Radiology T2

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What is the function of the radiographic cassette?: To provide close/tight contact between the film & intensifying screen. To provide a light tight container for the film. To protect the screen & film from physical damage.
What is the radiographic cassette made up of (construction)?: Aluminum or plastic on the front surface which doesn't impede x-rays. A metallic black which is lined with lead to prevent "backscatter". A 7X3 cm rec. of lead on the front to allow use of the photoimprinter during processing.
What's the function of the intensifying screen?: To line the front & back of cassette. Made of plastic sheet coated with "phosphor"material suspended in binding agent. Emit light in exposed x-rays. Reduces the amount of radiation necessary to expose film.
What is the screen speed determined by?: The size of the "phosphor" crystal.
What are the two types of screen speeds?: High and low.
What is a high speed screen?: Large crystal=higher amounts of light emitted. Less radiation needed. Poor resolution. More grainess (picture not as clear).
What is a slow speed screen?: Smaller cyrstals=less light emitted. More radiation needed. Better resolution. Less grainess.
What are the 3 different types of intensifying screens?: Rare earth screens
Hi-Plus screens
Ultra Detail screens
Characteristics of a rare earth screen:: High speed screen. Larger cystal(rare earth elements). Higher cost screen. An attempt to combine high speed with good resolution.
What is a quantum mottle?: A "mottling" that can be seen on the film when using rare earth screens and very low exposures. This is due to extremem sensitivity of rare earth phosphors to x-ray radiation. Seen in rare earth screens.
Characteristics of a Hi-plus screen:: A medium screen speed. Medium size crystal. Crystal is calcium tungstate. Has average resolution. Used for general x-rays.
Characteristics of a Ultra detail screen:: Slow speed screen. Small crystals. Excellent resolution. Often used in orthopedics.
What are some things you need to do to keep the screen clean?: Clean monthly or more often. Use a commercial screen cleaner (or mild soap & water). Write down when you've cleaned (log). Check the adhesion to cassette when cleaning.
What is the film constructed of?: Silver halide crystals suspended in gelatin on both sides of a plastic acetate base. Covered wth a protective coating.
What is the latent image?: The image on the film before processing.
What happens during latent image production?: X-rays hit screen phosphor crystals. The screen phosphor crystals emit visible light. The light causes a change in the silver halided on the film producing an invisible latent image. The latent image is made visible through processing.
What are the 2 film types?: Screen film
Non-screen film
Characteristics of a screen film:: Has silver halide crystals that are more sensitive to visible light than x-rays. Need less x-ray radiation to expose film. Has two types - regular and rare earth.
What type of light are regular screen films more sensitive to?: Blue light
What type of light are rare earth films more sensitive to?: Green light
Characteristics of non-screen film:: More sensitive to x-ray radiation than visible light. There is no screen, so need more x-ray radiation to expose film. Increased detail due to lack of screen. Common for dental & orthopedic film.
What are the 3 types of film speed?: Fast, medium and slow.
Characteristics of fast speed film:: "Ultraspeed". Large silver halide crystals. Need less exposure. Get less detail - grainier.
Characteristics of medium speed film:: "Par" film/"standard" film. Most common. Has medium size crystals. Medium amount of exposure needed. Get moderate detail.
Characteristics of slow speed film:: "High detail" film. Small crystals. Increased exposure. Increased detail. Greater range in exposure factors.
What do you do to take care of films?: Store film vertically. Keep in cool area/low humidity. Avoid formalin, hydrogen peroxide & ammonia vapors. Check film expiration date.
What are grids?: Alternating thin strips of lead w/ spacers between them. Absorb any x-rays that are not parallel to the primary beam. Absorbtion of non-parallel x-rays produce a better picture/better contrast. Grids have an optimal focal distance grid ratio vs. height.
What is the grid ratio?: The height of the lead strip divided by the distance between them. The greater the grid ratio the more primary beam is also absorbed - increase the exposure to compensate. The greater the grid ratio, the more efficient the grid.
What are the 3 types of grids?: Parallel Grid
Focused grid
Crisscross grid
Characteristics of a parallel grid:: The lead strips are penpendicular to the table. May have less detail to the edges.
