system that uses a two-part process involving a scintillator and a photodetector.
Indirect Acquisition systems include?
include those that use photostimulatable storage phosphor imaging plates(IP), charged coupled devices(CCD) and silicon.
directly convert incoming xray photons to an electronic signal
Direct Acquisition systems use?
selenium and are sometimes referred to as direct radiography(DR) systems.
also called flat field detectors-are being used to describe both the indirect amorphous silicon and the direct amorphous selenium plates that are being used in some digital systems
The most common phosphor favorable to CR?
barium fluorohalide bromides and iodides with europium activators.
Why is it important to process the cassette shortly after exposure?
the latent image will lose about 25 percent of its energy in 8 hours.
when the laser beam frees the trapped electrons, allowing them to return to a lower energy state.
electrons moving to a lower energy state release what?
blue-purple light photons in proportion to the absorbed radiation.
the light emitted from the imaging plate does what?
its emitted in all different directions and is collected by an optical system that directs it to one or more photomultiplier(PM) tubes, which are only sensitive to blue light.
PM tubes do what?
convert the visible light into an electronic signal whose output is in analog form.
residual image left on the imaging plate is erased how?
by exposure to an intense light to release any remaining trapped electrons.
primary advantage of dual sided PMT reading?
improved spacial resolution
the smaller the pixel, the higher the ________?
exposure data recognition- method used to recognize the clinically useful area on the imaging plate
modes of EDR?
automatic(auto), semiautomatic(semi), and fixed.
automatic mode of EDR? when is it used?
adjusts latitude and sensitivity for the image and is also used when placing more than one image on a cassette.
expectations when placing more than one image on a plate?
the beam and part should be centered within each pattern and collimation should be parallel and equidistant from the edges of the imaging plate
semiautomatic mode of EDR? when is it used?
automatically adjusts only sensitivity while the reading latitude is fixed. it is used when the image is centered but the collimation borders are not parallel or equidistant from the plate edges.
fixed mode of EDR?
similar to film screen in that latitude and sensitivity are fixed, requiring correct technique factors to be used to obtain a diagnostic image since this mode will not correct density problems.
histogram is generated by?
from image data that allows the CR system to find the useful signal by locating the minimum and maximum signal within the anatomical regions of interest in the image.
spatial frequency processing should be used when?
when it is necessary to increase image sharpness
properly exposed imaging plates should produce S values of?
S value directly or inversely proportional to mR?
look up table?
a histogram of the luminance values derived from the image receptor pixel values.
stitching together multiple images from CR systems.
Thin Film Transistors- collects the electric charges produced either by the selenium or silicon as an array or matrix of pixel-size detector elements. Each TFT element collects the charge and then when the gate is activated by the computer sends the signal.
Charge Coupled Device- a photodetector device that is capable of converting visible light into an electric charge and storing it in a sequential pattern. the stored charge is then released line by line to the ADC.
Digital Imaging and Communications in Medicine- a system of computer software standards that permit a wide range of digital imaging programs to understand one another.
scintillator does what?
converts incoming xray photons to light
photodetectors do what?
converts light into an electronic digital signal
most common digital radiography artifacts?
fogging, quantum mottle, heat blur, histogram error, and nonparallel collimation.
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