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Radiographic Film
Film Exam
| Layer | Description and purpose |
|---|---|
| Invisible image on the film after exposure before development (processing) | Latent Image |
| What are some things that occur to create the latent image? | Primary useful beam exits the source or x ray tube; it hits the patient (air, fat, muscle, bone - contrast media or metal artifact); Interacts with pt. (absorption, penetration, scatter); exit radiation (image from xrays); latent image on IR |
| What are the layers of the film? | Overcoat, emulsion, adhesive layer, base |
| What is the purpose of the base layer? | Provides support for the emulsion |
| Until WWI what base was used? WWI?1920's? what is used today? | Until WWI glass was used; During WWI cellulose nitrate (it was very flammable); in the 1920's cellulose triacetate (known as saftey film); Today - polyester |
| What are some characteristics of the base we use today? | inflammable (saftey film), non-tear, flexible; stable, rigid, uniform density |
| What is on the base to help to reduce eye strain for the radiologists? | blue tint (dye) |
| This is the heart of the x ray film. It is the material with which x rays or light photons from screens interact and transfer information. | Emulsion layer |
| What two things make up the emulsion layer? | gelatin and silver halide crystals |
| What are some characteristics of the gelatin in the emulsion layer? | colloid; chemically non reactive; clear so it may transmit light, porous to allow chemicals in processing to penetrate to crystals; provides support to crystals so they may be evenly spread |
| What term is used to describe clumping of the silver halide crystals? | Film graininess |
| What is double emulsion film? | Emulsion coated on either side of the base; and captures an image on both sides |
| A problem that occurs with double emulsion film. Exposure of adjacent emulsion and the emulsion on the other side of base. When the light crosses over the base and causes increase blur on image. | Crossover |
| How can we reduce image blur due to crossover? | By using flat tabular grain; light absorbing dye, reduced by screens that emit short wavelength, polyester |
| what is the purpose of the adhesive layer? | Uniform adhesion of emulsion to the base |
| What is the active ingredient (photosensitive agents) of the emulsion.? | Silver halide crystals |
| Giving off of light. | Halation |
| Antihalation | prevent the giving off of light |
| What are two ways film graininess can occur? | clumping of the crystals or increase in mAs |
| What makes up the silver halide crystals? | silver bromide, iodide, chloride |
| Why are the silver halide crystals the active ingredient in the emulsion? | Due to their high atomic number their interaction with x ray and light photons results in the formation of the latent image. |
| what shape are the crystals? | flat tabular grain shape (this helps with the absorbing more photons, even dispersement of light, reducing crossover and reducing silver coating required, allows for processing |
| What is the impurity or imperfection that allows for the latent image formation? | Sensitivity Specks |
| Supercoat or overcoat | top layer, hard protective coat; prevents scratches and handling artifacts; antistatic |
| What is a manifest image? | It is what is created after the latent image is treated with proper chemical processing. |
| The silver halide crystals form a ________ _________. | crystal lattice |
| What is processing? | It is the chemical reactions that transform the latent image into a manifest image. |
| Film used with radographic intensifying screens. | screen film |
| What are the four film characteristics? | contrast, speed, latitude, resolution |
| Contrast is ____________. | density differences; degree of difference between the light and dark areas of a radiograph. |
| The range of exposure techniques that produce an acceptable image. | Latitude (degree of error) |
| Contrast is ___________ related to latitude. Resolution is _________ related to speed. | inversely; indirectlyinversely; indirectly |
| The sensitivity of the screen film combination to xrays and light. | Speed (how fast responds to minimal exposure) |
| Resolution | ability to image an object faithfully (a measure of the ability of a system to image two separate objects and visually distinguish one from the other) |
| What are two types of equipment that we use to help us to compare the film characteristics? | Sensitometer and densitometer |
| Exposes film to a light sensitometric 21 step wedge. | Sensitometer |
| Meter that reads the density value f each step 1-21. | Densitometer |
| What is the characteristic curve? | It is a graph that shows the relationship between optical density and radiation exposure; aka H&D curve (Hurter and Driffield) |
| What axis is the optical density on? | y axis |
| What axis is the amount of exposure (log relative exposure) on? | x axis |
| What are the three parts to the line of the characterisitic curve? | toe, straight line portion (useful density), shoulder (peaked portion) |
| What are the two controlling factors of film characteristics? | emulsion thickness (thin, thick) and crystal size (small, large) |
| What is the Gurney-Mott Hypothesis? | Theory in the formation of the latent image |
