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Basic UltrasoundMAPA Fall Conference
October 9, 2015
10/19/2015 1
Introduction
Ultrasound
Uses high-frequency sound waves to characterize tissue
Relies on the properties of acoustic physics
Uses frequencies in the range of millions of cycles per second (megahertz, MHz)
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Introduction
Basic physics
A transducer sends an ultrasound impulse into tissue and the receives echoes back
The echoes contain spatial and contrast information
Some characteristics can be selected out to provide additional information
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Why use ultrasound?
Advandages
Uses non-ionizing sound waves
More readily available than CT or MRI
Less expensive
Few, if any, contraindications to the use of ultrasound
Real time nature useful for evaluation of physiology
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Why use ultrasound?
Disadvantages
Operator dependent
Not capable of evaluating all tissue types or structures encased in bone
Potential risk of thermal heating or mechanical injury to tissue at a micro level
Has its own set of unique artifacts which can potentially lead to misinterpretation
May be limited by abnormally large body habitus
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Physical principles of ultrasound
The ultrasound beam originates from mechanical oscillations of numerous
crystals in a transducer
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Physical principles of ultrasound
Ultrasound waves are sent from the transducer, propagate through different
tissues, and then return to the transducer as reflected echoes
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Physical principles of ultrasound
Ultrasound waves are reflected at the surfaces between the tissues of
different density
The reflection being proportional to the difference in impedance
The acoustic resistance to sound traveling through a medium
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Ultrasound frequencies
Frequencies in diagnostic radiology range from 2 MHz to 15 MHz
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Ultrasound glossary
Echogenicity
The ability to reflect or transmit US waves
Based on echogenicity, a structure can be characterized as:
Hyperechoic (white on the screen)
Hypoechoic (gray on the screen)
Anechoic (black on the screen)
10/19/2015 10
Ihnatsenka B, Boezaart AP. Ultrasound: Basic understanding and learning the language.
International Journal of Shoulder Surgery. 2010;4(3):55-62. doi:10.4103/0973-6042.76960.
10/19/2015 11
Ihnatsenka B, Boezaart AP. Ultrasound: Basic understanding and learning the language. International Journal of
Shoulder Surgery. 2010;4(3):55-62. doi:10.4103/0973-6042.76960.
10/19/2015 12
Ultrasound appearance of various tissues and structures
Bone Black or anechoic with a bright hyperechoic rim
Cartilage Gray or hypoechoic
Blood vessels Black or anechoic
Muscles Hypoechoic with striate structure
Fat Almost anechoic
Fascia Hyperechoic lines
Lymph nodes Anechoic or hypoechoic
Nerves Variable depending on size and location
• Proximal nerves-hypo to anechoic
• Distal nerves-hyperechoic with stippled structure
Ligaments and
tendons
Similar appearance to distal nerves
Adapted from : Ihnatsenka B, Boezaart AP. Ultrasound: Basic understanding and learning the language. International Journal of
Shoulder Surgery. 2010;4(3):55-62. doi:10.4103/0973-6042.76960.10/19/2015 13
Ultrasound glossary
Scanning planes
Similar to the anatomical planes
Axial
Sagittal
Coronal
Ultrasound views
Long axis
Short axis
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Ultrasound glossary
Angle of incidence
The angle at which the US waves encounter the surface of the structure
Affects the way it is presented on the screen
10/19/2015 15
Ihnatsenka B, Boezaart AP. Ultrasound: Basic understanding and learning the language. International Journal of
Shoulder Surgery. 2010;4(3):55-62. doi:10.4103/0973-6042.76960.
10/19/2015 16
Improving needle visualization during “in plane” needle placement. To
improve needle visualization, one can change the US probe position (from 1
to 2) and the needle approach (from 1 to 2 to 3) to optimize the angle of
incidenc between US waves and the needle.
Ihnatsenka B, Boezaart AP. Ultrasound: Basic understanding and learning the language.
International Journal of Shoulder Surgery. 2010;4(3):55-62. doi:10.4103/0973-6042.76960.
10/19/2015 17
Ultrasound wave frequency, image
resolution, and penetration
High (10-15 MHz) and midrange (5-10 MHz) frequency probes provide better
resolution but have less penetration
Low frequency (2-5 MHz) have better penetration but poor resolution
10/19/2015 18
Curvilinear versus straight probe
Curvilinear probes generate a wedge-shaped US beam and corresponding
image on the screen
The curved probe can roll on its scanning surface affecting the direction of the US
beam
Provides a broader view obtained via a smaller acoustic sindow
Straight probes produce a straight beam and an image with a width equal to
the size of the transducer footprint
10/19/2015 19
Ihnatsenka B, Boezaart AP. Ultrasound: Basic understanding and learning the language.
International Journal of Shoulder Surgery. 2010;4(3):55-62. doi:10.4103/0973-6042.76960.
10/19/2015 20
Color Doppler function
Helps to distinguish structure with movement
Blood moving in vessel
Blue Away Red Toward
ligaments
10/19/2015 21
Ihnatsenka B, Boezaart AP. Ultrasound: Basic understanding and learning the language. International Journal of Shoulder
Surgery. 2010;4(3):55-62. doi:10.4103/0973-6042.76960.
10/19/2015 22
Knobology: gain and depth
Changing the gain will change the amount of white, black, and gray on the
monitor
May improve the operator’s ability to distinguish structures on the screen
Most US machines have:
Near gain
Far gain
Auto gain
The depth adjustment determines how far away the US beam from the probe
will reach
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Ultrasound artifacts
Acoustic shadowing
A signal void behind structures that strongly absorb or reflect ultrasonic waves
Acoustic enhancement
Increased echoes deep to structures that transmit sound exceptionally well
Reverberation artifact
Occurs when an ultrasound beam encounters two strong parallel reflectors
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Acoustic shadowing and enhancement
Reverberation artifact
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