X-ray phisics 3
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| What are the five basic interactions between x-ray and matter? | Photoelectric absorption, Compton scattering, coherent scattering, Pair production, photodisintegration.
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| Which 2 interactions have a significant impact on x-ray image? | Photoelectric absorption and Compton Scattering.
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| How does photoelectric absorption occurs? | Incident electron interacts with an inner-shell electron (K-shell), ionizing the atom. The K-shell vacancy is then filled by an electron of L-shell or less common M-shell, producing a characteristic photon known as secondary radiation.
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| The percentage of photoelectric interactions_______ with an _____ Kvp | decreases, increased.
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| photoelectric absorption interactions ___ as atomic number ___ | Increases, Increases.
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| Photoelectric interactions occur more in? | Bone
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| For a photoelectric absorption to occur what should happen? | Incident photon energy must be higher than the binding energy of the inner-shell electron.
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| How does Compton scattering occurs? | Incident photon interacts with an outer-shell electron, removes the electron from its shell, proceeding in different directions as scatter radiation.
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| The ____ the initial energy of the photon, the ____ the energy of scatter photon. | Higher, higher.
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| zero angle deflection | no energy is transferred
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| The percentage of Compton interactions ____ with ___ kvP | increases, increased.
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| As the angle of deflection increases to ___, more energy is transmitted to the____ and less energy remains with the____. | 180 degrees, recoil electron , scattered photon.
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| When a scattered photon is deflected back toward the source and travels in opposite direction to the incident photon. these photons are called? | Backscatter radiation.
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| when photoelectric effect is more prevalent,what type of contract ww will have in the image? | High contrast. (more differences between black and white, less grays)
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| Photoelectron travels with kinetic energy which is equal to what? | the difference between incident photon and binding energy of the inner-shell electron.
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| Photoelectic equation | Ei= Eb+Ekc
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| Energy transferred in a Compton effect is | Ei= Es+Eb+Ekc
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| Coherent scattering | interaction between very low energy x-ray photons and matter, also called classical or unmodified scatter.
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| occurs with photons less than 10 KeV, is outside the range of diagnostic imaging. | Coherent scatter
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| Pair Production | Occurs with high energy x-ray photons, with an energy of at least 1.02 Mev. Therapeutic x-rays.
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| It loses all of its energy when high energy incident photon comes close to the strong nuclear field. | Pair production
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| Photodisintergration | Interaction between extremely high-energy photons. Above 10 MeV and the nucleus.
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| Why are Iodine and barium useful contrast agents in diagnostic imaging? | because they absorb a greater percentage of the photons through photoelectric interaction.
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| In the human body, which interaction is more predominant? | Compton scattering
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| When photoelectric interactions is more predominant? | In lower energy ranges 25-45 KeV (40-70 KvP) and when high atomic number elements are introduced. (Iodine and Barium)
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| High contrast, low KvP, High mAs = | Higher patient doses.
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| When compton interactions prevail, the result inthe image will have? | Low-contrast. (more gray shades in between)
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| Low contrast, High kvP/ low mAs = | reduces patient doses.
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| Magnetic force field is created | when a charge particle is in motion
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| Electromagnetic induction | Moving the conductor, moving magnetic lines of force, change in magnetic flux.
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| Generator | Converts mechanical energy into electrical energy
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| AC generators uses ____ rings. DC generators uses ____ rings. | Slip
Commutator
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| Conventional electric current goes from ____ to ____. | Positive to negative poles.
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| Electron flow | from negative to positive.
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| Alternating Current AC | electrons first move in one direction and then reverse and move in the opposite direction.
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| Direct current DC | all electrons travel in the same direction.
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| In the x-ray circuit, where is the rectification? | High voltage side.
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| Where is the stator located? | Outside the envelope. (Anode side)
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| mA selector is located where in the x-ray circuit? | Filament circuit variable resistance
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| High contrast, low KvP, High mAs = | Higher patient doses.
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| When compton interactions prevail, the result inthe image will have? | Low-contrast. (more gray shades in between)
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| Low contrast, High kvP/ low mAs = | reduces patient doses.
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| How is a magnetic field created? | when a charge particle is in motion and is created by electrons spinning.
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| Conductor in presence of magnetic field. | Moving the conductor, moving magnetic lines of force, change in magnetic flux.
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| Generator | Converts mechanical energy into electrical energy
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| AC generators uses ____ rings. DC generators uses ____ rings. | Slip
Commutator
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| Conventional electric current goes from ____ to ____. | Positive to negative poles.
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| Electron flow | from negative to positive.
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| Alternating Current AC | electrons first move in one direction and then reverse and move in the opposite direction.
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| Direct current DC | all electrons travel in the same direction.
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| In the x-ray circuit, where is the rectification? | High voltage side.
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| Where is the stator located? | Outside the vacuum of the envelope. (Anode side)
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| mA selector is located where in the x-ray circuit? | Filament circuit variable resistance
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| High contrast, low KvP, High mAs = | Higher patient doses.
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| When compton interactions prevail, the result inthe image will have? | Low-contrast. (more gray shades in between)
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| Low contrast, High kvP/ low mAs = | reduces patient doses.
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| How is a magnetic field created? | when a charge particle is in motion and is created by electrons spinning.
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| Conductor in presence of magnetic field. | Moving the conductor, moving magnetic lines of force, change in magnetic flux.
