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screen film rad
screen film radiology
| Question | Answer |
|---|---|
| emulsion | area on film that captures the latent image |
| single emulsion | little notch to load the film correctly. you have better resolution but the disadvantage is that you use more technique |
| double emulsion | |
| purpose of the base for film construction | provides mechanical support |
| prior to W.W.1 film was highly what? | flammable |
| what are the three types of film? | 1. cellulous nitrate/ 2. cellulous tiracetate/ 3. polyester |
| 1.cellulous nitrate | highly flammable, was the emulsion base prior/ after W.W.1 |
| 2. cellulous triacetate | safety film (inflammable 20s), emulsion base that teared like paper |
| 3. polyester | safety film (inflammable 60s-today), flexible, not breakable and not easily tearable |
| film construction/ good characteristics of base | safety film, non tear, flexible, stabile, rigid, uniform lucency, blue tint vs clear base, archival quality |
| blue tint | reduced eyestrain to radiology |
| clear base | which we achieve by shuttering to reduce eyestrain |
| cross over | double emulsion film. front and back images are not perfectly superimposed so they apear blurry. with thinner film construction this is not seen |
| adhesive layer | holds the emulsion in place |
| gelatin | glue like or sticky substance that holds the silver halide crystal |
| halide | gives off light |
| what are the two types of silver halides | silver bromide and silver iodide |
| silver halide crystals | tabular grains- flat= more even dispersion |
| tabular grain | absorb more photons, reduce crossover, and reduce Ag coating required |
| silver halide crystal lattace | ionic bonds which permits free Ag & e- to drift, sensitivity specks (impurity)- gold silver sulfide. forms latent image |
| over coat, top coat, super coat | hard protective gelatin, prevents soft emulsion from scratches, etc. antistatic |
| antistatic | built into top coat |
| what are the three classifications of film? | pancromatic, othrchromatic, and blue sensitive |
| panchromatic | sensitive to all colors |
| orthochromatic | sensitive to green film/red light spectrum |
| blue sensitive | controlled by dyes |
| calcium tungstate = | blue film |
| resolution | ability to image an obj faithfully |
| resolution is better with what? | smaller crystals or thinner emulsion |
| speed | how fast responds to min. exp |
| what gives you a faster speed? | larger crystals or thicker emulsion |
| fast systems gives you what? | less MAs and less pt dose |
| what is a disadvantage of a fast speed? | loss of recorded detail |
| contrast | ability to image density differences which depends on crystal size |
| true or false do you get better contrast with thinner emulsion and smaller crystals? | true |
| latitude | range of exposures to produce a quality image which is indirectly related to contrast |
| with low contrast what increases? | exposure |
| what decreases with high contrast? | exposure |
| film handling/storage | below 68 degrees. film is 8x more sensitive than non film. once opened 45 days and an unopened box for 18 months |
| what is film sensitive to | pressure, heat, and radiation |
| if film is to cold or to dry what happens | you have static |
| what happens if film is to hot | fogging or film sticks together |
| added pressure can cause what on film | unwanted density known as an artifact |
| what are the 4 possible states of film | green film, clear film, black film, and diagnostic film |
| green film | film prior to processing |
| clear film | can be found in repeat bin |
| black film | how you get rid of mistakes, pop open cassette etc |
| diagnostic film | acual image that is on film |
| cassette | housed to protect film and screen |
| what makes up the cassette | tube side, back side and blocker |
| tube side | made out of radiolucent material, which absorbs good x ray forming beam to penetrate in order to get an image |
| back side | made out of radiopaque material, which absorbs backscatter from patient |
| blocker | housed the patient information |
| what is the purpose of the cassette | it is light tight and promotes good film/ screen contact |
| safe light | white 20 watt bulb. most rooms used a red filter |
| is laser film sensitive to red light T or F | true |
