Term
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Definition
| is the support for the radiographic film emulsion. It provides a rigid structure onto which the emulsion can be coated. It is rigid yet flexible. It has a uniformed lucency. They are made of polyester. |
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Term
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Definition
| most film has this on both sides, called duplitized or double-emulsion film. This is encased by a protective covering of gelatin called supercoating. The emulsion is the most important part of the film. It is the material where x-rays (or light photons) from screens interact and transfer information. It is made of a mixture of gelatin and silver-halide crystals. The silver-halide crystals are 95% silver bromide and 5% silver iodide. |
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Term
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Definition
| protective covering of gelatin encasing an emulsion film |
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Term
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Definition
| layer between the base and the emulsion. |
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Term
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Definition
| the differences in speed, contrast, and resolution among various radiographic films are determined by how these are manufactured and by how they are mixed in the gelatin. The concentration of these determines the film characteristics. |
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Term
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Definition
| protective layer made of gelatin |
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Term
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Definition
| the crystals may be imperfect and can result in the imaging property of the crystal. The type of imperfection thought to be responsible is a chemical contaminant called ___________. |
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Term
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Definition
| silver sulfide contaminant |
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Term
| Latent Image (photographic effect) |
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Definition
| is the invisible change induced in the silver-halide crystals after exposure of x-rays. It becomes the manifest image after processing. It is made by the remnant radiation exiting the patient and hitting the radiographic film depositing energy into the atoms of the silver-halide crystals. |
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Term
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Definition
| after processing the latent image becomes this |
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Term
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Definition
| the medium that converts the X-ray beam into visible beam. The most common is photographic film. |
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Term
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Definition
| most commonly used. x-ray film type. Uses intensifying screens. |
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Term
| direct-exposure film - "nonscreen film" |
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Definition
| it is not sensitive to light. Used to x-ray thin body parts. Has a high radiation requirement. Only used when benefit outweighs the risk. |
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Term
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Definition
| films respond to violet and blue light |
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Term
| Green-sensitive film - Orthochromatic |
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Definition
| type of film that respond to blue and green light. |
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Term
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Definition
| type of film used in photography and is sensitive to the entire visible light spectrum. |
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Term
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Definition
| type of film that is a single emulsion screen film with fine grained crystal distribution. |
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Term
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Definition
| type of film with a digital electronic signal from an imaging device is written on film by a laser beam (called a modulation). Used with CT, MRI, and computed radiology. |
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Definition
| different sizes of rolled film that are viewed on a conventional view box or with a projector. |
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Definition
| type of film where image is made from a CRT (or single emulsion film). |
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Term
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Definition
| type of film used with CT, MRI, and computed radiology |
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Term
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Definition
| matching the film with the type of light it absorbs. Films must have this. If they do not match the image receptor speed will be greatly reduced and patient exposure will be increased. |
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Term
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Definition
| is film sensitivity to light photons. The thicker the emulsion, the more sensitive to light, therefore the higher the speed. Most films are double emulsion for this reason. |
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Term
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Definition
| produce black and white images |
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Term
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Definition
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Term
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Definition
| is the range of the exposure techniques (kVp and mAs) that will produce an acceptable image. |
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Term
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Definition
| when light is emitted from an intensifying screen, it exposes not only the adjacent film emulsion but also the emulsion on the other side of the base. Causes blur on the radiographic image. |
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Term
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Definition
| intensifying screens and radiographic film speed vary if very short or very long exposures are used. Exposure = intensity x time |
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Term
| 68 degrees with a humidity between 40-60% |
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Definition
| temp at which films should be stored |
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Term
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Definition
are any unwanted marks on the film. Static artifacts appear as tree like.
