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CR and DR

QuestionAnswer
__________ means having no definite shape. Amorphous
Semi-conductor material which means allows some flow of electrons between atoms. silicon
Direct conversion detectors to detect exit radiation and form latent image. selenium
TFT thin film transistors; electronic switch to allow charges to be collected at each pixel.
Automatic rescalling software that adjusts gray scale values in histogram
Number of shades of gray bit depth
How is bit depth calculated? 2 to the n power; n= 8; 2 to the 8th power = 256 shades of gray
Bit depth is also known as ______ _______. Contrast resolution
Dynamic range range of exposures over which a detector can acquire image data
Detective Quantum Efficiency (DQE) ability to detect or absorbe x rays (dose level required for optimal image)
Field of view or detector size useful acquisition area of imaging device
Software must detect collimated edges for proper histogram analysis. beam part alignment latitude
Histogram identifies all densities on an IP; pattern varies for body part
Unwanted density image noise
Spatial resolution ability to image an object faithfully
Measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution modulation transfer function
Look Up Table (LUT) results image with correct contrast and brightness; maps adjusted data through s curve
How is the LUT adjusted? By changing window width or range after initial processing
Number of pixels in rows and columns Matrix size
Highest spatial frequency that can be recoreded by a digital detector. Nyquist Frequency
Pixel pitch distance from the center of one pixel to the center of another pixel
Photodiode electronic element that converts light into electronic charge; indirect
photoconductor TFT detector that converts x ray directly into electrons without photodiode
Pixel picture element
Processing algorithm mathematical codes used by software to provide image
3E picture element of tissue voxel
_____ _____ determines resolution. pixel size
What are the five things that affect spatial resolution? time, SID, OID, FSS, IR
Fourier transformation mathematical method to convert data
What is being described:indirect capture, cassette-based, film less Computed Radiography
What are the five layers of the cassette based image plate? backing, base, anti-halo/reflective, phosphor, protecftive
What is the purpose of the backing layer? protects from handling artifacts; contains bar code info
The base is made of what material? polyester
What is the purpose of the base? To support the phosphor layer.
This layer prevents the IRD laser light from penetrating but allows reflected light to be emitted to strike phosphor to produce latent image anti-halo/reflective layer
What is the PSP layer made of? barium fluorohalide doped with europrium
Which layer captures the latent image? phospor layer (photostimuable phosphor layer)
Image created after exposure but before developing. latent image
What layer provides protection and a cleaning surface? protective layer
What are the steps of the PSP IP luminance? 1. Stored energy is released to photomultiplier tube and produces light;2. light converted to electrical energy;3.analog to digital conversion;4. digital signal sent to computer
Exposed film is ____ more exposable to light. 8x
IRD image reader device
What are some advantages to using an Image Plate for digital radiography? indefinite life, hold image up to 48 hrs, cassette does not need to be light tight,
What is the most common compression ratio? 1:1-1:3
What happens when the IP is placed within the IRD? 1. pre-read: sets boundaries of collimation 2. main read: scanned by laser that causes phosphors to emit stored latent image in form of light photons
S value # proper range of exposure ; 100-200
If the s value is over 200 the image is _______, and if the s value is under 100 the image is ________. Underexposed, overexposed
Is the s value # and exposure direct or indirectly related? indirect
Dose Area Product (DAP) digital radiography systems proper range of exposure
Image noise is ________ related to contrast. inversely
Is it beter to have a high or low signal to noise ratio? high which will decrease noise
Window level controls _______ . Their relationship is _______. density; direct
If you increase your window width, what will happen to your contrast? decrease (indirectly related)
Smoothing software function that reduces noise
Edge enhancement artificial increase in contrast of displayed image at an edge
TFT thin film trnsisistors - collects electronic signal as a matrix
DICOM standars Digital Imaging and Communications in Medicine; system of standards that permits a wide range of digital imaging programs to talk to one another ex. Konica to communicate with GE
HL7 health level 7; standard needed to allow HIS to communicate with RIS (Meditech to PACS)
PACS Picture Archiving and Communication system; sotrage and transmission for digitized images
PACS can be manipulated by: windowing, enlargement, tissue density readings, subtraction
Created by: sr4095 on 2009-01-08



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