the size of the image files to increase the speed of the network transfer of the images
Another test for data integrity is?
periodically pull up images from the archive to make sure the same images sent initially are still in the study after archival
A constant measure to be monitored is?
whether all images completed @ the modality make it to PACS
Image transfer speed should be monitored?
from the modality to PACS & from the archive to a workstation
Dry laser Imager Daily/weekly QC?
1. Monitor each film
2.print test patteren
3.observe the printed test
4.measure steps using densitometer
5. complete prventative maintenance
wet Laser Imager Daily/ weekly QC?
1. monitor each film
2.paint a test pattern from PACS
3.observe-steps of test pattern
4.measure- steps of test pattern
5. monitor- processing mechanism
6.complete all preventative maintenance
photometer
device used to measure the luminescence of areas on the monitor
The highest quality monitors are?
the radiologist workstation
The Joint Commission is formerly known as?
the joint commission on the accreditation of Healthcare organizations (JCAHO)
Most health care institutions are accredied by?
the joint commission (TJC)
TJC is?
voluntary but necessary to obtain medicaid certification, hold certain licenses, obtain reimbursement from insurance companies & recieve malpractice insurance
CQI?
continuous quality improvement
TQM?
total quality management
QUality assurance?
a plan for the systematic observation & assessment of the different aspects of a project, service, or facility to make certain that standards of quality are met
QA services are focused around what?
people & service
Most QA activities will produce?
quantitative data that can be analyzed
Quantitative data can be used for what?
to monitor the processes & determine whether the process is working as it should & whether the standard of quality has been met
Quality Control?
a comprehensive set of activities designed to monitor & maintain systems to produce a product
Why are QC measurements taken?
~ensure procedures are performed safely
~appropriate for the pt
~performed efficiently
~produce a high-quality image
Why are tests performed on a room?
make sure that all the parts are functioning properly such as the collimator, generator & focal spots
_________ measures are required by law to maintain the license for the room or dept.
QC
Most QC activities are part of what?
a QA program
Monitor has a direct effect on?
quality of the image that is presented to the radiologist for reading or to the referring physician
Often the weakest link in the digital imaging chain?
the monitor
AAPM suggests that testing be performed?
on acceptance & annually
ACR suggests QC tasks be performed?
atleast monthly
What test is performed to ensure continuity of measurements?
society of motion pictures & television engineers test pattern
ACR?
American college of Radiology
What is the most important concept to understand with CQI?
all levels of people within the organization must be involved in the process of improvement
CQI focuses on?
improving the process or system within which the people function as team members rather than focus on an individuals work
The QA/QC programs focus on?
maintaining a certain level of quality, not improving to a higher quality
If the process is good?
healthcare workers will follow it and service will be good
Continuous Quality Improvement?
focuses on process rather than people
Error maintenance?
~if corrective action must occur
~performed by service personel employed by the vendor
Acceptance testing is used?
to determine whether the equipment is performing within the vendors specifications as promised
When is acceptance testing performed? By whom?
~Before newly installed or majorly repaired equipment can be accepted by the dept
~Designated tech, radiation physicist, or service personnel
Digital imaging systems have _______ DQE latitude than screen/film systems?
wider
Each pixel contains a photodiode and does what?
generates electrical charges
absorbs light from scintillator
What is spatial frequency resolution?
detail or sharpness
In direct conversion DR TFT;the info is?
discharged onto the data colums & is read out with dedicated electronics
DR technology has increased DQE over CR bc it does not have the _______ conversion step & bc of this, less dose is required than for CR & higher Quality images are produced?
light (no light increase)
In flat- panel detectors that use indirect conversion technology convert _______ to _______ _______.
xray photons to electrical signals
DR is what?
~hard-wired
~cassetteless
~detectors are permanently enclosed inside a rigid protective housing
WHat if the transistor that includes a photosensitive array and small pixels?
thin-film transistor
Low KVp gives a _______ histogram & high Kvp gives a ______ histogram?
wider; narrower
Process of direct capture dtectors?
