AMSSM Beginner Ultrasound Course
KNOBOLOGY 101
David M. Harsha, MD
St.Vincent Sports Performance
January 17th, 2014
Ultrasound Components
Pulser - applies high amplitude voltage to
energize the crystals
Transducer - converts electrical energy to
mechanical (ultrasound) energy and vice
versa
Receiver - detects and amplifies weak signals
Display - displays ultrasound signals in a
variety of modes
Memory - stores video display
Generation of image
Electrical signal sent to transducer
Transducer produces sound waves
Sound waves transmit into soft tissues and
interact with soft tissue interfaces, some of
which reflect back to the transducer
Transducer converts sound waves into
electrical current to produce an image
Attenuation
Attenuation
• Loss of amplitude, power, and intensity as
sound travels.
• Three contributing factors:
• Absorption
• Scatter
• Reflection
• Sound degrades 0.5dB/1MHz/1cm
• @3cm, 6dB w 4MHz
Compound spatial imaging
Transducers
Band Width-Range of frequencies
that come out of a transducer
Frequency of transducer determines
image quality
Higher frequency
Higher resolution and less sound beam
penetration
Lower frequency
Lower resolution and increased depth
of sound beam penetration
Transducer types
Curved
Increase field of view
Generate lower frequency waves
than linear transducers and
provide images of lower
resolution
Increased depth of penetration
Transducer types
Linear
Field of View
 Large >40mm
 Medium<40mm
 Small-hockey stick
Transducer Movement
Heel-Toe
Maneuver
Transducer Movement
Tilting
Transducer Movement
Rotation
Modes
B mode (brightness)
M mode (motion)
• Most common standard
• Represents movement of
scanning mode
• 2-D cross sectional view of
the underlying structures
• Made up of numerous Bmode (brightness mode)
scan lines.
• Field of view is the tissues
that are intersected by the
scanning plane
structures over time
• Initially a 2-D image is
acquired and a single scan
line is placed along the area
of interest
• M-mode will then show how
the structures intersected by
that line move toward or
away from the probe over
time
Modes
Power Doppler
• Very sensitive assessment
of presence of flow
• Does not show direction of
flow or Velocity of flow
Important to adjust the color
gain optimally or Doppler
imaging causes artifact
Color Doppler
• Shows presence of
vascularity and direction of
flow
• Does not show flow Velocity
• Useful for differentiating
vascular from non vascular
structures
Modes
GE Logic e
Sonosite Edge
Power Doppler
PD detects flow only
And not direction
Color Doppler
Color Doppler detects
Bidirectional flow
Frequency
Higher frequency
Higher resolution and less sound beam
penetration
Lower frequency
Lower resolution and increased depth
of sound beam penetration
Select the highest frequency
transducer possible for the required depth
of penetration
Frequency
Frequency
Depth
• Structures get smaller and smaller as the
depth is increased
• Select the appropriate depth setting to target
the structure of interest
• Center structure of interest
Depth
GE Logic e
Sonosite Edge
Depth
Focus
Number of focal zones
Focal zones will decrease frame
rate that produces a windshield-wiper effect
•
•
•
Image quality and beam focus best at the
focal zone
Move depth of focal zones to depth where
structure is located in order to optimize
resolution
Sonosite has auto-focus feature
Near field
Focal zone
Far Field
Focus
Focus
Focus
Proper focal points
Focal point too deep
Gain
• Compensates for attenuation (reduction in sound amplitude)
as sound travels deeper into tissue
• Returning signals amplified by receiver-turning up the volume!
•
Displayed image is brighter and more visible
•
•
•
Near field
Far field
Entire field (overall gain)
• Gain can be adjusted
• Excessive GAIN will cause "noise" to the image.
• Time gain compensation (TGC) is adjusted to selectively
amplify weaker signals
Gain
GE Logic e
Sonosite Edge
Gain
Time Gain Compensation
Time Gain Compensation
Auto-optimization
• Machine provides optimal
• Gain
• Frequency
• Only available in B and Doppler modes
Image Optimization
1. Select Transducer and Frequency
2. Adjust Depth
3. Adjust Focal Zones if present
4. Adjust Gain/TGC
Other Features
• Instructors can explain as needed:
• Virtual Convex
• Measurement
• Extended Field of View
• Beam steer or SonoMBe for needle guidance
• Saving images to the machines
Measurement
Measurement