Characteristics of a focused grid:: The lead strips are parallel with the natural divergence of the primary beam. Focal distance is very important!
Characteristics of a crisscross grid:: 2 parallel type grids superimposed on each other. Produces a cross hatch pattern. Must keep tube exactly parallel & centered over grid.
What is the grid cut-off?: It refers to the absorption of part of the primary beam due to improper use of the grid and is cause by 4 factors.
What can affect the grid cut-off?: The focus grid (fg)is used upside down. The fg is used w/primary beam not centered/focused over grid. The focus or parallel grid not perpendiculat to tube (cockeyed). Fg used with incorrect SID.
What are the two types of Bucky's?: Stationary
Potter-Bucky diaphram
What is a stationary grid?: Placed between film and patient on top of cassette. Shows grid lines when processed.
What is a potter-bucky diaphram?: It's inside the x-ray table. Connected to exposure switch to move grid in 2 directions at moment of exposure. This eliminates grid lines on the film.
What can be done to compensate for the primary beam being partially absorbed by the grid? (it's normal): The exposure factors are increased by doubling the MAS and adding a "grid factor" value to the KVP whenever a grid is used.
What is film proessing?: It refers to the process of turning the "latent image" into the visible image on the film. It's estimated that 90% of poor quality radiographs can be traced to poor processing.
What are the 5 general steps to film processing?: Develop, Rinse, Fix, Wash and Dry
What are 4 darkroom essentials?: Must be kept clean.
Must be kept organized & uncluttered.
Must be light proof.
Must be well ventilated.
What is kept on the dry side of the darkroom?: Counter - load & unload cassette.
Film is stored.
Film hanger storage (manual).
What is contained on the wet side of the darkroom?: Processing tanks.
Film viewer.
Drying area for film.
What are 5 darkroom rules?: 1.Keep area clean-avoid artifacts. 2.Keep developer & fixer tanks covered to prevent evap. & oxidation. 3.Stay organized. 4.Handle film by edges-avoid artifacts. 5.Remove film from the film bins slowly to avoid static electricity artifacts.
Characteristics of the safelight:: Provides enough illumination to work efficiently, but not enough to "fog" the film. Uses 15 W. re-light. Keep safelight at least 4 ft. from the film during processing to prevent film "fog".
What happens during the developing step of processing?: The process of reducing the exposed silver halide crystals to black metallic crystals.
What does the developer consist of?: Reducing agents(chemical to reduce exposed crystal to black metallic crystals). Alkalinizer(an accelerator). Restrainer(limit the reaction). Preservatives(keep developing rate stable. Water.
What is the rinse bath stage of developing film?: It's usually water. Can also be acid "stop bath". Removes developer. Reduces carry-over of developer into fix.
What does the fixer do in the developing process?: It removes unexposed silver halide crystals.
What determines the length of time the film is in the fixer?: Time needed to remove the unexposed crystals. Time needed to harden the film emulsion.
What does the fixer consist of?: Acidifier. Hardener(prevents sogginess on emulsion). Preservative(prevents fixing agents from decomposing). Water.
What does the washing stage do during film developing?: It removes fixing agent. Inadequate wash time causes artifacts and discoloration due to residual fix agent.
What does the drying stage do during the process of film developing?: If processed manually, cannot touch films until completely dry. Automated processing speeds up the drying process.
What are two things that must happen during manual processing?: All solutions should be ideally at 68*. Always stir solutions before starting processing procedure.
Manual - developing stage.: Av. developing time 5 mn. Agitate film for 15 sec once in developer to remove air bubbles. Carry developer solution over into rinse bath-decreases vol. in developer, removes depleted developer solution, allows room to add replensishing solution.
Manual - rinsing stage.: Films are briefly agitated in the water to minimize the amount of developer solution being carried into the fix.
Manual - fixing stage.: RULE OF THUMB: fix the film twice the developing time. Film may be viewed briefly after its been in the fix for 1mn, then back into fix. As the fixer ages the clearing time will lengthen.
Manual - washing stage.: Final wash time in usually for 20-30 mns. The use of "photoflow" for manual processing(a surface tension reducing agent) speeds drying time and reduces streaking.