1.xray photons are absorbed by the material
2.Photons are immediately converted into an electrical signal
3. Electrical signal is detected by TFT array
What is high-pass filtering?
when frequencies of areas of interest are known, those frequencies can be amplified & other frequencies suppressed
Loss of detail in a digitally processed image occurs bc of the number of conversions. T of F.
True
Excessive digital processing can affect spatial resolution in cassetteless system which can lead to what?
excessive noise
Exposure latitude for digitally imaging is less than that of film/screen imaging. T or F.
false; greater
Archive Query?
software function that allows historical info to bo gathered from digital storage, such as multiple exams, a range of dates, or by pathology
Typically, ________ pixels/ row are adequate for most diagnostic examinations?
2000
Specialized silicon integrated circuits are?
connected along the edges of the detector matrix
(Direct conversion DR TFT)
Used to describe images recorded on an electronically readable device?
digital radiography
The DR plate has a radiation-conversion material or scintillator typically made of a- Se. This material absorbs x-rays & converts them to electrons, which are stored in the ______ detectors?
TFT detectors thin-film transistor
When dealing w/ Amorphous silicon detectors photodiodes are coated with what?
a crystalline cesium iodide scintillator
a rare-earth scintillator
field-effect transistor?
Isolates each pixel element
reacts like a switch to send the electrical charge to the image processor
TFT?
thin film transitor
A histogram displays the useful signal by locating the ______ (S1) and _______ (S2) signal within the anatomical region of interest on the image.
minimum (S1); maximum (S2)
Explain edge enhancement
occurs when fewer pixels in the neighborhood are included in the signal average; the smalle the neighborhood, the greater the enhancement
explain what you would do to the Look-up table (LUT) to increase or decrease contrast & what you would do to change the brightness (MAS)?
contrast=by changing the slope of the graph
brightness=by moving the line up or down the y-axis
Image stitching?
process of "sewing" together mulitiple image to form one continuous image
If too few pixels are sampled, the result will be _______ resolution?
lack
MTF?
(modulation transfer function)
ability of a system to record available spatial frequncies
A device that acts like a camera in an indirect conversion detector is known as ______ _______ device.
charge-coupled devices (CCDs)
Which of the following has the greatest spatial resolution?
film/screen radiography
Pixel pitch refers to the ?
the spacing between the pixels
DR includes?
computed radiography & direct or indirect methods of digital image capture
An FET or silicon TFT does what?
isolates each pixel element
reacts like a switch to send the electrical charges to the image procssor
Flat-panel detectors consists of?
a photoconductor such as amorphous selenium, which converts the xray photons directly into electrical signals
Flat-panel detectors consists of?
a photoconductor such as amorphous selenium (converts the xray photons directly into electrical signals)
When dealing with Amorphous silicon detectors, the light photons are?
converted into an electric charge by the photodiode arrays
The device that acts like a switch to send electrical charges to the image processor; Also isolates each pixel?
field-effect transistor (FET)
Explain smoothing (AKA low-pass filtering)
smoothing occurs by averaging each pixel's frequency with surrounding pixel values to remove high-frequency noise
How efficiently a system converts the x-ray input signal into a useful output images(this is the measurement of the percentage of x-rays absorbed) is known as?
detective quantity efficiency (DQE)
Data collected within the collimated area is represented by a ________?
the vendor- specific exposure data
Amorphous selenium?
Holds a charge on its surface that can then be read out by a TFT
During Indirect conversion light strikes the amorphous silicon allowing what?
the conduction of electrons into the detector
Automatic rescaling means that images are produced, regardless of the amount of exposure with uniform contrast & density. T of F.
False; with uniform brightness & contrast
A line of TFT switches allows?
electrical charge info to discharge when switches are closed
Each pixel contains what?
a photodiode
What is image sampling?
amount of information gathered from pixel storage
The DQE of detectors changes with changes in _____?
KVP
What does the transport layer of the OSI model do?
makes sure data packets are sequenced correctly and that they do not contain errors
In conventional radiography was film used or phosphor plates?
film
What are the different parts that make up a PACS system?
reading stations
physician review stations
web-access
tech quality control stations
administrative stations
archive system
interfaces
A network in which all devices are physically attached to & listen for communication on a single wire
BUS
Special type of memory chip that uses small rechargable or lithium battery to retain info about the PCs hardware while comp. is on?