| blue sensitive film | amber safelight filter w/ low wattage white bulb |
| panchromatic film | red safelighter filter w/ low wattage white light bulb. turn off red safelight when processing laser film |
| screens purpose | allows us to control small quantity mAs of xrays into larger quantity of light photons to expose film |
| what is the advantage of screens | less pt dose and less wear and tear on equipment |
| disadvantages of screens | loss of spatial resolution due to spread of light when it hits the surface of the film |
| construction of screen | base, reflective layer, and phosphor |
| base/ purpose & characteristics | polyester which sole purpose is to provide mechanical support. rigid, radiolucent, and chemically inert |
| reflective layer and purpose | magnesium oxide & titanium. the reflective layer is a mirror that redirects the light |
| phosphor (active) layer material & purpose | calcium tungstate which gives off blue light. purpose is to convert xray to light |
| luminescence | gives off light |
| fluoresence | stops immediately when energy stops |
| phosphoresce *afterglow or lag | after light is off (glow) |
| photostimuable | gives off light twice |
| isotropic propagation | light is emitted equally from screen phosphor in all directions |
| rare earth | green - pure rare earth |
| what are the rare earth phosphors | gadolinium, lanthanum, and yttrium |
| what are phosphor characteristics | a high DQE/ absorption efficiency and conversion efficiency |
| what is conversion efficiency | x ray is converted to light |
| examples of phosphors | calcium tungstate (blue light) rare earth (blue or green light) |
| construction of screen/protective coating | surface to clean. gauze and baby oil was used to help decrease static |
| how are artifacts shown on screens | as white marks |
| spatial resolution | the ability to see small structures |
| recorded detail or resolving partner | ability to accurately image an object. indirectly to screen speed. |
| to increase resolving power, you must increase mAs (use slower sytem)= increase in pt dose T or F | true |
| spatial resolution depends upon | phosphor crystal size, phosphor layer thickness, phosphor concentration, type of phosphor, reflective layer and yellow light absorbing dye |
| yellow light absorbing dye | put into reflective layer. |
| with a slower system what is the disadvantage | a higher pt dose |
| line pair bar phantom | LP/mm (7-15)normal resolution |
| density | the degree of blackening |
| line spread fuction | used a microdensitometer to measure the film screen combos ability to accurately measure boundaries of images |
| MTF | modulation transfer function- information lost between subject and IR caused by light diffusion |
| intensification factor | exposure w/out screens amnd exposure w/ screens |
| film/screen contact | use wire mesh to test which is used to rule out poor screen film contact. poor= area of blur on image |
| film/ screen contact causes | broken hinges or latches. foreign matter, warped cassettes, bent frame, worn felt, and air trapping which is transitory |
| mottle- noise | film graniness, screen structure mottle, and quantum mottle |
| film graniness | clumping of the silver hylide crystals |
| screen structure mottle | graininess cuased by clumping of the phosphurs |
| quantum mottle | (more common) noise from random interaction of x rays w/ screen (more common w/ high speed systems |
| asymmetric screens | tube side- slow for resolution and contrast (mediastinum) back side- high speed as less radiation hits for wide latitude/low contrast structures (lungs) |
| order of automatic film processing | develop, fix, wash, dry |
| 1. develop | converts latent image into manifest image |
| 2. fix | chemicals remove unexposed silver hylide emulsion |
| 3. wash | washes off chemical |
| 4. dry | permanant image thst emerges from processor |
| the manifest image is only seen after processing T or F | TRUE |
| control panel | 92 degrees F/ wash 4-5 degrees lower |
| development | conversion of latent image into black metallic image |
| reduction vs oxidation | rduction- adding electrons to positive ions to reduce them to a stabile state. oxidation- the lost of free electrons by a chemical |
| most important relationship in development | time- direct relationship to short underd temperature- 20 sec in developer @ 93 degrees F |
