Radiation protection in radioimmunotherapy with yttrium-90

Full text: Unsealed sources of radioactive isotopes have widely used in the clinical practise. For therapeutic use and with oncological aims, Yttrium-90 has been implemented recently in our hospital. Isotope injection is made by intravenous way slowly at an approximated rate of ten microlitres per second. Low-volume injection, less than ten millilitres, entails the possibility that an important fraction of the prescribed activity could be retained and not incorporated into the patient if a pumping injection system controlled in the distance had been used. To avoid this adversity and in order to get the therapeutic effect, in our hospital the injection is applied directly using a syringe by infirmary personnel of the nuclear medicine department. This circumstance and the radiation emission scheme of Yttrium-90 entails a meticulous radiation safety plan. Measurement of the radiation levels in some different phases of the treatment and at its end, was made by the medical physics department. Also, and before the injection, this department made with the received dose other additional measurements, using ant not using shielding materials, to choose the best option of radiation protection. The use of a syringe protector made of plastic with a thickness between 12 and 17 mm in combination with the use of a leaded apron of 0.25 mm lead thickness worn by the nurse, has been the chosen option. In addition, it was evaluated the most optimized positions for the injection, moving away the nurse from the patient to prevent the risk of radioactive contamination; also the worker was wearing double gloves, glasses and additional protection covering the leaded apron and preventing any kind of accidental contamination. Once the isotope is administrated and bio distributed in the patient's organism, it could be verified that the dose rate around it fell rapidly. The involved personnel were wearing all the time two thermoluminescent dosimeters: for body and for wrist. A maximum of one patient per month has been treated. Once it was obtained the reading of both dosimeters by an authorized personal dosimetry service, it was reported that the body dosimeter did not receive any larger values than usually, and the wrist dosimeter globally presented a personal surface dose equivalent Hp (0.07) around 1 mSv per month. (author)