Biological Effects of Radiation Safety and Protection PDF

Biological effects of radiation Safety and protection Professor Zainab H. AL-Ghurabi  TYPES OF RADIATION  Ionizing Radiation: Radiation that has sufficient energy to dislodge orbital electrons. ex.: alpha particles, beta particles, neutrons  Non-ionizing radiation: Radiation that does not...

Biological effects of radiation Safety and protection Professor Zainab H. AL-Ghurabi  TYPES OF RADIATION  Ionizing Radiation: Radiation that has sufficient energy to dislodge orbital electrons. ex.: alpha particles, beta particles, neutrons  Non-ionizing radiation: Radiation that does not have sufficient energy to dislodge orbital electrons. ex.: microwaves, ultraviolet light, lasers, radio waves All the atoms in human body has electrical stability when x- ray photon strikes An electron in the atom of living tissues it displace the electron leaving the atom electrically unstable so such process called ionization This ionized atom has a strong tendency to seek its stability by accepting an electron from somewhere else By doing so a new chemical is form and the cell of which the atoms and molecules are parts can be altered. So that the basic effects of ionization are Molecular alteration and creation of new chemicals. Radiation biology : is the study of the effects of ionizing radiation on living systems. They may result in injury or death of the cell or organism. Effects of ionizing radiation: Direct effect : When the energy of a photon or secondary electron ionizes biologic macromolecules, the effect is termed direct. Those effects occurred in specific area of the body where all exposed cells in this area are altered directly by ionization process and death occurred at the time of mitotic cell division. Indirect effect: It happened in several ways where new chemicals result from process of ionization are in compatible with body tissues ,ex: when photon absorbed by water in an organism, ionizing the water molecules. The resulting ions form free radicals (radiolysis of water) that in turn interact with and produce changes in the biologic molecules.  Radio sensitivity of tissues and organs Body tissues differ in their susceptibility to ionizing radiation. Cells are most sensitive to radiation when they are immature, undifferentiated, and rapidly dividing. As cells mature and become specialized they are less sensitive to radiation. The following tissue and organs are listed in order to their susceptibility to x-ray : High radio sensitivity:  lymphoid organs  Blood forming tissues (bone marrow)  Intestines  stem cells  lymphocyte and reproductive cells. Intermediate radio sensitivity:  Young or growing bone  Growing cartilage  glandular tissue  salivary glands  Kidney  liver  lungs and epithelium of alimentary canal. low radio sensitivity:  Skin  muscle and optic lens.  The least effect seen in nerve tissue and adult bone.  *Short term effects of radiation on tissue seen in the first days or weeks after exposure while long term effects seen months and years after exposure. ALARA principle (The law of radiation protection) As Low As Reasonably Achievable : Radiographs should only be taken at the minimum dosage with reasonable information, so the benefit from radiograph should be weighed against the radiation dose and then decide to take radiograph or not. Latent period : Is a period of time interposed between exposure and clinical symptoms such period varies with the dose. So the more is sever dose the shorter is the latent period. sometimes the latent period is as long as 25 years for some minimum doses. Protection of patients from x-ray :  Using faster (film speed) : because the faster the film the less is the amount of radiation required to produce a radiographic image so it need less exposure time. Collimation : this done by collimating device to prevent the un necessary beam divergence, especially rectangular collimator.  Filtration : in order to absorb the long wave length X-ray photons (soft radiation) which have no diagnostic value.  Exposure and developing techniques : in order to prevent exposure of patient to much more radiation, we should know the exposure time for each segment of the jaw, if higher Kv. technique is used, its possible to use a constant exposure time for whole dentition.  Distance and kV : the purpose of using cylinders and cones in the X-ray machine is to limit the path for X-ray , the long cone mean increase tube film distance and when use higher kV With this cone we reduce the radiation dose absorbed by skin surface.  Film placement and angulations : this is important to prevent retakes and get a radiograph with best diagnostic information.  Protective apron and thyroid collar: - sheet of lead used to cover chest and reproductive areas of the patient so must be used in pregnant and young adult also thyroid collar used for protection of thyroid gland. (lead apron used by operator also for protection). Protection of operator and dose limits : Operator received secondary radiation and generally workers in X-ray clinic should not receive more than 5 rem of whole body radiation each year. Operator received 3 types of radiation (source of exposure) : 1. Scattered radiation from the patient 2. Primary beam if he stands in its path. 3. Leakage radiation from the tube head. To minimize the exposure of operator:  Position: operator must stand behind the patient because the head of the patient will absorb scattered radiation operator must stand with an angle of 90 - 135˚ to the radiation beam because in this area we have less scattered radiation.  Barrier: it interpose between the source of radiation and the operator it is the most effective method of providing safety to the operator and barrier is made of lead or steel or concert or barium plaster of 1/16 inch.  Distance: the intensity of radiation inversely proportional to the distance (inverse square law) so it's recommended for him to stand 6 feet away from the source of X-ray radiation.  * position and distance rule: if no barrier is available, the operator should stand at least 6 feet from the patient, at an angle of 90 to 135 degrees to the central ray of the x-ray beam when the exposure is made. Film badge Is a blue plastic frame containing a variety of metal filters and a small radiographic film which exposed to X-ray. it provide a permanent record of the dose received by operators (radiographers and dentists) and it used for 1 – 3 months before being processed for monitoring of dose received by operator.