Chapter 4- Radiographic imaging and exposure

With CR, when the x-ray photons are absorbed by the phosphor, the ___________ atoms become ionized. a. barium fluorohalide b. tungsten c. europium d. silver halide

c. europium

In the CR reader unit, the IP is scanned with a(n): a. PMT. b. electron gun. c. helium-neon laser beam. d. PSP.

c. helium-neon laser beam

The spatial resolution of flat-panel receptors is generally superior to that of CR.

true

If the FOV is 500 mm and the matrix size is 1024, what is the pixel size? a. 0.49 mm b. 0.69 mm c. 1.4 mm9 d. 2.1 mm

a. 0.49 mm

Pixel bit depth is determined by the: a. ADC. b. FOV. c. matrix. d. tissue type.

a. ADC

_________ the CNR increases the visibility of anatomic details. a. Increasing b. Decreasing c. Maintaining

a. Increasing

_________ the SNR increases the visibility of anatomic details. a. Increasing b. Decreasing c. Maintaining

a. Increasing

What dose monitoring value measures the exposure in air and estimated absorbed dose? a. KAP b. MTF c. DQE d. DMV

a. KAP

What is the term generally used to describe the emission of light from a substance as the result of stimulation by radiation? a. Luminescence b. Phosphorescence c. Fluorescence d. Incandescence

a. Luminescence

Which of the following is not a component of the CR IP? a. Thin film transistor layer b. Support layer c. Phosphor layer d. Protective layer

a. Thin film transistor layer

Which of the following is true about the indirect conversion DR systems? a. X-rays are converted to light then converted to electrical charges. b. X-rays are converted to electrical charges. c. X-rays are converted to electrical charges then converted to light.

a. X-rays are converted to light then converted to electrical charges

The indirect conversion detector uses: a. a scintillator and a photodetector b. a scintillator and amorphous selenium c. a photodetector and amorphous selenium d. All options are correct.

a. a scintillator and a photodetector

The CR latent image consists of: a. electrons trapped in the phosphor layer. b. clumps of metallic silver in the emulsion. c. light trapped in the phosphor layer. d. the image as seen on the display monitor.

a. electrons trapped in the phosphor layer

A system that can digitize and display a greater number of shades of gray will have ____________ contrast resolution. a. increased b. decreased c. no

a. increased

With CR, a higher sampling frequency results in: a. increased pixel density and smaller sampling pitch b. increased pixel density and decreased spatial resolution c. smaller sampling pitch and decreased spatial resolution d. All options are correct.

a. increased pixel density and smaller sampling pitch

A larger bit depth: a. increases contrast resolution. b. decreases contrast resolution. c. has no effect on contrast resolution. d. increases the pixel density.

a. increases contrast resolution

With a fixed matrix CR reader system, changing to a larger IP, for the same FOV, will result in: a. larger pixels. b. smaller pixels. c. improved spatial resolution. d. higher contrast resolution.

a. larger pixels

A combination of rows and columns (array) of pixels is called a: a. matrix. b. field of view. c. voxel. d. liquid crystal display.

a. matrix

How often the analog signal is reproduced in its discrete digitized form is: a. sampling frequency. b. sampling pitch. c. pixel frequency. d. pixel pitch.

a. sampling frequency

A high SNR means that the: a. signal strength is high. b. signal strength is low. c. noise is high. d. fog is greater.

a. signal strength is high

A method of describing the strength of the radiation exposure compared with the amount of noise apparent in the digital image is the: a. signal-to-noise ratio. b. contrast-to-noise ratio. c. modulation transfer function. d. detective quantum efficiency.

a. signal-to-noise ratio

If the matrix size is increased for a given FOV: a. spatial resolution is increased. b. spatial resolution is decreased. c. spatial resolution is not affected. d. contrast resolution is increased

a. spatial resolution is increased

The greater the pixel bit depth: a. the more precise digitization of the analog signal and a greater number of shades of gray will be displayed b. the more precise digitization of the analog signal and spatial resolution will be increased c. a greater number of shades of gray will be displayed and spatial resolution will be increased d. All options are correct.

a. the more precise digitization of the analog signal and a greater number of shades of gray will be displayed

what is fov?

