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RAD 465
ARRT registry review covering image production and evaluation
| Question | Answer |
|---|---|
| recorded detail is? | sharpness and abruptness of structural detail borders, measured in lp/mm p.298 |
| recorded detail and magnification are related how? | inversely, as magnification decreases recorded detail will increase. p.299 |
| How is SID and recorded detail related? | as SID increases the magnification from divergent ray will decrease and recorded detail will increase, they are directly related p.299 |
| Structures that do not sit parallel to the image receptor will appear how? | elongated or foreshortened p.302 |
| how is focal spot size relate to recorded detail? | the smaller the focal spot size the better the recorded detail p.303 |
| actual focal spot verses effective focal spot? | the AFS is a finite area on the tungsten target that is actually bombarded by electrons. The EFS is the foreshortened size of the focus as it is projecting down to the image receptor. p.303 |
| how does the angle of the anode effect the x ray? | the smaller the angle the larger area the anode has to be hit by electrons and therefore creating a smaller EFS getting better recorded detail. p303 |
| What is the greatest adversary of recorded detail? | motion p304 |
| what is the ingredient in intensifying screens? | fluorescent phosphor that functions to change x ray photons into light, more than 98% of the exposure is from the fluorescent light.p.309 |
| recorded detail increases as: | focal spot decreases, SID increases, OID decreases, motion decreases, distortion decreases, screen speed decreases p.311 |
| reciprocity law is? | when any mA and time (second) produces a given mAs p.318 |
| what is a grid | device place between the patient and the image receptor that absorbs a large percentage of scatter radiation before it reaches the IR, it works by having lead strips in the same direction of the x ray photons, so those that opposing will be absorbed |
| Grid ratios? | no grid- 1 5:1-2 6:1-3 8:1-4 10:1 or 12:1-5 16:1-6 |
| what is the total filtration of x ray tubes that operate above 70 kvp? | inherent filtration(collimator and envelope) 1.5 aluminum and then added filtration of 1.0 to meet the minimum requirement of 2.5 mm AL equivalent total filtration. |
| Pathologies that require an increase in technique to acquire the adequate densities | INCREASE: ascites, RA, paget disease, pneumonia,atelecxtasis, CHF,edematous tissue DECREASE: osteoporosis, osteomalacia, pneumopeitoneum,emphysema,, degenerative arthritis,atrophic and necrotic conditions |
| Voltage ripple | single phase-100% three phase 6 pulse-13% three phase 12 pulse-4% high voltage- |
| kvp verses contrast | High contrast: short-scale contrast, displays few number of grays and tissue difference, product of low kv LOW CONTRAST: long scale, displays many similar tissue differences, product of a high kv |
| subject contrast? | is regulated by selection of x ray beams, result of differential absorption of x rays struck by body tissues having different attenuation coefficients |
| fixed kv technique chart? | extremities-55 GRID- skull-75 abdomen-75 lateral lumbar-90 barium studies-120 chest -120 |
| what is SNR | SNR is used to describe contrast resolution, the higher the SNR the better the resolution, SNR increases as mAs increase however so does patient dose p.364 |
| what happens when matrix size increases? | as matrix size increases, pixel size smaller,and better spatial resolution |
| film processing steps | developer, fixer, wash, and dryer |
| what does each processing step do? | developer- reduces exposed silver bromide to black metallic silver fixer- clears the film of unexposed silver bromide and rehardens the emulsion, wash- removes processing chemicals dryer- rfemoves water from film and dries emulsion |
| what is DQE | ability of receptor material to perceive and interact with x photons |
| two types of AEC | phototimer and ionization chamber |
| where are the AEC at? | ionization chambers are located between the x ray table and cassette, phototimers are located beneath the cassette |
| the higher the grid ratio results in what type of contrast? | higher contrast (short scale) because more scatter is absorbed |
| structures that high higher subject contrast have what type of gray scale? | longer scale gray scale, because has more tissue differences |
| kv selection determines what? | energy of the x-ray photons and therefore the degree of penetration of various tissues thereby determining the contrast characteristics of the image. |
| factors that determine scatter radiation | field size, beam restriction, kvp, thickness or volume and density of tissue |
Created by:
amcoker
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