Photoconductors are materials that:
a. produce light when absorbing x-rays.
b. produce x-rays when absorbing light.
c. absorb light and produce electric charges.
d. absorb x-rays and produce electrical charges
absorb x-rays and produce electrical charges
Scintillators are phosphors that:
a. produce light when absorbing x-rays.
b. produce x-rays when absorbing light.
c. absorb light and produce electrical charges.
d. absorb x-rays and produce electrical charges.
produce light when absorbing x-rays.
A device that includes a photosensitive array and small pixels that convert light into electrical charges is known as a ______ transistor.
a. thin-field
b. field-effect
c. thin-film
d. field-energy
thin-film
A device that acts like a switch to send electrical charges to the image processor in a direct conversion flat-panel detector is known as a ______ transistor.
a. thin-field
b. field-effect
c. thin-film
d. field-energy
field-effect
In a flat-panel detector, specialized silicon integrated circuits control:
a. line scanning sequence.
b. readout.
c. amplification.
d. analog-to-digital conversion
line scanning sequence.
Amplifiers perform all of the following functions except:
a. readout.
b. amplification.
c. noise cancelling.
d. analog-to-digital conversion.
noise cancelling.
Which of the following is used as a photoconductor?
a. Gd2O2S
b. a-Se
c. a-Si:H
d. Cesium iodide (CsI)
a-Se
Which of the following is not considered a scintillator?
a. Gd2O2S
b. CsI
c. a-Se
d. None of the above
a-Se
Flat-panel detectors that use indirect conversion technology convert:
a. electrical signals to light.
b. light to x-rays.
c. x-rays to electrical signals.
d. x-rays to visible light
x-rays to visible light
Indirect conversion in flat-panel detectors is a ____-step process.
a. one
b. two
c. three
d. four
two
The type of flat-panel detector that uses thin films of silicon integrated with arrays of photodiodes is known as a(n):
a. CsI detector.
b. charge-coupled device.
c. CMOS.
d. amorphous silicon detector
amorphous silicon detector
CsI detectors use:
a. rare-earth scintillators.
b. thin crystalline needles.
c. miniature cameras.
d. specialized pixel sensors
thin crystalline needles.
In CsI detectors:
a. there is very little light spread.
b. crystalline needles block light from the detector.
c. x-rays are converted into an electrical signal.
d. light spread causes resolution to decrease
there is very little light spread.
A Gd2O2S scintillator is known as what type of phosphor?
a. Turbid
b. Unstructured
c. Structured
d. Both a and b
Both a and b
Detector performance is measured with all of the following except:
a. spatial resolution.
b. observation of flow contrast objects in a phantom.
c. DQE.
d. contrast.
contrast.
Defective pixels can result from all of the following except:
a. chemical corrosion.
b. static discharge.
c. software programs.
d. age
software programs.
Manufacturers make efforts to maintain a standard of less than ________ defective pixels.
a. 0.01% to 0.02%
b. 0.1% to 0.2%
c. 1% to 2%
d. none of the above
0.1% to 0.2%
Possible causes of image lag include all but:
a. rapid succession images.
b. overexposure.
c. lack of beam attention.
d. underexposure
underexposure
All of the following statements are true except:
a. as the detector ages, the number of dead pixels increases.
b. software programs identify and isolate dead pixels.
c. interpolation uses information from surrounding pixels to “fill in” missing information.
d. dead pixels at the edge of the detector are easily identified
dead pixels at the edge of the detector are easily identified
Which of the following can be done to decrease the chance of having image lag occur in the next image?
a. Decrease the amount of time between exposures.
b. Increase the amount of time between exposures.
c. Leave collimation open.
d. Acquire the image requiring the highest technical factors first.
Increase the amount of time between exposures.
The absorption material can be attached to the pixel array electrically or physically.
True
False
True
The 2-D array determines whether the imager is direct conversion or indirect conversion
True
False
False
Gain calibration will remove inherent detector artifacts from an image
True
False
True
Offset correction is used to remove inherent signal that remains in a detector.
True
False
True
All flat-panel detector systems have the ability to take images faster than the detector can accommodate
True
False
False