Sensors and Digital Imaging part 1 Flashcards
dental film packet, D speed film:
slower- more radiation
dental film packet, F speed film:
faster- less radiation
film packet contents
moist/light proof sleeve, lead foil (protects from scatter radiation), and black, light-proof paper wrapper folded around film
film composition:
1
2
3
4
- supercoat- thin layer of hard plastic
- emulsion- gel and Ag- halide crystal
- adhesive
- base-plastic
during film processing, chemicals are used to form
elemental Ag from silver halide salt
during film processing, chemical changes are ____, ___, and _____ dependent
time
temperature
concentration
digital image can be conceived as a table with columns and rows, each cell (pixel) being assigned:
a number value which is then assigned a grey intensity
in a digital image, the composite collection of pixel values are used by a
computer’s software processing ability to construct an image for visual display
derived from the words PEL (picture element)
pixel
smallest portion of a sensor, image or display that is capable of being recorded and then printed or displayed
px (pixel)
what are the general steps in digital image formation
- x-ray shadow
- shadow image detected by digital sensor
- numerical pixel values sent to the computer [pixel values assigned a number which ten corresponds to a gray scale value]
- digital image on the computer screen
pixels are electrified.
each pixel has a ___________ electrical charge
pre-exposure
in digital image formation, x-ray photons that make it to the sensor change the
electrical charge in those pixels
the ______the body part adjacent to the sensor, the ____ x-photons can affect the electrical charge
thicker/denser
less
the net effect of digital image formation, is that there is a shadow of electrical charges on the sensor reflective of the
thickness/density of the body part
(step 2)
during step 3 of digital image formation, the electric charge value of each pixel is read by computer chip and the electrical voltage is:
then, the pixel values are sent to the computer for:
converted to a numerical value
(digitized)
for processing
the last step of digital image formation is when the computer assigns the gray value of each number to the
location on the X:Y grid axis of the sensor
gray values are displayed in a visual format on a display monitor
what are the different types of dental digital radiography
- historic (indirect)
flatbed scanner
slide scanner
digital cameras - indirect (semidirect)
phosphor storage plate (PSP) - direct
charge-coupled device (CCD)
complementary metal oxide semiconductor (CMOS)
loss or alteration of information due to partial volume averaging
indirect digital radiography
the first film like sensory was introduced in 1994:
hybrid system
PSP plate: photostimulable phosphor PSP plate
what are the components of semidirect digital system
- xray source
- psp plate
- laser scaner
- screen monitor
- cpu, server, or PACS
- printer EPR PACS
what are the principles of PSP detector
1
2
3
4
5
6
7
- xray
- PSP plate coated with crystalline
- 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 a digital data
- expose to strong light to erase residual images by neutralizing charges in ionized fluorophophors
PSP plate is coated with
crystalline halide emulsion made up of barium fluorobromide
what is psp scanned with
red laser beam
once PSP is scanned with red laser beam that emits fluoroscent light from excitation of of valence electrons in ionized fluorphophors it is then
intensified by a photomultiplier tube
the light intensity of psp is converted to:
and then exposed to strong light to erase:
by neutralizing charges in ionized fluorophophors
digital data
residual images
