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111 Cards in this Set
- Front
- Back
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Kilovoltage (kV)
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controls the penetrability power of the x-ray beam
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Milliamperage (mA)
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controls the quantity or number of x-rays produced
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Exposure time (ms)
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controls the duration of the exposure, usually expressed in milliseconds.
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What are the three main exposure factors? What is another name for exposure factors?
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1. kV
2. mA 3. ms Another name for exposure factors is technique factors. |
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AEC- Automatic Exposure Control
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Systems that provide automatic termination of exposure time when sufficient radiation is received by the selected ionization chamber cell.
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What are the four quality factors that film-based radiographs are evaluated on?
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1. Density
2. Contrast 3. Resolution 4. Distortion |
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What is density?
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Density is described as the amount of "blackness" on the processed film image.
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What is the primary controlling factor of density?
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mAs is the primary controlling factor of density.
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What happens to the amount of radiation produced and the density when mAs is doubled.
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When mAs is doubled, the amount of radiation produced is doubled, and so is the density.
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What 6 other factors that influence density?
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1. SID (source to image distance)
2. kV 3. part thickness 4. chemical development time/temperature 5. grid ratio 6. film-screen speed |
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How does the Source to Image Distance affect the density of a film?
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According to the inverse square law, if the source to image distance is double then the density of the film will be reduced to one-fourth.
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What is the anode heel effect?
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The intensity of the radidation emitted from the cathode end of the x-ray tube is greater than at the anode end.
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When is the anode heel effect most pronounced?
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when using a shorter SID and a large field size, the anode heel effect is more pronounced.
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How can the anode heel effect be applied?
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When radiographing body parts that have a significant difference in thickness, the patient should be positioned so that the thicker portion of the part is at the cathode end and that the thinner portion is at the anode end.
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What are compensating filters used for?
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they are sometimes used to filter out a portion of the primary beam toward the thin or less dense part of the body being imaged.
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What is radiographic contrast?
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It is the difference in density on adjacent areas of a radiographic image. The greater this difference the higher the contrast, the less the density differences, the lower the contrast.
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What is short scale contrast?
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It is when there are greater differences in adjacent densities and fewer visible density steps.
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What is the primary controlling factor contrast in film-based imaging?
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kVp is the primary controlling factor.
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If the kVp was increased what would happen to the contrast?
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The contrast would decrease.
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Is kVp a primary or secondary controlling factor of density?
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kVp is a secondary controlling factor of density.
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How does kVp influence density on a radiograph.
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Higher kVp results in both more x-rays and greater energy x-rays, and that causes more x-ray energy to reach the image receptor which increases the density of the radiograph.
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How much do you have to increase the kVp by inorder to double the density?
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The kVp would have to be increased by 15% to double the density.
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What is scatter radiation?
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Scatter radiation is radiation that has been changed in direction and intensity as a result of interaction with patient tissues.
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How do you reduce the amount of scatter radiation? 2 ways
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Scatter radiation is reduced by collimating down, and by using a grid,
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What is resolution?
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Resolution is the recorded sharpness of structures on the image.
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What other terms can be used to describe detail?
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detail, recorded detail, image sharpness, and definition.
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How is resolution generally measured and expressed in film-screen based imaging?
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Resolution is generally measured and expressed as line pairs per millimeter (lp/mm), typically 5 to 6 lp/mm.
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What is blur or unsharpness?
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It is the lack visible sharpness or resolution.
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What are the 3 controlling factors of resolution?
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Geometric factors, Film-screen system, motion.
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What 3 geometric factor control (or influence) resolution?
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focal spot size, SID, and OID
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What size focal spot is recommended to ensure the best resolution?
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Small focal spot will result in less geometric unsharpness.
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What is penumbra?
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It is the unsharp edges of the projected image.
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What will a faster film-screen system do?
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It allows shorter exposure times; which are helpful in prevent patient motion and reducing dose; however, the image is less sharp than if a slower system were used.
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What are the two types of motion?
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1. Voluntary
2. Involuntary |
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What is voluntary motion?
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Motion in which the patient can control it.
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How can voluntary motion by prevented or minimized during a radiographic exam? 2 ways
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1. Controlled breathing
2. Patient immobilization- use of support blocks, sandbags, or other immobilization devices. 3. high mA and short exposure time. 4. And most importantly communication with the patient. |
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How is voluntary motion visualized on a radiograph?
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it is visualized as generalized blurring of linked structures.
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How is involuntary motion visualized on a radiograph?
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It is visualized as localized unsharpness or blurring.
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What are some examples of involuntary motion?
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Peristalic action of abdominal organs, tremors, or chills.
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What is distortion?
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It is the misrepresentation of object size or shape.
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What are the two types of distortion?
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1. size distortion.
2. shape distortion. |
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What is x-ray beam divergence?
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It is the expanding (diverging) ray of x-rays from the source (focal spot) to the image receptor (flashlight example)
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What are the 4 primary factors of distortion?
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1. sid
2. oid 3. object image receptor alignment. 4. central ray alignment/centering |
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What happens to the magnification when the SID is increased.
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It is decreased.
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What is the standard SID used?
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40 inches or 100 cm.
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What is becoming the most commonly used SID?
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44 to 48 inches.
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How does the OID affect distortion?
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The closer the object being radiographed is to the image receptor, the less magnification and shape distortion and the better the detail of resolution.
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What is Object Image Receptor Alignment?
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It is the alignment or plane of the object being radiographed in relation to the plane of the image receptor.
