Test 2 Flashcards
what do digital images lack compared to film-based imaging?
visual cues
Digital images lack the ___ ____ of film-based imaging
visual cues
what can digital imaging compensate for?
what can it not compensate for?
scatter (fairly well)
quantum mottle
(does well with excessive information, but not lack of info)
what is the goal of radiologic technique?
ensure that adequate signal reaches the detector
_____ ______ will always appear for all imaging system with not enough photons have reached the imaging receptor
quantum mottle
what is the exposure latitude of film based?
digital?
-30% to +50%
-50% to +400% (leads to dose creeping) excessive dose for no reason)
what are the benefits of CR? (4)
adaptability
not sensitive to light
different size imaging plates
different speed class
what is exposure latitude?
margin of error in setting techniques
(range of techniques)
it takes ____ _____ the normal exposure to saturate a digital image
8-10 times
what are the two special considerations for CR?
CR plates lose 25% of the image after 8 hours
CR plates are sensitive background radiation and should be erased every 24 hours
what are the limitations of CR? (3)
processing time
sensitive to background radiation
prone to artifacts
what are the benefits of DR?
operates at a consistent speed class
high compatibility with PACS (MIMPS)
increased department efficiency
what are the limitations of DR?
only can image a single image at a time
bulky, difficult to manage image receptor
what is detector element (DEL)?
what is its function?
core of the DR system
DELs capture radiation energy and transfer it into digital information
what are the three part of a DEL?
what are there functions?
detector surface (largest part of DEL, absorbs/captures radiation energy)
capacitor (stores the electrical energy from detector surface)
thin-film-transistor (TFT) gateway that releases the electrical charge once the image data is read)
Direct conversion systems use _____ _______ to:
Direct has?
amorphous selenium
convert x-rays into an electrical charge
has higher spatial resolution
what happens when the detector surface decreases in size?
spatial resolution increases
capacitor & TFT cannot decrease in size
the efficiency of the detector (fill factor) decreases & technique must increase
indirect conversion systems use ____ ____ to:
indirect has higher?
amorphous silicon
capture the energy of light from phosphor screen made of cesium iodine
efficiency & therefore lower dose
what is photostimulable phosphors?
the core of the CR system
barium-fluorobromide & barium-flurochloride crystals ____ with _____
doped
europium
After ___ hours an unprocessed PSP will lose ___ of the latent image
8 hours
25%
what is a fast scan?
laser beam rapidly moves across the CR plate in rows (crosswise)
what is a slow scan?
CR plate is removed from the cassette and pulled into the processor (lenthwise)
what is the stimulated phosphorescence?
gives of light energy when struck by x-rays & or stimulated by a laser beam (stores & releases)
what does the photomultiplier tube amplify?
light signal from the light channel guide and coverts the signal into a digital signal (electrons)
Light emitted by the PSP is channeled by the _____ _____ to the ______ ______
light channel guide
photomultiplier tube
CR is exposed to ___ ____ to:
white light
erase all remaining image data and the plate is returned to the cassette
Luminescence refers to:
any emission of light in general
phosphorescence is the:
delayed emission of light sometime after the original stimulus (exposure) has occurred
(glow in the dark)
fluorescence refers to the:
immediate emission of light under stimulation
what is detective quantum efficiency (DQE)?
detector efficency that can covert input exposure into an output (image)
stimulated phosphorescence requires:
re-stimulation
what is pitch?
the distance from the center of one DEL/pixel to center of the adjacent DEL/pixel
liquid crystal display (LCD) monitor benefits:
lightweight
portable
inexpensive
generate less heat
long life
less reflective
perfect geometry
Display systems are the weakest link:
in the imaging chain
what is polarization?
polarizing lenses that use a grid of long slender aligned chains of iodine molecules
The pixel is in the _____ _____ allowing:
on state
Light to pass through, if no electrical current is applied to the pixels
what are LCD monitor limitations?
viewing angle (steradian)
no true black
warm up time (long 20-30 minutes)
how much better spatial resolution does monochrome display monitors have compared to color monitors?
monochrome has three times the spatial resolution of color
Spatial resolution of a active display matrix is often stated in terms:
of the total number of pixels on the entire screen such as 3 megapixels
brightness decreases when temperatures are below:
or higher than:
60 degrees
80 degrees
what is ambient lighting?
lighting in the radiologist reading room should be 2-25 lux, approximately 1/4 of natural background light
what is MIMPS?
medical image management and processing system
what is processing?
