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x ray interaction
x ray interaction w/ matter
| Question | Answer |
|---|---|
| what is matter? | anything that takes up space and has form. |
| what are five basic x ray interactions? | 1. classic (coherent) scattering 2. compton effect= brems 3. photoelectric effect= characteristic 4. pair production (coincidence)NM 5. photodisintegration |
| which are important to diagnostic a ray? | compton effect= brems and photoelectric effect= characteristic |
| 1) what is classic (coherent) scattering? | the x ray photon in classical s/sing will interact w/ an e- in matter. the e- will be completely absorbed and the e- will vibrate and give off energy in the form of another x ray photon of the same energy but in a different direction (thompson). |
| compton scattering is mostly seen with and energy level of what? | below 10 kv/ <10 kv |
| what are the two types of classical s/s? | thomson classical s/s which is the s/s of an x ray with an e-. rayleigh classical s/s which is the s/s of an x ray with the target atom. |
| 2) what is compton scattering effect = (brems)? | moderate energy x rays (incident x ray photon) interact with outer shell e-s. in turn the incident looses some of its energy. s/s changes direction and also has less energy vs. incident. causes ionization in atom |
| T or F incident x ray photon becomes weaker due to the compton s/sing effect? | true |
| what is the difference between compton s/s effect and classical s/s? | compton s/s has less energy, long wavelength, and a lower fequency |
| T or F s/s photon energy and recoil e- energy equal = incident | true |
| what is the ejected e- called? | a compton recoil e- which is also considered the secoundary e- |
| compton s/s can be deflected into what direction? | any direction from 0 (no energy is transferred) to 180 degrees (more energy is transferred to compton e-) |
| At what point is s/s considered back s/s? | at 180 degrees s/s retains 2/3 of its original energy and is then considered back s/s |
| the probability of s/s increases with what? | with an increase in kvp |
| what are the four types of the tissues in the body? | air, muscle, fat, bone |
| you get higher s/s with which two? | fat and muscle |
| what type of pathology creates s/s ? | edema or ascites |
| does barium create s/s? | yes, because you need a higher kvp. in turn this incr. s/s which is a direct relationship |
| what are the affects of s/s? | the production of fog, a loose in contrast, and a dull flat appearance if excessive |
| what are some radiation safety issues? | s/s can incr exposure to operator during fluoro. also in mobile radiology can influence other pts dose |
| s/s is what percent of the primary beam? | .1% or 1/1000 of the primary beam |
| most s/s is directed in which direction? | forward w/ 3% seen at 70 kvp range that cuases fog on the IR |
| the highest quantity of x ary s/s is directed? | backwards |
| the highest intensity of s/s in x ray is | 90% |
| 3). what is photoelectric (PE) effect = (characteristic)? | x ray photons ionize atoms by interaction with inner shell e-. the incident x ray photon looses all of its energy (absorbed) to the atom. depends on type of material. |
| does PE give you contrast on an image T or F? | true |
| atomic number and k-edge of iodine | 53/33 |
| atomic number and k-edge of barium | 56/37 |
| atomic number and k-edge of tungsten | 74/69 |
| atomic number and k-edge of lead | 82/88 |
| PE interactions | incident x ray photon is completely absorbed by atom. atom releases an inner shell e- due to excess energy gained from ionizing. E- is called a photo electron |
| the energy from a PE interaction is formed into what? | characteristic radiation or secondary radiation |
| PE interactions: the sum of the photoelectron and all characteristic radiation must equal what? | the incident energy (x ray photon) |
| PE effect interaction is the predominant interaction at all diagnostic energy ranges T or F ? | True |
| high z# increases what? | absorption ( air, fat , muscle , bone) |
| incident x a ray energy must be = or > k-edge T or F? | true |
| probability depends upon what of an atom? | the kvp and z# of an atom |
| 4.)what happens in pair production (coincidence) (nm) | incident photon must have > 1.02 mev. escapes e- interaction and comes near nucleus. |
| 1 st interaction of PP | nuclear electrostatic field causes x ray photon to disappear (looses all its energy/absorbed) and 2 particles to appear |
| what are the two particles? | a positron + and negatron - = pair production |
| 2 nd interaction of PP | the e+ interacts w/ an e- and the 2 particles annihilate each other giving off 2 photons with .51 mev of energy. each photon produced has 1/2 the total incident x ray photon energy. happens in NM rarely dx |
| 5.)what happens in photodisintegration (Rad therapy)? | only happens if energy is > 10 mev. strong enough to be totally absorbed (destroyed or gives off all its energy) by the nucleus. nucleus is excited and emits a nucleon or other nuc fragments to gain stability. rarely occurs in dx range |
| what is mev ? | million electron volts |
| T of F photodisintegration is used in RT to treat cancer cells? | true |
| what type of cells are cancer cells? | displastic cells which are abnormal cells. |
| which interaction is primarily responsible for absorption and density differences? | photoelectron interaction |
| which interaction decreases density differences and increases operator exposure? | compton |
| what happens if an interaction is in air? | it goes right through, penetates |
| what is attenuation? | weakening of the beam |
| what are four attenuation factors? | kvp, type of tissue (air, fat,muscle, bone), A# of tissue (protons/electrons), and # of e-/ gram |
| where is the filtration housed (placed)? | it is placed within the tube housing between the tube and pt. it also has nothing to do with s/s. |
| what is HVL ? | half value layer which reduces the initial intensity by half |
| what is the purpose of filtration? | to reduce low energy high wavelength that would just result in skin dose to the pt. |
| how much aluminum filtration is required? | below > 50 kvp = .5 50-70 kvp = 1.5 70-100 kvp = 2.5/required above 100 kvp = 3 |
Created by:
eckoultd1972
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