Download
author lototska o v n.
Skip this Video
Loading SlideShow in 5 Seconds..
Author: Lototska O.V PowerPoint Presentation
Download Presentation
Author: Lototska O.V

Author: Lototska O.V

165 Views Download Presentation
Download Presentation

Author: Lototska O.V

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Ionizing radiation as a factor of environment. Problem of contamination of environment by radionuclide. Hygienic setting of ionizing radiations norms as basis of radiation protection. Author: Lototska O.V 1

  2. THE PLAN Introduction Sources of radiation exposure. Ionizing radiation and radioactivity. Radiation quantities and unit. Biological manifestations of radiation exposure. Principles of radiation protection. The concepts of "maximum permissible dose" and "dose limit“ Conclusions

  3. The Chernobyl accident occurred on April 26, 1986 at the Chernobyl nuclear power plant in Pripyat, Ukraine It is regarded as the worst accident in the history of nuclear power

  4. There are two types of radiation exposure: One is internal exposure from radioactive material taken into the body; the other is external exposure from radiation sources outside the body. Internal exposure can continue if the radioactive material remains in the body. In contrast, external exposure will not occur again once radiation has penetrated the body, if no additional radiation reaches the body.

  5. Components of Environmental Radiation

  6. Naturally occurring sources • cosmic radiation originating in outer space and reaching the earth's surface after reacting with, and being partially absorbed by, the earth's atmosphere; • 30 millirem/year 2. terrestrial radiation coming from natural radioisotopes present in the earth's crust;30 millirem/year 3. radiation from natural radioisotopes that have been accumulated in the body as a result of the consumption of food and water and the inhalation of air containing such radioisotopes. 40 millirem/year

  7. Man-made radiation 1. radiation to patients from the medical uses of radiation 2. radiation to occupationally exposed persons 3. radiation from "fallout" from nuclear tests 4. radiation from other forms of radioactive contamination 5. radiation from radioactive consumer goods and from electronic devices.

  8. Examples of radiation doses from common medical procedures are: • chest x-ray (14 x 17 inch area) - 15 mrem, • dental x-ray (3 inch diameter area) - 300 mrem, • spinal x-ray (14 x 17 inch area) - 300 mrem,

  9. Ionizing radiation and radioactivity

  10. "Radiation" is generally defined as the process of emitting energy as waves or particles, and the energy thus radiated. Ionizing radiations include all electromagnetic and particulate radiations that are capable of producing ions, either directly or indirectly, during their passage through matter.

  11. What is the difference between radiation and radioactivity? Radioactivity is the property or capacity of radioactive materials to emit radiation. Radiation means particle beams carrying energy emitted from radioactive materials (radioactive isotopes). To put in an analogy, a flashlight is a radioactive material and the light from a flashlight is radiation.

  12. Ionizing radiations Corpuscular radiations electro­magnetic radiations X-ray gamma rays protons alpha particles beta particles (electrons)

  13. Alpha radiation is simply helium nuclei, that is, each particle consists of two protons and two neutrons. Because the nuclei have no electrons, they have a +2 charge. Beta radiation consists of electrons. They have negative charges. Because they are energetic and have no rest mass, they can be more of a potential health threat than alpha radiation. Gamma radiation is closely related to X-rays. Like light, gamma radiation consists of photons. Gamma rays are extremely energetic and potentially dangerous.

  14. Other types of particulate radiations include neutrons, protons and deuterons Protons and deuterons are usually produced in high-energy particle accelerators used in high energy physics research work and are not commonly encountered in medical applications.

  15. Neutrons may come into more common usage in departments of radiology as the techniques of neutron radiography and radiation therapy are developed. Although neutrons do not produce ionization themselves, they may do so indirectly. They can also be absorbed by the nuclei of stable atoms to produce another isotope of that atom. If the nucleus of the new atom is unstable, the atom will be a radioactive isotope.

  16. RADIATION QUANTITIES AND UNIT

  17. Dose equivalent (H) Four of the most important quantities to be defined are: Activity Exposure (X) Absorbed dose (D)

  18. Activity: The nuclei of atoms may be unstable as a result of too much mass, too much energy, or both. Such atoms are said to be radioactive. We can define radioactivity as a process of nuclear transformation, resulting in a new nucleus and the emission of particles and/or electromagnetic energy from the nucleus. The emitted radiation consists of particles and/or electromagnetic rays carrying a certain amount of energy. The unit of measure for energy is the joule (noted J). Another unit of measure, the eV - electronvolt, is more practical.

  19. The activity of a radioactive source is defined as the rate at which the isotope decays. Radioactivity may be thought of as the volume of radiation produced in a given amount of time. The unit of measure for activity, in SI, is disintegrations per second. To honour the discoverer of radioactivity (Henri Becquerel, 1896), the unit of activity (disintegrations per second) was named the Becquerel and the notation used is Bq .

  20. Historically, another unit was used - the Curie - noted Ci. It was named after Marie Curie, the discoverer of Radium, and other radionuclides. One curie (or 1 Ci) is the activity of 1 gram of pure Radium. This activity is equal to 3.7x1010 disintegrations per second, or 3.7x1010 Bq.

  21. Radiation Units Coloumb / kg (C/kg) = roentgen (R) 1 sievert (SV) = 100 rem

  22. Quality factor is a modifying factor that is introduced to take into account the different degrees of biological effect that can result following exposure to the same absorbed doses of different types of radiation. The Q factors for several types of radiation.

