Digital imaging test 2 (Bennett) Flashcards

Cr
Terms Definitions
Does CR, DR, or both use computers to analyze and manipulate the image?
Both
What uses an image detector system that is cassette-less and hard-wired to a computer network?
DR
What term refers to general x-ray procedures as distinct from other digital modalities such as CT, MRI, and US?
radiographic
What takes place of film in CR?
Imaging plate
How does cassette in CR differ from F/S cassette?
CR cassette is simply a light-proof container that protects an imaging plate from light and handling
What is capable of storing an image formed by incident x-ray photon excitation of phosphors?
imaging plate
After reader releases light stored in imaging plate, the light is converted into a(n) ________, which is then __________
electrical signal; digitized
What is easy about changing from a F/S to CR system?
No room reconfiguration required
What is added to the workflow when you convert from a F/S to a CR system?
Work station and image reader (replace daylight processor)
In F/S, what allowed you to process films without a darkroom?
daylight processor
Does work station in CR increase or decrease throughput?
Decrease (because of time spent in front of computer)
Every CR system has an...
ADC (analog-to-digital converter)
At first, CR cassettes matched sizes of F/S cassettes. Now, CR is limited mainly to what sizes?
10x12 and 14x17
F/S cassette is designed to ___________ and to ___________
keep light out (to prevent imaging fogging); maintain film-screen contact
What type of cassette had lead backing?
F/S cassette
What measures F/S contact?
Wire-mesh grid
What material is CR cassette made of?
plastic
Why is CR cassette light-tight?
To keep accuracy of gathered data (not as concerned about light fogging image). Close association of high, intense light will erase image in CR
CR cassette protects...
imaging plate
Does CR cassette contain intensifying screens?
No
What does CR cassette have inside to protect against static electricity buildup, dust collection, and mechanical damage to plate?
Antistatic material (usually felt)
What type of backing does the CR cassette have, and what is its purpose?
Aluminum; to absorb x-rays
Imaging plate acquires and holds...
latent image data
An imaging plate is used in...
CR
What is imaging plate made of?
plastic
What layers may imaging plate include?
Protective, phosphor, reflective, conductive, color, support, and backing layers
The layers of the imaging plate may vary depending on the...
manufacturer
What is the outermost layer of the imaging plate?
Protective layer
What is protective layer of imaging plate made of?
Thin, tough, clear plastic
What protects phosphor layer of imaging plate?
Protective layer
What is active/functional layer of PSP?
Phosphor layer
What is active/functional layer of imaging plate?
Phosphor layer
PSP
photostimulable phosphor
What is phosphor layer of imaging plate made of?
Barium fluorohalide phosphors
What layer of the imaging plate may contain a dye to differentially absorb the stimulating laser light to prevent as much spread as possible?
Phosphor layer
Which layer of the imaging plate reduces light spread?
Reflective layer
Which layer of the imaging plate sends light in a forward direction when released in the cassette reader?
Reflective layer
In CR: Since light represents _______, light spread would be _____________
data; data degradation
Reflective layer may be _____ to reduce spread of stimulating light and escape of emitted light
black
Not all imaging plates have a ________ layer or a ______ layer
reflective; color
Reflective layer can cause loss of...
detail
What layer of the imaging plate absorbs and reduces static?
Conductive layer
What layer of the imaging plate consists of added dye between active layer and support layer?
Color layer
What is the purpose of the color layer of the imaging plate?
Light control (dye absorbs stimulating light but reflects emitted light)
What does the support layer of the imaging plate consist of, and what is its purpose?
Semi-rigid material; added strength
What does the backing layer of the imaging plate consist of, and what is its purpose?
Soft polymer; to protect back of cassette
Barcode label/sticker on cassette or imaging plate allows technologist to match image info with...
patient-identifying barcode on examination request
Why should imaging plates be read as quickly as possible?
To avoid losing image info, since energy stored in the IP dissipates over time
Device that extracts the latent image info from the imaging plate
reader
Does CR require a chemical processor?
No
Does CR require a darkroom?
