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Test and Measures > Medical Imaging > Flashcards

Medical Imaging Flashcards

1
Q

What do PTs look for?

A
  • More comprehensive Eval
  • Alignment
  • Fracture configuration

Want to move into ordering X-rays

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2
Q

History

A
  • form of electromagnetic radiation

- made without contrast enhancement

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3
Q

X-Ray Wavelength

A
  • Shorter the wavelength, the higher the energy & greater penetration of dense substances
  • Produces ionization of atoms and molecules (loss of electrons)
  • Results in a gray image on the radiograph
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4
Q

Requirements to produce a radiograph

A
  • An x-ray beam source
  • A pt
  • A x-ray film or image receptor
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5
Q

X-Ray Tube

A
  • Cathode (negative) and anode (positive) enclosed in glass envelope which maintains a vacuum.
  • High voltage current passes through a vacuum
  • Electrons are driven from cathode & strike the anode- decelerate & creates x-rays via energy consumption
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6
Q

Making a Radiograph

A
  • Current is beamed through a series of shutters and directed toward the body [At or near a 90° angle]
  • X-ray beam passes through the body and undergoes a process of Attenuation
  • Human body absorbs rays in various amounts depen. on tissue characteristics
  • X-ray film sensitive to light & radiation, chemical reaction occurs causing an image to be produced in shades of gray on a black film- Film is coated in silver causing an ionization of molecules to occur
  • Final image is a representation of the radiodensity of the anatomical structures the x-rays have passed through [shows density of structure]
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7
Q

Attenuation

A

Defined as the gradual loss of intensity as a result of passing through a medium

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8
Q

Radiodensity

A
  • Refers to the amount of blackening on the radiograph
  • Determines how much radiation will be absorbed
  • Radiolucent
  • Radiopaque
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9
Q

Radiolucent

A
  • Doesn’t absorb much radiation
  • Appears dark grey or black
  • Air and Fat
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10
Q

Radiopaque

A
  • Absorbs a lot of radiation
  • Appears more white
  • Metal and bone
  • Teeth are the most radiopaque
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11
Q

Radiodensity determined by…

A
  1. Atomic weight or composition
    - The greater the atomic weight the greater the radiodensity- Lead used as a shielding device (high atomic weight) to prevent radiation into body
  2. Thickness of the object
    The thicker the object, the more radiation absorbed = more radiodense
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12
Q

Densographs

A
  • Radiographs are not photographs
  • represent tissue density
  • Normal tissues are gray, with any observed density changes, one can assume pathology is present.

75% of film-reading skill is knowledge of anatomy.

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13
Q

Density of tissues

A
  • The greater the density of the tissue, the less penetration of the x-rays
  • Highest density tissues appear white [ex: teeth]
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14
Q

Third Dimension Perception

A
  • Need more than one radiograph to get information about a structure
  • One view is no view

-2 projections are taken at 90° orientation [Minimizes 2D Error]

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15
Q

2D Error

A

Avoid making definitive statements regarding anatomical relationships based on a single x-ray view

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16
Q

Body positioning

A
  • specific
  • provide best visualization of body area with least # of radiographs
  • routine views: AP, lateral and oblique
17
Q

Viewing Radiographs

A
  • Place film on view box as if the viewer (you) are the x-ray beam
  • Consider the area x-rayed
  • Consider this area must be closest to the film to get an accurate picture
  • Consider the x-rays must pass through the person to get to the film
18
Q

Image Quality Factors -Radiographic Density

A
  • Controlled by varying the milliamperage (mA) and exposure time
  • Distance of body part from beam affects this as well
  • Underexposure or Overexposure
19
Q

Image Quality Factors -Radiographic Contrast

A
  • Anatomical detail more visible on the x-ray
  • Greater the variation in anatomical structures, the higher the contrast
  • Chest radiograph = low contrast
  • Skeleton = high contrast
20
Q

Contrast

A
  • Contrast is controlled by: kilovoltage (kVp)
  • Higher the kVp, the greater the energy of the x-ray beam which causes greater penetration through the body parts.
  • More penetration, more uniform is the picture & will have less variation in tissue absorption & a low contrast radiograph occurs
21
Q

General Rule

A

Use the highest kVp and lowest mA which will yield the best diagnostic information necessary for pt intervention

22
Q

Recorded Detail

A

-Lack of detail = Blur [Primary controlling factor is MOTION]
-Other Factors:
Beam source diameter
Distance between beam source and film
Distance b/w beam source and pt

23
Q

Radiographic Distortion

A
  • Difference b/w the actual object & it’s recorded image
  • Radiographs are 30% larger than actual structure
  • Shape Distortion:Unequal magnification of structure
  • -Central ray accurate
  • -More inclined the structure = greater distortion
24
Q

Size Distortion

A

Enlargement
Elongation
Shortening

25
Q

Radiographic Distortion Causes

A 
Beam Source
Patient
Film
Alignment of the Body
Position of the Central Ray
26
Q

Superimposition

A
  • Occurs when anatomic structures are stacked or superimposed on one another so that the x-ray beam must penetrate multiple structures before arriving at the film plate.
  • -This may create artificial lines, shapes, & forms that appear unrecognizable or pathological in nature.
  • -Can also serve to falsely obscure pathology
  • Again, 2-D representation of a 3-D structure.
27
Q

Evaluating Plain Film Radiographs

A

ABCD’S:

  • Alignment
  • Bone Density
  • Cartilage Space
  • Disc Space
  • Soft Tissue
28
Q

ABCD’S: Alignment

A
  • General structural architecture
  • General contour of bone
  • Alignment of bone relative to adjacent bones
29
Q

ABCD’S: Bone Density

A
  • General bone density
  • Texture abnormalities
  • Local bone density changes
30
Q

ABCD’S: Cartilage Space

A
  • Joint space width
  • Subchondral bone
  • Epiphyseal plates
31
Q

Epiphyseal Plates

A
  • growth plate

- Hyaline cartilage plate in the metaphysis at each end of a long bone.

32
Q

ABCD’S: Soft Tissue

A
  • Muscles
  • Fat pads
  • Joint capsules
  • Periostreum
  • Mescellaneous soft tissue findings
33
Q

Contrast-Enhanced Radiographs

A

-Contrast medium injected or ingested into the body
Improves visualization in areas with low contrast
-Can be radiolucent: Air
-Can be radiopaque: Barium sulfate or Iodide
-Can be dual [ex: gastointestinal dual-contrast]

Test and Measures (8 decks)

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