measure the radiation dose of indoor nature. Within24hsafter the operations, to scan the dose rate of30cm、100cm from the skin of 20patients, simulating the close contacts with pocket-size radiometer. Theeffective dose, precaution time and safety distance of different persons werecalculated according to the formula. While an algorithm was developed fromthese measurements to determine the required precaution times that maintainpublic effective doses below50%of the limits for specified exposuresituations relationship dose rate. With the same way，we scan the dose rate of30cm、100cmfrom the skin of20patients covering the0.05mm lead equivalentshielding materials. According to the formula we can calculate the effectivedose、 precaution time at different distances between different groups. Alsowe can get the relationship of dose rate and precaution time between differentgroups.Results: Patients at30cm from the surface, measured after day withoutshielding materials group and0.05mm lead equivalent shielding materialsgroup, the difference between the median dose rate is4.07（P25:2.92,P75:9.92）, the difference was statistically significan（tZ=-5.443, P＜0.05）. Patients at100cm from the surface, measured after day withoutshielding materials group and0.05mm lead equivalent shielding materialsgroup, the difference between the median dose rate is0.2（3P25:0.08,P75:0.49）,the difference was statistically significan（tZ=-5.443, P＜0.05）. Table1shows,Patients at30cm from the surface without shielding materials after1d,45d,69d,114d dose rates were as follows:11.44（9.57,18.30）、6.78（5.67,10.84）、5.13（4.29,8.20）、3.04（2.54,4.86）， the difference was statisticallysignificant（Friedman M test，P＜0.05）, Patients at100cm from the surfacewithout shielding materials after1d,45d,69d,114d dose rates were as follows:0.95（0.81,1.59）、0.56（0.48,0.94）、0.43（0.36,0.71）、0.25（0.22,0.42）,the difference was statistically significant（Friedman M test，P＜0.05）. Table2shows, Patients at30cm from the surface with shielding materials after1d、7d、54d dose rates were as follows:6.89±2.78μSv/h、6.35±2.56μSv/h、3.68±1.48μSv/h, the difference was statistically significant（Friedman M test，P＜0.05）; Patients at100cm from the surface with shielding materials after1d、7d、54d dose rates were as follows:0.79±0.37μSv/h、0.72±0.34μSv/h、 0.42±0.20μSv/h, the difference was statistically significant（Friedman M test，P＜0.05）. Postoperative day, after covering shielding materials, reducing thedose rate at the same distance when compared to unshielded material（P＜0.05）. For the same persons, the effective dose decrease as the time, when theycontact with patient after operations. The dose rate at the30cm point are morethan that at the100cm point at the same time（P＜0.05）. For the same personwithout shielding material, the effective dose decrease as the time, whenthey contact with patient after operations, the Precaution time of commonadults, children and pregnants, coworkers, adults who sleep with the patientsare0day,45days,69days and114days. For the same persons, the effectivedose decrease as the time,when they contact with patient covering0.05mmlead shielding material after operations, the Precaution time of commonadults,children and pregnant,coworkers,adults who sleep with the patientsare0day,0day,7days and54days. Without shielding materials the formula ofthe dose rate and the precaution time was Y=2.53+86.00㏑X for pregnantadults, children who live with the patient; the formula of the dose rate and theprecaution time was Y=-112.00+86.00㏑X for adults who sleep with thepatient. The formula of the dose rate and the precaution time wasY=26.41+86.00㏑X for coworkers who work with the patient. With shieldingmaterials, the formula of the dose rate and the precaution time wasY=-110.76+84.91㏑X for adults who sleep with the patient; The formula ofthe dose rate and the precaution time was Y=26.28+84.14㏑X for coworkerswho work with the patient.Conclusions:1¹²⁵I radioactive seed implantation, while unleaded clothing covering,patients in contact with different groups of people to be safe after114days,within the precaution time, you need to take protective protect works. Whilecovering0.05mm lead equivalent shielding materials, patients in contact withdifferent groups of people to be safe after54days, within the precaution time,you need to take protective protect works;2Radioactive¹²⁵I seed operations, different people give different precaution time,0.05mm lead equivalent shielding material covered caneffectively reduce the precaution time. Recommended protective shield earlyafter radioactive¹²⁵I seed operations;3Guide individual patient protection measures at the same timeaccording to the relationship between the dose rate and the precaution time.