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-happens with double emulsion film
-front and back images are not perfectly superimposed, so image appears blury
-not seen with thinner film construction
-front and back images are not perfectly superimposed, so image appears blury
-not seen with thinner film construction
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-substratum coat, used to glue emulsion to base
-prevents bubbles during handling and processing
-prevents bubbles during handling and processing
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Film
Film Review
| Question | Answer |
|---|---|
| -happens with double emulsion film -front and back images are not perfectly superimposed, so image appears blury -not seen with thinner film construction | cross over |
| -substratum coat, used to glue emulsion to base -prevents bubbles during handling and processing | adhesive layer |
| -made of gelatin -actually captures latent image -colloidal substance -chemically non reactive -distributes crystals evenly(prevents clumping=mottle) -clear, flexible -contains silver halide crystals | emulsion layer |
| when would single emulsion film be used | mammography |
| what is the emulsion # | identifies the batch of film (batch #) |
| what is the chronological history of the film screen base layer | -glass until WW1 -cellulose nitrate after WW1(flamable -cellulose tiacetate in 1920's(called safety film because it was non-flamable, but it tore easily) -beginnigng in the 1960's we started using polyester based film |
| provides mechanical support -inflamable -non-tear -flexible -stable/rigid -uniform lunicy -blue tint to reduce eye strain -archival quality | polyester film screen base layer |
| -photosensitive agents in film | silver halide -95-98% are siver bromi -2-5% are silver iodide or silver chloride *the halides are bromide and iodide -this is what captures the latent image |
| -Tabular grain(flat)=more even dispersion -absorbs more photons -higer detective quantitive efficiency -ruduce cross over -reduce silver coating required, which reduces cost -allows for 45 sec. processing(most diagnostic processers are 90 sec.) | silver halide crystals used in film today |
| what are the alternate crystal shapes | -cubic -octhedral -polyhedral -irregular |
| what is the silver halide crystal lattice | -has lattice formation -chemically combined with ionic bonds(+ charged silver ions and - charged bromide and iodide ions) -each crystal has a point of imperfection called the sensitivity speck,this allows for latent image acquisition |
| what are sensitivity specks made of | -gold-silver sulfide |
| what are the clsifications of film | -panchromatic -orthchromatic -blue sensitive |
| -most common -sensitive to all colors -uses red safe light | panchromatic film |
| -not sensitive to red light spectrum -uses red safelight -green sensitive | orthochromatic film |
| -uses amber color safelight -used with older tungsten screens(mammography) | blue sensitive film |
| -hard protective gelatin -prevents soft emulsion from sctratches, etc. -antistatic -do not paper clip or staple processed images=scratch | super(top)coat |
| what controls the color that film is sensitive to | dyes |
| what are the characteristics of film | -resolution -speed -contrast -latitude |
| ability to image an object faithfully | resolution |
| how fast film responds to minimal exposure | -speed(aka sensitivity *more silver=higher speed *thicker emulsion layer gives more silver(speed), but less resolution |
| ability to image density differences | contrast *related to crystal size(smaller crystals=high contrast) |
| range of exposures to produce quality image(degree of error) | latitude *higher contrast=less latitude |
| what kind of film would be used for chest and abdominal imaging | low resolution |
| what kind of film would you use for bone work | high resolution(requires more mas) |
| what is the purpose of film screens | to significantly reduce pt dose |
| -does not require use of screen -today it is used in manufacturing | direct exposure film |
| -mostly used in diagnostic film | screen film |
| -used for copies of digital images | laser film |
| -used for copies of film images | duplication film |
| -used to remove unwanted anatomy on images | subtraction film |
| -used to show movement frame by frame | cine film |
| -rolls of small film use to take blown up spot images | spot film |
| what is inportant for film handling | -inventory(first in first out) -sensitive to heat and humidity, radiation and light -store on end -static artifacts if too dry -store at <68 degrees 30-60% humidity -store 18 months unopened -store for 45-60 days once open |
| what is the film ID | contains: -date -pt name -MR # -intitution name -exposed by xray or light -do not write on |
| what are the 4 possible states of film | -green film-unprocessed -clear film-processed -black film-exposed to white light before processing -diagnostic film-regular film with an image on it |
| how is the cassette constructed | -tube side-radiolucent -back side-radiopaque -blocker-pt info -purpose-light tight and good film/screen contact |
| how should a safelight be mounted | at least 4ft from loading bench |
| what are the four main steps of the latent image formation Gurney-Mott hypothesis in film screen | -light source -e- given off -e- attracted to SS -SS attract Ag |
| what are the different types of static artifact | -rubbing or friction=tree static -touching with finger=smudge -touching with fingernail-crown -bending-crinkle marks |
| what are some things film is sensitive to | -light -heat -radiation -pressure |
| what is the main difference between direct exposure and screen film | less dose with film screen |
| how can you check for safe light fog | 1.make a light exposure on a film 2.take in a dark room with no lights on 3.cover half off film with lead 4.turn on safe light for 30 seconds 5.turn light of and process film 6.you can then see if there is fog or not |
Created by:
bigad1982
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