DR & CR test

What is   spatial resolution?	ability   to define or separate 2 objects close togetherspatial resolution of 0.1 mm means that a lesion that is 0.1 mm can be   discerned
Exposure   factors are usually (higher/lower) w/ digital systems vs. film-screen   systems.	higher
What is   main difference b’twn film-screen systems & digital systems?	method   by which radiation is detected after x-rays pass thru patientdigital: x-ray exposure measured on electronic medium & converted to a   digital image in DICOM format
What   are the characteristics of CR?	computed   radiography $60-100K-CR cassettes are physically similar to film cassettes but contain an imaging   plate rather than intensifying screens & film -imaging plates must be read in a plate reader before x-ray exposure   information is sent to computer: ~90 s/plate -images better than w/ film (better latitude): as good as DR?
What   are the characteristics of DR?	direct   digital imaging $100K+imaging plate is independent of any cassette (built directly into x-ray table   or is portable) -imaging plates send signal measured from x-ray beam directly to a computer   –> faster image generation than w/ CR -excellent quality image
What   are some advantages of digital radiography systems?	-better   image contrast: easier to see some lesions -very forgiving of radiographic technique settings: less retakes d/t exposure -post-processing: can adjust blackness & contrast after the fact -clients will be impressed -can transmit images electronically for consulation -more convenient storage -no more lost images, assuming backup -don’t have to maintain darkroom, buy film, etc. -wide latitude (dynamic range)
What   are some disadvantages of digital radiography systems?	-don’t   have degree of spatial resolution possible w/ film-screen radiography: of   little clinical relevance -initial investment can be considerable -must be compatible w/ rest of hospital system
What is   PACS?	picture   archiving & communication system (PACS): centralized computer storage   systemprovides storage, dissemination functions, & links images w/ demographic   data
What is   DICOM?	digital   imaging communications in medicine (DICOM): specific image file format   analogous to JPEG and TIF formats commonly used in manipulation & storage   of digital camera images-must have DICOM viewing software to view files -file sizes are very large compared to regular digital photos -make sure your images are really DICOM compliant: some vendors change files   slightly so they aren’t compatible w/ all viewers
Inherent   detail in digital rads (is/is not) as good as with film based rads.	is NOTit is the improved contrast resolution that appears to give digital rads more   detail
What is   latitude (dynamic range)?	range   of exposures that result in useable imageenables the viewing of both soft tissues and bone on the same image without   repeat exposures at different techniques, as would be needed for a   film-screen system
More   pixels/area = (greater/less) detail	greater

What is   the makeup of a digital image?

-all   digital images are composed of a grid of rows & columns (matrix) of tiny   picture elements called pixels
-each pixel has a color or shade of gray
-most exposed pixel in a digital rad is assigned black, least exposed pixel   is assigned white, regardless of technique

What is   digital radiography?	recording   a map of x-ray transmission throught patient in a digital file -file is viewed as a digital image -conventional x-ray machines are usedit is not photopgraphing radiographs with a digital camera or running rads   through a scanner
How is   a digital image made?	computer   prepares a row by colume matrix of digital data file -each row X column intersection is termed a pixel (picture element) -each pixel is assigned a color in a digital camera and a shade of grey in a   radiographrows X columns = matrix size more pixels/area = greater detail more pixels = bigger file size
What is   a DICOM file?	Digital   Imagine COmmunications in Medicine-need DICOM viewing software to view -very large files
What is   digital radiography	computer   radiography – image plate in cassette like housingdirect digital radiography – flat panel detector
How   does computer radiography work?	x-ray   -> patient -> detector -> reader -> digital signal -> computer   DICOM file output
How   does direct digital radiography work?	x-ray   -> patient -> detector -> digital signal – > DICOM file output
What   are the components of computer radiography?	-cassettes   appeal similar to film-screen -cassettes must be processed in plate reader; 90sec/plate -images better than film -most labor intensive digital system
What   are the components direct digital radiography?	-no   cassette to process -image available immediately -types –CCD (charged couple device) –Flat Panel -indirect digital detector -direct digital detector
What is   the benefit of a CCD system?	-image   quality is a function of light collection, lens and number of pixels in   camera chip -light collection and lens is most crucial*hard to retrofit so usually have to purchase entire unit including x ray   tube and table
What   are the benefits of flat panel digital radiographs?	-no   cassettes, camera or lens -immediately after exposure, image is viewable and ready to archive -excellent quality image -image plate is portable but subject to damage
What is   the detail with digital imaging?	detail   as good with digital although it looks it at first glance there are other advantages that offset the slight reduction in spatial   resolution
What   are the advantages of digital imaging if the detail isn’t better?	-no   darkroom, film, envelopes -no exposure latitiude -contrast optimization -post processing -consultation -professional image
What is   exposure latitude?	the   extent to which a film, image or flat panel can be over or underexposed and   still achieve an acceptable result
What is   contrast optimization?	the   range of light intensities a medium can capture
T/FLow exposure image is more grainy appearance or more noise on digital   imaging?	true
What is   the advantage of imaging post processing?	ability   to change image contrast and blackness after acquisition
What   are still problems of digital imaging like with traditional radiographs?	positioning motion radiation safety

