Sensors and Digital Imaging pt. 1 Flashcards
The X-ray film market is expected to register a CAGR of —% over the forecast
period 2020-2025.
5.4
film packet contents (2)
lead foil
black cardboard
intraoral film size
0 - pediatric
1 – PA , pediatric
2 - Standard
4 - occlusal
film composition (4)
supercoat- thin layer of hard plastic
emulsion- gel and AG - halide crystal
adhesive
base- plastic
Chemicals used to form
elemental Ag from
silver halide salt
Chemical changes are (3) dependent
time, temperature
and concentration
what is a digital image?
Digital image can be conceived as a table with columns and rows,with
each cell (aka pixel) being assigned a number value which is then
assigned a gray intensity. The composite collection of pixel values
are used by a computer’s software processing ability to construct an
image for visual display
pixel
definition
derived from the words PEL (picture element).
A px (pixel) is the smallest portion of a sensor, image or
display that is capable of being recorded and then printed or
displayed.
Large amounts of information can
be stored in a small amount of
space
Convenience of space saving is
exponential for (2)
physical and
financial considerations
general steps in digital image formation (4)
X-ray shadow
Shadow image
detected by
digital sensor
Numerical pixel
values sent to the
computer
Digital image
on the computer
screen
Pixels are
electrified
Each pixel has a
pre-exposure electrical charge
X-ray photons that make it to the sensor change the
electric charge in those pixels
The thicker/denser the body part adjacent the sensor, the
less the x-photons can affect
the electrical charge
The net effect is that there is a shadow of electric charges on the sensor reflective of the
—- of the body part.
thickness/density
Electric charge value of each pixel is converted to a
numerical value
i.e, digitized
Pixel values sent to the computer for processing
The computer assigns a
to each number
gray value
The gray values are displayed in a
visual format on a display monitor
different types of dental digital radiography (3)
historic (indirect)
indirect (semidirect)
direct
Historic(Indirect)
(3)
Flatbed scanner
Slide scanner
Digital cameras
Indirect(Semidirect)
(1)
Phosphor Storage Plate (PSP)[aka Photostimulable Phosphor Storage Plate (PPSP)]
Direct
(2)
Charge-Coupled Device
(i.e., CCD)
Complementary Metal Oxide Semiconductor
(i.e., CMOS)
indirect digital radiography
* Loss or alteration of information due to-
partial volume averaging
• The first film-like sensor was introduced in 1994
(2)
• Hybrid system
• Photostimulable phosphor (PSP) plate
components of a semidirect digital system (6)
Laser scanner
Screen monitor
CPU, Server, or PACS
Printer- EPR- PACs
X-ray source
PSP plate
skipped
principle of PSP detector
→ X-ray
→ PSP plate coated with crystalline
halide emulsion made up of BaFBrEu2+
i.e. Europium doped Barium Fluorobromide
producing a latent image of ionized phosphors
→ scanned with red laser beam
→ emits fluorescent light from excitation of
valence electrons in ionized fluorophophors
→ intensified by a photomultiplier tube
→ light intensity is converted to digital data
expose to strong light to erase residual
images by neutralizing charges in ionized
fluorophophors
reuse
skipped
PSP plates and accessories (air techniques)
(3)
ScanX PSP plates
available in same
sizes as dental
film
Barrier Envelopes
Plate Transfer Box
skipped
PSP plate scanners (3)
ScanX (Air techniques)
ScanX Intraoral (Air techniques)
DenOptixScanX (Gendex Dental Systems)
components of direct digital system
Analog-to-Digital Converter for CCD only
Screen monitor
CPU, Server, or PACS
Printer- EPR- PACs
Digital interface cord
CCD/CMOS
X-ray source
skipped
sensor components (4)
electronic substrate
CMOS imaging chip
fiber optic face plate (FOPO)
CSI scintillator
CCD/CMOS area
Sensors have:
(2)
1) External Size
2) Internal Active Area – the portion of the sensor
producing the image.
