Chapter 11 Display Modes

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Chapter 11Display Modes
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Display Modes

• Three basic modes (formats)
• Amplitude mode (A-mode)
• Brightness mode (B-mode)
• Motion mode (M-mode)

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A-mode

• Appears as a series of upward spikes
• Sound is emitted by transducer
• Dot moves across the systems
  display
• When a reflection returns to the
  transducer, it is processed and
  the moving dot is deflected upward
  on the screen
• x-axis represents reflector depth derived from
  time-of-flight
• y-axis represents reflection amplitude
  height is directly proportional to
  amplitude of the returning
  echo

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A-mode Display

• Display looks like a big city skyline
• Accurate in determining depth of reflectors
• Utilized extensively in ophthalmology

Actual A-mode display superimposed upon
2-dimensional image of eye
Actual A-mode display
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B-mode

• Appears as a line of dots of varying brightness
• As a sound pulse is emitted by the transducer
• Invisible dot moves at a constant speed across
  the display
• When a reflection returns to the transducer, it
  is processed the dot is turned on
• Brightness of the dot indicates the strength of
  the reflection
• Weaker reflections appear as darker shades of
  gray
• Stronger reflections appear as brighter white
  dots
• The basis for all other types of grayscale
  imaging
• X-axis represents reflector depth
• Amplitude information is routed into the z-axis
  of the cathode ray tube (CRT)

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B-mode
Diagram of a B-mode display
B-scan, static image
Reflector depth is determined by time-of-flight
Brightness of each dot is related to the strength
of the returning reflection
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M-mode

• Appears as a group of horizontal wavy lines
• Sound pulse is emitted by the transducer
• Photo-sensitive paper is moved at a constant
  speed across a B-mode display
• Squiggly lines represent changing depth of the
  reflecting surfaces
• Undulating lines indicate a reflector which is in
  motion
• Straight horizontal line indicates a stationary
  reflector
• X-axis represents time
• Y-axis represents depth, derived from
  time-of-flight information

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M-mode

• Sampling rate is very high, equal to the systems
  PRF
• Primarily utilized to assess motion of cardiac
  walls and structures
• The only mode that provides information about a
  reflectors changing depth over time

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Display Mode Axes