Basic Principles of Digital Radiography Flashcards
pixel
picture element
these small little dots are what make up the images on computer displays, whether they are flat screen or tube monitors
pixel/picture element
it is the cell of a digital image matrix
pixel/picture element
are the horizontal and vertical measurements of an image expressed in pixels
pixel dimensions
it is the amount of resolution in an image is determined by the size of the pixels and the spacing between them or pixel pitch
pixel size/matrix size
PACS
picture archival and communication system
how many pixels in a row are adequate for most diagnostic examinations?
2000 pixels/row
it consists of a photoconductor, amorphous selenium, which holds a charge on its surface that can then be read out by a TFT
flat panel detectors
in _____ ________, xray photons are absorbed by the coating material and immediately converted into an electrical signal
direct conversion
TFT
thin film transistor
it is a photosensitive array made up of small pixels. each pixel contains a photodiode that absorbs the electrons and generates electrical charges
thin film transistor (TFT)
each pixel contains a________ that absorbs the electrons and generates electrical charges
photodiode
FET
field effect transistor
field effect transistor or _____ TFT
field effect transistor or silicon TFT
it isolates each pixel element and reacts like a switch to send the electrical charges to the image processor
field effect transistor (FET)
or
silicon TFT
it is a two step process: xray photons are converted to light and then the light photons are converted to an electrical signal
indirect conversion detectors
a ______ converts xray into visible light
scintillator
CCD
charge-coupled device
this type of flat panel sensor uses thin films of silicon integrated with arrays of photodiodes
amorphous silicon detector
the oldest indirect conversion DR system is based on ______ ________ ________
the oldest indirect conversion DR system is based on charge coupled devices (CCDs)
it acts like cameras that reduces the size of the projected visible light image and transfer the image to one or more small CCDs that convert the light into electrical charge
fiberoptics
DQE
detective quantum efficiency
it is one of the fundamental physical variables related to image quality in radiography and refers to the efficiency of a detector in converting incident xray energy into an image signal
detective quantum efficiency (DQE)
SNR
signal to noise ratio
it refers to the amount of error that can be made and still result in the capture of a quality image
latitude
what is the result if the exposure in CR is more than 50% below the ideal exposure?
quantum mottle
what is the result if the exposure is more than 200% above the ideal exposure?
contrast loss