CMOS
BIOS oversees what?
the basic functons of recieving & interpretting signals from the keyboard & interchanging info with various ports
CMOS?
complementary metal oxide semiconductor
In CR & DR mAs has more influence on what?
Image processing LUTs
With conventional radiography density is controlled by?
mAs
What are some common In-put devices?
keyboard
mice
microphones
bar code readers
touch screens
image scanners
CPU stands for what?
central processing unit
What are the 3 main types of CD/DVD drives available in todays market?
ROM (read-only memory)
R (write once-read many)
RW (read & write many times)
In CR & DR, contrast is primarily controlled by?
linear, wide exposure latitude; kvp & LUTS
In conventional radiography contrast is primarily controlled by what?
kvp & film response curve
What are the components of the motherboard?
CPU basic input
output systems
memory
bus ports
complementary metal oxide semiconductors (CMOS)
The intermediary between the operating systems & the hardware?
BIOS
a computer that manages resources for other computers,servers, & networked devices; many also house applications, provide storage for files or manage various other networked tasks
a server
CPU?
a small chip found on the motherboard
Aspect ratio?
the ratio of the width of the monitor to the heighth of the monitor
What are the different types of monitors?
cathode ray tube (CRT)
liquid crystal display (LCD)
plasma screen
Operating system?
the software that controls the computer hardware & acts as a bridge between applications & hardware
The measurement of how close the dots are located to one another within the pixel;
smaller the dot the finner the resolution
dot pitch
Small area of network with a series of cables & wireless access points that allow comp. to share info & devices on the same network(much faster)
LAN
In Direct Capture, typically using a photoconductor for what?
as the xray absorber & send the electrical signal to the computer for processing & viewing
CR was first introduced commercially in the United States by whom?
Siemens
In what decade was MRI first introduced? CT?
early 1980's; 1970's
What was the last modality to incorporate digital imaging?
mammography
What is used in Radiology?
CRT; bc of its superior resolution
Scatter radiation is more sensitive with what type of system?
DR & CR
Where was the first full scale PACS system?
VA medical center in Baltimore in 1993
What is WAN?
*wide area network
A network that spands a large area-city, state nation, continent or world
Resolution?
number of pixels on a display
digital imaging & communication tech standard that allows network communication between modality & PACS?
DICOM
No computer has ultimate control over another, this describes what?
peer-to-peer
2 types of keyboards are?
click/soft
centralized computer that controls the operations of the network
client based
Has a centralized storage & retrieval on the network
server based
What does PACS stand for?
picture archival & communicaton system
An individual collection of dot triads (a group of one red, green, & blue dot)
pixel
Device with 2/3 buttons that allows the user to move comp cursor to activate & perform function within software?
mouse
What is digital radiography/
cassetteless system
Explain indirect capture?
devices absorb x-rays
provides interface between the network & computer
network interface
DICOM is accepted where?
almost universally accepted standard for exchanging medical images amoung networked medical devices
sends data only to devices to which the data are directed
network switch
A physical wired connection from one network segment to another?
network bridge
Advice found on a network that requests services & resources from a server?
thin-client
Sound card can be in what form?
expansion card or built in
DICOM
digital imaging & communications in medicine
The network layer breaks up data & what?
decides which network path the frame will take to its destination
Network card
*AKA* network interface card*
will have an RJ-45 adaptor jack @ the rear of PC
enables PC to connect to other on same network
What advantage does DR have over conventional & CR?
It is done right at the room's console
Images appear in 3 to 5 seconds (this allows the tech to know if the image needs to be repeated)
With PACS you can review stations from where?
In other departments in the hospital
LUT stands for what?
Look-up table
A programmable electronic device that can store, retrieve, & process data?
a computer
What is a binary code based on?
1s & 0s
Delivers all electricity to the PC & contains a fan to cool the computer & also contains transformer that converts the current to the appropriate one for that device?
power supply
Main repository for programs & documents on a PC
Hard drive
DR takes how long for the image to appear?
3 to 5 sec
What is the most common connection medium for a LAN?
