digital imaging Flashcards
digitization
to represent a particular object in form of numerical digits
digital image
radiographic image represented in a digital format
direct digital imaging
radiographic images obtained by xray exposure of solid state image detectors
2 types of direct digital imaging
charge coupled device (CCD)
complementary metal oxide semiconductor (CMOS)
pixel
picture element (2 dimensional structure that makes up a voxel)
voxel
3 dimensional structure
advantages of CCD
instant availability of images
better image quality
durable
consistent image quality
disadvantages of CCD (4)
expensive
bulky
wire attachment
smaller active area compared to film
advantages of CMOS (5)
instant availability of image durable consistent image quality less expensive than CCD slightly more rugged than CCD
disadvantages of CMOS
expensive
bulky
wire attachment
smaller active area compared to film
indirect digital imaging
radiographic images obtained by exposing a digital image detector and scanning or digital photo capture of film radiographs
3 types of indirect digital imaging
photostimulable storage phosphor plate (PSP)
scanning a film
taking digital photos of film
which type of indirect digital imaging is best for pediatric dentistry?
PSP
phosphor
europium doped barium fluorohalide (BaFBr:Eu)
which layer absorbs xray photon?
phosphor layer
the number of electrons stored is proportional to
xray photons
advantages of PSP
well tolerated
economically priced
disadvantages of PSP (5)
short life span read out should be done ASAP requires processing semi-dark room is required requires exposure to bright light for erasing previous image before reuse
contrast resolution
ability to distinguish different densities in radiographic image
8 bit equals how many densities
256
16 bits equal how many densities
65536
human eye is capable of distinguishing ____ gray levels
60
less than ____ gray levels are distinguishable in dental office
30
spatial resolution
ability to identify 2 objects placed very close to each other
d speed film: more than ___ line pairs/mm
digital image: __-___ line pairs/mm
normal untrained eye: __-__ line pairs/mm
20
7-24
4-6
detector latitude
ability of an image detector to capture a range of xray exposures of tissue densities ranging from gingiva to enamel
what is useful range of detector latitude?
0.5-2.5
detector sensitivity
ability of detector to respond to a smaller amount of radiation
monitor consists of what 3 things
display device
circuitry
enclosure
what is part of the display device
cathode ray tube
thin film transistor
organic light emitting diode
image processing
an operation that acts to improve, restore, analyze or change a digital image
what does image processing improve?
diagnostic accuracy
diagnosis
image analysis
designed to extract important info from an image
tools for measurement
digital rulers
densitometers
trabecular bone pattern (osteopenia and osteoporosis)
advantages of digital imaging
instant images lower radiation dose consistent quality high signal/noise ratio image manipulation digital subtraction radiography
disadvantages of digital imaging
relatively lower resolution than film
quality depends on monitor and printer
higher initial cost
DICOM
digital imaging and communication in medicine
why DICOM
Portability
Integrity
Efficiency
spatial resolution (CCD, Film, CMOS, PSP) ranking
Film
CCD, CMOS
PSP
exposure latitude ranking
PSP
CCD, CMOS
Film
receptor dimensions ranking
CCD, CMOS
PSP, Film
time required for image acquisition ranking
PSP, Film
CCD, CMOS
image quality is…
subjective
image adjustment/processing is…
equal
cost
high initial cost of digital systems
reliability
digital systems are more susceptible to problems
image storage and retrieval
back up is critical for digital systems
transmission of images ranking
PSP, CCD, CMOS
Film