Manual - drying stage.: Warm air cabinet drying is ideal.
If drip dry: don't let films touch, don't touch until dry & avoid fan drying.
How do you file films?: File only when dry. Cut off corners if using "stretch" hangers.
Advantages to automatic film processing.: Reduces developing & drying time. Reduces artifacts. It's more consistent processing. Less expertise required.
Disadvantages to automatic processing.: Higher initial cost. Periodic maintenence.
What is automatic processing?: An alternative to hand processing that used a machine and completes the entire processing procedure in approx. 90 sec. Principles and steps are the same as manual, only faster.
When do you replace the developer solution?: Completely replace when it's green or brown. Film will have less contrast & appear over-exposed if needing replenishing. Adding replenishing solution to developer to return to original strength.
When do replace the fixer solution?: Replenish when clearing time is more than 3 minutes of manuals. Remove some of the fix solution when necessary & add fix replenisher.
Why do you recover silver?: It saves money. Allows legal disposal of corrosive processing chemicals. Conservation of precious metal.
How do you recover silver?: Sell exhausted fix to silver recovery company. Sell old x-rays, after legal statutes have expired, to silver recovery company. Use electroplating recovery system. Use silver ion exchange system.
What are the 3 legal methods for identifying film?: Lead letter in a holder placed on cassette at time of exposure. Lead labeling table on cassette at time of exposure. Photo imprinter used in dark room after exposure, but before processing.
What's an important factor about film identification?: It must be permanent and unalterable to be legal.
If you forget a label you can do the following, but they're not legal:: Pencil to scratch information onto film before or after developing. Use a photographic white ink or permanent marker on clear areas of exposed film. Use a piece of white tape on a clear area.
What needs to be included for identifying film?: Name of hospital or practice.
The date.
The name or number of patient.
Owner's name.
X-ray view or orientation.
How long must you legally keep x-rays?: 7 years.
Films are stored, how?: In envelopes with the owners name, pets name, views and dates of exposure.
Definition of radiographic quality.: It's a qualitative term, which reflects the ease by which structures (details) on the film can be detected.
What 3 things determine radiographic quality?: Density-the degree of blackness on x-ray. Contrast-the visible difference between 2 radiographic densities. Definition.
What 4 things will a "diagnostic radiograph" have on it?: Sufficient densitiy, definition, contrast and penetration.
What is density on a radiograph?: Adquate blackness on radiograph. Reveals all structural details of the object. Too much density will hide detail.
What is definition on a radiograph?: To be able to differentiate different body parts from one another.
What is contrast on a radiograph?: It proved variation in tissue opacity.
What is penetration on a radiograph?: It provides internal details - not just tissue silhouettes.
What 3 factors affect x-ray penetration?: Wavelength, subject composition and tissue thickness.
How does wavelength affect x-ray penetration?: The shorter the wavelength the more penetration.
How does subject composition affect x-ray pentration?: Bone and metal are very dense and hard to penetrate.
How does tissue thickness affect x-ray penetration?: Incease thickness equals decreased pentration.
What 4 factors can affect the radiographic image?: MA, KVP, Time and SID (distance).
What does the MA do?: It controls the quality of the x-ray. Controls the density on the film.
What does the KVP do?: It controls the quality of x-rays. Controls the penetrating power of the x-ray. Controls the contrast.
What does time do?: It determines the length of exposure. Determines the quantity of x-rays. Controls the density of the film.
What does distance do?: Increase distance=decrease amount of radiation per square inch reaching film=caused decrease in density on film. (Inverse square law).
What is film density?: The amount of blackness in the radiographic image.
What does alot of black mean on the film?: High density.
What does alot of white on the film mean?: Low density.
What is the film density controlled by?: Directly by the MAS. It's the result of the deposition of metallic silver in the film.
What is radiolucent?: Gases. It's black on the film=the most radiation hitting the film.
What is radiopaque?: Bone, metal. White on the film=the least radiation hitting the film.
What 4 variable affect film density?: KVP, SID, Processing and film brand.
