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Medical Imaging- Nicole Calvin > Chapter 3- Image Formation and Radiographic Quality > Flashcards

Chapter 3- Image Formation and Radiographic Quality Flashcards

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USMLE® Step 1 flashcards
1
Q

Anatomic tissues absorb and transmit x-rays differently based on their composition (atomic number and tissue density)

A

Differential Absorption

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2
Q

______ absorbs more x-rays than muscle?

A

Bone

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3
Q

The primary x-ray beam loses some of its energy (number of photons) as its interacts with anatomic tissue.

A

Attenuation

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4
Q

What are the two types of attenuation?

A

Absorption and scattering

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5
Q

Complete absorption of the incoming photon

A

Photoelectric effect

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6
Q

During absorption, the energy of the _______ beam is deposited within the atoms comprising the tissue

A

Primary

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7
Q

What are effects of photoelectric

A

X-ray ionizes atom
low energy secondary x-ray photon created
probability of photoelectric effect dependent on the energy of the incoming x-ray photon and tissue atomic number

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8
Q

Occurs when an incoming photon loses some but not all of its energy, then changes its direction

A

The Compton effect (Scattering)
* It can occur within all diagnostic x-ray energies and is dependent only on the energy of the incoming photon, not the atomic number of tissue

  • Higher KVP reduces the number of interactions, but the the Compton interactions increases in comparison to the number of photoelectric interactions
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9
Q

Factors affecting beam attenuation: (att)

A

Tissue thickness- reduce by 50% for each 4 to 5cm
Type of tissue- higher atomic # will increase beam att.
Tissue density- increase compactness of atomic particles will increase beam att.
X-ray beam quality- higher KVP increases the energy of the x-ray beam will decrease beam att

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10
Q

Scatter radiation reaching the image receptor creates _______ exposure called ______

A

Unwanted

Fog

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11
Q

______ or exit radiation is composed and transmitted and ________ radiation

A

Remnant

Scattered

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12
Q

What radiation creates an image that structurally represents that anatomic area of interest?

A

Transmitted and Absorbed (Exit Radiation)

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13
Q

X-ray beam passes through matter there is a gradual reduction in the number of photons, what is this called?

A

Absorption or Attenuation

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14
Q

What does an x-ray beam produce on a image receptor?

A

Latent Image

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15
Q

What is an excellent demonstration of the different absorption characteristics

A

CT

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16
Q

Dense structures and those of high atomic number appear _______ areas on the image

A

lighter

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17
Q

_____ and _______ appear as dark areas on the image

A

Air (low density)

Fat (low atomic #)

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18
Q

Dense and high atomic numbers appear _______ shadow on the film and are usually ________?

A

Light

Bone

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19
Q

What are technical factors radiation therapist use for differential absorption on the film?

A

KVP or MA

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20
Q

_______ structures represent areas of _______ atomic numbers

A

Dark

Low

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21
Q

_______ structures represent tissue that is dense with ______ atomic numbers

A

Light

High

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22
Q

Density = __________

A

Darkness

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23
Q

_______ radiation reacts with an image receptor such as film screen system to create latent image until processed to produce the manifest or the _______ image.

A

Exit

visible

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24
Q

Low Density = ____________

A

Brightness

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25
Q

______ radiation creates higher brightness or low density on the displayed image

A

Absorbed

26
Q

________ radiation creates lower brightness or high density on the displayed image

A

Transmitted

27
Q

The various shades of gray recorded in the image make atomic tissue _________.

A

Visible

28
Q

Visibility of anatomic structures

A

Density

Contrast

29
Q

Accuracy of structural lines (sharpness)

A

Resolution or recorded detail

Distortion

30
Q

True of False- A quality radiographic image accurately represents the anatomic area of interest, and its information is well visualized for diagnosis.

A

True

31
Q

A film image is evaluated by the amount of ________ or overall blackness after processing

A

Density

32
Q

A digital image is evaluated by the amount of _______ or ______ (Light emission)

A

Brightness

Luminescence

33
Q

The range of brightness levels are a result of the tissues _______ _______ of the x-ray photons

A

Differential Absorption

Ex: Barium (contrast material)

34
Q

True or False- The ability to distinguish among types of tissues is determined by the difference in brightness levels or densities in the image or contrast

A

True

35
Q

Gray scale is?

A

The number of different shades of gray that can be stored and displayed in a digital image

36
Q

Scale of contrast is?

A

The range of densities visible on film

37
Q

_______ resolution describes and imaging receptors ability to distinguish between objects similar in subject contrast?

A

Contrast

38
Q

True or False- Anatomic details do not have to be recorded accurately?

A

False- They must be, with the greatest amount of sharpness

39
Q

_______ resolution refers to the smallest object that can be detected in a digital image?

A

Spatial

40
Q

_______ detailed refers to the distinctness or sharpness of the structural lines that make up the recorded film image?

A

Recorded

41
Q

True of False- All radiographic images have some degree of unsharpness

A

True

42
Q

Size distortion or magnification is an _______ in the objects image _____ compared to its true or actual _______.

A

Increase
Size
Size

43
Q

True or False- Shape distortion is a representation of an object’s image shape

A

False- Its a misrepresentation

  • Elongation and foreshortening
  • Central ray (CR) alignment of the x-ray tube, part and image receptor affect distortion
44
Q

Does scatter and fog decrease image contrast?

A

YES

45
Q

True or False: Digital image receptors can detect lower levels of radiation intensity and therefore are less sensitive to scatter?

A

False- They are MORE sensitive to scatter

46
Q

Visible as brightness or density fluctuations and is photon dependent

A

Quantum Noise

  • Provides no useful information
  • More visible in digital imaging
  • Too few x-ray photons result in increase
47
Q

Classified as plus density and minus density

A

Image Artifact

48
Q

In digital imaging what is the column and the rows called

A

Matrix

49
Q

What are the small boxes in a digital image called

A

Pixel- picture element or smallest component of matrix

50
Q

Recorded a single numerical value representing a brightness level on a display monitor

A

Matrix

51
Q

True or False: Location of pixel in the matrix corresponds to an area within the patient or volume of tissue

A

True

52
Q

True or False: If the Matrix size is smaller the greater number of smaller pixels?

A

False: the quality is improved with a larger matrix. This will increase digital storage, processing time and network transmission time.

53
Q

Numerical value assigned to a _______ is determined by the relative attenuation of x-rays passing through the volume of the tissue

A

Pixel

54
Q

What determines the shade of gray in image

A

pixel bit depth or number of bits (2”) determines the number of gray that can be displayed

55
Q

Active layer of film that contains the crystals that serve as latent imaging centers?

A

Film Emulsion

56
Q

Used to convert exit radiation intensities to visible light and expose the emulsion crystals

A

Intensifying Screens

57
Q

Is chemically processed to display the range of densities created as a result of the x-ray attenuation characteristics of anatomic structures

A

Film

58
Q

_______ _________ image receptors have a limited dynamic range that vary greatly in x-ray attenuation

A

Film Screen

59
Q

Receptors have a wide dynamic range, and therefore anatomic areas of widely different attenuation properties can be more easily visualized on a digital image.

A

Digital Image

60
Q

The range of exposure intensities an image receptor can accurately detect

A

Dynamic Range

Medical Imaging- Nicole Calvin (9 decks)

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