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Chapter 15

Chapter 15. Radiation Safety and Production of X-Rays. Radiation Physics. Benefits of Radiographs (box 15-1) Definition: weightless bundles of energy (photons) with out electrical charge, that travel in waves at the speed of light

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Chapter 15

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  1. Chapter 15 Radiation Safety and Production of X-Rays

  2. Radiation Physics • Benefits of Radiographs (box 15-1) • Definition: weightless bundles of energy (photons) with out electrical charge, that travel in waves at the speed of light • Atomic Structure: all matter made of atoms, extremely minute, composed of Inner core- (positive charge), electrons (negative charge) orbit the nucleus, protons make up the nucleus, Fig. 15-1,pg.221 • Electrons remain stable unless disturbed • Molecule- smallest particle of substance that retains the property of the original substance • Ionization: harmful effect of x-rays have on humans, disruption of cellular structure and causes permanent damage to cells and tissue, when x-rays strike tissue ionization results • During ionization, electrons are removed from stable atoms by collisions with photons (minute bundle of pure energy)

  3. Properties of X-Rays • Form energy that can penetrate matter and have unique properties Table 15-1,pg. 222 (discuss) Review Fig. 15-2, pg. 222 • Shorter the wave length, the greater the energy. High energy of short wave lengths can penetrate matter more easily, than longer

  4. Types of Radiation • Primary Radiation: (aka) central ray or primary beam, emitted from the xray head, travels in a straight line, contains powerful short waves, short wave produces the diagnostically useful radiographs (fig. 15-3, A, pg.222 • Secondary Radiation: given off after the primary beam comes into contact with the soft tissue of the head, bones, teeth. Less penetrating, weaker after they contact tissue, patient may still absorb these rays (fig. 15-3, B, 222) • Scatter Radiation: occurs when x-ray is deflected from its path, during impact. Travels in all directions, unable to confine, with out barriers, patient/operator may be affected to the exposure (15-3, c, pg.222) • Leakage: radiation that escapes in all directions, usually faulty xray head, check equipment frequently

  5. Radiation Measurement • Radiation is Measured in two types of systems: Traditional/Standard and the newer system is the SI • Traditional: units of measurement include: the roentgen-R, radiation absorbed dose-RAD, roentgen equivalent (in) man (rem) • SI- Coulomb/Kilogram (c/kg), the gray (Gy), the sievert (Sv) • See Table 15-2, pg. 223 • Radiation Exposure: refers to the amount of radiation a person is exposed to, measured in SI units, per (c/kg). The traditional term R- one coulomb per Kilogram (c/kg) equals one R • Absorbed Dose: energy actually absorbed by tissue, SEE 15-2 (table) • Dose Equivalence: compares biologic effects of types of radiation

  6. Radiation Hazards and Protection • Back ground radiation: comes from natural resources (radioactive materials) • Maximum Permissible Dose: the exposure limit for those who are occupationally exposed to radiation when observing all safety practices. Amount of radiation to the whole, produces little injury. MPD for the operator (0.05 SV) 5 rem. Pregnant women only 0.005 sv (.05 rem) per year • Alara Principle: all exposure to radiation must be kept As Low As Reasonably Achievable, any proctection must be used to reduce all possible radtion, for both the patient and operator

  7. Biologic Effects of Radiation • Can bring changes in chemical, cells, tissues, and organs of the body • Latent Period: effects of radiation exposure that is evident years later is called the latent period (time Lag) Table 15-3, pg. 224 • Cumulative Effects: builds up, over the life time • Acute Radiation Exposure: occurs when large dose is absorbed in a short time • Chronic Radiation Exposure: small amounts absorbed repeatedly over a long period of time • Genetic Effects: reproductive cells, passed on succeeding generations (mutations) • Somatic Effects: other cells of the body, can damage tissue, not passed to generations (fig. 15-4, pg. 225)

