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Exposure
Density/contrast/detail
| Question | Answer |
|---|---|
| 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
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