| chemicals in developer | reducing agents phenidode- gray tones/contrast hydrquinone- black tones/density |
| synergism | two medicines work better than seperate |
| activator agent | sodium cabonate- swells emulsion/makes alkaline base ph |
| restrainer= | starter/ potassium bromide- antifoggant |
| preservative | sodium sulfite- prevents oxidation |
| hardener | glutaraldehyde- hardens emulsion |
| solvent | water- dissolves chemicals/maintains temperature |
| sequestering agent | chelate- removes metallic impurities |
| fixer | clears unexposed emulsion- silver recovery, metallic replacement, E lectrolytic. provides archival quality |
| oxidation | loss of free electrons |
| fixer agent/ammonium thiosulfate (hypo) | actual chemical that removes unexposed silver hylide cystals (emulsion) |
| activator | acid based which stops development |
| preservative | sodium sulfate, same as developer |
| solvent | same as developer, water |
| hardener | potassium alum, hardens the emulsion 90-93/ 20-22 sec in the fixer |
| developer | alkaline based |
| activator | acid based |
| buffer | acetate maintains acid ph |
| sequestering | boric acid/salt which removes aluminum ions |
| wash 3rd tank | washes away chemicals |
| temp of wash | 5-7 degrees lower to maintain temp |
| what happens if you forget to turn the water off | you get overexposed or fogged film |
| if you smell ammonia what does it mean | cross contamination |
| dryer | dry image, manifest image |
| film feed tray | metallic food tray |
| guide shoes | if missalined or dirty may cause scratches |
| feeding film into processor | 2- 8x10s LW all other film sizes CW |
| film is ran singularly every 14" to run the replenisher T or F | true |
| transport system | controls development and processing times, solution and rollers (rubberized) |
| rollers | detector w/microswitch. entry - guide shoe artifacts and pi line artifacts |
| replenishment system | 2 tanks 1 extra developer solution and 1 fixer solution |
| you do not want an over replenished system T or F | true. an over replenished system = over developed and vice versa |
| processor maintenance | is to be done every day, measuring developer temp, density, contrast on a film also for consistency |
| what are the three types of maintenance | scheduled, preventative, and non-scheduled |
| steps in maintenance | start up- turn on to warm up/run films to clear rollers. may have to turn on rollers shut down- some departments lift lids, may have to turn off water supply |
| what are three types of static artifacts | tree stag- friction smudge- crown- |
| trouble shooting tips/ static from feed tray | ground |
| underdevelopment = | underexposure, which will decrease contrast |
| time and temp too low | reset |
| exhausted chemicals | clean and replace |
| under-replenishment | reset rates |
| diluted developer | clean and replace density light/loose contrast |
| over development | time or temp too long- reset forgot restrainer - add over replenishment- reset rate. high density/loose contrast |
| dichroic stain | yellowish stain from improper washing exhausted or oxidized developer or fixer insufficient rinse contaminated developer |
| green | was not clear insuff fix or wash |
| brown | insufficient washing hypo retention |
| deposits | dirty filter water most likely metallic oxidized silver load in fixer |
| deposits/ white | milky fixer - hardener, too much acidity , developer contamination |
| deposits/ black flaky marks | due to dirty city water |
| if film comes from the processor wet | dryer |
| if film comes from the processor wet and sticky | lack of hardener in fixer |
| if film jams | lack of hardener and improper aligned rollers or guide shoes |
| if scratches | lack of hardener. improperly or dirty rollers or guide shoes. pi lines/ guide shoe marks |
| wire mesh test | checks for warped cassettes |
| artifacts | runs- fixer prob |
| frilling | weak fixer or too hot of solutions |
| blisters | gas bubbles in emulsion |
| reticulation | non uniform processing |
| streaks | water on semi-dried emulsion, air flow to high, poor squeegee |
| buckshot (puddies) | water or semi dried emulsion |
| exposed film is 8x more sensitive than unexposed film T or F | true |
Created by:
eckoultd1972
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