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The   ability to display two or more closely spaced objects as separate images	Spatial   Resolution
The   size of the relevant image displayed on the cathode ray tube (CRT)	FOV
Through   application of software programs, possible to assign pixels a different gray   scale value	Gray   scale enchancement
Mathematically   measures image against original object: 0 represents no image, 1 represents   perfect image	Modulation   transfer function
Aberrant   movements of electrons in electonic equipment seen as flashes of light (snow)   that degrades the image	Electronic   noise
Analog   signal sampled twice per cycle by ADC to gain accurate digital signal	Nyquist   Criterion
Displaying   small differences in subject contrast	Contrast   resolution
The   number of shades of gray assigned to the pixles	Dynamic   range
Determines   the number of density values available in each pixle. If affects density   (brightness) and contrast of system and is controlled by the ADC	Pixle   Depth
Loss of   image quality caused by random variations in the number of photons striking   the IR	Quantum   Mottle
The   number of densities from black to white on the x axis, the number of each   density on the y axis	Histogram
A   pre-set “ideal histogram” for each projection	Look up   table (LUT)
CR   provides optimal brightness and enhanced contrast	Normalization
A high   “S” number indicates a need to move the center point (Sm) over   ____.a. more b. less	a. more
“S”   values greater than 400 indicates _______________.a. Overexposure b. Underexposure c. Perfect exposure	b.   Underexposure
“S”   values greater than 400 will demonstrates _________.a. Quantum Mottle b. Improved MTF c. Lose of contrast	a.   Quantum mottle
Three   different type of reference histogram models used for LUT’s include one that   must have a direct exposure “spike” to locate S2. This is a:a. Type 1 b. Type 2 c. Type 3	a. Type   1
Histogram   shape is NOT influenced by…a. Type of exam b. Patient positioning c. mAs d. Type of generator	c. mAs
Which   of the following does NOT use thin film transistors (TFTs).a. Indirect photostimuable phospher imaging plate system b. Direct selenium flat panel imaging plate system c. Indirect silicon flat panel imaging plate system	a.   Indirect photostimulable phospher imaging plate system
CR or   DR? [1] Uses cassettes-   more familiarity for technologists [1] More adaptability   for positioning and technique	Computed   Radiography
CR or   DR? [1] Direct hookup to   the computer- no cassettes [1] Attached to a   table/chest bucky, contains a grid, and AEC sensors [1] Flexibility of   positioning limited [1] No ability to   split fields for multiple views [1] Increased patient   throughput [1] Higher detective   quantum efficiency (DQE)	Digital   Radiography
Does   comptued or digital radiography use Indirect Photostimulable Phosphor Imaging Plate Systems (Computed Radiography)?	Comptued   Radiography
The_______   _____ ______ is designed to look and act to perform many functions of standard cassette	Computed   Radiography
The   computed radiographic (CR) cassette….a. Comes in many of the same sizes as standard film cassettes b. Can be used with tabletop or bucky c. Can be used with manual or AEC techniques d. All of the above	d. All   of the above
Name   some features of a CR cassette	Aluminum or plastic Low absorbing carbon front Back panel has lead foil- backscatter Has a memory chip in one corner to   download information on the exam and patient Front and back lined with felt to   reduce static electricity and cushion plate
PSP   stands for…	Photostimulable   phosphor
IP   stands for…	Imaging   plate
How   thick is an CR plate?	1mm in   thickness
Which   layer in a CR plate is supported by a firm base and protected by a thin   plastic layer?	The   active phosphor later
Name   the following Layers
The   ______ layer and/or __________ layer grounds static charge; reverses light   emissions	Refletive   and or conductive layer
What   type of emulsion must be facing forward?	Single   emulsion
What   are some common phosphers?	Europium   activated barium fluorohalides
What is   the average energy (keV) of 80 KVP beam?	35
True or   false: Digital screens will absorb more low energy scatter thus the plate is   senesitive	True
Since   Photostimulable phosphor (PSP) absorb more low energy radiation than radiographic film they are more……..	More   sensitive to scatter both before and after exposure than radiographic film. Thus, Masking is needed to achieve   optimal images
In a   Latent image, where are the electrons stored?	Electron   pattern is stored in active layer of exposed IP
How is   a latent image made?	Energy transferred to photoelectrons Several photoelectrons liberated Liberated electrons have extra energy Blue-violet light given off by   fluorescence More electrons freed by photoelectrons
In a   latent image Fluorohalides absorb beam through ____________ interactions	Photoelectric
In a   Latent Image Production, Some electrons get trapped in the fluorohalides to create holes at the   Europium site, this is called…?	Electron   Holes