Twisted-pair wire (cat 5)
What are real-time operating systems found?
modern x-ray equipment
2 or more objects sharing resources?
a network
What are the 2 component role classifications?
peer-to-peer (considered equal)
server/client based
Explain the processing of film in conventional radiography?
Image processed by chemicals
Image appearance based on tech factors & film/screen combination
What are some of the image processing capabilities that the PACS reading stations can have?
It allows Radiologists to remain @ their workstations & do 3D reconstructions of a CT, stitch a complete spine together to perform specialized measurment functions for scoliosis, some orthopedic surgeons can plan jt replacement surgery before even beginning the operation
What is another name for exposure latitude?
dynamic range
Maps the image gray scale values into some visible output intensity on a monitor or printer film?
LUT
Most modern computers use?
SDRAM-DDR
~for higher graphics some may use RDRAM
What are some factors to consider when designing a PACS system for an institution?
volume of pts
#of areas where images are interpreted
locations where images are viewed by physicians other than radiologists
money available for purchase
Output devices?
monitors
printers
speakers
Indirect capture converts energy into what?
converts into light
What is the info highway of the computer?
BUS
A PC with a 3.0-GHZ CPU would have a system clock that would what?
tick 3 billion times per sec
Most modern keyboards connect using what kind of connection into the back of the box?
IBM programming system 2 (PS/2) connection
What is a box?
the computer encasement mode from a heavy metal
What is the most fragile type of network connections?
fiberoptic cable
What was the early storage capacity?
10 WB could be accessed in about 80 ms
Information storage capacity of a DVD is what?
9.4 single sided
17 GB double sided
Converts the incident xray energy directly into an electrical signal
direct capture
What is known as the brain of the computer?
central processing unit (CPU)
Computer that can work independently of the network & process & manage its own files
thick-client
Explain the processing of the film in CR?
Processed by light
Takes place in a quality control station based on preset image algorithms
The personal computer's box (AKA microprocessor)
CPU
The measurement of how fast the monitor rewrites the screen or the # of lines that the image is redrawn on display each sec
refresh rate
RAM?
random access memory
Why would some keyboards use a USB?
bc of its versatility & ease
What is the current capacity?
modern-100GB
access speed of 8.7 ms
Different types of RAM are?
DRAM
EDO
RAM
VRAM
SRAM
SDRAM
SIMM
DIMM
ECO
What are found in configurations?
bytes
Give examples of bytes?
128 MB, 512MB & 1GB
What is the location of the system clock?
CMOS
Which 2 modalities were easily converted to digital imaging?
ultrasound & nuclear medicine
A series of connections, controllers, & chips that creates the info highway of the computer
BUS
Contains all the circuitry 4 recording & reproducing sound on the PC
sound card
A rectangular or square table of #s that represent the pixel intensity to be displayed on the monitor
matrix
What are the 2 major geographic categories for networks
local area network (LAN) ~~~ Least expensive
WAN- wide area network
What does the network interface plug into?
The motherboard
Network in which the devices are connected in a circle
RING
What is the biggest advantage of wireless networks?
mobility & convenience
Agreed on set of rules that allows data to travel along the network; most send in packets from one device to another
network protocol
made by using either infrared or radio frequencies as its means of communication
wireless connections
Cable that is similar to telephone wiring
Coaxial cable
Coaxial cable is used for what? where is it found?
cable television that is run into a house; in the network infrastructure throughout a building
~sturdiest wire used~
faster then its metal counter parts, more expensive & much more fragile; uses glass threads to transmit data on the network consists of a fiberoptic core that is surrounded by a plastic protective case
fiberoptic cable
similar to a telephone wire,except it consists of four twisted pairs of copper wire that are insulated & bundled together with an RJ-45 terminator
twisted-pair wire
Temporary memory?
