Radioisotopes and Radiation Protection PDF

Radioisotopes and Radiation Protection % Copyright © 2014 by Mosby, an imprint of Elsevier Inc.  Isotopes  Atoms that have the same number of protons within the nucleus but have different numbers of neutrons  Most elements in the periodic tab...

Radioisotopes and Radiation Protection % Copyright © 2014 by Mosby, an imprint of Elsevier Inc.  Isotopes  Atoms that have the same number of protons within the nucleus but have different numbers of neutrons  Most elements in the periodic table (see Appendix C in textbook) have associated isotopes.  Not all the nuclei of these isotopes represent stable configurations of protons and neutrons. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 2 100% HL (0 days) 50% IHL 10 days Gamma z0 days 25% ZHL Alpha Radioisotopes 30 days 12 5% 3HL. 33 3 days Beta particles 10 % 3 3HL let out.. Th are 6 75 % 4HL. 40 days  Isotopes of a particular element that are unstable because of their neutron-proton configuration (some have too many neutrons, whereas others have too many protons)  Isotopes that have too many neutrons or those that have too many protons spontaneously undergo changes or transformations to rectify the unstable arrangement. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 3  Medical Usage  Radiation therapy  Well-oxygenated, rapidly dividing cells are very sensitive to damage by radiation.  This causes cancerous growths or tumors to be either eliminated or at least controlled by irradiation of the area containing the growth.  Radiation may be delivered internally to such regions by infusion or implantation of certain radioisotopes.  Therapeutic isotopes are characterized by relatively long half-lives that are measured in terms of multiple days or multiple years and, with the exception of a few of them, by quite-high-energy radiation.  Radiation may be in the form of gamma rays or fast electrons (beta radiation). Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 4  Medical Usage (Cont.)  Radiation therapy (Cont.)  Most important therapeutic radioisotopes Iodine-125 (125I) has been used quite extensively since 2000 in the form of titanium-encapsulated cylindric seeds to give a tumoricidal radiation equivalent dose (EqD) to cancers that are confined within the prostate gland (see - slide 5).  Treatment goal is to deliver 145 Gy to at least 90% of - the prostate’s volume while limiting radiation dose as much as possible to adjacent structures such as the o urethra, bladder, and anterior rectal wall.  Decays by a process called electron capture  Distance and time are best radiation safety practices. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 5  Medical Usage (Cont.)  Radiation therapy (Cont.)  Most important therapeutic radioisotopes (Cont.) Iodine-125 & Figure 14-01. A, Iodine-125 (125I)-titanium–encapsulated cylindric seed. B, 125I seeds before encapsulation. (Implant Sciences Corporation) Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 6  Medical Usage (Cont.)  Radiation therapy (Cont.)  Most important therapeutic radioisotopes (Cont.) Iodine-131 (131I)  Has a half-life of 8 days  Can be joined chemically with sodium to form a radioactive compound called sodium iodide 131I, which can be orally administered in the form of tablets that are an efficient way of delivering a destructive radiation dose to a specific cancer site, such as the remainder of any residual thyroid tissue after can cancer surgery  Personnel radiation protection considerations and measures while providing care for 131I therapy patients  Radioactive decay process: beta decay Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 7  Medical Usage (Cont.)  Nuclear medicine  Employs radioisotopes to Study organ function in a patient Detect the spread of cancer into bone Treat certain types of disease  Diagnostic techniques in nuclear medicine typically make use of short-lived radioisotopes as radioactive tracers.  Common radioisotopes used in nuclear medicine - Iodine-123 (123I): When chemically coupled with sodium, e it forms the radiotracer compound sodium iodide 123I that preferentially concentrates in the thyroid gland and - achieves levels of concentration that can be directly correlated with the thyroid gland’s performance status. Average half life 13 3 hrs. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 8  Medical Usage (Cont.)  Nuclear medicine (Cont.)  