Radiation Dose Monitor And Protection Of Close Contacts From Radiators After Implantation Of Radioactive¹²⁵I Seeds

Radiation is naturally occurring physical phenomena since ancient timeswidely known as the natural background radiation in the universe and humanliving environment. The average annual effective dose due to natural radiationof the American people is about3.6mSv[1]. Radiation according to the natureof radiation is defined into electromagnetic radiation and particle radiation.Radiation according to the mode of action of radiation with matter is definedinto ionizing radiation and non-ionizing radiation. Radioactive¹²⁵I seed emitsthe low-energy γ-rays, that is electromagnetic radiation and ionizing radiation.Ionizing radiation refers to material effect that causes material ionizing[2]. Thelow-energy ionizing radiation on living organisms injury occurs mainly in theenzymes, nucleic acids and proteins and other macromolecules, that results incell damage and even ultimately leads to the damage of organs and/ororganizations of the body’s affected by radiation. Inter-organizationalimplantation treatment of radioactive¹²⁵I seed is internal exposure, but closecontact with the implanted¹²⁵I seed postoperative patients if not pay attentionto radiation protection, may be affected by external exposure to radiationinjury. Because some patients fears ray irradiation that may lead to radiationdamage, who reject the use of radioactive¹²⁵I seed implantation therapy. Inorder to avoid with family members or colleagues caused by high doseradiation exposure[3]. The medical staff in the¹²⁵I seed implantation process,such as non-compliance with the rules, do not pay attention to radiationprotection, may also be subject to radiation damage. With the wide applicationof radioactive¹²⁵I seed implantation treatment technology, ray irradiation doseof the general public officer may also increase. The security of ray irradiationis needed to be properly assessed[4-6]. Radioactive¹²⁵I seed implantation therapy belongs to brachytherapyimplant treatment. Both at home and abroad, radioactive¹²⁵I seed implantationtherapy is widely used in the comprehensive treatment of solid tumors[7]. Theparticles that are used radioactive¹²⁵I seed implantation treatment of tumorsare implanted tumor or tumor-infiltrating organizations. The particle sourceemitt continuous low-energy gamma-rays, that destroy and break thedouble-stranded DNA of the tumor cells, leading to tumor cells and losing theproliferative capacity of the original[8]. There is small scope pathologicaldamage from the normal tissue around particle sources[9]. This technology hasthe advantages of high dose target area and a high degree of conformal,peripheral tissue dose steep drop of biophysics characteristics. Thepathological damage of this technology is lighter, damage range limited to5mm away from sources[10]. Radioactive¹²⁵I seed brachytherapy has aminimally invasive, the characteristics of the local control rate and achievedgood results. However, another study showed that long-term low-dose-rayradiation on the health of the radiology medical staff has some impact[11].With the wide application of the technology to generate a worrying problem-radiation safety. There is part of the study data regarding radiation effectivedose rates from postoperative close contacts of the brachytherapy patients tovalidate these instructions in the foreign countries. There is few reportsregarding the warning time, a safe distance and radiation protection frompostoperative close contacts of the brachytherapy patients at home.Within24hs after the operations, to scan the dose rate of30cm,50cm,60cm,70cm,80cm,90cm,100cm,110cm,120cm,130cm,140cm,150cmfrom the skin of20patients, simulating the close contacts with pocket-sizeradiometer. The effective dose, precaution time and safety distance of differentpersons including adults, pregnant adults, childred who live with the patient,adults who sleep with the patient and coworkers were calculated according tothe formula. After their precaution time, it’s safe to contact with the patientsfor the groups; otherwise, it’s necessary to take some protect works includingtime protection, distance protection and shielding protection within the precaution time and/or the safety distance. In order to reduce radiation damagescientific guidance and provide a theoretical basis.Objective: To study effective dose, precaution time and safe distancewith the aim of guiding close contacts scientifically and avoiding radiationdamage.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. Within24hs after the operations, toscan the dose rate of30cm,50cm,60cm,70cm,80cm,90cm,100cm,110cm,120cm,130cm,140cm,150cm from the skin of20patients,simulating the close contacts with pocket-size radiometer. The effective dose,precaution time and safety distance of different persons were calculatedaccording to the formula. While an algorithm was developed from thesemeasurements to determine the required precaution times that maintain publiceffective doses below50%of the limits for specified exposure situationsrelationship dose rate.Results: The dose rates at30cm from the vertical skin surface were13.05±9.36μSv/h and1.81±1.11μSv/h at100cm for¹²⁵I implantationpostoperative1d. The dose rates at30cm from the vertical skin surface were6.96±5.00μSv/h and0.97±0.59μSv/h at100cm for¹²⁵I implantationpostoperative54d. The dose rates at30cm from the vertical skin surface were5.27±3.78μSv/h and0.73±0.45μSv/h at100cm for¹²⁵I implantationpostoperative78d. The dose rates at30cm from the vertical skin surfacewere3.67±2.64μSv/h and0.51±0.31μSv/h at100cm for¹²⁵I implantationpostoperative109d. At the30cm and100cm point from patients after theoperations, the dose rates decrease （P＜0.05）.The dose rate at the30cm pointare more than that at the100cm point at the same time（P＜0.05）.For the samepersons, the effective dose decrease as the time, when they contact withpatient after operations, the Precaution time of common adults, children andpregnants, coworkers, adults who sleep with the patients are0day,54days,78days and109days. The safety distance was60cm for adults who sleep with the patient and the effective dose of this distance was3.393±2.207mSv. Thesafety distance was100cm for adults who live with the patient and theeffective dose of this distance was0.934±0.572mSv. The safety distance was120cm for pregnant adults, childred who live with the patient and the effectivedose of this distance was0.604±0.341mSv. The safety distance was130cmfor coworkers who work with the patient and the effective dose of thisdistance was0.623±0.328mSv. The formula of the dose rate and theprecaution time was t（d）=3.58+85.14㏑D（t） for pregnant adults, childredwho live with the patient. The formula of the dose rate and the precaution timewas t（d）=-111.02+86.015㏑D（t） for adults who sleep with the patient. Theformula of the dose rate and the precaution time was t（d）=26.84+85.99㏑D（t）for coworkers who work with the patient.Conclusions:1After their precaution time, it’s safe to contact with the patients for thegroups; otherwise, it’s necessary to take some protect works within theprecaution time;2After their safety distance （outside130cm）, it’s safe to contact with thepatients for the groups; otherwise, it’s necessary to take some protect workswithin the safety distance;3Guide individual patient protection measures at the same timeaccording to the relationship between the dose rate and the precaution time.