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x ray interaction

x ray interaction w/ matter

QuestionAnswer
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