Must be stored and handled in the dark. If low light exposes the film it will appear as a fog on the image. If bright light exposes the film you get a dark artifact. |
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Term
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Definition
| Most film has an expiration date of ________ |
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Term
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Definition
| this is a reasonable maximum storage time for radiographic films. |
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Term
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Definition
| First step of film processing. The film must be wet with water to loosen the emulsion so that subsequent chemical baths can reach all parts of the emulsion uniformly. |
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Term
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Definition
| 2nd step of film processing. is the step where the latent image is converted to a manifest image. Chemicals used here |
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Term
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Definition
| is a developing agent that produces shades of gray. It is a reducing agent. |
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Term
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Definition
| is also a developing agent, but it produces black tones. Also a reducing agent. |
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Term
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Definition
| is a buffering agent. Helps swell the gelatin, produces alkalinity, and controls pH. |
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Term
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Definition
| is a restrainer. It is an anti-fog agent, and it keeps unexposed crystals from being chemically attacked. |
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Term
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Definition
| is a preservative. It controls oxidation and maintains balance among developer components |
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Term
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Definition
| is a hardener. It controls emulsion swelling and aids archival quality. |
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Term
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Definition
| is a sequestering agent. It removes metallic impurities and stabilizes developing agent. |
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Term
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Definition
| is a solvent. It dissolves chemicals for use. |
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Term
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Definition
| 3rd step of film processing. after development the film is rinsed in an acid solution that is designed to stop the development process and remove excess developer chemicals from the emulsion. |
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Term
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Definition
| 4th step of film processing. the silver halide that was not exposed to radiation or light is dissolved and removed from the emulsion. The gelatin portion of the emulsion is hardened to make the film more sound |
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Term
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Definition
| They are part of the cassette. They act as an amplifier of the remnant radiation reaching the film. It results in considerably lower patient dose and increased subject contrast. It is constructed from 4 layers |
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Term
| 4 layers of intensifying screens |
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Definition
Protective Coating
Phophor Layer
Reflective Layer
Base |
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Term
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Definition
| it is the layer closest to the x-ray film. 10-20micrometers thick and is applied to the face of the screen to make it resistant to abrasion caused by handling. Also helps to eliminate static electricity build-up. It is transparent to light. |
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Term
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Definition
| This is the active layer, it emits light during stimulation by x-rays. It is 150-300micrometers thick depending on the type of screen. It converts the energy of the x-ray beam into visible light. |
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Term
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Definition
| it is a reflective layer between the phosphor and the base. It is about 25micrometers thick and is made of a shiny substance such as magnesium oxide or titanium dioxide. It intercepts light headed in other directions and redirects it to the film. It increases the efficiency of the intensifying screen, nearly doubling the number of light photons reaching the film. Rare-earth screens do not need this layer |
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Term
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Definition
| the layer furthest from the film. It is 1mm thick and serves principally as a mechanical support for the active phosphor layer. It is made of high grade cardboard or polyester. |
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Term
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Definition
| the percent absorption of x-rays by the phosphor layer. |
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Term
| screen conversion efficiency |
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Definition
| converting x-ray energy into light energy. An increase in conversion efficiency will make a screen brighter thus changing image receptor speed |
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Term
| Image Noise (the fewer the x-rays used, the greater the noise) |
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Definition
| term used to describe the deterioration of the radiographic image. This may be caused by the number of x-rays used to expose a patient (or mAs). |
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Term
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Definition
| another term for image noise - the limited absorption efficiency of x-rays in the intensifying screen; the randomness of the x-ray to light conversion process. |
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Term
| spacial resolution or image blur |
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Definition
| the ability to produce an accurate and clear image. |
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Term
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Definition
| is determined by the number of x-rays interacting with the screen phosphor layer and the efficiency of conversion of x-ray energy into visible light that interacts with the film |
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Term
Phosphor composition
T or F ? |
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Definition
| rare earth phosphors efficiently convert x-rays to usable light |
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Term
phosphor thickness
T or F ? |
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Definition
| high speed screens have thicker phosphor layers ; fine detailed screens have thin phosphor layers |
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Term
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Definition
| the presence of a ___________ increases screen speed, but also increases blur |
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Term
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Definition
| light absorbing dyes are added to some phosphors to control the spread of light. These _______ improve spatial resolution but reduce speed. |
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Term
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Definition
| larger individual phosphor crystals produce more light per x-ray interaction. The crystals of detail screens are approximately half the size of the crystals of high speed screens. |
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Term
concentration of phosphor crystals
T or F ? |
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Definition
| higher crystal concentration results in higher screen speed. |
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Term
radiation quality
T or F ? |
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Definition
| as x-ray tube potential is increased, the intensification factor increases as well |
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Term
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Definition
| excessive developing time for screen-film results in a lowering of the IF b/c the emulsion nearest the base contains no latent image, yet it can be reduced to silver if the developer is allowed sufficient time to penetrate the emulsion depth |
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Term
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Definition
| radiographic intensifying screens emit more light per x-ray interaction at low temps. |
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Term
Radiation Quality
Image Processing
Temperature |
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Definition
| 3 properties that effete screen speed that are controlled by radiologist |
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Term
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Definition
| is determined by the number of x-rays interacting with the screen phosphor layer and the efficiency of conversion of x-ray energy into visible light that interacts with the film |
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Term
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Definition
| is defined as the ratio of the exposures required to produce the same optical density with and without the use of screens. The information is used for reduction of dose from non-screen radiography to intensifying screen radiation. |
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Term
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Definition
| To be fully effective, screens must be used only in conjunction with film emulsions with proper spectral matching. |
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Term
| Care of intensifying screens |
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Definition
Make sure not to scratch the screens with your fingernails or edge of radiographic film.
