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physics test 7/28
x-ray production & interaction test
| Question | Answer |
|---|---|
| describe the 2 types of x-rays produced in the tube | brems & characteristic |
| list at least 5 properties of x-rays | travel in straight lines, cant focus with lens, travel at speed of light in a vacuum, polyenergetic, can ionize matter, EM, produce small amount of heat in matter, affect IR, produce secondary & s/s radiation |
| what is the definition of: Angstrom | wavelength |
| what is the wavelength range for diagnostic x-rays? | .1-.5 Angstroms |
| what is the definition of: LET | a measure of the energy transferred to material as an ionizing particle travels through it. This measure is used to quantify the effects of ionizing radiation on biological specimens |
| what are examples of high & low LET? | high = alpha & beta ...... low = x-ray & gamma |
| particulate vs photon radiation | particulate = alpha, beta ...... photon = x-ray, gamma |
| what is the definition of: NBR types | natural background radiation = cosmic, radon, air-line travel, UV |
| what is the definition of: RBE | ability of ionizing radiation to produce biologic effect relative to same amount of 200 keV x-ray required to produce similar effect. EX. epilation & errythema |
| what is the definition of: R (c/kg) | exposure in air of x or gamma up to 3 meV (usded with skin entrance exposure) |
| what is the definition of: Rem (sV) | dose equivalent (used with our radiation monitors -employee) (applies to a single organ) |
| what is the definition of: Rad (Gy) | absorbed dose of any type of radiation in any type of matter (used with pt dose) |
| what is the definition of: HVL | amount of absorbed required to reduce initial intensity by 1/2 |
| what is the definition of: attenuation | weakened compaired to promary beam |
| list 4 factors that affect attenuation | 1.) atomic # (air, fat) 2.) mass # (# of photons & neutrons) 3.) kVp 4.) # of e- per gram |
| what is the definition of: physical half life | time it takes a radioactive substance to reduce by 1/2 its original energy |
| what is the definition of: biological half life | in the body, its the amount of time, with the bodies metabolism, that it takes to break down to 1/2 initial intensity |
| what is the definition of: filtration | added absorber that hardens beam by absorbing low energy, long wavelength that would only contribute to skin dose |
| high kVp is _________ energy? | high |
| high kVp is _________ beam quality? | high |
| high kVp is _________ frequency? | short |
| high kVp is _________ s/s? | high |
| high kVp is _________ penetration? | high |
| high kVp is _________ attenuation? | low |
| high kVp is _________ contrast scale? | long |
| what is the interaction that is most common in diagnostic? | Photoelectric Effect |
| what interaction gives you contrast? | Photoelectric Effect |
| what interaction reduces contrast? | Compton |
| how does compton s/s affect image contrast | it reduces contrast because the more the s/s the lower (gray) the contrast |
| what happens to the incident x-ray photon in: Photoelectric Effect | the incident x-ray photon is completely absorbed giving up all its energy to the atom |
| what happens to the incident x-ray photon in: Compton | the incident x-ray interacts with an outer shell e- and ejects it from the atom, ionizing the atom. The ejected atom is called a compton electron. The x-ray continues in a different direction with less energy |
| name the predominant interaction in the diagnostic x-ray range | Photoelectric Effect |
| Differentiate between secondary and s/s radiation | secondary = created from interaction & comes from pt ..... s/s radiation = x-ray photon changes direction & loses strength |
| in order for Pair production to occur, the incident photon must have energy of at least ______ | >1.02 meV |
| in order for photodisintregration to occur, the incident photon must have energy of at least ______ | >10 meV |
| describe PE interaction | when an incident x-ray is totally absorbed during the ionization of an inner-shell e-. The incident photon disappears & the k-shell e-, now called a photoelectron, is ejected from the atom w/ the same energy as the incident x-ray called CHARACTERISTIC RAD |
| why does the probability of PE interaction decrease with increasing kVp? | increasing kVp increases penetration & decreases absorbtion, so if theres less absorbtion, there will be NO PE |
| the wavelength of EM radiation ________ as the energy decreases | increases (longer) |
| the _________ of an x-ray beam refers to its penetrating ability | quality or HVL |
| Differentiate between the 2 types of classical s/s | 1.) Thomson s/s = scattering of an x-ray with an e- ...... 2.) Rayleigh s/s = scattering of an x-ray with the target atom |
| what is coherent s/s | aka classical = scattering in a change in direction of an inicident x-ray WITHOUT A LOSS OF ENERGY |
| in the diagnostic range the highest quantity of s/s is backcatter of _____ | 180 degrees |
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sr4095
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