Chapter 5 Thin-Film Transistor Flat Panel Array Image Acquisition

Which 3 of the following components are included in indirect capture flat-panel digital image detector systems? (select 3)

a. photodiode

b. scintillation layer

c. analog-to-digital converter

d. thin-film transistor (TFT) array

e. photoconductor

a. photodiode

b. scintillation layer

d. thin-film transistor (TFT) array

Which component of an indirect capture flat-panel detector converts incident x-ray photons into visible light photons?

a. thin-film transistor (TFT) array

b. scintillation layer

c. photodiode

d. charge-coupled device (CCD)

b. scintillation layer

Which component of an indirect capture flat-panel detector converts the visible light into electrons?

a. thin-film transistor (TFT) array

b. scintillation layer

c. photodiode

d. amorphous selenium detector

c. photodiode

Flat-panel detector systems typically use a thin-film transistor (TFT). This device functions to:

a. convert x-rays into light

b. convert light into electrons

c. collect electrical charge

d. convert electrical charge into a digital signal

c. collect electrical charge

Which 2 of the following flat-panel detector components can collect and convert light into an electrical signal? (select 2)

a. analog-to-digital converter (ADC)

b. thin-film transistor (TFT) array

c. photodiode

d. charge-coupled device (CCD)

c. photodiode

d. charge-coupled device (CCD)

Which element used in the construction of a flat-panel detector is able to convert x-ray photons directly into an electrical signal?

a. cesium iodide

b. amorphous selenium

c. amorphous silicon

d. gadolinium

b. amorphous selenium

Which of the following devices acts as a switch within a flat-panel detector to release the electric charge collected by the detector element?

a. scintillation layer

b. photodiode

c. charge-coupled device (CCD)

d. thin-film transistor (TFT)

d. thin-film transistor (TFT)

Cesium iodide is the preferred material for the scintillation layer because it can be formed into:

a. columns which focus x-ray photons

b. squares which focus x-ray photons

c. columns which focus light photons

d. squares which focus light photons

c. columns which focus light photons

In a charged coupled device (CCD) system, the scintillation layer is connected to the CCD sensor chips by which of the following?

a. lenses or thin-film transistors (TFTs)

b. thin-film transistors (TFTs) or fiber optics

c. thin-film transistors (TFTs) or complementary metal oxide semiconductor (CMOS)

d. lenses or fiber optics

d. lenses or fiber optics

When compared to computed radiography (CR), digital radiography (DR) is:

a. faster, and produces lower quality images

b. slower, but produces lower quality images

c. faster, and produces higher quality images

d. slower, but produces higher quality images

c. faster, and produces higher quality images

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

d. 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

a. 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

c. 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

b. 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

a. line scanning sequence

Amplifiers perform all of the following functions except:

a. readout

b. amplification

c. noise cancelling

d. analog-to-digital conversion

c. noise cancelling

Which of the following is used as a photoconductor?

a. Gd2O2S

b. a-Se

c. a-Si:H

d. Cesium Iodide (Csi)

b. a-Se

Which of the following is not considered a scintillator?

a. Gd2O2S

b. CsI

c. a-Se

d. None of the options are correct

c. 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

d. x-rays to visible light

Indirect conversion in flat-panel detectors is a ___-step process

a. one

b. two

c. three

d. four

b. two

The type of flat-panel detector that uses thin film 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

d. amorphous silicon detector

CsI detectors use:

a. rare-earth scintillators

b. thin crystalline needles

c. miniature cameras

d. specialized pixel sensors

b. 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

a. there is very little light spread

A Gd2O2S scintillator is known as what type of phosphor?

a. turbid

b. unstructured

c. structured

d. both "turbid" and "unstructured"

d. both "turbid" and "unstructured"

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

d. contrast

Defective, or dead, pixels can result from all of the following except:

a. chemical corrosion

b. static discharge

c. software programs

d. dust

c. software programs

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 options are correct

b. 0.1-0.2%

Possible causes of image lag include all except

a. rapid succession images

b. overexposure

c. lack of beam attenuation

d. underexposure

d. 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

d. 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

b. increase the amount of time between exposures

True/False: The absorption material can be attached to the pixel array electrically or physically.

True

True/False: The 2-D array determines whether the imager is direct conversion or indirect conversion

False

True/False: Gain calibration will remove inherent detector artifacts from an image.

True

True/False: Offset correction is used to remove inherent signal that remains in a detector.

True

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

False