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What is the effect of having improper object IR alignment?
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It causes distortion.
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What is central ray alignment?
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It is the centering of the x-ray to the area of interest.
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What are digital images in radiologic technology?
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There are a numeric representation of the x-ray intensities that are transmitted through the patient.
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What is brightness?
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It is the intensity of the light that represents the individual pixels in the image on the monitor.
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What controls brightness?
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processing software through the application of predetermined digital processing algorithms.
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What is contrast (digital imaging)?
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The difference in brightness between light and dark areas of an image.
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What is contrast resolution?
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It refers to an imaging system's ability to distinguish between similar tissues.
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What does a pixel represent?
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It represents a single shade of gray when viewed on a monitor.
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What does the bit depth control?
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It controls the range of possible shades of gray demonstrated.
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What is the benefit of greater bit depth?
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It gives greater contrast resolution.
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What is resolution in digital imaging?
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It is the recorded sharpness or detail of structures on the image, the same as described for film-screen imaging.
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What factors control resolution in digital imaging?
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1. focal spot size
2. geometric factors 3. motion 4. pixel size 5. display matrix |
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What is Distortion in digital imaging?
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It is a numeric value that is representative of the exposure the image receptor recieved. May also be called the sensitivity number.
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What is post-processing?
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It is the changing or enhancing the electronic image in order to improve its diagnostic quality.
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what is windowing?
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It is how a user can adjust image contrast and brightness on the monitor.
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What are the two types of window adjustment?
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1. Window width- control the contrast of the image.
2. Window level- controls the brightness of the image. |
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What is smoothing?
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Brightness values of adjacent pixels can be brought closer together.
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What is magnification?
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All or part of an image can be magnified.
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What does edge enhancement do?
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Brightness can be increased along the edges of structures to increase the visibility of the edges.
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What does subtraction do?
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Background anatomy can be removed to allow visualization of contrast media-filled vessels.
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What does image reversal do?
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The dark and light pixel values of an image are reversed- the x- ray image reverses from a negative to a positive.
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What does annotation do?
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Text may be added to images
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What are 3 advantages of CT?
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1. contrast resolution is superior
2. structures are visualized without superimposition 3. acquired data may be viewed in alternative planes. |
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what does fluoroscopy provide?
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It provides dynameic (moving) imaging of structures.
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What is computed radiography (CR)?
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It is a method of digital image acquisiton for general diagnostic radiography.
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What are the main components of a CR system?
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image plates, image plate reader, technologist workstation.
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What is direct digital radiography?
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it is a direct conversion method, wherein a digital detector detects the radiation intensities transmitted through the patient, which are then converted to digital format.
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What is PACS?
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It is a array of hardware and software taht connect all modalities with digital output.
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What do the letters stand for in PACS
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p- picture
a- archiving c- communication s- system. |
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What is ALARA?
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The principle that radiation exposure should be kept as low as reasonably achievable.
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What is attenuation?
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A reduction in intensity of the x-ray beam due to absorption and scattering.
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What is brightness?
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The intensity of light that represents the individual pixels in the image on the monitor.
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What is the Central Ray (CR)?
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The center point of the x-ray beam (point of least distortion of projected image)
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What is computed radiography?
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A method of acquiring radiographic images digitally. the main components of a CR system include photostimulable phosphor image plates, an image plate reader, and a workstation.
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What is contrast?
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The density difference on adjacent areas of a radiographic image.
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What is density?
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the amount of blackness on a film.
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What is direct digital radiography (DR)?
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A method of acquiring radiographic images digitally. The DR detector replaces film-screen system and the CR imaging plate as the image receptor, utilizing a more direct approach to image capture.
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what is a display matrix?
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Series of "boxes" that give form to the image.
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What is a display pixel size?
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It is the pixel size of the monitor, related to the display matrix.
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What is distortion?
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misrepresentaton of object size or shape as projected onto radiographic recording media.
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What is exposure latitude?
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It is a range of exposure factors that will produce an acceptable image.
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What is an image plate (IP)?
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with computed radiography the image plate records the latent images, similar to the film in a film-screen cassette used in film-screen imaging systems.
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what is kilovoltage?
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The energy of the x-ray photon.
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What is Milliamperage?
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The quantity of x-ray photons.
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What is Milliamperage seconds?
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The quantity of x-ray photons and the duration of the exposure.
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What is noise?
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Random disturbances that obscures or reduces clarity. In a radiographic image this translates into a grainy or mottled appearance of the image.
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What is penumbra?
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The unsharp edges of the projected image.
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What is a pixel?
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Picture element; an individual component of the image matrix.
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What is radiology information system (RIS)?
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A computer stystem that supports the operations of a radiology department. Typical functions include exam order processing, exam scheduling, patient registration, report archiving, film tracking, and billing.
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What is the sensitivity "S" number?
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A term used by some equipment manufacturers to indicatie exposure index. The S number is inversely proportional to the radiation striking the detector.
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What is windowing?
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The user adjusting the window level andd window width.
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CAD
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Computer-Assited Detection
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DICOM
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Digital Imagig Communication in Medicine
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HIPAA
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Heath and Insurance Portability and Accountability Act
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HIS
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Hospital Information System
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HL7
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Healthcare Level 7
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IHE
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integrated health care enterprise
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IMAC
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Image and information Management and communication
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IR
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Image Receptor
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PACS
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picture archiving and communication system
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IP
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Image plate
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RIS
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Radiology Information System
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SNR
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Signal-to-noise ratio
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