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FEESICKS BUSHBIRD III > Chapter 4 - Image Quality > Flashcards

Chapter 4 - Image Quality Flashcards

1
Q

Describes the level of detail that can be seen on an image

A

Spatial Resolution

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2
Q

Spatial resolution relates to how small an object can be seen on a particular imaging system

  • a single number value that characterizes the approx. resolution limit of an imaging system
  • often considered to be the frequency at which the MTF crosses the 10% level or some other agreed-upon and specified level.
A

LIMITING Spatial Resolution

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3
Q

Refers to the two dimensions of a single image, or to the three dimensions of a set of tomographic images such as computed tomography (CT) or magnetic resonance imaging (MRI)

A

Spatial domain

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4
Q

Most basic measure of the resolution properties of an imaging system; the response of the imaging system to a point source (input to the imaging system)

A

Point Spread Function (PSF)

- also called the impulse response function

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5
Q

An imaging system with the same POINT SPREAD FUNCTION (PSF) at all locations in the fields of view

A

STATIONARY or SHIFT INVARIANT

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6
Q

A systems that has POINT SPREAD FUNCTIONs (PSFs) that vary depending on the position in the field of view

A

NONSTATIONARY

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7
Q

When an imaging system is stimulated with a signal in the form of a line, the _____________ can be evaluated.

A

LINE SPREAD FUNCTION (LSF)

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8
Q

Device required in analog imaging system to measure the optical density as a function of position

A

Scanning microdensitometer

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9
Q

Particularly useful when the spatial resolution characteristics of glare or scatter phenomenon are the subject of interest

A

EDGE SPREAD FUNCTION (ESF)

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10
Q

An integral calculus procedure that accurately describes mathematically what the blurring process does physically

A

Convolution

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11
Q

A process wherein convolution techniques are used to restore (improve) spatial resolution

A

Deconvolution

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12
Q

Another useful way to express the resolution of an imaging system is to make use of the _________.

A

SPATIAL FREQUENCY DOMAIN

***page 69

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13
Q

An algorithm that decomposes a spatial or time domain signal into a series of sine waves that, when summed, replicate that signal

A

Fourier Transform

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14
Q

Resulting data after a spatial domain signal is Fourier transformed

A

Frequency Domain

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15
Q

Perfect line source input

A

Delta function

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16
Q

Sets the upper bound on the spatial frequency that can be detected for a digital detector

A

Nyquist Frequency

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17
Q

The center-to-center distance between adjacent deal extortion elements

A

Detector Pitch

18
Q

Refers to the ability to detect very subtle changes in gray scale and distinguish them from the noise in the image

-characterized by measurements that pertain to signal-to-noise ratio(SNR) in an image.

A

Contrast resolution

19
Q

Image noise…the actual distribution of the silver grains is random and is a function of the manufacturing and development process.

-image is formed by millions of silver grains attached to the clear film substrate

A

Grain noise

20
Q

Typically additive noise from various sources that does not scale with the signal level

  • worst in areas of low actual signal in the detector
A

Electronic noise

21
Q

Image noise that represents a reproducible pattern on the image that reflects differences in the gain of individual detector elements or groups of detector elements

-can be corrected using a flat film algorithm

A

Structured Noise

22
Q

Characterized by exposing the detector to radiation in the absence of an object

A

Gain image

23
Q

Measured with no radiation incident on the detector

A

Offset image

24
Q

Image noise which refers to anatomy in the patient which is not pertinent to the specific imaging system

A

Anatomical noise

25
Q

Any number of particles or objects that can be counted, such as electrons, X-Ray photons, optical photons, or even brush strokes on impressionist paintings.

A

Quanta

26
Q

***page 80

A

Quantum noise

27
Q

A)halfway point in the observed data set

B)most frequent observation, the highest point in the histogram

C)width of the distribution

A

A) median

B) mode

C) range

28
Q

Most widely used statistical distribution in scientific analysis and other observational settings

A

Normal distribution(also called the Gaussian Distribution)

29
Q

Statistical distribution governed by only one parameter

A

Poisson Distribution

30
Q

Characterizes frequency dependence of the noise variance

A

Noise Power Spectrum (NPS)

31
Q

A type of uncorrelated noise wherein the noise in each pixel of a 2D image is NOT DEPENDENT upon the noise values in any of its surrounding pixels producing a flat horizontal line in the noise power spectrum and no noise correlation

A

White noise

32
Q

Fundamental contrast that arises in the signal, after it has interacted with the patient but before it has been detected

A

Subject contrast

33
Q

…the incident beam of energy from the imaging system will eventually reach the detector(s)…

***page 88

A

Detector contrast

  • screen-film radiography- nonlinear response to X-rays
  • digital radiography- linear response
34
Q

Raw image information is processed into an image that is finally meant for physician viewing

A

Displayed Contrast

35
Q

Most commonly used look-up table (LUT) in radiological imaging

A

Window/level

36
Q

An object size-independent measure of the signal level in the presence of noise

A

Contrast-to-Noise ratio (CNR)

37
Q

Object size DEPENDENT measure of the signal level in the presence of noise

A

Signal-to-Noise ratio

38
Q

SNR >or= 5 : an object will almost always be recognized (detected)

Detection performance continuously degrades as SNR approaches zero

A

ROSE CRITERION

39
Q

A conceptual visual method for combining the concepts of spatial resolution and contrast resolution

A

CONTRAST DETAIL DIAGRAM (CD Diagram)

40
Q

Characterization of an X-ray imaging system which describes the over-all frequency-dependent SNR performance of the system

  • combines concepts of spatial and contrast resolution but the methods of analysis are less visual and more quantitative
  • defined as the ratio of the SNR2 OUTPUT from the system the SNR2 of the signal INPUT into the system
A

Detective Quantum Efficiency (DQE)

41
Q

Refers to the probability that the patient is actually abnormal (TP)

A

Positive predictive value (PPV)

42
Q

Refers to the probability that the patient is actually normal (TN)

A

NEGATIVE PREDICTIVE VALUE

FEESICKS BUSHBIRD III (13 decks)

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