introduction to radiation
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Radiation can be ionizing or non-ionizing. Ionizing radiation like x-rays and gamma rays can damage cells by ionizing them. Non-ionizing radiation like visible light and microwaves do not have enough energy to ionize atoms. The health effects of radiation depend on dose, exposure time, and radiation type. Proper safety protocols aim to keep radiation exposure as low as reasonably achievable.
introduction to radiation
- 1. Radiation Dr . Ehab Hegazy
- 2. Radiation Nonionizing Ultraviolet, visible, infrared, microwaves, radio & TV, power transmission Ionizing Radiation capable for producing ions when interacting with matter – x-rays, alpha, beta, gamma, cosmic rays
- 3. Electromagnetic Spectrum 10-14 10-12 10-10 10-8 10-6 10-4 10-2 1 102 104 106 108 Wavelength in Meters 1010 108 106 104 102 1 10-2 10-4 10-6 10-8 10-10 10-12 10-14 Broadcast Short wave TV FM Radar Infrared Near Far Visible Ultraviolet X Rays Gamma Rays Cosmic Rays Power Transmission Ionizing Radiation Nonionizing Radiation Energy - Electron VoltsHigh Low
- 4. Nonionizing Radiation Sources • Ultraviolet light • Visible light • Infrared radiation • Microwaves • Radio & TV • Power transmission
- 5. Ultraviolet - Sources • Sun light Most harmful UV is absorbed by the atmosphere
- 6. Biological effect of UV • High ultraviolet kills bacterial and other infectious agents sun burn – increased risk of skin cancer • Pigmentation that results in suntan Suntan lotions contain chemicals that absorb UV radiation ( e.g Vitocare sun protection ) • Reaction in the skin to produce Vitamin D that prevents rickets. disease of childhood, characterized by softening of the bones as a result of inadequate intake of vitamin and insufficient exposure to sunlight, also associated with impaired calcium and phosphorus metabolism
- 7. Infrared Radiation (IR) • The energy of heat • Can damage – cornea, iris, retina and lens of the eye
- 8. Microwaves & Radio Waves • Wave length between 0.1 cm to 1 kilometer • Varity of industrial and home uses for heating and information transfer (radio, TV, mobile phones) • Health effects – heating, cataracts
- 9. Microwave heating Many molecules (such as those of water) are electric dipoles, meaning that they have a partial positive charge at one end and a partial negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field of the microwaves. Rotating molecules hit other molecules and put them into motion, thus dispersing energy. This energy, when dispersed as molecular vibration in solids and liquids
- 10. Ionizing Radiation Ionization Defined Radiation capable for producing ions when interacting with matter – in other words enough energy to remove an electron from an atom. Sources x-rays, radioactive material produce alpha, beta, and gamma radiation, cosmic rays from the sun and space.
- 11. 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 – time for radioactive material to decay by one-half
- 14. Ionizing Radiation Paper Wood Concrete Alpha Beta Gamma Energy Low Medium High
- 15. Alpha Particles • 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
- 16. Beta Particles • Small electrically charged particles similar to electrons • Charge of -1 • Ejected from nuclei of radioactive atoms • Emitted with various kinetic energies • Shielded by wood, body penetration 0.2 to 1.3 cm depending on energy • Can cause skin burns or be an internal hazard of ingested
- 18. • Beta particles are electrons or positrons (electrons with positive electric charge, or antielectrons). • Beta decay occurs when, in a nucleus with too many protons or too many neutrons, one of the protons or neutrons is transformed into the other. • In beta minus decay, a neutron decays into a proton, an electron, and an antineutrino • In beta plus decay, a proton decays into a neutron, a positron, and a neutrino:
- 19. Electron capture one of the orbital electrons, usually from the K or L electron shell (K-electron capture, also K-capture, or L-electron capture, L-capture), is captured by a proton in the nucleus, forming a neutron and an electron neutrino.
- 20. Gamma-rays • Electromagnetic photons or radiation (identical to x-rays except for source) • Emitted from nucleus of radioactive atoms – spontaneous emission • Emitted with kinetic energy related to radioactive source • Highly penetrating – extensive shielding required • Serious external radiation hazard
- 24. Since the proton is changed to a neutron in electron capture, the number of neutrons increases by 1, the number of protons decreases by 1, and the atomic mass number remains unchanged. By changing the number of protons, electron capture transforms the nuclide into a new element. The atom, although still neutral in charge, now exists in an energetically excited state with the inner shell missing an electron. While transiting to the ground state, the atom will emit an X-ray photon (a type of electromagnetic radiation) and/or Auger electrons. Often the nucleus exists in an excited state as well, and emits a gamma ray in order to reach the ground state energy of the new nuclide just formed.
- 26. PET • Positron emission tomography (PET) is a test that uses a special type of camera and a tracer (radioactive chemical) to look at organs in the body. The tracer usually is a special form of a substance (such as glucose) that collects in cells that are using a lot of energy, such as cancer cells. • During the test, the tracer liquid is put into a vein (intravenous, or IV) in your arm. The tracer moves through your body, where much of it collects in the specific organ or tissue. The tracer gives off tiny positively charged particles (positrons). The camera records the positrons and turns the recording into pictures on a computer. • PET scan pictures do not show as much detail as computed tomography (CT) scans or magnetic resonance imaging (MRI) because the pictures show only the location of the tracer. The PET picture may be matched with those from a CT scan to get more detailed information about where the tracer is located. • A PET scan is often used to evaluate cancer, check blood flow, or see how organs are working.
- 28. X-rays • Overlap with gamma-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
- 29. Ionizing Radiation Health Effects We evolved with a certain level of naturally occurring ionizing radiation from cosmic radiation, radioactive materials in the earth. We have mechanisms to repair damage.
- 30. Dose Response Tissue Examples of tissue Sensitivity Very High White blood cells (bone marrow) Intestinal epithelium Reproductive cells High Optic lens epithelium Esophageal epithelium Mucous membranes Medium Brain – Glial cells Lung, kidney, liver, thyroid, pancreatic epithelium Low Mature red blood cells Muscle cells Mature bone and cartilage
- 31. Time Reduce the spent near the source of radiation. Distance Increase the distance from the source of radiation. Shielding Place shielding material between you and the source of radiation. Reducing Exposure
- 32. Biological Effects of Radiation •Somatic –Affects cells originally exposed (cancer) –Affects blood, tissues, organs, possibly entire body –Effects range from slight skin reddening to death (acute radiation poisoning) •Genetic –Affects cells of future generations –Keep levels as low as possible (wear lead) –Reproductive cells most sensitive 32
- 33. 33 Units of Measurement • Effect of ionizing radiation is determined by: – Energy of radiation – Material irradiated – Length of exposure – Type of effect – Delay before effect seen – Ability of body to repair itself
- 34. 34 Radiation Units of Measurement Roentgen (R) - expression of exposure to x- rays/gamma rays Radiation Adsorbed Dose (rad) – amt of energy released to / absorbed by matter when radiation comes into contact with it Radiation Equivalent Man (rem) - Injury from radiation (depends on amt of energy imparted to matter)
- 35. 35 Permissible exposure radiation doses Body Part Exposed Permissible Dose (rem per quarter) Whole body 1.25 Hands, forearms, feet, ankles 18.75
- 36. 36 Purple and yellow Radiation Symbol
- 37. 37 Basic Safety Factors • Keep exposures As Low As Reasonably Achievable (ALARA) – Time - Keep exposure times to a minimum – Distance - Inverse square law: by doubling distance from a source, exposure is dec by a factor of 4 – Shielding – wear lead, use lead wall