No
After exposure, CR cassette is fed into a _____ that removes the _________ and scans it with a _______ to released the stored ____
reader; imaging plate; laser; e-
Does the reader use chemicals?
No
LASER
light amplification of stimulated emission of radiation
Laser creates and amplifies a...
narrow, intense beam of coherent light
Laser light is coherent because...
all the photons are traveling in the same direction at the same frequency
Laser beam passes through __________ to a(n) ____________ that directs laser beam to surface of imaging plate
beam-shaping optics; optical mirror
Laser scans across imaging plate multiple times in a process known as...
translation
Reader contains a ______ mechanism
drive
Translation can be divided into...
slow scan direction or fast scan direction
Laser beam direction
Fast scan
Direction of plate travel or of laser head
Slow scan
What refers to movement of laser across imaging plate?
Fast scan direction
What refers to movement of imaging plate through CR reader?
Slow scan direction
Scan process produces lines of light intensity information that are detected by a _______ that amplifies light and sends it to a _________
photomultiplier; signal digitizer
Translation speed of plate must be coordinated with...
scan direction of laser
What in the reader collects light?
Fiber optic collecting system (may or may not include photomultipliers)
All readers have ADC after the...
light-gathering mechanism (ex. photomultiplier)
What term refers to a device or system that represents changing values as continuously variable physical quantities?
analog
What digitizes the electronic signal in a CR system?
ADC
ADC assigns each pixel a __________ that corresponds to a level of brightness (and to its position)
numerical value
The entire image in CR is divided into a matrix of _____ based on...
pixels; brightness of each pixel
# of pixels in a matrix increases for the same field of view->Pixels must be ______ to fit into that area
smaller
Smaller pixels->______ spatial resolution
greater
Image in CR is digitized by both position (__________) and intensity (_________)
spatial location; gray level
What does gray level depend on?
How many photons struck the imaging plate in that particular location
Number of bits per pixel
bit depth
Larger bit depth->____ shades of gray possible->_____ detail the image can display
more; more
The available gray scale for image acquisition and display
bit depth
Bit depth is equal to 2^n where n is the...
number of bits
What does the erasure lamp in the reader do?
Bright light releases remnant/latent info (erases plate) before plate is reinserted into cassette
Does reader return all of e- to a lower energy state?
No, just most of the e-
Since imaging plates are very sensitive to background and scatter radiation, they should be...
erased to prevent a buildup of background signal
When do you need to run imaging plate on an erase cycle to remove background radiation and scatter?
Every 48 hours OR when in doubt about the presence of exposure to the plate OR if last time of erasure is unknown
CR readers have an _______ mode that allows surface of imaging plate to be scanned without recording the generated signal
erasure
Reader may contain ___________ (ex. laser filters) that vary from vendor to vendor
ancillary components
What is typical reader throughput?
50 cassettes/hour
Ability of the system to image small high-contrast objects
spatial resolution
What determines spatial resolution in CR (according to book, not Bennett)?
Phosphor layer thickness and pixel size (number of pixels)
Thinner phosphor layer in CR->_____ spatial resolution
higher
What is spatial resolution measured in?
lp/mm
What is the spatial resolution of F/S?
10 lp/mm
What is the spatial resolution of CR?
2.55-5 lp/mm (2.55 is average; 5 is best)
What predicts maximum spatial resolution of a CR system?
Nyquist frequency
What is one advantage of CR?
Contrast resolution
Can you obtain more recorded detail with F/S or CR?
F/S
___________ (number of recorded densities) is much higher/wider for CR, so loss in ______ resolution is made up for by increase in ______ resolution
Dynamic range; spatial; contrast
Most CR systems sample at __ lines per mm
10
To image a line pair, you must sample both ____ and ______
line; space
If you sample at 10 lines per mm, the maximum number of lp/mm you can image is __ lp/mm
5
In F/S, speed of system is determined by...
crystal type, size, and layer thickness
In F/S, you must choose a technique appropriate to _________. In CR, speed class can vary depending on __________
speed of system; what you select
________ represents the level of exposure to the plate required to deliver an acceptable image
Speed class (speed class of operation)
What indicates the speed class of operation?