Common radioisotopes used in nuclear medicine (Cont.) Technetium-99m (99mTc)  Most commonly used radioisotope in nuclear medicine  Produced from the radioactive decay of another unstable isotope, molybdenum-99 (99Mo)  Is an extremely versatile radioisotope because it can be incorporated into a wide variety of different compounds or biologically active substances, each with a specificity for different tissues or organs of the body  Has many uses Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 9  Medical Usage (Cont.)  Positron emission tomography (PET) and computed tomography (CT)  Makes use of annihilation radiation events that are a byproduct of pair production  Annihilation radiation is initiated by the radioactive decay of the nucleus of an unstable isotope having too many protons within the nucleus.  Excess proton transmuted into a neutron and positron (antimatter)  Emission of a neutrino  Positron, when passing close to an electron, will interact destructively. Both particles disappear, having annihilated one another. Their respective masses will be converted into energy that will be carried off by two photons emerging from the annihilation site in opposite directions, each with a kinetic energy of 511 keV. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 10  Medical Usage (Cont.)  PET and CT (Cont.)  Imaging  Concept of PET scanning  Importance as an imaging modality  Fluorine- 18 (18F):  Positron-emitter; most important isotope used in PET scanning It can be attached to a glucose molecule, yielding the compound, fluorodeoxyglucose (FDG), a radioactive tracer that will be taken up or metabolized by cancerous cells. As such it reveals location of these cells through its positron emission decay and subsequent generation of oppositely traveling annihilation photons.  Concept of a PET/CT scanner Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 11  Medical Usage (Cont.) Figure 14-02. Combined positron emission tomography/computed tomography (PET/CT) system. (Frank ED, Long BW, Smith BS: Merrill’s Atlas of Radiographic Positioning & Procedures, ED 12, St. Louis, 2012, Mosby) Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 12  Medical Usage (Cont.)  Radiation protection (Cont.)  Radiation safety shielding considerations for PET/CT scanners  Considerations  Scattered radiation by the CT scanner portion  High-energy annihilation photons  Presence of a third high-energy source of radiation  Patient “prep” time  Necessary protection for technologist(s) and other personnel  Necessary shielding  Considerations  Shielding in a well-designed facility Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 13  Medical Usage (Cont.)  Radiation protection (Cont.)  Radiation safety shielding considerations for PET/CT scanners (Cont.) Figure 14-03. Layout diagram of a positron emission tomography/computed tomography (PET/CT) imaging facility. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 14 Radiation Emergencies: Use Of Radiation as a Terrorist Weapon  Most hospitals have radiation emergency plans for handling emergency situations involving radioactive contamination.  Radiologic technologists should become aware of the radiation emergency plans that exist in the facilities in which they work. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 15 Radiation Emergencies: Use Of Radiation as a Terrorist Weapon (Cont.)  Contamination  Radioactive dispersal device, or “dirty bomb”  A radioactive source mixed with conventional explosives  Intended to contaminate an area with radioactive material and thereby cause panic  Use of Geiger-Műller (GM) detectors  Long-term health effects Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 16  Radiation Emergencies: Use Of Radiation as a Terrorist Weapon (Cont.)  Decontamination  Removal of contaminated clothing  Immersion in a shower  Wound containing radioactive material  Simple rinse of the area is usually sufficient  Use of GM detectors  Environmental protection agency (EPA) dose limit recommendations  For individuals engaged in non–life-saving activities  For individuals engaged in life-saving activities Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 17 Radiation Emergencies: Use Of Radiation as a Terrorist Weapon (Cont.)  Cleanup of a contaminated urban area  Risk limits for radioactive contamination set by the EPA  Considerations  Medical management of people experiencing radiation bioeffects  Surface contamination procedures  Dealing with patients with acute radiation syndrome (ARS) (see next slide)  Internal contamination procedures Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 18 Radiation Emergencies: Use Of Radiation as a Terrorist Weapon (Cont.)  Medical management of people experiencing radiation bioeffects (Cont.) Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 19