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radiographic imaging
chapter 7,8
Question | Answer |
---|---|
x-rays are high energy waves called photons. true or false? | true |
can x-rays be focused with a lens? | no |
Name the three things x-rays can do. | transmit, absorb, or scatter |
how fast do x-rays travel? | at the speed of light |
true of false: since x-rays are waves, the do not travel in straight lines. | false |
x-rays are perfectly safe, true or false? | false, they have a biologic effect. |
What two things are produced by x-ray production? | heat and x-rays |
Name the two main components of an x-ray tube | anode and cathode |
what is the source of electrons in the x-ray tube? | cathode |
what two components make up the cathode? | filament and focusing cup |
how many filaments are found in the cathode? | two. one small and one large |
what are contained in the focusing cup during the production of x-rays? | electrons |
define isotropic. | equal all the way around. |
how many focal spots are on the target in the anode? | two. one large and one small. |
define primary radiation. | useful beam from the window. |
define leakage radiation. | any radiation emanating from the tube housing. |
define extrafocal radiation. | radiation that hits just outside the focal spot and still exits the window. |
what is the function of the tube housing? | provide support for the x-ray tube. protection from leakage radiation. dissipate heat away from the tube. protection for high voltage cables. |
the process of boiling off of electrons is called what? | thermionic emission. |
what controls filament circuit and measures tube current? | mA |
what alters x-ray beam wavelength? | kVp |
compare filament and tube current. | filament current = high amps and low voltage. tube current = low amps and high voltage. |
What controls quantity? | mA |
What controls quality? | kVp |
Increasing atomic number increases/decreases attenuation? | increases. |
a filter absorbs long or short wave radiation? | long-wave radiation. |
a filter increases or decreases the amount of overall radiation to the IR? | decreases. |
what is the purpose of a grid? | to decrease secondary and scatter radiation. |
a grid increases or decreases the amount of overall radiation to the IR? | decreases. |
define radiopaque. | substance that absorbs more radiation. |
define radiolucent. | substance that absorbs less radiation. |
define exit/remnant radiation. | radiation it leaves the patient's body. |
what is the difference between scatter and secondary radiation? | scatter strikes an OUTER shell electron. secondary interacts with an INNER shell electron. |
scatter and secondary radiation have a lower energy level. Is it a longer or a shorter wavelength? | longer. |
define density. | overall blackening of the x-ray image. |
define SID | source to IR distance. |
define OID | object to IR distance. |
If the OID increases, what happens to exposure? | decreases. |
How do you get mAs? | mA x time = mAs |
what factors affect contrast? | kVp beam restriction (collimation, coning) fog (lengthens scale) filtration (decreases contrast) patient (more tissue increases secondary and scatter and decreases contrast) grid (increases contrast) |