  23. Biological Effects

  24. The biological effect of ionizing radiation

  25. Can lead to:

  26. The occurrence of particular health effects from exposure to ionizing radiation is a complicated function of numerous factors including: • Type of radiation involved. • Size of dose received. • Rate the dose is received. • Part of the body exposed. • The age of the individual. • Biological differences.

  27. Biologic effects of ionizing radiation Characteristic of effects Deterministic effects Stochastic effects Genetic Somato-stochastic Somatic Object genetic mutation Acute radiation sickness skin and tissue burns cancerogenic effect Chromosomal aberration teratogenic effect chronic radiation sickness alopecia ray cataract clinical registered frustration of hemopoesis temporary or constant sterility

  28. Somatic effects • The early effects are normally observed within a few days or weeks of exposure; • the late effects are observed after a period ranging from a few months to years.

  29. Relationship between Exposure Doseand Acute Radiation Effect in adult humans

  30. A latent period supervenes after initial symptoms of malaise, loss of appetite and fatigue. The length of this period is roughly inversely proportional to the radiation dose received. The end of the latent period is followed by the onset of the illness: • early lethality, • destruction of bone marrow, • damage to the gastrointestinal tract associated with diarrhea and hemorrhage, • central nervous system symptoms, • Epilation (loss of hair), • dermatitis, • sterility. • Pathological acute effects arise after exposure to doses hundreds of times greater than those likely to be received from environmental contamination, except in major accidents.

  31. Deterministic effects have a clear relationship between the exposure and the effect. In addition, the magnitude of the effect is directly proportional to the size of the dose. These effects will often be evident within hours or days. Stochastic effects are those that occur by chance and consist primarily of cancer and genetic effects. Stochastic effects often show up years after exposure. As the dose to an individual increases, the probability that cancer or a genetic effect will occur also increases.

  32. Late effect Cancer is any malignant growth or tumor caused by abnormal and uncontrolled cell division. Cataracts - a clouding of the lens of the eye

  33. Leukemia Leukemia is a cancer of the early blood-forming cells. Usually, the leukemia is a cancer of the white blood cells, but leukemia can involve other blood cell types as well. Leukemia starts in the bone marrow and then spreads to the blood. From there it can go to the lymph nodes, spleen, liver, central nervous system (the brain and spinal cord), testes (testicles), or other organs. Leukemia is among the most likely forms of malignancy resulting from overexposure to total body radiation. Chronic lymphocytic leukemia does not appear to be related to radiation exposure.

  34. Genetic effects If the information that is jumbled is in a germ cell that subsequently is fertilized, then the new individual may carry a genetic defect, or a mutation. Such a mutation is often called a point mutation, since it results from damage to one point on a gene. Most geneticists believe that the majority of such mutations in man are undesirable or harmful. In addition to point mutations, genetic damage can arise through chromosomal aberrations.

  35. Nonstochastic (Acute) Effects Nonstochastic effects have a clear relationship between the exposure and the effect. In addition, the magnitude of the effect is directly proportional to the size of the dose. Nonstochastic effects typically result when very large dosages of radiation are received in a short amount of time. These effects will often be evident within hours or days. Examples of nonstochastic effects include erythema (skin reddening), skin and tissue burns, cataract formation, sterility, radiation sickness and death.

  36. the particular organs or tissues that are critical because of the damage they may suffer is the essential simplifying step. For example, in the case of radioisotopes of iodine, the critical organ is the thyroid, since the concentration of such isotopes in it, and therefore the dose received, is far greater than for any other organ. Critical organs

  37. For general irradiation of the whole body, the critical organs and tissues are the gonads (fertility, hereditary effects), the haematopoietic organs, the bone marrow (leukemia), the eye (cataracts).

  38. PRINCIPLES OF RADIATION PROTECTION

  39. Rods for Internal Radiation External Radiation of a Tumor

  40. The physical protection against external radiation is based on the following three principles: • distance from the source of radiation (distance), • limitation of the time of irradiation (time), • absorption of radiation (shielding). Shortening the time of exposure, increasing distance from a radiation source and shielding are the basic countermeasures (or protective measures) to reduce doses from external exposure.

  41. To reduce doses from intake of radioactive substances, the following basic countermeasures can be considered: • shortening time of exposure to contaminants; • preventing surface contamination; • preventing inhalation of radioactive materials in air; • preventing ingestion of contaminated foodstuffs and drinking water.

  42. The duration of exposure during fluoroscopy can be minimized by the fluoroscopist by using image hold technique, intermittent beam on-off imaging, and avoiding long static imaging. The picture above demonstrates how image hold techniques can be useful in decreasing radiation exposure to the patient during dynamic fluoroscopic imaging procedures. The high resolution of modern monitors allows the physician to make observations not easily seen with archaic imaging equipment. It can be seen in this picture that an ERCP procedure is being done; this imaging department uses two monitors in their fluoro room, one for dynamic imaging the other for last image hold.

  43. Distance is the most effective means of radiation protection I1/l2 =(D2/D1)2 Area "A" is smaller and the radiation is more concentrated than in an equal area "A1" which is some distance from "A." Each square A1 is the same size as "A" but only 1/4 the number of photons occupies it because of the divergence of the radiation with increasing distance.