Module 4

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johndc3476
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179209
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Module 4
Updated:
2012-10-22 21:58:17
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  1. True or False:
    The casette-based digital image receptor uses torage phosphor technology to create the image
    • True.
    • Computed radiography plates are made fo phosphors that capture the enrergy of the x-ray beam nad release the energy during the processing phase.
  2. A digital image is ocmposed of series of rows and columns known as matrix.
    • True:
    • A matrix is made up fo all pixels in a digital image arranged in rows and columns
  3. The brightness of a digital image is the equivalent of the term density used to describe the appearance of analog images.
    • True 
    • The computer algorithms used to create the digital image can somewhat compenstae for underexposure or overexposure; therefore the visual cues of a dark and light images do not apply in computed radiography.
  4. Calcium Tungstatei sa phpspho material used for intesnifying screens.
    • True:
    • Calcium tungstate, non-calcium tungstate, and rare earths are the three phosphor types used in intesnifiying screens today.
  5. Relative speed measures the amount of exposure needed to achieve a specific optical density.
    True:
  6. The lower the exposure level needed to achieve a specific optical density reflects an increase in the receptor speed.
    • True:
    • Relative speed refers to howe much exposure is needed to create an acceptable image. In order to compare screens, a measured density of 1.0 above base+fog is used.
  7. The silver halide component of film is suspended in a gelatin emulsion.  
    • True:
    • Silver haldie crystasl are suspended in gelatin. This allows the processign chemicals to interact with the silver halide crystals more efficiently.
  8. Direct exposure radiographic film has a lower silver content than film used with intensifying screens.  
    False:
  9. The term used to describe the speed of a digital imaging system is: 
    Speed Class
  10. The ability of a digital imaging system to accurately create an output signal that matches the input signal is known as: 
    Detective Quantum Efficiency
  11. The photostimulable phosphor stores the energy deposited by the x-ray beam in the plate.
    • True:
    • The photostimualble phopsphor is a storage phosphor
  12. Flat-panel image receptors are classified as scintillator based or non-scintillator based.
    • True:
    • A scintilator is a device that absorbs x-ray photons and release light photons. Some flat-panel detectors use a scintilattor and some do not.
  13. The portion of the flat-panel detector receptor that is responsible for collecting  individual electrons is the:
    Thin FIlm Transistor
  14. The actual matrix of the flat panel detector is composed of DELs.
    • True:
    • Detectro elements are the portion of the TFT that collects elcetrons and produces na indiovidual pixel
  15. The number of electrons deposited in the DEL corresponds to the amount of radiation that strikes each area.  
    • True:
    • Individual DELs contain charges proprotinal to the x-rays that strike each one.
  16. CCD is the acronym for charge-coupled device.
    • True:
    • The Charge-coupled device is another form of direct image capture that differs from PSP or FPD technology
  17. A CCD-based receptor requires the use of a scintillator material.
    • True:
    • The charged-couple device uses a scinitilattor to produce light photons
  18. A lens focuses the light produced by the scintillator onto a CCD
    • True:
    • The light photons released by x-rays strikign the scintillator reflect off a mirror to a lens that focuses the energy onto the CCD.
  19. Gas filled CT detectors have a smaller acceptance angle than scintillator based CT detectors
    • True:
    • Gas fillewd detrectors have smaller acceptance angles, meaning they are less sensitive to radiation than scintillator based detectors.
  20. CT scanners can produce images with greater contrast than many image receptors used in diagnostic imaging.  
    • True
    • The tightly collimated x-ray beam in CT decreases scatter, which increases image contrast.
  21. When comparing two receptors, the receptor with the highest DQE can produce an optimal image with less radiation exposure.
    • True:
    • DQE is am easure of how effeiciently an image cna reproduce thei nput signnal. A high DQE means that htis iwll occur mor efficiently there for a lower dose to the patient is necessary
  22. Increased absorption efficiency increases the DQE of a receptor. 
    True
  23. Spatial resolution relates to the ability of an image receptor to record adjacent small objects as separate and distinct.
    • True:
    • When an image recpetor is able to iiamge small objects effectively, ti is said to provide increased spatial resolution
  24. The lp/mm is the only unit of measurement for spatial resolution.
    • False:
    • Spatial resolution can also be measured in cycles/mm
  25. Pixel size influences the spatial resolution of an image.
    • True:
    • The pxiel is the smallest part of a digital image. THe smalelr hte pixel is, the higher hte resolving pwoer of hte image receptor.

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