| What is spectral matching? | Choosing of a film whose sensitivity to various colors of light is properly matched to the spectrum of light emitted by the screen. |
| What is orthochromatic film? | Film that is sensitive to blue light but also to green light |
| What is panchormatic film? | Film that is sensitive to the entire visible light spectrum. |
| Film only exposed to x rays and used without intensifying screens. | Direct exposure film |
| Film sensitive from light emitted by the screen; commonly used; used with intensifying screens | Screen film |
| Used to make copies of film; A single emulsion film that is exposed to ultraviolet or blue light through existing radiograph to create a copy. | Duplicate film |
| A method of removing all unnecessary anatomic structures from the image and enhance only those of interest. | Subtraction film |
| Used for motion in GI and cardiac cath. | Cine film |
| What are safelights? | Incandescent lamps with a color filter; provide enought light to illuminate the darkroom while ensuring that the film remains unexposed |
| What safe light do you use for panchromatic film? | Red filter |
| what safe light do you use for orthochromatic film? | Red filter |
| What safe light do you use for blue sensitive film? | Amber filter |
| What does FIFO mean? | First in first out |
| What is film sensitive to? | Heat, radiation, light, humidity, handling |
| How is film stored? | Stored on its end to reduce pressure artifact |
| what temperature is film stored at? | less than 68 degrees F, 30-60% humidity |
| What is the shelf life of film? | 45-60 days |
| Exposed film is _ times more sensitive to heat, light, pressure handling artifacts than film that has not been exposed. | 8 |
| What will happen if the film is to hot? | It will fog |
| If the film is sticky, what has occured? | Too much humidity |
| Static is caused by what? | cold temperature with an increase in humidity |
| What are three types of static? | Tree, smudge, crown |
| Touching film with fingernails causes _______. | Crown static |
| Touching film with fingertips causes _______. | Smudge static |
| Rubbing film surface against another surface causes _________. | Tree static |
| Large crescent mark is due to? | folding of film |
| What must be on every film to be legal in court of law? | date, patient name, medical record number, institution name and address, DOB, correct marker |
| What distance should the light source be from the workstation? | 4 ft |
| What type of light source do you use? | 15 watt white light bulb |
| What type of filter do you use for blue sensitive film? | amber filter |
| What type of filter do you use for gree/blue sensitive film? | red rilter |
| How many times more sensitive is exposed film than unexposed film? | 8 timesq |
| what is the percentage composition of the silver halide crystals? | 95% silver bromide, 3-5% silver iodide |
| What are the 3 layers of the radiographic film? | base, emulsion, top coat (overcoat or supercoat) |
| What is the purpose of the film base? | mechanical support |
| What is the purpose of the gelatin in the emulsion? | spread and hold the silver halide crystals evenly |
| What is the purpose of the film coat? | protects from handling artifact |
| What is the purpose of the sensitivity speck (center)? | imperfection on each crystal that captures latent image and becomes developable |
| Image created after exposure but before processing. | latent image |
| Gives off light. | halides |
| Two latent images were not perfectly superimposed. | Crossover |
| What base material do we use today? | polyester |
| What is the difference between single emulsion and double emulsion film? | In single emulsion film the emulsion is on one side and in double emulsion the emulsion is on either side of the base |
| Gelatin is chemically considered to be ______. | Colloid |
| Film emulsion is composed of silver halide and potassium bromide. T/F | False - It is composed of silver halide and gelatin. |
| Panchromatic film is defined as sensitive to what kind of light? | all light |
| What is the characteristic curve of radiographic film? | The graphic relationship between optical density and radiation exposure. |
| What is another name for the curve? | H & D curver (hurter and driffield) |
| Film contrast is related to the _____ of the straight line portion. | Slope |
| Latitude is inversely realted to _______. | Contrast |
| What are the 3 layers of a radiographic film? | base, emulsion, top coat |
| Silver Halide crystals are composed of ____% silver ______ and _____% silver iodide. | 95;bromide,3-5;iodide |
| Wat is the purpose of the film base? | mechanical support |
| What is the gelatin in emulsion? | evenly spread and hold silver halide crystals |
| Protects film from handling artifact | Film overcoat (super coat) |
| Imperfection on each crystal that captures latent image and becomes developable. | sensitivity speck (center) |
| Gives off light. | halides |
| Why is the film base tinted blue? | Color reduces eye strain for radiologist |
| What is the base material used today? | polyester |
| What are some characteristics of a good base material? | inflammable, nontearable, rigid and flexible |
| What two things is the film emulsion composed of? | silver halide and gelatin |
| Panchromatic film is defined as sensitive to : red light, gree light, blue light or all light | all light |
| What is meant if film is referred to as saftey? | inflammable |
Created by:
sr4095