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QM Registry Terms

Digital Radiography and PACS

acceptance testing testing that occurs to ensure equipment or processes are functioning within acceptable limits
archive historical collection of images stored in PACS
archive query software function that allows historical information to be gathered from digital storage, i.e. multiple exams, range of dates, or by pathology
aspect ratio ratio of width of the monitor to the height of the monitor
automatic data recognition processing mode in which computer analyzes data according to set parameters
automatic rescaling occurs when exposure is greater or less than the optimal amount to produce a diagnostic image; it is the effort of the computer to "fix" exposure errors
backing layer soft polymer that protects the back of the cassette
barium fluorohalide photostimulable phosphor located in the imaging plate
basic input/output system (BIOS) contains a simple set of instructions for the computer to perform several basic functions, i.e. boot up, run hardware diagnostics, interpret keyboard signals, and so on
central processing unit (CPU) small chip found on the motherboard that manipulates data sent from a program; brains of the computer
cesium iodide scintillator (CsI) newer type of amorphous silicon detector that uses this; scintillator is made by growing very thin crystalline needles (5 μm wide) that work as light-directing tubes, much like fiberoptics
charge-coupled device (CCD) coupling devices that act as cameras that link phosphor signals to a signal
collimation type of wire that consists of a center wire surrounded by insulation and then a grounded shield of braided wire; shield minimizes electrical and radio frequency interference
color layer area within the conductive layer where electrons are trapped
computed radiography (CR) or cassette-based digital radiography is the digital acquisition modality that uses storage phosphor plates to produce projection images
conductive layer layer of material that will absorb and reduce static electricity
continuous quality improvement alternative set of terms for total QM that includes maintenance of equipment, image acquisition, and processing standards
detective quantum efficiency (DQE) measurement of how efficiently a system converts x-ray input signal into a useful output image
detector size actual physical size, length, and width of x-ray detector
digital imaging and communications in medicine (DICOM) global information technology standard that allows network communication between modality and PACS
digital imaging any imaging acquisition process that produces an electronic image that can be viewed and manipulated on a computer
digital radiography (DR) or cassette-less systems use an x-ray absorber material coupled to a flat panel detector or a charged-coupled device to form the image
direct capture digital radiography these devices convert incident x-ray energy directly into an electrical signal, typically using a photoconductor as x-ray absorber and a thin-film transistor as signal collection area, and send electrical signal to computer for processing and viewing
direct conversion conversion of x-ray energy to electrical signals without the light-conversion step
display workstation generally a display monitor where postprocessing occurs or where images can be viewed
distributed system PACS workflow where acquisition modalities send the images to a designated reading station and possibly review stations
dot pitch measurement of how close the dots are located to one another within a pixel
dry imager printer that uses heat to develop the film
edge enhancement enhancement occurs when fewer pixels in the neighborhood are included in the signal average; the smaller the neighborhood, the greater the enhancement
exposure index (EI) term used by Kodak to express exposure values
exposure indicator number numerical representation of the amount of exposure, usually the mean value
field effect transistor (FET) device within an iamging detector that isolates each pixel element and reacts like a switch to send the electrical charges to the image processor
film digitizer device that scans hard copy x-ray images and converts them to digital images
fixed mode postprocessing mode in which the user selects exposure index: latitude is set by the menu selection; no histogram is generated, and there is no recognition of imaging plate division; resultant image is direct reflection of exposure value
flat panel detector detector that consists of a photoconductor, which holds a charge on its surface that can then be read out by a thin-film transistor
focused grid grid in which the scatter absorbing lead lines are tilted so that at a prescribed distance, the lines will converge
grid frequency number of grid lines per inch
grid ratio ratio of height of grid line to width of interspace material
high-pass filtering technique for enhancement of contrast and edge that amplifies the frequencies of areas of interest that are known and suppresses frequencies outside the area of interest
histogram graphic representation of all of the digitally recorded signals of a digital ex-ray exposure
image sampling amount of information gathered from pixel storage
image stitching process of "sewing" together multiple images to form one continuous image
imaging plate thin piece of plastic with several layers of material that capture and store image data
indirect capture digital radiography devices that convert absorb x-rays & convert them into light; light is then detected by area-charged-coupled device or thin-film transistor array in concert w/photodiodes, & then converted into electrical signal thats sent to comp for processing & viewing
indirect conversion two-step process in which x-ray photos are converted to light and then the light photons are converted to an electrical signal
laser amplification of stimulated emission of radiation, a device that creates and amplifies a narrow, intense beam of coherent light
latitude amount of error that can be made in exposure factor choice and still result in the capture of a quality image
logarithm of the median exposure (IgM) term used by Agfa to express exposure to the imaging plate
look-up table (LUT) reference histogram of luminance values derived during image acquisition
low-pass filtering result of averaging each pixel's frequency with surrounding pixel values to remove high frequency noise; the result is a reduction of noise and contrast; useful for viewing small structures i.e. fine bone
matrix rectangular or square table of numbers that represent the pixel intensity to be displayed on the monitor
modulation transfer function ability of a system to record available spatial frequencies
moire grid line or image noise pattern that occurs when either the alignment of the grid to the laser scan direction is incorrect or when spatial frequency is greater than the Nyquist frequency; a wraparound image will result
Nyquist theorem when sampling a signal such as the conversion from an analog to digital image, the sampling frequency must be greater than twice the bandwidth of input signal so that reconstruction of original image will be nearly perfect
picture archival and communications system (PACS) consists of digital acquisition, display workstations, and storage devices interconnected through a network; networked groups of computers, servers, and archives that can be used to manage digital images
phosphor layer layer of photostimulable phosphor that "traps" electrons during exposure; usually made of phosphors from the barium fluorohalide family
photometer device used to measure the luminescence of areas on the monitor
photomultiplier electronic device that amplifies light energy
photostimulable luminescence (PSL) light produced by a phosphor when stimulated by light or x-ray photons
pixel basic picture element on a display
protective layer very thin, tough, clear plastic covering in the imaging plate for protection of the phosphor layer
quality control (QC) subdivision of QM that focuses on equipment functions
quantum mottle failure of imaging system to record densities usually caused by a lack of x-ray photons
quantum noise recording error in the digital image
raster zigzag electron scanning pattern
reflective layer layer in imaging plate that sends light in a forward direction when released in cassette reader; this may be black to reduce spread of stimulating light and escape of emitted light; some detail is lost in this process
refresh rate measure of how fast the monitor rewrites the screen or the number of times that the image is redrawn on the display each second
resolution number of pixels contained on a display
S, sensitivity number term used by Fuji Medical to express exposure
semiautomatic mode postprocessing mode in which latitude value of histogram is fixed, & only small reading area is used; no collimation detection; proper kV must be used to maintain subject contrast because latitude value does not change
shuttering used to blacken out the white collimation borders in a digital image, effectively eliminating veil glare
smoothing AKA low-pass filtering; result of averaging each pixel's frequency with surrounding pixel values to remove high frequency noise
spatial frequency resolution amount of detail or sharpness in a digital image
speed (in conventional radiography) determined by size and layers of crystals in the film and screen
speeds (in CR system) reflection of the amount of photostimulable luminescence given off by the imaging plate while being scanned by the laser
support layer semirigid material in the imaging plate that gives the imaging sheet some strength
thin-film transistor (TFT) photosensitive array, made up of small (about 100 to 200 μm) pixels, converts light into electrical charges
wet imager printer that uses chemicals to develop the film
window image manipulation parameter that changes screen image brightness usually through the use of a mouse
Created by: sspatel