crdr 6

Question 1

2 principal characteristics of medical image

Answer 1

spatial resolution
contrast resolution

Question 2

ability of an imaging system to resolve and render on the image a small high-contrast object.

Answer 2

spatial resolution

Question 3

refer to the line pair

Answer 3

spatial frequency

Question 4

The unit of spatial frequency as used in medical imaging describes

Answer 4

line pair per millimetre (lp/mm)

Question 5

term borrowed from radio electronics that has been applied to the description of the ability of an imaging system to render objects of different sizes onto an image.

Answer 5

modulation transfer function (MTF)

Question 5

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Question 6

MTF can be viewed as the ratio of image to object as a function of spatial frequency.

Question 7

• The higher frequency that occurs in set distance results in more blur.
• The amount of blurring can be represented by the reduced amplitude of the representative frequency.

Question 8

ability to distinguish many shades of gray from black to white.

Answer 8

contrast resolution

Question 9

principal descriptor for contrast resolution is

Answer 9

grayscale or dynamic range

Question 10

number of gray shades that an imaging system can reproduce

Answer 10

dynamic range

Question 11

• The dynamic range of digital imaging systems is identified by the bit capacity of each pixel.

Question 11

CT & MRI dynamic range

Answer 11

12-bit

Question 12

DR system dynamic range

Answer 12

14-bit

Question 13

Digital mammography dynamic range

Answer 13

16-bit

Question 14

signal in a radiographic image is that portion of the image-forming x-rays that represents anatomy.

Answer 14

signal-to-noise ratio (SNR)

Question 14

principal advantage of digital imaging is the ability to pre-process and post- process the image for the purpose of extracting even more information.

Answer 14

post-processing

Question 15

The signal represents the difference between those x-rays transmitted to the image receptor and those absorbed photoelectrically

Answer 15

signal-to-noise ratio (SNR)

Question 15

noise limits contrast resolution; therefore, radiographers strive for high SNR by selecting appropriate digital radiographic techniques, in keeping with ALARA

Question 16

increased mAs results SNR to increased

Question 17

Another method for evaluating the spatial resolution and contrast resolution of an imaging system is the contrast-detail curve. This method involves information similar to an MTF curve,

Answer 17

contrast-detail curve

Question 18

With acceleration to all-digital imaging, we have the opportunity to reduce patient doses by 20% to 50%, depending on the examination

Question 18

Spatial resolution in screen-film radiography is determined principally by ?

Answer 18

focal-spot size

Question 19

Spatial resolution in digital imaging is determined by ?

Answer 19

pixel size

Question 19

Radiographic technique for screen-film imaging requires:

Answer 19

1. that an appropriate kVp be selected on the basis of the anatomy that is being imaged 2. that the proper mAs be selected to produce proper optical density (OD) on the finished image.

Question 20

result will be patient radiation dose reduction.

Answer 20

technique creep

Question 21

problem with very low technique for digital imaging

Answer 21

low SNR

Question 21

probability that an x-ray will interact with an image receptor is determined by the thickness of the capture layer and its atomic composition.

Answer 21

detective quantum efficiency (DQE)

Question 22

descriptor used for medical imaging

Answer 22

DQE

Question 22

regarded as the absorption coefficient

Answer 22

DQE

Question 23

relative value of DQE for various image receptors means that fewer x-rays are required by the higher DQE receptors to produce an image; this translates into lower patient radiation dose.

Answer 23

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Question 24

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Answer 24

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