Level of exposure received by imaging plate
Since speed class is determined by exposure to plate, you should select the _______ possible level of exposure factors to produce a quality image
lowest
After IP has been read, signal is sent to computer where it is _________->Data goes to a monitor where tech can _____ image, _________ it, and send it to _________ for analysis; and then send it to ________ for long-term storage
preprocessed; review; manipulate (post-process); quality control (QC) station (which may also be tech workstation); PACS
Post-processing of an image is not possible after...
it is sent to PACS
Prior to positioning patient and exposing IP, you must select _____ or _______ from the menu choices on your workstation
exam; body part
Selecting proper body part and position on CR workstation is important for the proper _______ to occur
conversion
Improper menu selections (in CR) may lead to...
overexposure of patient and/or repeats
5 areas to consider in CR imaging
-technical factors-equipment selection-exposure indicators-image data recognition-artifacts
What is the largest area of confusion and largest area of poor ALARA?
Technical factors
Anatomical programmer can adjust __________ depending on area you select and depending on system/vendor
contrast resolution
kVp range in CR
45-120 (60-110 is optimal because of the k-edge of the PSP)
kVp must be chosen for ________ and type and amount of _______ desired
penetration; contrast
In CR, mAs must be enough to provide proper...
phosphor stimulation
No amount of ____ will compensate for insufficient mAs; however, CR will allow it to compensate slightly for low mAs
kVp
For F/S: Toe of response curve means exposure is too _______. Shoulder of response curve means exposure is too _______.
light; dark
CR plates have a _____ exposure response curve (no toe or shoulder)
linear
Quantum mottle is a result of...
insufficient mAs
2 factors to consider when selecting CR imaging cassette
type and size
For systems that vary pixel size according to cassette size, use the ______ imaging plate possible for each exam to get the highest spatial resolution
smallest
2 types of imaging plates
high-resolution and standard resolution
High-resolution imaging plates are most often used for...
extremities, mammography, and other exams requiring increased spatial resolution
When sampling lines (scanning laser) and grid lines are parallel, what occurs?
Moire aliasing artifact
When does Moire aliasing artifact occur?
When grid lines and sampling lines are parallel
Is use of a grid more critical in F/S or CR?
CR (since CR IPs are very sensitive to scatter)
Grid selection factors are _____, ____, and ______
frequency; ratio; focus
Number of grid lines per cm or inch
Grid frequency
Higher grid frequency->_____ grid lines
Finer
Height of lead strips vs. space between lead strips
Grid ratio
Higher grid ratio->_____ scatter absorbed
More
Higher grid ratio->Positioning is _____ critical
more
Use a _____ grid ratio for portables; use a _____ grid ratio for Buckys
smaller; higher
What is the biggest grid problem?
Focus grids
What is the preferred SID now?
48"
_________ consist of lead strips angled to coincide with beam divergence and must be used within specific distances using a precisely centered beam
Focused grids
Most focused grids tap out under __"
48
Parallel grids do well at __"
48
Are parallel grids or focused grids less critical to beam centering?
Parallel grids
Reduction of the area of the beam that reaches the patient through the use of 2 pairs of lead shutters encased in a housing attached to the x-ray tube
collimation
Compton interactions (scatter) is more likely when _____ volume of tissue is irradiated and _____ kVp is used
large; high
High kVp->Greater chance of ______ interactions
Compton
Collimation results in better ________ due to reduced scatter fog
image contrast
Does collimation affect patient dose?
Yes; reduces patient dose
Adding a black background behind the image (in post-processing) around the original collimation edges to aid in viewing the image
shuttering
______ is aka black border
Shuttering
Shuttering helps in...
viewing the image
Always use lead markers at time of ______
exposure
Measurement of the amount of light given off by the imaging plate
exposure indicators
Amount of light given off by imaging plate is a result of the ___________ the plate has received
radiation exposure
Light from IP is converted into a signal that is used to calculate...
exposure indicator number
Is exposure indicator number a measure of patient dose?