  8. Protection For the Patient • All patients must wear a lead apron • Patients must let dental personnel know if they are pregnant, should postpone until after the pregnancy, unless it is an emergency • Each patient should be evaluated for dental radiograph needs, Box 15-2 pg. 225 • Usually x-rays are taken once a year • Fast speed film: most effective for lower radiation, ranges of speed are from A-F, F being the fastest (this will be discussed in Chp. 16) • Proper Equipment: tubehead must be equipped with appropriate aluminum filter, lead collimator, position indicator device (PID) Further discussed in ch. 16 • Filtration: aluminum filter- filter out the longer wave length, low-energy x-rays from the x-raybeam (fig. 15-5) not useful for producing a diagnostic image, results in a higher energy beam, more penetrating , useful beam

  9. Patient Protection, con’t. • Collimation: limiting the diameter of the x-ray beam to project adjacent areas from exposure to radiation • Collimator: lead disk with an opening (either rectangle or circular) designed to limit the dimension of the beam of radiation- Fig. 15-6, pg. 226 • Position Indicator Device: (PID) to direct the x-ray beam, has a round or rectangle shape, available in two lengths (short) 8” or (long) 16” fig. 15-7, pg. 227 • Film- Holding Instruments: holds the film and keeps patients fingers from being exposed, fig. 15-8, also stable position for x-ray • Lead Apron: thyroid collar must be used on all patients, Fig. 15-9, pg 227

  10. Protection of The Operator • Radiation Monitoring: badges worn by the operator, or placed on walls/equipment. Personnel can also where badges, in their pockets, to measure occupational exposure (fig. 15-11, pg. 228) • See Rules of Radiation Protection (box 15-3) pg. 228 • Equipment should also be monitored and check regulary • See Fig. 15-12, pg. 228, Fig. 15-13, pg. 229

  11. X-Ray Machine • Components of the Dental X-Ray Machine: Tubehead, extension arm, control panel (fig. 15-3 (a) pg. 229 • Tubehead: house dental x-ray tube, made of metal, protective lining of lead: prevents radiation from escaping, • Dental X-ray Tube: made of glass, about 6 inches long, see fig. 15-14, pg. 229, air has been removed to create a vacuum to allow electrons to flow with minimal resistant between the cathode and anode • Cathode: (-), tungsten filament, tungsten can with stand intense heat given off during the generation of x-rays, electrons are generated in the tube at the cathode • Focusing Cup: part of the cathode, keeps electrons suspended in the cloud at the cathode • Anode: (+) target for electrons, composed of tungsten target embedded into larger copper stem

  12. X-Ray Machine • Filter: aluminum disk located at the port of the tube head, removes low-energy, long wave lengths which maybe absorbed Fig. 15-15, pg. 230 • PID: lead lined, placed against the patients face, aims x-ray beam at the film in the patients mouth, • Extension Arm: hollow, encloses wires between the tube head to control panel, positions the tube head, never hold the tube head during exposure • Control Panel: master switch, maybe left on all day, • Exposure Timer: electronically controlled, to provide precise exposure time, x-rays are only = generated when this is pressed (impulse 1= 1/60 second) • Milliamperage Selector: mA, number of electrons that is produced, up the mA = increased electrons availible Table 15-4, pg. 231 • Kilovoltage: kV used to control the penetrating power, or the quality of the x-ray

  13. Image Characteristics • Radiolucent: appear dark or black on radiograph. Air spaces, soft tissue, dental pulp appear • Radiopaque: appear white or light gray on radiograph. Metal, enamel, dense areas of the bone appear

  14. Radiographic Quality • Density: overall blackness or darkness of the radiograph, to correct see Table 15-4, pg. 231, controlled by the mA settings • Contrast: range of shades from black to white, difference between them is contrast, controlled by the kVp settings Box 15-4 • Image distortion: object-film distance, source-film distance, movement play factors in a distortion of the image • Object-film Distance: distance between the teeth and the film, place film close to the teeth • Source-film Distance: distance between the source and the film, length of the PID determines the distance, longer reduces the distortion, fig. 15-17, pg. 232 • Movement: of patient or the film can distort the image

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