ch 25 digital rad
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| Digital radiography can be divided into two groups | cassette base, cassette less
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| Which system uses a photostimulable storage phosphor imaging plate | cassette base
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| T/F A cassette base system can be used in a bucky or for portables | True
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| Computed radiography is considered | indirect digital
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| Cassette-less systems are considered | direct digital
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| A system that uses a two part process involving a scintillator and a photodetector is called | indirect acquisition
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| A system that directly convert incoming x-ray photons to an electronic signal is called | Direct acquisition
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| What phosphor imaging plate is a rigid sheet with several layers that are designed to record and enhance transmission | photostimulable
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| The photostimulable phosphor imaging plates layers include | protective layer, phosphor layer,support layer, conductor layer, light shield layer,backing layer
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| Which photostimulable phosphor layer insulates the imaging plate from handling | protective layer
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| In order for CR to function, the imaging plate material must have the ability to___and____the image in formation in a usable form. | Store, release
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| The halides are approx.85%______and 15%____ | bromide, iodine
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| The most common phosphor with characteristics favorable for CR is | barium flurohalide bromide, iodides with europium activators
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| What does not release all the energy absorbed from the incident x-ray beam | Fluorohalides luminesce
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| Although some light is emitted, the phosphors retain sufficient energy in the form of a | latent image
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| The latent image is actually created by energy transfer during | photoelectric interaction
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| The latent image will lose about ___ % of its energy in __hrs | 25,8
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| Image acquisition begins with x-ray exposure to the | imaging plate
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| Radiation exposure causes___of the imaging plate but some of the energy of the beam is also stored on the plate. | Fluorescence
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| A latent image is stored in the imaging plate, similar to a image on film, but with a | wider latitude
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| Reading the imaging plate involves a finely focused laser beam that frees the trapped____, allowing them to return to a_____ energy state | electrons,lower
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| Residual image left on the imaging plate is erased by exposure to an____ ___ to release any remaining trapped electrons | intense light
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| The___ and ____ of an imaging plate can occur in a single processor unit | reading, erasing
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| The finely focused laser beam that scans each line of the imaging plate correlates to one | line spacing or pixel dimension
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| The number of ___ determines and affects the density and contrast of an imaging system | bits/ pixels
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| During processing the CR system must determine the ____of the part and the number of____ per plate | orientation, projections
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| raw data from scanning will have a range of values related to how much__ the plate received. | radiation
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| The areas outside the collimation lines will have the ____ exposure or value. | lowest
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| The area within the collimated field will have the____ values | highest
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| T/F A marker placed outside the collimation field will appear in the processed image. | F
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| T/F There are certain expectations that need to be met when placing more than one image per plate. | T
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| T/F The plate can't be programed and then used for a number of different scanning detection patterns. | F
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| During initial processing what is created form the image data | Histogram
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| The CR system finds the useful signal by locating the _ and _ singal within the anatomical regions of interest in the image | minimum, maximum
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| T/F Image processing will provide the proper gray scale, regardless of variations in kvp and mas | T
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| The appropriate anatomical menu is selected by the body part by the _ when the imaging plate is loaded into the reading unit. | Radiographer
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| The correct anatomical menu should be selected prior to processing the image plate; otherwise the image will not process the correct_ and _. | Density, contrast
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| It is critical to adhere to uniform positioning and collimation procedures when using a CR system. | T
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| T/F The reading system must be given consistent data to analyze if it is to provide consistent diagnostic quality results. | T
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| New generation CR readers store the _ data in the workstation. | Raw
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| Many manufacturers state in their technical usage information that _ has little effect on the visualization of image density | Mas
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| Diagnostic information content in digital radiology is generally___ than in conventional radiology if equivalent dose parameters are used. | higher
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| The_____ of the digital detectors and the capabilities of post processing allow us to obtain more information from the radiographic images then a film/screen system can. | wider dynamic range
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| Conventional films allows mistakes if a wrong radiographic technique is used: | images are too white or too black
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| Almost always, Digital technology provides user with a___since its dynamic range compensates for wrong settings even if the dose is higher than necessary | good image
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| Digital images can be numerically processed This is not possible in___ radiology!!. | conventional
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| ____ can be easily transmitted through networks and archived | Digital images
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| makes anatomic structures more visible and distinguishable | Contrast enhancement
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| results in smoothing of the structures | Contrast reduction
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| Another benefit to having a wider latitude or dynamic range as well as magnification | use windowing and leveling within this same image to see the various structures with different levels of density and contrast, Magnification of the entire image or specific structures
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| Factors that produce low contrast include | High KVP
No grid or inadequate grid efficiency
Inadequate beam limitation (i.e., collimation)
Increased part size or tissue thickness
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| with film/sceen,___ selection should be based on desired subject contrast and grid selection | KVP
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| when it comes to using CR plates: they have a___ (more than a film/screen cassette). | wide dynamic range
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| CR plates are especially sensitive to | fogging, from both scatter and background radiation
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| The increased latitude allows for correction of exposure errors,but as the.. | exposure error increases, image quality will decrease!