anatomic area of interest

A 10-bit pixel depth can display how many shades of gray? a. 10 b. 1024 c. 4096 d. 16,384

b. 1024

What type of image receptor converts the exit radiation into electrical charges and stores them before readout and digitization? a. CR b. DR c. AEC d. ADC

b. DR

Which of the following is the sequence of events for production of a DR image using direct conversion detectors? a. Electronic signal goes to ADC, charge is stored briefly in TFT array, exit radiation is converted to electrical charge b. Exit radiation is converted to electrical charge, charge is stored briefly in TFT array, electronic signal goes to ADC c. Exit radiation is converted to electrical charge, electronic signal goes to ADC, charge is stored briefly in TFT array d. Electronic signal goes to ADC, exit radiation is converted to electrical charge, charge is stored briefly in TFT array

b. Exit radiation is converted to electrical charge, charge is stored briefly in TFT array, electronic signal goes to ADC

The _____________ collects, amplifies, and converts visible light to an electrical signal. a. ADC b. PMT c. PSP d. DEL

b. PMT

This material is composed of barium fluorohalide and makes up the primary component of the CR IP. a. Luminescence b. Photostimulable phosphor c. Photostimulable luminescence d. Phosphorescence

b. Photostimulable phosphor

Which of the following is the sequence of events, from beginning to end, of what happens in the CR reader unit? a. Analog electrical signal is sampled and digitized, stored energy is released as visible light, PMT converts light energy to electrical signal b. Stored energy is released as visible light, PMT converts light energy to electrical signal, analog electrical signal is sampled and digitized c. Analog electrical signal is sampled and digitized, PMT converts light energy to electrical signal, stored energy is released as visible light d. Stored energy is released as visible light, analog electrical signal is sampled and digitized, PMT converts light energy to electrical signal

b. Stored energy is released as visible light, PMT converts light energy to electrical signal, analog electrical signal is sampled and digitized

DR imaging systems briefly store the electrical charge in the: a. ADC. b. TFT. c. CRT. d. DQE.

b. TFT

The CR phosphor layer is composed of: a. gadolinium oxysulfide with terbium. b. barium fluorohalide with europium. c. lanthanum oxybromide with thulium. d. yttrium oxysulfide with terbium.

b. barium fluorohalide with europium

The number of bits that determines the amount of precision in digitizing the analog signal and the number of gray shades that can be displayed in the image is the: a. matrix. b. bit depth. c. binary code. d. analog to digital converter.

b. bit depth

A method of describing the contrast resolution compared with the amount of noise apparent in a digital image is the: a. signal-to-noise ratio. b. contrast-to-noise ratio. c. modulation transfer function. d. detective quantum efficiency.

b. contrast-to-noise ratio

The higher the DQE of a system, the radiation exposure required to produce a quality image is: a. increased. b. decreased. c. not effected.

b. decreased

The ability of the detector to accurately capture the variety of photon intensities in the remnant radiation is: a. pixel depth. b. dynamic range. c. ALARA. d. pixel sensitivity.

b. dynamic range

The percentage of x-rays that have reached the detector and have been captured is the: a. TFT array. b. fill factor. c. ADC. d. quantization.

b. fill factor

With CR, a larger sampling pitch results in: a. increased pixel size and increased pixel density b. increased pixel size and decreased pixel resolution c. increased pixel density and decreased spatial resolution d. All options are correct.

b. increased pixel size and decreased pixel resolution

The measure of the imaging system's ability to display the contrast of anatomic objects varying in size is the: a. spatial frequency. b. modulation transfer function. c. maximum intensity. d. minimum intensity.

b. modulation transfer function

The pixel spacing, or distance measured from the center of a pixel to an adjacent pixel is called the: a. matrix. b. pixel pitch. c. bit depth. d. pixel density.

b. pixel pitch

With CR, trapped electrons are: a. proportional to the exit exposure intensity and in a lower energy state b. proportional to the exit exposure intensity and released during the readout stage c. in a lower energy state and released during the readout stage d. All options are correct.

b. proportional to the exit exposure intensity and released during the readout stage

The distance between the analog points being sampled is the: a. sampling frequency. b. sampling pitch. c. pixel frequency. d. pixel pitch.

b. sampling pitch

If the matrix size is increased for a fixed field of view (FOV): a. the pixel size is increased. b. the pixel size is decreased. c. the pixel size is not affected. d. the pixel pitch is increased

b. the pixel size is decreased

An MTF of -_____ means a maximum difference in brightness levels: a. 0. b. 0.5. c. 1.0. d. 1.5.

c. 1.0

What term refers to the range of exposures that should be used to produce a diagnostic image? a. Contrast resolution b. Spatial frequency c. Exposure latitude d. Dynamic range

c. Exposure latitude

The ____________ array is divided into square detector elements (DEL). a. ADC b. IP c. TFT d. SNR

c. TFT

The measurement of the efficiency of an image receptor in converting the x-ray exposure it receives to a quality radiographic image is the: a. quantum noise. b. modulation transfer function. c. detective quantum efficiency. d. photostimulable luminescence.

c. detective quantum efficiency

The measurement of the efficiency of an image receptor in converting the x-ray exposure it receives to a quality radiographic image is the: a. quantum noise. b. modulation transfer function. c. detective quantum efficiency. d. photostimulable luminescence.

c. detective quantum efficiency.

