Deck 5: Thin-Film Transistor Flat-Panel Array Image Acquisition

Question 1

CsI detectors use

A) rare-earth scintillators.
B) thin crystalline needles.
C) miniature cameras.
D) specialized pixel sensors.

Answer 1

thin crystalline needles.

Question 2

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

Answer 2

thin-film

Question 3

Indirect conversion in flat-panel detectors is a ____-step process.

A) one
B) two
C) three
D) four

Answer 3

two

Question 4

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.

Question 5

A Gd₂O₂S scintillator is known as what type of phosphor?

A) Turbid
B) Unstructured
C) Structured
D) Both A and B

Question 6

Which of the following is used as a photoconductor?

A) Gd₂O₂S
B) a-Se
C) a-Si:H
D) Cesium Iodide (CsI)

Question 7

Which of the following is not considered a scintillator?

A) Gd₂O₂S
B) CsI
C) a-Se
D) None of the above

Question 8

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

Question 9

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.

Question 10

Possible causes of image lag include all except

A) rapid succession images.
B) overexposure.
C) lack of beam attention.
D) underexposure.

Question 11

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.

Question 12

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.

Question 13

Defective pixels can result from all of the following except

A) chemical corrosion.
B) static discharge.
C) software programs.
D) age.

Question 14

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.

Question 15

Manufacturers make efforts to maintain a standard of less than ________ defective pixels.

A) 0.01-0.02%
B) 0.1-0.2%
C) 1-2%
D) None of the above

Question 16

Amplifiers perform all of the following functions except

A) readout.
B) amplification.
C) noise cancelling.
D) analog-to-digital conversion.

Question 17

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.

Question 18

In a flat-panel detector,specialized silicon integrated circuits control

A) line scanning sequence.
B) readout.
C) amplification.
D) analog-to-digital conversion.

Question 19

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.

Question 20

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.

Question 21

Gain calibration will remove inherent detector artifacts from an image.

Question 22

The 2-D array determines whether the imager is direct conversion or indirect conversion.

Question 23

Offset correction is used to remove inherent signal that remains in a detector.

Question 24

The absorption material can be attached to the pixel array electrically or physically.

Question 25

All flat-panel detector systems have the ability to take images faster than the detector can accommodate.