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| Basic principles regarding the production of poor____ when using film/screen do not change with the use of digital | low-contrast images
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| Digital can maintain a useful density over a____ then that allowable with film/screen. | wider latitude
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| Failure to use a high enough___ setting produces quantum mottle | MAS
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| quantum mottle is | grainy, reticulated image for which digital post processing cannot compensate
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| Adequate___ is required to activate any digital image receptor! | MAS
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| a minimum CR ___ or ___ is required by many radiologists to ensure they are diagnosing from an image that meets the minimum data requirements of the CR system. | sensitivity number,index number
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| Underexposures in digital results in a “too noisy” image or | quantum mottle
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| Overexposures in digital___ be detected unless patient dose measurements are performed | cannot
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| Over exposure in digital yields good images with unnecessary but | high dose to the patient.
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| Over range of digitizer (extreme over exposure) may result in___ with potential loss of information | uniformly black area
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| A lack of sufficient incoming data to process an image: | Quantum Mottle,also known as quantum noise.
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| How is Digital Radiography different from traditional film/screen systems? | Digital Radiography utilizes a reusable detector
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| Digital Radiography can be divided into two groups: | Computed Radiography (CR)
Cassette-based (indirect digital)
Direct Digital Radiography (DR)
Cassette-less (direct digital)
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| what has a rigid sheet with several layers that are designed to record and enhance transmission of the image from a beam of ionizing radiation | Photostimulable Phosphor Imaging Plates
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| The layers of a plate (PSP or IP) include: | a protective layer, a phosphor layer,a support layer, a conductor layer-
a light shield layer and backing layer-
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| insulates from “handling trauma” | protective layer
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| active component” photostimulable phosphor | phosphor layer
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| the base on which to coat the other layers | support layer
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| grounds the plate to eliminate electrostatic problems and absorb light to increase sharpness | conductor layer
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| prevents light from erasing data on the imaging plate or leaking through the backing | light shield layer and backing layer
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| In order for CR to function, the imaging material must have the ability to__ and__the image information in a usable form. | store,release
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| The imaging plate phosphor will absorb more___ than the rare-earth phosphor and film, | low-energy scatter
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| The imaging plate is more sensitive to scatter both__ and___it is sensitized through exposure to the x-ray beam. | before and after
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| what begins with an x-ray exposure to the imaging plate. | Image acquisition
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| Radiation exposure causes__ of the imaging plate but some of the___of the beam is also stored within the plate. | fluorescence,energy
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| The latent image is stored within the____, similar to a latent image on film, but with wider___ | imaging plate,latitude.
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| The incident x-ray beam produces a___ within the photostimulable fluorohalide (phosphors) | latent image,
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| CR utilizes the principle of | photostimulable phosphor luminescence
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| The imaging plate is scanned by a___ laser beam | helium-neon
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| These laser beam scan causes the phosphors to emit the stored latent image in the form of | light photons,
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| These light photons are detected by the photosensitive receptors and then converted to an | electrical signal.
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| This electrical signal is, in turn, converted to a unique digital value for that particular level of | luminescence
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| Reading the imaging plate involves a finely focused____ that frees the trapped ___, | laser beam,electrons
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| After reading the imaging plate the electrons to return to a | lower energy state
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| Electrons moving to a lower energy state release blue-purple____ in proportion to the absorbed radiation | light photons
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| light photons or visible light is converted into an ____ which is in an analog form. | electronic signal
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| analog signal must be converted into a____ before the computer can work with the image information. | digital signal
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| The finely focused laser beam that scans each line of the imaging plate correlates to one line___ or___ dimension. | spacing,pixel
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| It is recommended that CR plates be erased____, if not used, to eliminate unwanted noise. | daily
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| the degree of geometric sharpness or accuracy of recorded detail of the structure | SPATIAL RESOLUTION
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| The smaller the pixel, the___ the spatial resolution. | higher
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| optimal processing from an CR imaging plate The__and __ should be centered within each pattern, and collimation should be parallel and equidistant from the edges of the imaging plate. | beam,part
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| a graphical representation or diagram that is generated by dividing a scanned area into pixels and determining the signal intensity for each pixel. | histogram
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| The shape of a histogram will correspond to the specific__and__ used for an exam. | anatomy,technique
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| Kilovoltage for computed radiography will control____ similar to film radiography | contrast
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| The Fuji computed radiography (CR) system uses an S number to assist in evaluating exposure and are | INVERSELY PROPORTIONAL
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| Kodak’s CR indicator system is called the Exposure Index and It is directly proportional. | directly proportional
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| Most CR systems do not send all the data acquired by the image receptor to the post-acquisition system because some data represents exposure below the diagnostic imaging range, while other data represents exposure far above the diagnostic range | Data Clipping
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| post-processed by algorithms that eliminate the overexposed portion of the image receptor output | Grossly overexposed images
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| a compound that absorbs x-rays and converts the energy to visible light by fluorescence | scintillator
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| A good scintillator yields many light photons for each incoming x-ray photon; __ to __ visible photons out per 1kV of incoming x-ray energy are typical. | 20,50
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| Scintillators usually consist of a___ number material, which has high x-ray absorption. | high-atomic
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| Scintillators may be___ like phosphors or crystalline like cesium iodide. | granular
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