No. It just indicates how much radiation was absorbed by the plate, which gives only an idea of what the patient received
__, __, and ___ are terms used by manufacturers to indicate amount of exposure
S, EI, IgM
Exposure range numbers represent the _______ to ________ diagnostic exposures
minimum; maximum
S value
sensitivity value
S values are all around 2 since...
CR is a 200 speed system
EI
exposure index
IgM
logarithm of median exposure
Higher S number->______ exposure
Lower
Higher EI number->_______ exposure
Higher
Higher IgM->_______ exposure
Higher
Image data recognition (exposure field recognition) is unique to...
CR
___________ establishes the data to be included in the image
Image data recognition
Process of image data recognition may be called...
"ROI finder," "segmentation," or "exposure data recognition"
Image recognition takes place through _________ that determine collimation borders and edges and histogram formation
computer algorithms
____________ determines edges, borders, and histogram relevant values
Image data recognition (exposure field recognition)
Graphical representation of the numerical data on the image plate
histogram
Graphic representation of the numerical tone values of an x-ray exposure
histogram
Histogram values are used to demonstrate the appropriate _______
shades of gray
4 image data recognition modes used by Fuji
-Automatic data recognition-Semiautomatic mode-Multiple manual selection mode-Fixed mode
Image data recognition mode in which image recording range is automatically determined
Automatic data recognition
Image data recognition mode in which collimation is automatically recognized
Automatic data recognition
In automatic data recognition mode, data recognition occurs...
as plate is scanned
Image data recognition mode in which standard histogram analysis is performed
Automatic data recognition
Image data recognition mode in which latitude value of the histogram is fixed, and only a small reading area is used; there is no collimation detection
Semiautomatic mode
Image data recognition mode that is used for smaller field sizes (ex. odontoid, L5/S1 spot, sinuses)
Semiautomatic mode
Part must be carefully ________ for semiautomatic mode of image data recognition
centered
Image data recognition mode in which the area of interest is selected by the technologist (and the image is derived from the selected areas imaged in semiautomatic mode)
Multiple manual selection mode (Semi-X mode)
Image data recognition mode in which user selects from 9 different areas on imaging plate
Multiple manual selection mode
Image data recognition mode which is useful in cross-table exams for which the body part may not align with automatically selected imaging plate region
Multiple manual selection mode
Image data recognition mode in which user selects exposure index, or sensitivity number, and the value of the latitude from a menu; there is no histogram analysis and no recognition of imaging plate division
Fixed mode
Image data recognition mode that makes IP act like film
Fixed mode
Image data recognition mode in which brightness of image directly reflects technique used
Fixed mode
Any undesirable densities on the processed image other than those caused by scatter radiation or fog
artifacts
5 common types of artifacts
-Imaging plate artifacts-Plate reader artifacts-Image processing artifacts-Printer artifacts-Artifacts caused by operator errors
Cracks in plate appear as areas of ________ in image
lucency
Adhesive tape residue can cause...
imaging plate artifacts
Static can cause dust and hair to stick to IP and cause...
imaging plate artifacts
Backscatter imaging caused by worn or cracked lead backing can cause...
imaging plate artifacts
Dirt on the light guide in the reader can cause...
horizontal white lines which are reader artifacts
Incorrect erasure lamps can cause...
reader artifacts
Moire pattern error is a...
reader artifact
Dirt/debris on mirror of laser in laser printer can cause...
fine white lines on image which are printer artifacts
Insufficient collimation is an ______ error
operator
Insufficient collimation can change the resulting ________ so it is outside the normal ________ for the body part selected
histogram; exposure indicator range
A backward cassette is an operator error that causes...
a white grid pattern on image
Underexposure is an ______ error that causes ______
operator; mottle
Overexposure _______ contrast
reduces
Digital imaging began with ____ and ____
CT; MRI
CR is based on the phenomenon of...
PSL
The most commonly used digital system is...
CR
The differences in F/S and CR are seen in...
the way the latent image is captured
F/S uses _________ as a scintillator
intensifying screen
Substance/object that emits light in response to an external stimulus
scintillator
CR uses the IR to store e- in __________
high-energy traps
In CR, response to x-ray interaction is seen as trapped ___ in a higher-energy _______ state
e-; metastable
PSL
photostimulable luminescence
Property of a material where light is emitted in response to external stimulation
photostimulable luminescence
What are used to store the latent image in CR?
