110 Unit 3 Sect B
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| attenuation | beam energy reduced when passing through tissue/material
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| contrast | difference between adjacent densities
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| density | degree of darkening of film
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| distortion | misrepresentation of true size of object
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| dynamic | with motion
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| half value layer | filtration needed to reduce beam to half its original value
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| intensifying screen | luminescent crystals inside cassette to expose film
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| Inverse square law | formula desribing relationship betwwen intensity and distance
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| Kilovoltage peak (kVp) | measure of electrical pressure, controls quality/quantity of photons in tube
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| latent image | invisible image after exposure but before processing
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| Milliampere Second (mAs) | milliamperage X seconds, controls quantity of photons produced in tube, exposure and density
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| penetrating ability | beam ability to pass through object, controlled by kVp
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| penumbra | fuzzy border
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| photon | particle of radiant energy
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| Positive Beam Limitation (PBL) | automatic collimation
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| primary radiation | beam before hitting object
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| radiolucent | permitting xray passage with little attenuation
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| radiopaque | not easily penetrable by xrays
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| recorded detail | representaion of objects true borders
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| relative speed | speed of film and intensifying screen, slow film, sharper image and more radiation
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| remnant radiation | radiation after beam exits object
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| resolution | measurement of recorded detail on radiograph, aka sharpness of detail, definition
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| scatter radiation | photon interacts with matter, goes in different direction, radiation produced
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| static | unmoving
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| umbra | true border of object as imaged
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| photographic qualities | density and contrast
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| geometric qualities | recorded detail and distortion
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| mAs formula | mA x time = mAs
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| Exposure/density influencing factors | patient factors, kVp, distance, beam modification, grids, film/screen combinations, processing
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| 15% rule | increase kVp 15% will double exposuredecrease kVp 15% will halve exposure
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| 15% rule with no change in exposure | increase kVp 15% and halve mAsdecrease kVp 15% and double mAs
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| inverse square law definition | intensity of beam is inversely proportional to the square of the distance from the source
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| inverse square law formula | I1/I2=D1squared/D2squared
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| inverse square law tip | halve the distance, X intensity by 4
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| exposure maintenance formula | mAs1/mAs2 = D1squared/D2squared
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| primary beam modification | modified beam before entering patient
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| scale of contrast | range of gray tones; few is high contrast, short scale and vica versa
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| Influencing factors of contrast | patient factors, mAs, beam modification, film/screen combinations, contrast media, processing
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| factors affecting recorded detail | motion, object unsharpness, focal spot size, SID, OID, and material unsharpness
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| SID | greater SID better recorded detail
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| OID | greater OID, decreased sharpness
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| size distortion | magnification
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| shape distortion | true distortion
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| shape distortion controlling factors | alignment of beam, part and IR
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| spot imaging | flouroscopy unit changes to radiographic mode
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| anode | positive electode, target, method to accelerate
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| cathode | negative electrode, filament
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| rotor exposure switch | device that begins the exposure
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| ALARA | (radiation exposure) as low as reasonably acheivable
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| Classic Coherent scattering | low energy photon absorbed and released with only a change in direction
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| Compton effect scattering | high energy photon strikes end removes electron from shell, remaining energy released as scatter photon, most harmful to RT
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| Curie (Ci), Becquerel (Bq) | measures the rate a radionuclide decays, 1Ci=3.7 x 10(to the tenth)Bq
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| SI Units | metric radiation measurement developed in 1948
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| Kilelectron Volt (keV) | equal to 1000 electron volts
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| pair production | interaction between matter and photon having 1.02 million electron volts, producing positron and negatron
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| photoelectric effect | photon strikes inner shell electron ejecting it and absorbing photons energy, most harmful to patient
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| vaccuum | tube housing
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| radiation | forms of energy emitted and transferred through matter
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| Radiation Absorbed Dose(rad), Gray(Gy) | units measure amount of energy absorbed 1 Gy=100 rads; Gy is SI units
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| Roentgen (R) | measures ionization in air
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| Radiation equivalent man (rem), Sievert (Sv) | measures biologic response of exposed individuals to same quantity of differing radiations 1Sv=100rem; Sv is SI unit;1rad=1rem
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| Somatic cell | all of body's cells except germ cells
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| xray | electromagnetic radiation traveling at the speed of light with the ability to penetrate matter
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| ionizind radiation | capable of creating ions by removing orbital electrons with which it reacts
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| Natural background radiation | uranium, radon; we get approx. 295 mrem/yr
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| man made radiation | nuclear power, xrays, ect. we get approx. 65mrem/yr
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| properties of xrays | penetrating electromagnetic waves, heterogenous(many energies), polyenergetic, travels in straight lines, can't be focused, electronically neutral, produce scatter, ionize gasses, cause biological change
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| absorbtion | transfers energy
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| transmission | xrays pass through matter with no reaction
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| photodisintegration | occurs in nuclear industry; energy interacts directly with nucleus, causes excitement, emits nuclear fragment
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