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Exposure

Density/contrast/detail

QuestionAnswer
When is scatter radiation produced? when the xray beam attenuates matter
When is scatter not produced? when the beam fully penetrates matter
What are the 3 types of scatter radiation produced when it is absorbed my matter? Coherent Scattering, Compton Effect, Photoelectric effect
What is secondary radiation? Radiation produced by the photoelectric effect.
What else besides the body can produce scatter? tabletop, IR or any other matter in the radiation field.
What is another name for Coherent scattering? Thompson scatter
When does Coherent scattering take place at low energy levels
When does the Compton effect occur? between 40 - 125 kVp
what is the compton effect? when an x-ray photon interacts with an outer orbital electron
what is back scatter? when x-rays or photons are traveling towards the tube instead of away from it
As the kVp is increased, Compton interactions are ...? increased
What kind of radiation is the photoelectric effect similar to? Characteristic radiation
With the photoelectric effect photons are interacting with what, instead of the tungsten? The body
In a photo electric interaction what happens? an x-ray photon interacts with an inner orbital electron
The majority of radiation interactions with the body are what type of effect? Compton effect
As the kVp is increased, photoelectric interactions are ...? decreased
What is Fog? Unwanted exposure to an image
mA is/controls what? overall blackness on your film/density
Scatter creates fog that reduces what? Contrast and visibility of detail
these 4 things affect scatter and fog.. volume of tissue, kVp, density of matter, field size
the denser the body part, the ..? the scatter. the less the scatter
What is the main source of scatter? The patient
what is the principal method for reducing scatter? A grid
When is a grid used? when the kVp is greater than 60 or the body part is 10-12 cm in thickness
Grids are usually held together by a radiolucent inter-spacing material which is? aluminum
What is radiation that is passed through the body to the IR called? remnant radiation
What is grid ratio? the relationship between the height and width of the lead strips
what is a general purpose/chest xray grid ratio? 12:1
what is grid frequency and what is it's range? the number of lead strips per square inch, 60-196
a buckey is what? a moving grid
Excessive absorption of useful radiation by the grid is what? Grid cutoff
When does grid cutoff happen? when the X-ray tube is off to one side instead of focused to the middle, or when the tube is angled to one side
Why are lower grid ratio grids used bedside or portable? because it is more difficult to get alignment exactly right bedside
What is a coned-down image? x-ray of a very small area of the subject.
What two ways does decreasing the kVp increase the contrast? narrows the scale of contrast, decreased scatter and fog
What manual technical factors are considered when using an exposure chart? SID, pt size, kVp, mA, exposure time, and grid notation.
True or false - Technique charts are unique to each x-ray machine and each facility. True.
A change in ...? kVp below 85, a change of ...? kVp is sufficient. below = 2 above=3
What is quantum mottle? noise, starvation of mA
what is the minimum change (in mAs) necessary to see change on a film? 30%
according to the 15% rule- To decrease contrast you... Increase kVp by 15% (10 kVp) and divide mAs by 2
the primary consideration that affects volume of scatter is? volume of tissue
Fixer solution does what? removes unexposed silver bromide crystals from the emulsion of the film
four prime factors of radiology are what? mA time kVp and distance
mAs is what to contrast? a secondary factor of contrast
1/2 mA, time or mAs = what? half density
to double the density, what do you do to your kVp? increase it by 15%
a muscular pt requires you to do what? increase kVp
Define Inverse square law. intensity of radiation at a given distance from the point source is inverse
When do you use the inverse square law? when you see MR, I, R... whenever you are dealing with intensity
when do you use mAs distance formula? when you are dealing with mAs, mA, or S
when do you use the rule of thumb? and what is it? if the distance is either doubled or cut in 1/2 you multiply or divide by 4. closer * farther /
What 5 factors can affect density? kVp, distance, processing, screen speed, anode heel effect
What is the law of reciprocity? when you can change the mA and the S but still maintain the same mAs
