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Chap 11 & 12 word1
Question | Answer |
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Air gap | a space between the patient and the film; used to reduce scatter (a large OID) |
Back scatter | scatter that is directed back toward the x-ray tube |
Coherent scatter (Thompson scatter) | interaction takes place at relatively low energy levels (below 10 keV). When the incoming photon is absorbed by the atom, the becomes excited, the excited atom produces a new x-ray photon but in a new direction and has the same energy and wavelength. |
Compton effect | Incoming x-ray photon interacts with an outer shell electron of an atom ejecting it from the atom and then proceeds in a different direction. The majority of the photon’s energy is converted into a new photon and has less energy and longer wavelength |
Crosshatch grid | a composite of two grid s with the lead strips at right angle to each other |
Focal range | the range of distance with in which the grid will not absorb an undue amount of useful radiation |
Focused grid | lead strips are aligned to the direction of the diverging primary x-ray beam, is precisely aligned to the to the x-ray beam at specific SID |
Grid | a device placed between the patient and the IR to reduce radiation fog; consists of closely placed lead strips aligned side by side |
Variable kVp chart | technique chart in which the mAs is constant and kVp changes per patient size |
Grid cutoff | excessive absorption of useful radiation by the grid and appears as decreased radiographic density on one side of the image |
Grid frequency | the number of lead strips per inch |
Grid ratio | the effectiveness of a grid, the relationship between the height of the lead strip to the width of the inner space material |
Parallel grid | a grid in which the lead strips are parallel; to each other and can be used for very long SID |
Photoelectric effect | the x-ray photon is totally absorbed in the body tissue; the incoming energy is an x-ray photon interacting with an atom in the body rather than an electron interacting with tungsten anode |
Characteristic photon | x-ray photon that is produced by the photoelectric effect |
Secondary radiation | radiation produced by the photoelectric effect |
Stationary grid | a high frequency grid that does not move |
Technique chart | a listing of various radiographic techniques for procedures done with all the exposure factors for each body part according to thickness. Includes type of exam projection, screen type, SID and part |
Compensating filter | specially designed filter that is used for areas of uneven densities to attenuate x-ray beam to improve detail |
Fixed kVp chart | a technique chart where the kVp remains the same (optimum range) and the mAs varies |
Coned-down image | a radiograph of a very small area of subject; a specific area of interest is centered to the field |
Grid cassette | a special cassette with a grid built into the front side; typically have lower ratios than the grid |
Grid lines | image of the grid itself, the strips used in a grid that absorbs radiation is seen on the radiograph |
Grid radius | the SID in which the primary beam is precisely aligned to the x-ray beam |
Scatter radiation | radiation hits an object (atom) and changes direction |
Caliper | tool used for body part measurement usually in cm |
Optimum kVp | the highest kVp setting that is sufficient to adequately penetrate the part regardless if size and will produce sufficient contrast for acceptable image quality |
Radiographic phantom | a human skeleton or portion of a skeleton, encased in a plastic material that is similar in density to human tissue |
Bucky | grid inside the table for taking x-rays |
Potter-bucky | the moving grid inside of the x-ray table that prevents grid lines/ is interchanged with the bucky. |