Radioisotopes and Radiation Protection PDF

Radioisotopes and radiation protection Electromagnetic Spectrum Visible Ionizing Radiation Nonionizing Radiation Infrared Ultraviolet Near Radar Far X Rays FM TV Gamma Rays Short wave Cosmic Rays 10-14 Broadcast 10-12 10-10 10-8 10-6 10-4 10-2 1 Power Transmission 102 104 10...

Radioisotopes and radiation protection Electromagnetic Spectrum Visible Ionizing Radiation Nonionizing Radiation Infrared Ultraviolet Near Radar Far X Rays FM TV Gamma Rays Short wave Cosmic Rays 10-14 Broadcast 10-12 10-10 10-8 10-6 10-4 10-2 1 Power Transmission 102 104 106 108 10-8 10-10 10-12 10-14 Wavelength in Meters 1010 High 108 106 104 102 1 10-2 10-4 10-6 Energy - Electron Volts Low Dr. Kholood Baron Man made radiation/ Medical exposure What is happening in nuclear medicine ? Radioisotopes Hospitalized individuals who undergo medical imaging procedures are exposed to a sources of ionizing radiation, either: - X - ray procedures - radioactive materials ( as in Nuclear Medicine) riot codpot Nuclear medicine   A medical specialty involving the application of radioactive substances (Radiopharmaceuticals containing radioactive isotopes.) in the diagnosis and treatment of disease. In a sense, is " radiology done inside out" because it records radiation emitting from within the body rather than radiation that is generated by external sources like X-rays. What is Radioactivity?   Radioactivity is the natural property of certain elements and individual nuclides to spontaneously emit RADIATION ENERGY, in the form of alpha, beta, and gamma rays. Radioactive material can be a solid, liquid or gas. Radioactive Material  Either natural or created in nuclear reactor or accelerator  Radioactive material is unstable and emits energy in order to return to a more stable state (particles or gamma-rays)  Half-life – is the time for radioactive material to decay by one-half its original energy. An Isotope ! Every chemical element can have many isotopes and at least one or more are radioactive isotopes. A X Z  X = Element  A = Total number of protons and neutrons in the nucleus  Z = Number of protons  N= Number of neutrons ( A – Z) A Radioactive Isotope radioactive isotope, radioisotope, radioactive nuclide, several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation 14 C 6 X = Carbon  A = 14 neutrons and protons  Z = 6 protons  N = 8 neutrons Radioactivity Units - Measure of the amount of radioactive material OR the rate at which radiation is being emitted. - Unit for this is the Curie (Ci) , or in the SI system, the Becquerel (Bq). 1 Bq = 1 decay per second (dps) 1 Ci = 3.7 x 1010 Bq 1 Ci = = 37,000 Bq Half-Life and Decay  Each radioactive nuclide has its own unique characteristic energy and pattern of decay, such as alpha decay, beta decay, spontaneous fission, and a few others.  The decay rate of a radionuclide is called its half-life.  A half-life is the amount of time it takes for one-half of the radioactive atoms present to disintegrate or decay away. Penetrability and Energy  All radiation has the ability to penetrate and transfer its energy to the material it is penetrating.  The term “Linear Energy Transfer”, or L E T, is used to describe the amount of energy imparted locally in a target.  The higher the value of L E T, the greater the amount of energy being transferred per interaction, and the lower its penetrating ability. This also means the greater the risk of damage to the material absorbing the energy. LET and Penetrability  Alpha particles have a high L E T. Their ability to penetrate anything is very low. Alpha particles can be shielded by a piece of paper.  Beta particles have a low L E T, and can only penetrate material of low density. They can be shielded with Plexiglas.  X and gamma rays also have a low L E T. Because they have no mass or electrical charge, they have the highest ability to penetrate material. High density materials are needed to shield against the EM waves. Alpha particles impart a large amount of energy in a short distance. Beta particles impart less energy than alphas, but are more penetrating. X and Gamma rays impart only a fraction of their total energy each time they interact with the target material. Alpha Particles What are the radiation particles that nuclear medicine deals with ?  