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DIGITAL RADIOGRAPHY. Digital Fluoroscopy. Input phosphor output phosphor electronic signal beam splitter video signal  TV monitor Video signal is a voltage signal which varies continuously  ADC (Analog Digital Converter) converts analog to digital.

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Presentation Transcript
digital fluoroscopy
Digital Fluoroscopy
  • Input phosphoroutput phosphor electronic signal beam splitter video signal  TV monitor
  • Video signal is a voltage signal which varies continuously 
  • ADC (Analog Digital Converter) converts analog to digital
what are some negatives of conventional film radiography
What are some negatives of conventional (film) radiography?
  • Difficult to image both soft tissue and bony structures in same image
  • Difficult to differentiate between the subtle differences of soft tissues (shades of gray---long contrast, low contrast)
  • Unable to gather quantitative info about attenuation characteristics of anatomy
  • Image is processed permanent as is
  • Amount of time needed to process
  • Archiving/storage/ acquisition issues
similarities between cr and film radiography
Similarities between CR and film radiography
  • Same x-ray tube and generator
  • Still select optimum kVp and mAs
  • Accurate positioning
  • Use cassette or image receptor
  • There is still a latent image which can be processed into a manifest image
differences
DIFFERENCES
  • Imaging plate rather than intensifying screen/film
  • Photostimulable phosphor-europium activated barium fluorohalide phosphor
  • 200 screen speed equivalent
  • Phosphors absorb photons
  • Capable of wider latitudes = better visualization of soft tissues and bone
differences cont
DIFFERENCES CONT.
  • Film made of minute strands of black metallic silver
  • Digital image = rows and columns called a matrix
matrix pixel and voxel
MATRIX, PIXEL AND VOXEL
  • Matrix made up of pixels ( picture element)
  • Pixels = x-ray intensity at that location and given a numeric value for the shade of gray
  • Voxel represent the volume of tissue of the patient
  • Matrix preferred size – 2048 x2048 or

4, 194,304 pixels

  • Larger matrix = more pixels and pixels are smaller
image acquisition
IMAGE ACQUISITION
  • Exit(remnant radiation) IP photons absorbed photoelectrically by phosphor LATENT IMAGE
  • Exposed IP reader unit (digitizer) scanned to release energy as light  photomultiplier tube (PMT) collects, amplifies and converts light to electronic signal to ADC manifest image
slide9
Manifest image is a matrix composed of pixels with assigned brightness levels
  • IP scanned again with intense light to erase plate
  • 10,000 readings
histograms window or index levels algorithms
Histograms/window or index levels/algorithms
  • Histogram-graphic display of digital data
    • Used to evaluate adequacy of IP to x-rays
    • PMT needs to be adjusted to compensate for errors
  • Window/index levels –
  • Algorithms – math formulas needed to formulate image construction based on anatomy imaged
    • Radiographer must indicate correct procedure so the correct algorithms are used.
ir ip
IR/IP
  • List some characteristics of an IP
  • What speed film screen system is associated with a typical IP?
  • How does this affect technique?
slide13
DR
  • DIRECT READOUT DIGITAL RADIOGRAPHY
  • FLAT PANEL DIRECT CAPTURE DETECTOR
  • CHARACTERISTICS?
  • COMPARE INDIRECT CONVERSION TO DIRECT
post processing
Post processing
  • Subtraction
  • Contrast enhancement
  • Edge enhancement
  • Black and white reversal
  • Compensate for errors
slide15
Misc.
  • Resolution =2.5 line pairs per millimeter
  • Window level = adjusts image brightness
  • Window width = adjusts radiographic contrast
  • Quantum mottle
  • Artifacts
  • Scatter
slide16
PACS
  • HIS
  • RIS
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