RAM
Memory is measured in?
bytes
When is the BIOS used?
contains a simple set of instructions for the computer used by the micrprocessor during the boot up process of the comp. to help bring it to life
also runs the start-up diagnostics to make sure the peripherals are functioning properly
BIOS=
Basic input/ output systems
Memory is generally talked about in?
kilobytes
megabytes
gigabytes
terabytes
the largest circutory board inside the computer
motherboard
What are the functions of a box?
holds the components in a relatively cod, clean, & safe environment
should the outside environment from the ratio frequncies being emitted by the electronic components of the computer
Made up of 8 bits & is the amount of memory needed to store one alphanumeric character
byte
a single unit of data
bit
A machine language
binary code
A collections of connectors sticking out of the back of the PC that link adaptor cards, drivers, printers,scanner,keyboards,mice, & other peripherals
ports
How is conventional radiography & CR similar?
both use cassette & are rated the same in the terms of ease & efficiency
A bucky apparatus is replaced w/ what?
a detector
the digital acquisition modality that uses storge phosphor plates to produce projection images (cassette-based)
computed radiography
moving images via telephone lines to & from remote locations
teleradiology
Digital imaging was first used with what? By whom?
the intro of the computed tomography; Godfrey Hounsfield
Used to store info currently being processed with the CPU?
memory of the computer
Early PACS were developed by whom?
U.S. military
Digital imaging?
an electronic image that can be viewed & manipulated on a comp; can be sent through a couputer network to a host of locations
What is the 1st step in acquiring an Image in CR?
the remnant beam interacts with electrons in the barium fluorohalide crystals contained within the imaging plate
when the exposure is made, this interaction gives energy to electrons in the crystals allowing them to enter the conductive layer where they are trapped in an area of crystals known as the color or phosphor center~ this describes which step in acquiring an image?
Step #2
The cassette is fed into a reader that removes the imaging plate from the cassette & scans it w/ a laser to release the stored electrons~ this describes which step in acquiring an Image in CR?
Step #3
the atoms or molecules of a crystal are excited so that more of them are at high energy levels rather than low energy levels~ this describes which step in aquiring an image?
Step #4
Surfaces at both ends of the laser cantainer reflect energy back & forth as atoms baombard eachother , stimmulating the lower energy atoms to emit secondary photons the same frequency as the bombarding atoms~this describes which stpe in acqiring an image?
step #5
As the energy builds, the atoms discharge as a burst of coherent light~this describes which step in acquiring an image?
Step #6
Laser beam passes through beam-shaping optics to an optical mirror thaat directs the laser beam to the surface of the plate~ this describes which step in acquiring an image?
step #7
The gray level is determined by what?
how many photons struck the imaging plate in that particular location
The image is digitized by?
position & by intensity
Explain what the phosphor center is?
electrons are trapped in an area of crystal
Grid construction can be described by what?
grid frequency & grid ratios
Typical # of pixels in a matrix can range from?
2500 X 2500
Each pixel contains bits of info & the # of bits per pixel defines the shade of each pixel & this is known as?
bit depth
Where is info about a grids construction?
tube side of grid
What happens as the plate moves through the reader?
it is scanned multiple times & this is called translation
Horizontal white lines may be caused by?
dirt on the light guide in the plate reader
In conventional Radiography how is speed determined?
by the size & layers of the crystals in emulsion
What is the exposure indicator number?
how much radiation is absorbed by the plate or in pt
The latitude value of the histogram is fixed & only a small reading is used~ this describes which mode?
Semiautomatic mode
What happens if you use the wrong imaging plate size?
decrease in resolution
Using an imaging plate that is much larger than the part being examined will _______ resolution?
decrease
Exposure indicator for Agfa?
TgM
What causes quantum mottle?
a grainy appearance due to insufficient light being produced
What will the image look like if you have insufficient light produced by the imaging plate phosphor?
grainy/quantum mottle
Do you use more Kvp with conventional radiography screens or CR systems?
CR systems
What is the range of kvp that can be used with CR?
45-120
In the early days of CR, what the kvp values set at?
70
kvp must be chosen for _______ & the type & amount of ________ desired?
penetration; contrast
CR Imaging plates are erased by what?
flooding the plate with bright light
How often should imaging plates be erased?
every 48hrs
Typical cassette through put is?
50 cassettes/ HR
The process of scanning the moving imaging plate?
translation
The laser scans the imaging plate in what kind of pattern?
raster
The laser beam passes through _______ to an optical mirror that directs the laser beam to the surface of the imaging plate?
the optics
Coherent light is formed by the laser bc the photons travel in what direction?
same direction
During laser beam formation, both ends of laser energy back & forth so that the atoms _______ eachother?