Two neutrons and two protons  Charge of +2  Emitted from nucleus of radioactive atoms  Transfer energy in very short distances (10 cm in air)  Shielded by paper or layer of skin  Primary hazard from internal exposure  Alpha emitters can accumulate in tissue (bone, kidney, liver, lung, spleen) causing local damage Beta Particles  Small electrically charged particles similar to electrons  Charge of -1  Ejected from nuclei of radioactive atoms    Gamma-rays  Electromagnetic photons or radiation (identical to x-rays except for source)  Emitted from nucleus of radioactive atoms – spontaneous emission Emitted with various kinetic energies  Shielded by wood, body penetration 0.2 to 1.3 cm depending on energy Emitted with kinetic energy related to radioactive source  Can cause skin burns or be an internal hazard of ingested Highly penetrating – extensive shielding required  Serious external radiation hazard In comparison to X-rays       Electromagnetic photons or radiation Produced from orbiting electrons or free electrons – usually machine produced Produced when electrons strike a target material inside and x-ray tube Emitted with various energies & wavelengths Highly penetrating – extensive shielding required External radiation hazard  Beta, gamma, and x-rays are forms of ionizing radiation used for medical purposes.  But they have different energy and hence different penetration and effects Paper Alpha Beta Gamma Wood Concrete Energy Low Egf Medium High 2- Nuclear medicine imaging Medical usage of radioisotopes 1- Radiation therapy  Use therapeutic isotopes that have long –lives (multiple days or years) + high radiation emission + preferably tow penetration  Examples:  Iodine -125 - electron capture decay - Half life -59.4 days ( titanium encapsulated cylindrical seeds ) used commonly to treat prostate cancer.  Iodine 131 – beta decay- Half life 8 days- (sodium iodide tablets) to treat thyroid cancer.  Use radioisotopes to study organ function in patients, to detect and diagnose many pathology including cancer. - use short lived radioisotopes as radioactive tracers, such as:  Iodine 123 - electro capture decay- half life 13.3 hours- l.e. thyroid gland.  Technetium 99m ( most commonly used)- gamma emission decay -half life 6 hours. can be incorporated into wide variety of biologically active compounds 3- Positron Emission Tomography (PET) / (CT) imaging PET make use of the annihilation radiation that Is initiated by the spontaneous decay of the unstable isotope nucleus (too much proton)  Positron (antimatter) interact with electron = disappear – matter transferred into energy (511 keV photons)  Imaging concept : similar to CT analogy (by detecting the annihilation photons)  Fluorine 18 ( commonly used) - can attach to glucose (FDG)  Radiation protection on NM Radium Girls "Not to worry," their bosses told them. "If you swallow any radium, it'll make your cheeks rosy.“ The women at Radium Dial sometimes painted their teeth and faces and then turned off the lights for a laugh. Late 1920s – Radium girls sue, win and receive compensation Occupational Exposures / Personal who work with radiation - Occupational Exposure is the radiation exposure you receive working with and around radioactive materials or X-ray systems as part of your work. - Regulations limit the amount of radiation dose allowed for occupational adult , members of the public, and the fetus of a declared pregnant radiation worker. Dose limits for occupational exposure Workers ≥ 18 years Effective dose Apprentices & Students 16-18 years 20 mSv per year averaged 6 mSv in a year over five consecutive years, and 50 mSv in a year  150 mSv in a year Extremities (hands 500 mSv in a year and feet) or the skin 50 mSv in a year 150 mSv in a year * Consideration is being given to: For workers: 20 mSv per year averaged over 5 consecutive years, and 50 mSv in a year Exposure – X (coul/kg) (Related to energy)  Equivalent dose to: Lens of the eye* NB: Radiation Units Absorbed Dose – Gray (Gy) (amount of energy absorbed)  Equivalent Dose – Sievert (Sv) (makes different sources of radiation equivalent) Tips for Radiation Protection in NM The penetrating gamma present an especial radiation hazard  Nursing staff  Nuclear medicine technologist,  Visitors 1- Minimize Exposure When working with radioactive material, remember to minimize your exposure at all possible times. 2- Use the correct shield - correct lead thickness - Especially designed faculty 3- ALARA principle 4- avoid repeats and errors 5- stay focus and alert Three cardinal Strategies -Time Minimize the time and you will minimize the dose.  Pre-plan the experiment/procedure to minimize exposure time. Three cardinal Strategies Distance Doubling the distance from the source can reduce your exposure intensity by 25%.  Use forceps, tongs, and trays to increase your distance from the radiation source.  Move the item being worked on away from the radiation area if possible.  Know the radiation intensity where you perform most of your work, and move to lower dose areas during work delays. Three cardinal Strategies Shielding Position shielding between yourself and the source of radiation at all permissible times. Take advantage of permanent shielding (i.e. equipment or existing structures).  Select appropriate shielding material during the planning stages of the experiment/procedure.  