Digital Imaging & PACS Chapter 5 & 6

Which of the following flat-panel detector technologies was developed by NASA?

A. CCD

B. Field-effect transistor

C. CMOS

D. Thin-field transistor

C. CMOS

When specialized pixels in a complementary metal oxide silicon system are struck with x-ray photons:

A. the x-ray photons are converted into light.

B. light photons are stored in capacitors.

C. light photons are converted into electrical charges.

D. all answers are correct

D. all answers are correct

Which of the following statements is true?

A. Quantum efficiency and detective quantum efficiency are the same.

B. Quantum efficiency will affect detective quantum efficiency.

C. Quantum efficiency has no effect on detective quantum efficiency.

D. Quantum efficiency is the absolute efficiency of the amount of light collected.

B. Quantum efficiency will affect detective quantum efficiency.

The indirect conversion detector system that requires optical coupling and image size reduction is known as a:

A. CCD.

B. field-effect transistor.

C. CMOS.

D. thin-field transistor.

A. CCD.

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.

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.

Some advantages to CCDs include:

A. less expensive to manufacture.

B. module design makes repairs and upgrades easy.

C. demagnification capabilities.

D. a and c only.

D. a and c only.

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%

B. 0.1% to 0.2%

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

A. one

B. two

C. three

D. four

B. two

A highly efficient indirect conversion system that takes up less fill space than CCDs is known as a(n):

A. analog to digital converter.

B. field-effect transistor.

C. CMOS.

D. thin-field transistor.

C. CMOS.

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.

D. amorphous silicon detector.

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

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.

The most popular base material used in integrated circuits is:

A. selenium.

B. sulfur.

C. silicon.

D. tellurium.

C. silicon.

The components that focus the signal from the scintillators to the CCD are called:

A. detector elements.

B. capacitors.

C. fiber optics.

D. analog-digital converters.

C. fiber optics.

Amplifiers perform all of the following functions except:

A. readout.

B. amplification.

C. noise cancelling.

D. analog-to-digital conversion.

C. noise cancelling.

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.

All of the following are considered impurities except:

A. gallium arsenide.

B. indium antimonide.

C. tellurium.

D. most metal oxides.

C. tellurium.

Defective pixels can result from all of the following except:

A. chemical corrosion.

B. static discharge.

C. software programs.

D. age.

C. software programs.

Possible causes of image lag include all but:

A. rapid succession images.

B. overexposure.

C. lack of beam attention.

D. underexposure.

D. underexposure.

A device that acts like a camera in an indirect conversion detector is known as a:

A. CCD.

B. field-effect transistor.

C. CMOS

D. thin-field transistor.

A. CCD.

A Gd2O2S scintillator is known as what type of phosphor?

A. Turbid

B. Unstructured

C. Structured

D. Turbid and Unstructured

D. Turbid and Unstructured

Which of the following statements about scintillators is true?

A. All scintillators absorb the same amount of x-ray photons.

B. The amount of x-rays absorbed depends on the type of scintillator.

C. Structured phosphors produce more light spread.

D. Unstructured phosphors are more efficient.

B. The amount of x-rays absorbed depends on the type of scintillator.

The readout process requires that _______ and _______.

A. electrons flow freely when the gates are open; voltage stays consistent

B. the flow of electrons is timed; voltage stays consistent

C. electrons flow freely when the gates are open; multiple voltage changes occur

D. the flow of electrons is timed; multiple voltage changes occur

D. the flow of electrons is timed; multiple voltage changes occur

Which statement best describes a capacitor?

A. It converts x-ray photons to light.

B. It converts light to an electrical charge and stores it.

C. It converts x-ray photons to light and stores it.

D. It stores light and converts it from an analog to a digital signal.

B. It converts light to an electrical charge and stores it.

When compared with a CMOS, CCDs:

A. are less light sensitive.

B. are more susceptible to noise.

C. use more than 100 times the power.

D. are inexpensive to manufacture.

D. are inexpensive to manufacture.

Which statement best describes a charge-coupled device (CCD)?

A. It is the oldest direct conversion technology that is still in use today.

B. It is the oldest direct conversion technology with limited use today.

C. It is the oldest indirect conversion technology that is no longer used in medical imaging.

D. It is the oldest indirect conversion technology used in a variety of image capture applications.

D. It is the oldest indirect conversion technology used in a variety of image capture applications.

Demagnification is:

A. reducing the phosphor output image to the size of the active area of the CCD.

B. reducing the field size of the CCD detector.

C. reducing the amount of light spread from the scintillator.

A. reducing the phosphor output image to the size of the active area of the CCD.

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.

Quantum efficiency is a measurement of the:

A. amount of electron-hole pairs held by the electrostatic force.

B. percentage of light that is absorbed.

C. amount of electrons produced relative to the incident light from the scintillator.

D. total amount of light that is absorbed.

C. amount of electrons produced relative to the incident light from the scintillator.

The most common types of noise that affect image quality include all of the following except:

A. quantum noise.

B. statistical noise.

C. "dark" current noise.

D. amplification noise.

A. quantum noise.

A detector in which each pixel has its own amplifier is known as a:

A. CCD.

B. field-effect transistor.

C. CMOS.

D. thin-field transistor.

C. CMOS.

Which of the following is not considered a scintillator?

A. Gd2O2S

B. CsI

C. a-Se

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.

Detector elements are formed by voltage gates that _____ at readout to _____ the flow of electrons.

A. close: allow

B. open: allow

C. close: stop

D. open: stop

B. open: allow

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 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 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

CsI detectors use:

A. rare-earth scintillators.

B. thin crystalline needles.

C. miniature cameras.

D. specialized pixel sensors.

B. thin crystalline needles.

Clinical applications for CCDs include all of the following except:

A. digital fluoroscopy.

B. computed tomography fluoroscopy.

C. digital mammography.

D. general radiography.

B. computed tomography fluoroscopy.

_______ turn semi-conductors into full electrical conductors.

A. Dopants

B. Amplifiers

C. Positive transistors

D. Negative transistors

A. Dopants

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.