How does the KVP affect film density?: If you increase the KVP you get 1. shorter wavelength x-ray 2.more x-rays pentrate the object 3.more scatter and more fog.
How does SID affect film density?: The inverse square law - double the distance from teh tube to film means 1/4 radiation reaches film (decrease film density).
How does processing affect film density?: It can affect the amount of metallic silver deposited in film.
How does film brand affect film density?: Different brands of film will contain different amounts of silver. Stay with the same brand and type of film.
Tissue density: The greater the tissue density the lesser the film density.
Least dense(black) Gas-fat-water-bone-metal - most dense(white).
What is radiographic contrast?: The difference between 2 adjacent densities. Describes the variations of density on the film. Controlled mostly by the KVP.
What are the 2 radiographic contrasts?: High and low.
What is high contrast?: Abrupt changes of density tones from black to white. Has mostly blacks and whites(some grey). Called short-scale contrast - used in orthopedics.
What is low contrast?: Gradual changes of density tones from black to white. Many shades of grey. Called long-scale contrast - used for soft tissue.
What besides high and low contrast can affect the radiographic contrast?: Subject contrast.
What is subject contrast?: It's determined by the tissue density and tissue thickness, which determines the amount of radiation which passes through the tissue.
ex. horse leg-muscle next to bone(high)
ex. abdomen-organs of similar density(low)
What do you do to increase the contrast of the subject on the film?: Decrease KVP and increase MAS.
What do you do to decrease the contrast of the subject on the film?: Increase the KVp and decrease the MAS.
What is wide latitude film?: Film that needs large changes in exposure to change visible density- less sensitive to radiation variation.
What is short latitude film?: Film that shows density changes in response to minor changes in exposure- more sensitive to radiation variation.
What 3 things affect definition or image sharpness?: Motion, geometric unsharpness and material unsharpness.
What are things that can affect motion in relation to definition or image sharpness?: The animal, table or tube.
How does geometric unsharpness affect definition or image sharpness?: Focal spot size. Object to film distance -keep patient as close to film as possible. Target to film distance.
How does material unsharpness affect definition or image sharpness?: Fast intensifying screens cause loss of sharpness due to large phosphor crystals. Poor screen film contact causes loss of sharpness(ex. if it's loose).
What is radiographic distortion?: Distortion of the size or shape of the image.
How does magnification affect radiographic distortion?: The object is not as close to the film as possible - causes the object to appear larger than it is.
How does elongation affect radiographic distortion?: The x-ray tube isn't perpendicular to object - causes the object to appear longer than it is.
How does foreshortening affect radiographic distortion?: Object is not parallel to the film - causes the object to appear shorter than it is, with the elevated portion distorted.
Rules to follow to avoid radiographic distortion:: Place the object of interest as close to the cassette as possible. Keep the area of interest parallel to the cassette. Keep the primary beam centered and perpendicular to the cassette.
What 2 questions should be asked when critiquing the quality of a radiograph?: Is the film to light or too dark (primarily due to KVP)? Is the density suitable?
Is there proper penetration in the x-ray(light or dark)?: Ona a film that is inadequately penetrated, the anatomical parts are indistinct or imperceptible. If over pentrated, it will be too dark. Distinguishing between overpenetration and excessive density depends on a consideration of contrast.
What do you adjust for proper film penetration?: The standard change in KVP to increase or decrease pentration is 10-15%. 10% KVP change is the least change the human eye can detect.
Is the contrast appropriate?, what controls the contrast?: KVP controls the scale of contrast. High KVP is responsible for low contrast & gives a radiograph an overall gray appearance. Low KVP is used to establish high contrast and generates many blacks/whites on the film (few greys).
What's the primary factor in evaluating overexposed radiographs and determining whether it is overpentrated or has to much density?: Contrast.
How do you change the density of the film?: To improve a radiograph by altering the density the MAS is increased or decreased by 30-50%.
What other questions should be asked when critiquing a film?: Was there proper positioning? Was there correct collimation? What the proper directional label in the right spot? Was the film properly labeled?
How can you tell if there's insufficient density in a film?: The film is too light and the anantomical silhouettes of interest are visible. The image is visible, but not dark enough to see well.

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