Plexiglas, plywood and lead are effective in shielding radiation exposure. Use the proper shielding for the type of radioactive material present. Room shielding Lead lined plaster board Lead glass viewing window Shielding X-Rays & Gamma Rays • • Lead shielding will reduce the intensity of x-rays and gamma rays emitted from source of radiation. To reduce exposure by a certain percent, lead shielding must be a certain thickness for each type of emitter. Radiation protection Individual monitoring when a lead apron is used   The presence of the lead apron greatly influences doses to different parts of the body If a single dosimeter only is worn, then:  If a lead apron is not always being worm. The dosimeter should be worn under the apron, between shoulder and waist, for estimating effective dose  If a lead apron is always being worn. The dosimeter should be worn above the apron, at collar level, for estimating equivalent dose to the lens of the eye, and can also be corrected to estimate effective dose Measuring Radiation Dose -DosimetersUse to measure the occupational dose equivalent from x-ray, gamma, and high energy beta emitters. ( rememberDosimeters cannot detect radiation from low energy beta emitters. Measures… Is worn… Can detect…  In the case of image guided interventional procedures two dosimeters should be considered (talk to the RPO) Different types of personal dosimeters… • Film • TLD • OSL • DIS • Electronic dosimeters • Worn at chest level, between the shoulders and the waist • The monitoring period should be one month, and must not exceed three months TLD Whole body exposure On the torso or area of highest likely exposure Ring Dosimeter Fetal Dosimeter Extremity exposure Exposure to a fetus On either hand under the At the waist line gloves with the name facing the radiation source X-rays & gamma rays: X-rays & gamma rays: 1 – 1,000,000 mrem 30 – 1,000,000 mrem High energy beta emitters: High energy beta emitters: 10 – 1,000,000 mrem 40 – 1,000,000 mrem Personal -safety Protective Equipment (to protect from direct contact with radioactive particles and contamination) Radiation Safety-Laboratory Rules- Radiation Safety -Laboratory Rules1. Smoking, eating, and drinking are not permitted in radionuclide laboratories. 5. Protective clothing shall be worn when working with radioactive materials. This includes laboratory coats, gloves, and safety glasses. 2. Food and food containers are not permitted in the laboratory. 6. Dosimeters shall be worn when working with radionuclides which emit penetrating radiation. 3. Radionuclide work areas shall be clearly designated and should be isolated from the rest of the laboratory. 7. All containers of radioactive materials and items suspected or known to be contaminated shall be properly labeled with tape or tagged with the radiation logo and the word “RADIOACTIVE”. 4. All work surfaces shall be covered with absorbent paper which should be changed regularly to prevent the buildup of contamination. Warning Label Requirements Warning Labels  Mark all items used to manipulate or store radioactive material.  Label all contaminated items.  Remove all radiation labels and warnings on containers that no longer contain radioactive material and are not contaminated. 8. All contaminated waste items shall be placed in a container specifically designed for radioactive waste. MUST be clearly visible, durable, and MUST state: “CAUTION: RADIOACTIVE MATERIAL” Labels must provide sufficient information on the container to minimize exposure and to make sure all proper precautions have been taken. CAUTION: Radioactive Material  Radionuclide(s)  Estimated  Date activity Radioactive Waste Disposal  Radioactive waste includes anything that contains or is contaminated with radioactive material.  Collect radioactive waste in proper containers.  Keep containers closed and secured unless you are adding waste.  Report the proper information on the radioactive waste tag when material is put in the waste container.  Keep a tag on the waste container at all times. Medical management of person experiencing radiation bio-effects Same procedure to infection control : i. e. : Wear gown , masks, gloves, when approaching patient.  Remove patient cloths + shower and rinse.  Some time > require skin graft   Medical treatment for symptoms In case of internal contamination:  - dilution  Blocking absorption ( laxatives. Emetics, charcoal)  For iodine > administer potassium iodide will block further uptake in thyroid Special Case Contamination- From dirty bomb  Radioactive dispersal device or ( dirty bomb) is a radioactive source mixed with conventional explosive - The Long term health effect depends on the size of the area contamination + can contaminate Dust and debris . Solution >> decontamination. + measure the radioactivity using Geiger Muller (GM) detector