Bombard
What is the purpose of the barcode label?
for pt info
In which type of grid pattern could a cross table work?
linear Grid pattern
Crossed or cross-hatched?
lines that run @a rt angle to one another
Lead lines run in only one direction in which Grid?
Linear grid
Most popular grid pattern? Why?
Linear grid; allows for angulation of the tube along the length of lead lines
What are the 2 types of grid pattern?
linear
cross-hatched
The linear pattern of the lead lines of a grid are?
Grid pattern
What is the ratio of the height of the lead strips to the distance between them?
grid ratio
What separates lead lines?
radiolucent interspace material typically made of aluminum
When is a grid used?
when the anatomic part being imaged is 10cm or more (knee) & more than 60 kvp is appropriate for the exam
The more shades of gray, the more what?
detail the image can display
Kilovoltage peak, mAs & distance are chosen in exactly the same manner as for ______ _____ radiography?
film screen
Grid frequency?
number of lead lines per unit length in inches, centimeters or both
Which type of grid requires more beam centering?
focused
Relationship between height of strips & space between them?
grid ratio
Image recognition is accomplished through complex mathematical computer algorithms, and if the improper part of position is selected the image will be displayed improperly. It results in improper______ & ______?
contrast & density
Histogram is?
numerical values of the xray exposure
Shuttering is?
black backgrounds is added (post exposure manipulation)
Collimation to a smaller area does what to Compton interaction?
decreases
Grid lines per inch is what?
grid frequency
What type of grid info is located on the tube side?
type of interspace material used
grid frequency
grid ratio
grid size
info about the range of SID
Grid use for CR examinations is more critical than in film/screen radiography bc CR....
imaging plates are very sensitive to scatter radiation
What is the moire' artifact in what & why?
if the grid lines & scanning layer are parallel
they should be perpendicular
The higher the # of pixels in a matrix, the higher the what?
image resolution
What happens as the # of pixels in a matrix increases?
the smaller the pixels have to be to fit into that area
the smaller the pixels
the greater the spatial resolution
The electronic signal is digitized by?
an analog to dogital converter
Why are mirrors used?
to ensure that the beam is positioned consistently
Translation can be divided into 2 directions?
slow scan direction
fast scan direction
The trapped electrons escape what layer?
active layer
The red light scans the plate is what pattern?
a raster pattern & gives energy to the trapped electrons
What scans the imaging plate?
the laser
What directs the laser beam to the imaging plate surface?
the laser beam passes through beam shaping optics to an optical mirror that directs the laser beam to the surface of the plate
What is spatial resolution?Lower in cassette-based or CR?
detail; lower in cassette based
Each pixel contains bits of information called?
bit depth
If a pixel has a bit depth of 8, then the # of gray tones that pixel can produce is?
2 to the power of the bit depth or 256 shades of gray
Some CR systems have bit depths of?
10 or 12 resulting in more shades of gray
2 to the power of 12 would result in 4096 shades of gray
The bit depth is a factor in determining what?
the quality of the image
A bit value of 21 or one represents what?
a black & white image
When was the grid invented? By whom?
1913; Gustave Bucky
What is a grid?
device that has very thin interspaced lead strips intended to absorb scatter radiation emitted fom the pt b4 it strikes the IR
Grids are made up of what?
lead strips or lines that have a precise height, thickness, & space between them
Grid ratio formula?
Grid ratio=h/D
Why should good collimation practices be applied?
bc if its bad it affects the histogram
Exposure indicator for Fuji?
S or sensitivity number
High-ratio grids do what?
remove or clean up more scatter radiation than lower-ratio grids & increase contrast
The phosphor layer is made of phosphors for what?
Barium fluorohalide
Bit depths determine the shades of gray which the gray level is a factor in determining?
the quality of the image
What directs the laser beam to the imaging plae surface?
the laer beam passes through beam shaping optics to an optical mirror that directs the laser beam to the surfaces of the plate
Devices that create & amplifies a narrow, intense beam of coherent light
laser
Where photons are traveling in the same direction @ the same frequency?
Coherent
The laser light is emitted @ what?