What is the relationship between the display field of view (FOV) and pixel size for a fixed matrix size: a. inverse proportional b. inverse c. direct d. direct proportional

c. direct

An example of a scintillator used in an indirect conversion detector is: a. amorphous selenium and gadolinium oxysulfide b. amorphous selenium and cesium iodide c. gadolinium oxysulfide and cesium iodide d. All options are correct.

c. gadolinium oxysulfide and cesium iodide

Overexposing a digital image receptor may result in: a. visible quantum noise and high SNR b. visible quantum noise and increased patient exposure c. high SNR and increased patient exposure d. All options are correct.

c. high SNR and increased patient exposure

Which of the following results in improved spatial resolution? a. increased pixel bit depth and increased pixel density b. increased pixel bit depth and decreased pixel pitch c. increased pixel density and decreased pixel pitch d. All options are correct.

c. increased pixel density and decreased pixel pitch

A larger bit depth: a. results in increased spatial resolution. b. reduces the number of shades of gray. c. increases the number of shades of gray. d. decreases the size of the pixel

c. increases the number of shades of gray

Immediately before leaving the CR reader unit, the IP is exposed to: a. the laser light. b. high speed electrons. c. intense white light. d. x-rays.

c. intense white light

The emission of light when stimulated by a high-intensity laser beam is: a. luminescence. b. photostimulable phosphor. c. photostimulable luminescence. d. phosphorescence.

c. photostimulable luminescence

What is matrix?

combination of rows and columns

Which of the following is true concerning computed radiography imaging plates? a. The CR cassette houses the imaging plate and the radiation exiting the patient interacts with the imaging plate b. The CR cassette houses the imaging plate and the photon intensities are absorbed by the phosphor c. The radiation exiting the patient interacts with the imaging plate and the photon intensities are absorbed by the phosphor d. All options are correct.

d. All options are correct

Which of the following is not part of a CR reader unit? a. Optical system b. ADC c. Photodetector d. Capacitor

d. Capacitor

Which of the following is not a component of a flat-panel detector? a. TFT array b. X-ray converter c. Glass substrate d. Phosphor layer

d. Phosphor layer

Digital image quality is improved with: a. larger size matrix and larger pixel bit depth b. larger size matrix and smaller size pixels c. larger pixel bit depth and smaller sizes pixels d. All options are correct.

d. all options are correct

The pixel bit depth determines the image's: a. brightness. b. subject contrast. c. spatial resolution. d. contrast resolution.

d. contrast resolution

Increasing the number of line pairs per millimeter resolved in the imaging system results in: a. higher contrast resolution. b. lower spatial frequency. c. decreased spatial resolution. d. increased spatial resolution.

d. increased spatial resolution

The size of a pixel is measured in: a. centimeters. b. inches. c. angstroms. d. microns.

d. microns

The number of pixels per unit area is called the: a. matrix. b. pixel pitch. c. bit depth. d. pixel density.

d. pixel density

An image with high SNR will have decreased detail visibility.

false

Because digital imaging has a large dynamic range, significantly lower than necessary x-ray exposure will still result in a quality image.

false

Bit depth is determined by the matrix size.

false

Both CR and DR are electronic detectors that combine image capture and image readout.

false

Exit radiation is converted to visible light with the direct conversion detector.

false

The quality of the CR latent image will remain the same for up to 6 h after exposure.

false

There is no light produced with CR when radiation interacts with the IP.

false

FOV

field of view

The size of a pixel is measured in:

microns

pixel

picture element

formula for FOV

pixel size=fov/matrix size

pixel bit depth

the number of bits

Bit depth is determined by the analog to digital converter (ADC)

true

Once the data is in digital format, there is no difference between image processing and display between CR and DR.

true

Small anatomic objects have higher spatial frequency.

true

The DQE is higher for DR when compared to CR.

true

The DR system does not require a separate reader unit.

true

With an FPD, electrical charges from each DEL are read out separately.

true