a control computer (server) that directs medical images where they need to go
what is CIS?
what is it responsible for?
clinical informational system (site wide)
patient scheduling, billing, & assigns patient number
what is acquisition?
actual imaging equipment (CR, DR, CT, MR)
or scanning device (analog to digital converter- ADC)
what is RIS?
what is the main purpose?
radiology information system
assigns accession number (unique to patient, time, and exam)
what is a HIS?
hospital information system
what is AIS?
administrative information system (individual department)
what is EMR?
electronic medical record
(pt chart for a single institution)
what is the display?
images sent via a network to a viewing station such as the radiologists reading room/home, office, or even patient portal
what is storage?
long-term storage in an optical jukebox, raid, or individual disk
what is lossless compression?
what is lossy compression?
medical images (8:1)
nonmedical images (10:1)
what is the DICOM?
who developed it?
digital imaging and communication in medicine (standard)
developed by ACR/NEMA
what is a DICOM header?
extensive & detailed information stored behind the scenes for every image
what are the common DICOM commands?
DICOM get worklist
DICOM query
DICOM send
DICOM print
prefetch- pulling prior studies for comparison (radiologists workstation)
what is communication language?
common computer language so all components of a PAC system can communicate, regardless of vendor
what is meta-data?
image data that cannot be easily seen by the end user
what is HL7?
common language for medical data
what is true header?
data that is displayed on the image and can be seen by the end user
what are mobile generators?
constant potential generator with little to no voltage ripple
In mobile radiography the CR is _______ to the IR?
perpendicular
In mobile radiography for air/fluid levels:
horizontal beam, patient is as upright as possible
what are low grid ratios?
5:1- 6:1
what is Cieszynski’s law?
1/2 angle between part & IR
what is minification gain?
image is minified from the input phosphor to the output phosphor
individual pixels are closer (together) & appear brighter
overall brightness of the fluoroscopic image is increased by two processes:
minification gain
flux gain
what is the minimum distance from tube to tabletop?
30cm (12 inches)
what are the components of the image intensifier?
large glass tube
input phosphor: convert x-ray radiation to light
photocathode: converts light into electrons (1:200 ratio)
electrostatic focusing lens: focus electron stream towards the anode and output screen
anode: attract electrons from photocathode and accelerates them towards the output screen
output phosphor: small (2.5cm) convert electron into light, image is seen upside down
what is flux gain?
conversion of light photons to electrons in the photocathode results in more light photons in the output phosphor
what is magnification mode?
adjusting the FOV (field of view) by moving the focal point
what does magnification mode accomplish?
smaller region of patient anatomy imaged
the image is magnified
spatial resolution to that anatomical part is increased (pixels per inch is increased)
image is dimmer due to fewer photons reaching the output phosphor
mA is automatically increased to compensate
patient dose is increased
what is automatic stabilization of brightness?
maintaining the brightness of image to compensate for part thickness, contrast, and patient position
what is automatic gain control?
increasing the electrical signal from output phosphor to the display monitor
pincushion distortion:
pronounced curve near the edges
what is automatic brightness stabilization (ABS)?
adjustment of the radiologic technique
what is the image intensifier subject to?
how can we compensate?
what is normal mA?
quantum noise
increase mA to compensate
around 5 mA
distortion is due:
to curved input phosphor
increases collimation reduces:
scatter production and increases contrast
vignetting is brighter:
in the center
what is charge-coupled device?
a small, flat plate about 1 inch n size
higher image quality than CMOS
what is the complimentary metal-oxide semiconductor (CMOS):
what is the main pro?
a small, flat plate about 1 inch in size
cheaper than CCD (coupled charged device)
what are dynamic flat-panel detectors similar to?
similar detectors to DR (indirect amorphous silicon; direct amorphous selenium)
What are the matrix sizes for dynamic flat-panel detectors?
large matrix sizes (2048 x 2048)
what do dynamic flat-panel detectors operate under?
a pulsed mode called “pulse-progressive mode)
what are the qualities of a dynamic flat-panel detector?
much higher mA
higher SNR than image intensifiers
less distortion
higher contrast
What is the exposure rate for fluoroscopy radiation protection?
should not be more than 50 mGy/minute
shall not be more than 100 mGy/minute
fluoroscopy has a ______ ____ timer that?
5-minute
alerts operator
In fluoroscopy tube to tabletop not less than?
30 cm (12 inches) for mobile c-arm
38 cm (15 inches) fixed
what is the normal fps in fluro?
30 fps