Screens must be cleaned every 2-3 months depending on amount of use and dust (monthly if in a busy office.) Make sure the screens maintain screen-film contact. |
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Term
1. Remnant x-rays that pass through tissue without interacting
2. X-rays that are scattered in tissue by Compton interaction. |
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Definition
| 2 types of x-rays that exit the patient are |
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Term
| Beam Restriction Devices and Grids |
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Definition
| These control and minimize scatter radiation and improve image contrast. |
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Term
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Definition
| as this increases, the radiograph loses contrast and looks dull, fogged, and blurred, mostly due to Compton interaction. |
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Term
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Definition
| these are the aperture diaphragm, cones or cylinders, and the variable aperture collimator. |
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Term
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Definition
| is the simplest of all beam restricting devices. It is a lead lined metal plate attached to the tube head. The opening in the plate is designed to cover just less than the size of the image receptor used. |
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Term
| Extension cones or cylinders |
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Definition
| use an extended metal structure to restrict the useful beam to the required size. The beam is usually circular, used for dental, skull, sinuses, and “coned-down” views of the spine. |
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Term
| Variable aperture collimator |
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Definition
| there is a set of primary shuttering devices inside the tube housing that help to decrease off-focus radiation. There are also secondary shutter devices that are independently controlled for longitudinal and transverse field changes by the operator. |
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Term
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Definition
| are carefully fabricated series of sections of radiopaque material (grid material), which are usually made of lead, alternating with sections of radiolucent material (interspace material), which are usually made of aluminum or plastic. The grid is designed to only allow those x-rays whose direction is straight from the source to the image receptor. X-rays that travel obliquely are absorbed by the grid material. In other words grids cleanup scatter radiation. A high quality grid will absorb 80-90% of scatter radiation; this is known as “good cleanup properties.” |
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Term
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Definition
height divided by the interspace thickness = h/D
There are 3 important dimensions in a grid:
1.The thickness of the grid material (T)
2.The thickness of the interspace material (D)
3.The height of the grid (h) |
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Term
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Definition
| grids that are more expensive, but clean up a higher ratio of scatter radiation. They are made by reducing the width of the interspace or increasing the height of the grid material or by combination of both. Require higher exposure factors to transmit a sufficient number of x-rays through to the image receptor. |
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Term
| Grid Ratio for most diagnostic x-rays |
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Definition
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Term
| grid ratios and mAs increase |
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Definition
No grid 1x (old mAs times 1)
5:1 2x
8:1 4x
12:1 5x
16:1 6x |
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Term
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Definition
| all lead grid strips are this type. This is the easiest to manufacture, but have undesirable properties. It has low absorption of primary x-rays, called grid cutoff. It may be partial or complete and can result in reduced optical density or total absence of film exposure. This mostly occurs with a short source to image receptor distance (SID) or with a large image receptor (14x17). |
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Term
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Definition
| 2. Crossed grid- has lead strips parallel and perpendicular, usually made by sandwiching two linear grids together perpendicularly. These have a restricted applications, the center ray of the x-ray beam must coincide with the center of the grid. Also, tilt-table techniques are possible only if the tube and the table are properly aligned. If not, you again get grid cutoff. |
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Term
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Definition
| designed to minimize grid cutoff. The lead strips run only along one axis and are tilted so that they lie on imaginary lines of the divergent x-ray beam. They are more expensive and the radiographer must take care when positioning a patient because of their source-to-image distance limitations. Have to keep the SID specific to the grid. |
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Term
| moving grids (aka potter-bucky diaphragm, bucky diaphragm, and bucky grid) |
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Definition
this grid moves when the exposure is being done, thus making the grid lines disappear (whereas the above grids all show grid lines.) There are 3 types of these:
single-stroke grid
reciprocating grid
oscillating grid |
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Term
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Definition
| causes the grid to move continuously across the film while the x-ray exposure is being made. Spring loaded and requires a manual cocking of the mechanism before each exposure. |
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Term
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Definition
| moving grid that is motor driven. It moves back and forth several times during exposure. Most commonly used. |
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Term
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Definition
| has some of the characteristics of both single-stroke and reciprocating grids. It is held center in the frame by four delicate spring-like devices on each corner. A powerful electromagnet pulls the grid to one side and releases it at the beginning of the exposure therefore the grid oscillates in a circular fashion around the grid frame. |
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