click below
click below
Normal Size Small Size show me how
Radiation Protection
Radiation Protection, Physics, and Radiobiology
Question | Answer |
---|---|
ELECTROMAGNETIC RADIATION VELOCITY | 186,000 miles per second pg.229 |
WAVELENGTH | distance between two consecutive wave crest pg.229 |
FREQUENCY | number of cycles per second (Hz) = 1 cycle per sec pg.229 |
Natural Background | 37% radon and thor on gases 5% space radiation 5% internal sources 3% terrestrial sources pg.231 |
PRODUCTION OF XRAYS Bremsstrahlung | "braking" electron pulled off course by positive nucleus, loss of energy causes X-ray pg.232 |
PRODUCTION OF XRAYS Characteristic Radiation | High speed electron encounters tungsten atom and ejects K-shell electron. Xray is formed when higher energy electron fills K shell. pg.232 |
Relationship between Wavelength and Frequency | Inversely related pg.234 |
Speed of light = | Frequency X Wavelength pg.234 |
Ionization is caused by... | High energy, short wavelength electromagnetic radiations that break apart electrically neutral atoms pg.234 |
Most common ionization interactions with tissue cells | Compton scatter and photoelectric effect pg.234 |
Exposure dose | Depends on beam attenuation and on which type of interaction occurs between xr |
Early effects of radiation | Appear a short time after exposure Usually as a result of high dose in short period of time should not be seen in diagnostic radiology Depends on beam attenuation and on which type of interaction occurs between X-ray photons and tissue. pg.236 |
Late effects | Can appear years after exposure: Carcinogenesis Cataractogenesis Embryologic effct lifespan shortening Depends on beam attenuation and on which type of interaction occurs between X-ray photons and tissue. pg.236 |
Types of Risks Nonstochastic/Deterministic | Threshold Nonlinear Includes all early effects Includes some later effects Depends on beam attenuation and on which type of interaction occurs between X-ray photons and tissue. pg.237 |
Types of Risks Stochastic/Probabilistic | No threshold Linear Genetic effects Cancer Includes most late effects Depends on beam attenuation and on which type of interaction occurs between X-ray photons and tissue. pg.237 |
Types of DNA Damage | Main chain, double side rail break Main chain, single side rail break main chain breakage, cross linking Base damage, point mutations Depends on beam attenuation and on which type of interaction occurs between X-ray photons and tissue. pg.239 |
Law of Bergonie' and Tribondeau | the most radiosensitive cells are young, undifferentiated, and highly mitotic cells pg.241 |
LET | means of expressing radiation quality and determining the radiation weighting factor. pg.241 |
Acute radiation syndromes | Hematopoietic gastrointestinal Central nervous system pg.246 |
Stages of Acute radiation syndrome | Prodromal Latent Manifest illness recovery or death pg.246 |
Beam Restriction | Reduces patient dose reduces production of scattered radiation improves image quality |
Beam restrictor types | aperture diaphragm cone/cylinder collimator pg.254 |
mAs | Controls quantity no effect on quality pg.257 |
kV | controls quality, affects quantity pg.257 |
Radiation protection rules | time distance shielding pg.276 |
Primary barriers | Protects from the useful beam pg.277 |
Secondary Barriers | Protect from scattered and leakage radiation pg.277 |
Roentgen | Measures ionization in air measures X or gamma radiation only is valid up to 3MeV pg.287 |
Traditional and SI units | roentgen Air kerma (Gy) rad Gray(Gy) rem Sievert (Sv) pg.288 |
Personal Radiation Monitors | Optically stimulated luminescence thermoluminescent dosimeter film badge picket dosimeter pg.289 |
ALARA | as low as reasonably achievable pg.275 |
Rules of selecting patient assistant | A male older than 18 is preferred, although female of 18 is acceptable must be provided with protective apparel must not stand in the path of the useful beam must be as far as possible from the useful beam. pg.275 |
Leakage radiation | radiation that is emitted from the X-ray tube housing in directions other than that of the primary beam. pg.274 |
Scatter radiation | when primary X-ray photons intercept an object and undergo a change in direction pg.274 |
Grid purpose | improves the radiographic image by reducing the amount of scattered radiation fog, but necessitate an increase in exposure. pg.268 |
AEC | require accurate positioning and centering to produce predicable results pg.265 |
Manual timer | Must be used as backup timer to avoid patient overexposure and tube overload. pg.265 |
Two types of AEC | Ionization chamber is positioned between the tabletop and IR. the photo timer is located below the IR pg.264 |
Male gonads | More easily and effectively shielded pg.263 |
PA projection whenever possible | To reduce exposure to reproductive organs and breast when possible. pg.263 |
Three types of gonadal shields | Flat contact shadow contour contact pg.262 |
Gonadal shielding | gonads lie in or within 5cm of collimated beam the patient his reproductive potential diagnostic objectives permit pg.262 |
Radiosensitive organs | include the gonads and blood forming organs pg.262 |
<50 kV | .5 mm Al equivalent pg.258 |
50-70 kV | 1.5 mm Al equivalent pg.258 |
>70 kV | 2.5 mm Al equivalent pg.258 |
how to keep patient dose to a minimum | Low mAs and high kV pg.258 |
Proper calibration of equipment | is essential for predictable results and patient safety pg.258 |
Reducing radiation exposure | Proper selection of technical factors and an effective QA system pg.258 |
Filtration | removes low energy X-rays from primary beam pg.258 |
Filtration | reduces patient skin dose increasing the average energy of the beam pg.258 |
Filtration | usually expressed in mm of Al equivalent pg.259 |
Inherent + added filtration = | total filtration pg.259 |
Inherent filtration | includes the glass envelope, oil coolant/insulation pg.259 |
Inherent filtration increases with | tube age, thereby dressing tube output pg.259 |