2eV
The active layer is where the electrons emit what?
visible blue light at an energy of 3 ev as they relax
The entire image is divided into what?
a matrix of pixels based on the brightness of each pixel
Logarithim of medium expose, Agfa uses
IgM
ADC?
analog to digital converter
fast scan direction
describes the movement of laser across the imaging plate
Slow scan direction?
describe the movement of the imaging plate through the CR reader
2eV is necessary for what?
to energize the trapped electrons
Backscatter from the cassette/ detector influences what from creating images?
dark lines artifacts; grid lines
When switching from conventional radiography to computed radiography? What must be adjusted? why?
tech factors; bc we are using a difficult speed; speed changes mAs; kvp for penetration
What is a laser?
scans the imaging plate
Different layers of the imaging plate?
protective layer
phosphor or active layer
reflective layer
color layer
support layer
backing layer
Aliasing?
when spatial frequency is greater than the Nyquist frequency & the sampling occurs less than twice per cycle; info is lost & a fluctuating signal is produced
The layer the bit depth, the more what?
shades of gray possible
What does a beam deflector do?
moves the beam rapidly back & forth across the imaging plate to stimulate the phosphors
The ADC assigns each pixel a?
value that corresponds to the level of brightness
Fixed mode?
good for cross-tbl hips
similar to film screen
user selects the exposure index or sensitivity # and value of the latitude
What are the components of the CR cassettes?
durable,lightweight plastic material
backed by a thin sheet of aluminum~absorbs xrays~
antistatic material(protects against static electricity, build up, dust,& mechanical damage)
CR system speeds are a reflective of what?
amount of PSL given off by the imaging plate
What are 2 things that determines the selection of the CR cassette?
type & size standards & high resolution
Area of interest is selected by the tech & the image is derived from the selected areas imaged in semiautomatic mode~ this explains?
multiple manual selection mode
What are other names for a laser?
helium-neon laser beam
solid-state laser diodes (more recent systems)
Automatic data recognition mode automatically adjusts what?
the image recording range is automatically determined & adjust reading:lattitude & sensitivity
The light collection optics do what?
direct the released phosphor energy to an optical filter & then to the photomultiplier
Overexposure for carestream?
>2500
Overexposure for Agfa?
>2.9
Underexposure for Agfa?
<2.1
position=
spatial location
underexposure for carestream?
<1600 tabletop
<1800 bucky
intensity=
gray level
Support layer?
semirigid material that gives the imaging sheet some strength
Sends light in a forward direction when released in the cassette reader; may be black to reduce spreed of stimulating light & the escape of emitted light; & some detail is lost~ this describes which layer?
reflective layer
located between the active layer & the support that absorbs the stimulating light but reflects emitted light~this describes which layer?
color layer
conductive layer?
absorbs & reduces static electricity
A phosphor layer?
aka~active layer~
layer of photostimulable phosphor tht "traps" electrons during exposure
usually made of phosphors from barium fluorohalide family
4 common artifacts?
plate artifacts
plate reader artifacts
image processing
printer artifacts
Backing layer?
soft polymer that protects the back of the cassette
Allows the tech to match the image formation with the pt identifying barcode on the exam request? This explains what?
Barcode label (aka barcode sticker)
In Cr speed is determined by?
size & layers of crystals in the film & screen
a graphic representation of the numerical tone values of an xray exposure
a histogram
Kvp must be chosen for?
penetration & the type & amount of contrast desired
In early days of CR, kvp minimum values were set at?
about 70 kvp
Kvp values now range from?
around 45 to 120
Quantum mottle?
aka quantum noise
when suddicient light is produced, the image is grainy
Exposure indicator for carestream?
(EI) or exposue index
Collimation results in increased what? why?
contrast; as a result of reduction of scatter as fog
Bc of high sensitivity of CR imaging plate to scatter?
using a grid is key
Printer artifacts?
fine white lines may appear
What is the plate reader artifact?
horizontal white lines caused by dirt
Kvp, mAs, & distance are chosen?
in exactly the same manner as for conventional film/screen radiography
A wavy artifact caused by grid lines that are projected onto the imaging plate when using stationary grid? (Grid selection)
