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Intro to Radiologic
Chapter 9 Basic Radiation Protection
Question | Answer |
---|---|
Radiographers responsibility regarding ionizing radiation? | minimize radiation dose to the patient, anyone else in the room and to himself. |
"back ground" radiation, 82% of exposure to humans. | Natural Radiation |
Artifical radiation, 18% of exposure to humans. | Man-made radiation. |
Why is it important to minimize raditaion dose? | Unknown risks, and the risk of biological change when exposed to radiation. |
Natural Radiation | Terrestrial & Cosmic radiation, Varies depending on location, higher altitude receives more radiation. |
Terrestrial Radiation | Radioactive elements in earth (radium, uranium), internal (within the body-potassium, carbon, tritium) Radon. |
Man-made Radiation | Medical xrays, nuclear medicine, consumer products, nuclear fallout and occupational. |
Three things possible when xray passes through a pts body. | Transmitted-gets to IR-dark. Absorbed-light. or scattered-gray |
2 important interactions with matter. | Photoelectric Intereaction(Photoelectric effect or Photoelectric absorption) & Compton Scatter. |
Photoelectric Effect | interaction with matter in which a photon strikes an inner shell electron, causing its ejection from orbit with the complete absorption of the photons energy. |
Photoelectric Effect | Secondary radiation will not make it out of the patient. It interacts and is absorbed. |
Photoelectric Effect | Occurs with a higher energy beam. |
Compton Scattering | Interaction with matter in which a higher-energy photon strikes a loosely bound outter electron, removing it from its shell and the remaining energy is released as scattered photons. |
Compton Scattering | Secondary radiation actively moving makes it out of the patient leaving the body as scatter. Occurs with a lower energy beam, interacts and leaves. |
Compton Scattering | Where most occupational exposure comes from. |
exposure in air | Roentgen(TI) Coulomb/kilogram(SI) |
Absorbed dose | Rad(TI) Gray(SI) |
Dose Equivalent | Rem(TI) Sievert (SI) |
Activity | Curie (TI) Becquerel (SI) |
RAD | Radiation Absorbed Dose |
REM | Radiation Equivalent Man |
Are all equal at 1 | R, rad, rem |
rem | 1 rem x age |
mSv | 10 x age |
ALARA | As low as reasonably achievable. |
Ionization | occurs when a human is exposed to xrays. |
4 possible results from radiation expsoure | cell undamaged, cell damaged but repairs, cell damaged with no repair, cell dies. |
Latent Period | ti,e between radiation dose and Sx, during this time nothing happens. |
Differentiation | simple cells are more sensitive to the xray then complex cells. |
Metabolic Rate | Cells that divid & multiply faster are more sensitive than those that replicate slowly. |
ARS | Acute Radiation Syndrome, main thing to occur. |
Acute Radiation Syndrome | Can happen within minutes, days or weeks of exposure. |
Late Efftects of Exposure | develope over a period of time 5-30 years. Somatic and genetic effects. |
Time, Distance, Shielding | 3 Cardinal Principles of Protection. |
Time | Fast exposure, high kVp to lower mAs, limit holding time. |
Distance | limit holding, double distance decreases exposure by 1/4 because of inverse square law. |
Shielding | aprons, flat contact shields, shadow shields, lead aprons, lead gloves. |
TLD | Thermoluminescent Dosimeter. reusable, used in hospitals. plastic holder with crystals that absorb radiation exposure. |