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| Generator | Converts mechanical energy into electrical energy
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| AC generators uses ____ rings. DC generators uses ____ rings. | Slip
Commutator
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| Conventional electric current goes from ____ to ____. | Positive to negative poles.
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| Electron flow | from negative to positive.
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| Alternating Current AC | electrons first move in one direction and then reverse and move in the opposite direction.
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| Direct current DC | all electrons travel in the same direction.
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| In the x-ray circuit, where is the rectification? | High voltage side.
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| Where is the stator located? | Outside the envelope. (Anode side)
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| mA selector is located where in the x-ray circuit? | Filament circuit variable resistance.
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| Backup Time | All AEC equpped units permit a manual backup time to be set to avoid errors.
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| What four conditions must exist for x-ray production to occur? | source of electrons, appropriate target material, high voltage, vacuum.
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| Parts of the cathode assembly | Focusing cup, filament(s), wiring.
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| Why is tungsten the best material for x-ray source? | High melting point, difficult to vaporize, high atomic number enhances diagnostic x-ray photons, heat conducting ability.
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| Anode | Positive side of x-ray tube. serves as target surface for high voltage electrons .
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| Cathode | Negative side of x-ray tube. produces a thermionic cloud
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| X-ray tube components | {Anode(positive) cathode(negative)}{envelope} {encased in protective housing}
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| Filtration | is the elimination of low energy x-ray photons by the insertion of absorbing materials into the primary beam.
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| Inherent Filtration | occurs inside the tube and housing.
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| Added filtration | Occurs outside the tube and housing
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| How is filtration expressed? | in terms of Half-Value layer.
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| HVL is the amount of absorbing material that will ___ the intensity of the primary beam by ___ its original value | decrease, one-half.
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| Purpose of filtration | To reduce patient exposure by eliminating low energy photons that would not enhance the image.
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| What is attenuation? | Is the reduction in the number of x-ray in the beam, and subsequent loss of energy as the beam passes through matter.
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| The ___ the atomic number of an element the ___ attenuation. | Higher, more
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| The ___ the atomic number of an element the ___ the attenuation. | Lower, less
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| What are the four major substances that account for the variation in x-rays absorption? | Air, fat, muscle and bone.
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| organize previous substances from higher atomic number to lower atomic number. | Bone(12.31), Air(7.78), Muscle(7.64)Fat(6.46).
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| Thicker and denser parts, absorb ___ radiation producing ___ image receptor exposure. | more, less.
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| The ___- the body part, the ___ absorption, ___ Image receptor exposure. | thicker, more, less.
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| What is the purpose of using a grid? | Improves contrast in radiographic image.
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| When should a grid be used? | When body part exceed 10 cm.
60 kvp or higher.
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| the ___ the grid ratio the____ scatter radiation. | Higher, less.
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| Are higher grid ratios more or less prone to errors? | More prone.
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| What is grid frequency? | Is the number of grid lines per inch, the most common grid frequency is 85-103 lines/inch.
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| Grid ratio= | h= lead strip height
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D= intespace width
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| Grid errors | Off-level, Off-center, upside-down.
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| Off-level | Results from improper tube and grid positioning.
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| Upside-down | Severe peripheral cut off will occur.
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| At techniques above 90KVp, it is best to use grids with ___ ratio or higher. | 8:1
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| which is the linear grid with the widest latitude for centering and focus? | 6:1
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| High ratio grid is designed to be used with | high Kvp techniques
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| An exposure with an off-level grid will show grid cutoff where? | Across the image
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| Grids generally have a frequency of ___ lines per inch. | 60-110
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| Contrast on a radiographic image is highest when the amount of ___ id the lowest. | Compton scatter
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| The amount of scatter absorption in a grid depends on? | angle of scatter photon, height of the grid strips, width of interspace material.
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| Film construction | Base (polyester)
adhesive
Emulsion with crystals
supercoat
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| Types of crystals | T-grain (flat and triangular) and conventional
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| What is the purpose of the gelatin in the emulsion? | is to act as neutral lucent suspension medium for the silver halide crystals.
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| During the crystal production what is the waste product that is washed away? | Potassium nitrate.
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| Silver halide crystals must have an impurity to form sensitivity specks. what is this impurity? | Gold silver sulfide.
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| Latent Image | refers to the image that exists on film after the film has been exposed but before it has been processed.
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| Latent image formation | -Bromide ion absorbs an incident photon and ejects and electron.-ejected electron is trapped in sensitivity speck, giving it a negative charge.- negative charge sensitivity speck attracts free silver ion.Silver ion neutralizes sensitivity speck.
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| Panchromatic films | sensitive to all colors
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| Orthochromatic films | Sensitive to red spectrum
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| Small crystals, ____resolution, ____ speed. | high , slow.
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| Large crystals, ____resolution, ____ speed. | low, fast.
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| Thin emulsion layer provides ____ resolution and ____ speed. | high, slow.
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| Thick emulsion layer provides ___ resolution and ___ speed. | low, fast.
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| How films should be stored and under what conditions? | Films should be stored on end, at a temperature of 20C (68F)or lower. The humidity must be maintained between 30-60%.
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| Subject Density | thicker and denser body parts absorb more radiation, thus producing less image receptor exposure and vice versa.
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| Subject Contrast | Is the degree of differential absorptions resulting from differing absorption characteristics of the tissues in the body.
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| Subject Detail | The recorded detail is dependent on their position within the body and also the bosy's placement in relationship to the receptor.
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| Subject Distortion | is the misrepresentation of the size or shape of the structure of interest.
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