Photostimulable phosphors
What screens are used in CR?
Storage phosphor screens (SPS)
SPS appears _____ because the small PSP particles scatter light excessively; such a scattering is called _______
white; turbid
SP
storage phosphor
PD
photodiode
___ is a 2-stage image acquisition system
CR
1st stage in CR image acquisition
Latent image is captured on PSP plate
2nd stage in CR image acquisition
Image data is extracted in reader
Does each image on the PSP plate have its own file, or does each whole PSP plate have its own file in the computer?
Each PSP plate is a separate file in the computer, no matter how many images are on the plate
Exposure is aka...
acquisition/capture
When x-ray beam exposes PSP, energy transfer results in excitation of ______ into a ________ state. About __% of these return to ground state immediately with prompt emission of ______. Those remaining return to ground state over time, causing latent im
e-; metastable; 50; light
The latent image in CR is formed by...
trapped e-
CR signal loss is objectionable after approx. __ hours
8
After 8 hours without processing, CR image...
is degraded so much that it is not of diagnostic quality
CR: Expose->________ and _______ (occur simultaneously)->_____ (not a stage of image acquisition)->Expose...
stimulate; read; erase
In CR reader, latent image is made visible by...
releasing metastable e- with a stimulating laser light beam
Does stimulation cycle of PSL signal acquisition transition all metastable e- to ground state?
No; some excited e- remain. Erasure lamps help to remove any residual latent image
If residual latent image remained on PSP plate, ________ could appear on subsequent use of IP
ghosting
What is it called when residual info from a prior image is shown on another image?
Ghosting/ghost images (NOT the same as a double-exposed image!)
What causes ghost images?
Overexposing the plate (makes it harder to erase plate) AND/OR improper/malfunctioning erasure lamps
IP should be used soon after _______ cycle has been completed
erasure
PSP can be ________ by background radiation
fogged
Components of reader include...
light collecting system, optics, mirror, track
Drive mechanism in reader moves IP at a slow steady rate (_____ scan)
slow
While IP is transported in slow scan direction, a deflection device like a mirror deflects the laser beam...
back and forth across IP (fast scan mode)
Fast scan and slow scan drive mechanisms are coupled so laser beam is _________ during retrace
blanked
Sampling and quantization process (simplified)
Plate scanned with laser, releasing trapped e- ->Light emitted->Light converted to electrical signal->Analog signal converted to digital signal
Optical features in reader include...
laser, beam-shaping optics, light-collecting optics, filters, and photodetector
In CR reader, _______ is the stimulator
laser
Laser in CR reader is a finely focused beam of _______ light
infrared
As laser beam intensity inc->Intensity of emitted signal ____
inc
Diameter of laser beam affects _____ resolution of CR imaging system
spatial
_________ of laser beam affects spatial resolution of CR imaging system
Diameter
As laser beam penetrates, it _______
spreads
PSP thickness inc->Laser beam spread ____
inc
Laser beam spreads as it travels to the...
rotating/oscillating reflector
_________ focuses light beam onto reflector in CR reader to keep beam diameter small and ensure high ___________
Lens system; spatial resolution
Beam-shaping optics keep beam _____, ______, _______, and _______ constant
size; shape; speed; intensity
Collectors in CR reader are...
fiber optics
Emitted light from IP is channeled into fiber optic collection assembly and directed at...
the photodetector, PMT, PD, or CCD
Where is light amplified and converted into an electric signal in CR reader?
Photodetector (usually a PMT or PD)
What prevents scattered laser light from reaching PMT in CR reader?
Filtration
What improves signal-to-noise ratio in CR reader?
Filtration
Optical filters allow only _____ light to reach photodetector while blocking __________ light
emitted; intense stimulated
Proper filtering improves signal-to-noise ratio. Signal is _______ light; noise is _________ light
emitted; stimulating
/ 254
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