what is the composition of film? (4 things) base, adhesive, emulsion, super coat
a preservative in the developer does what? helps decrease oxidation
Exposed silver bromide has what electrical charge? negative
The restrainer in the developer does what? limits developer to only exposed silver halide crystals
what is found in both the developer and the fixer to prevent oxidation? preservative
what temp does the dryer dry the film? 110
what part of the intensifying screen emits light? phosphor layer
why is rare earth more desirable? is more efficient, 1200 times faster
why is the back of a cassette lined with lead? to absorb back scatter
a sensitometry checks what? the processor and varying scales of density
safe light should be? 3-4 feet from the work bench
what is quantum mottle? phenomenon that may dramatically affect recorded detail when high speed intensifying screens are used with low mAs. "starvation of mAs"
what do you get when quantum mottle occurs? uneven density
when you increase the developer time, temp, and/or replenishment rate, what happens to the density? it is increased
What is the practical application of the inverse square law formula? mAs distance formula
small focal spot gives you what? more detail and less heat capability
in manual processing, if the developer temp is up, what should happen to the developing time? should be decreased
what controls the processing time? roller transport system
you can increase kVp how? majors by 10, minors by 2
what is the temperature and humidity of the darkroom? 60-70 degrees at 40-60% humidity
The amount of silver hilide crystals that are exposed determine what on your film? amount of black
attenuation is what? absorption with scatter
scale is refers to what? so a small scale would mean what? contrast, small scale= high contrast
mA stations range from 25-300
the higher the scree speed the ..? mAs you need less
generally when you use a grid you need ... times the mAs 4 times
what occurs when phosphors absorb radiation and produce light? florescence
who was credited with permanent photographic process? Joseph Niepce
where do the photons come from? effective focal spot
the sensitivity speak is made of what? gold-silver sulfide
the size of the lattice gate determines what? the amount of blackness on your film
yellow smudges are a result of what? exhausted fixer
high contrast is considered to be more consistent in radiographic quality? t/f? False
the grid ratio is determined by the height and amount of lead strips? T/F False, it's measured by the height and the width
Contrast, Density, Distortion and Detail are examples of what? Image quality factors
small focal spot is usually how many mm? Large focal spot? .6mm and 1.2mm
what affects the size of penumbra? focal spot
When OID decreases, penumbra... decreases. better recorded detail
what is the digital phrase for recorded detail, density and what controls contrast? Spatial resolution, brightness, window width
Shape distortion is controlled by what? Unequal magnification
What geometric factors affect spacial resolution? OID SID focal spot size
Air gap technique gives you as much clean up as what? And is done with a ... inch air gap 15:1 grid, 10
Films will show low contrast if the developer is set too ....? Low
High contrast... 4 things about it Few shades of gray, increased contrast, low kVp, short scale contrast
Low contrast... 4 things about it Many shades of gray, decreased contrast, high kVp, long scale
What is the purpose of contrast? to enhance detail on the film and differentiate structures
What are the 3 types of contrast? Subject, Film, Radiographic
Bone absorbs more or less radiation? more
the primary cause of fog is ? secondary (scatter) radiation
When you increase the kVp by 10 you .... or else you are doubling your density Cut the mass in 1/2
what size are bucky grids? 17x17
What types of grids movements are there? reciprocating and oscillating
how do you calculate grid ration and grid frequency? ratio = h/D freq= 1/t+D (D= inter space distance, t = lead height)
If height remains the same, then a decrease in width will cause a decrease/decrease in grid ratio? increase
Radius refers to the alignment of the focusing of the lead strips to the diverging primary beam t/f? True
What is the HLV? Half Layer Value, amount of absorbing material that will reduce the density by 1/2
Compound filtration does what? Absorbs the characteristic photon of the previous filter .
T/F what ever you collimate to will be the size of the divergent beam no matter the OID True
Created by: christina325