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Disclosure Statement of
Financial Interest
ULTRASOUND BASICS
Christian R. Falyar, CRNA, DNAP
Department of Nurse Anesthesia
Virginia Commonwealth University
Disclosure Statement of
Unapproved/Investigative Use
• I, Christian Falyar,
DO NOT have a financial
interest/arrangement or affiliation with
one or more organizations that could
be perceived as a real or apparent
conflict of interest in the context of the
subject of this presentation.
OBJECTIVES
•  3$4-#*#6,$,),)2(
I, Christian Falyar,
DO/DO NOT anticipate discussing the
unapproved/investigative use of a
commercial product/device during this
activity or presentation.
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WHAT IS SOUND?
WHAT IS SOUND?
Rarefactions (low pressure)
A
Transducer
λ
Compressions (high pressure)
PROPAGATION VELOCITY
ROLE OF FREQUENCY...
High frequency
Low frequency
•  More cycles per second
•  Fewer cycles per second
•  Images are higher
•  Greater tissue penetration
resolution
•  Increased attenuation
•  Imaging limited to shallow
depths
but lower resolution
•  Less attenuation allows
for imaging of deeper
structures
ROLE OF FREQUENCY
High frequency
Low frequency
BEAM PROPERTIES
IMAGE CREATION
+(,2+
TRANSDUCER BASICS
•  It’s all in the math
•  Depth of the echo is
determined by time from
when the echo was sent to
when it was received
•  The brightness of an echo
is results from differences
in acoustic impedance
between adjacent tissues
ACOUSTIC IMPEDANCE
IMAGE CREATION
Transducer
Incident
Wave
($(-
3
Reflected
Wave
Incident
Wave
Incident
Wave
!-
3
Impedance Z1
Impedance Z1
Impedance Z2
Impedance Z2
Refracted
Wave
Attenuated
Wave
REFLECTION
Specular
REFRACTION
Diffuse
($(-
3
!-
3
+-
3
RAYLEIGH SCATTERING
ATTENUATION
•  The decreasing intensity of a sound wave as it
•  Rayleigh scattering occurs
at interfaces involving
small structures (red blood
cells).
•  This creates a low uniform
amplitude reflection in all
directions.
ATTENUATION COEFFICIENTS
passes through tissue.
•  The attenuation coefficient is the relation of
attenuation to distance; it is dependent on the
tissues traversed and ultrasound frequency.
•  Higher frequencies are attenuated more than
lower frequency waves.
ATTENUATION
Attenuation
TISSUE APPEARANCE
•  Nerves – in cross section appear as round “honeycomb” structures
NERVES
Popliteal Fossa
Brachial Plexus
•  Tendons – appear similar to nerves at the joint, but become flat and
disappear when followed toward the muscle belly
•  Vascular Structures – anechoic circular structures in cross-section;
appear tubular in longitudinal view
•  Fat – hypoechoic areas with streaks of irregular hyperechoic lines
•  Fascia – thin linear hyperechoic structures marking tissue boundaries
•  Muscle – feather-like in longitudinal view; “starry night in cross-
section
•  Pleura and Air – pleura appears as thin hyperechoic lines, while lung
parenchyma appears hypoechoic; reverberation artifact present
•  Cysts – similar vascular structures, however appear as hypoechoic
circles in longitudinal view
•  Bone – hyperechoic linear structures with shadowing underneath
NERVES AND TENDONS
•  Nerves and tendons can
both appear as hyperechoic circles near joints
•  They can be differentiated
by following their course
into the muscle
ADIPOSE TISSUE
•  Adipose appears as hypo-
echoic areas with streaks
of irregular hyperechoic
lines
•  It is the most superficial
layer imaged
Adipose
FLUID-FILLED STRUCTURES
ARTERIES
Arteries
•  Round in short-axis, and
tube-like in long-axis view
•  Pulsatile in nature
•  Difficult to compress
•  Display color on Doppler
•  Arteries, veins, and cysts
all appear as circular
anechoic structures in
short-axis
VEINS
MUSCLE
Veins
•  Muscle appears
•  Ovoid in short-axis and
tube-like in long-axis
•  Easily compressible
•  Valves may be visible
•  Display color on Doppler
heterogeneous on
ultrasound due to the
different acoustic
impedances between cell
structures, the water
content within the cells,
and the fascia
BONE
PLEURA
Pleura appears
as a hyperechoic
line with “comet
tails” beneath it
•  Bone is a significant
DOPPLER EFFECT
DOPPLER EFFECT
reflector, creating a
hyperechoic area with
significant shadowing
beneath it
"Über das farbige Licht der Doppelsterne und
einige andere Gestirne des Himmels Versuch einer das Bradleysche Theorem als
integrirenden Theil in sich schliessenden
allgemeineren Theorie"
Christian Andreas Doppler
1803-1853
DOPPLER EFFECT
DOPPLER EFFECT
•  Doppler is not used to
create an image
•  Doppler is dependent on
the angle of insonation
•  Either the sender or
receiver must be moving
ARTIFACTS
AIR ARTIFACT
•  Any phenomenon that affects the acquisition or
interpretation of an ultrasound image
•  Artifacts occur because:
•  properties of sound
•  tissue
•  created by the provider
•  The most common artifacts are air artifact,
shadow artifact, acoustic enhancement,
mirror image and reverberation
•  Transducer does not fully
contact the skin
•  Commonly occurs when
imaging smaller structures
•  Add gel and apply even
pressure to correct this
SHADOW ARTIFACT
•  When ultrasound contacts
tissue that is a strong
reflector, the amplitude of
the beam distal to structure
is diminished, resulting in a
hypoechoic
ACOUSTIC ENHANCEMENT
•  When sound passes
through tissue with low
acoustic impedance and
contacts tissue with a
much higher impedance,
making it appear more
echogenic than it actually
is
REVERBERATION
MIRROR
IMAGE
•  When sound reflects off
Sound trapped
between two
highly reflective
surfaces
two strong specular
reflectors separated by a
thin layer of air or fluid an
illusion of “multiple”
structures are displayed
below the actual one
SCANNING BASICS
TRANSDUCERS
•  Successful procedures begin with choosing the
•  The transducers used for USRA are either linear
correct transducer and holding it properly
•  Several basic functions will improve outcomes as
well. These include:
or curved linear array transducers
•  Transducers are the link between the ultrasound
system and the tissue. They play a significant
role in determining the resolution and accuracy of
an image
•  Transducer selection is determined by the depth
of the structures to be imaged
•  Depth
•  Contrast adjustment (gain)
•  Color-flow Doppler
LINEAR ARRAY
CURVED ARRAY
HANDLING
HANDLING
•  Notch to the anesthetist’s
left or the patient’s head
•  Hold the transducer flat
against the skin for
maximal contact
•  Hold the transducer like a
pencil
•  Support the scanning arm;
rest it on a firm surface
•  Apply firm, but gentle
pressure
HANDLING
Transducer Perpendicular
Correct Hand Position
Improper Hand Position
B-MODE IMAGING
Transducer Angled
Cross-Section/Short-Axis
Longitudinal/Long-Axis
DEPTH
DEPTH – MEDIAN NERVE
Proper depth
•  Depth determines how far
into tissues echoes are
interpreted
•  Increasing the depth,
decreases resolution
•  The structure of interest is
kept in the center of the
screen
GAIN
GAIN – JUST RIGHT
•  Gain compensates for
attenuation
•  It amplifies RETURNING
echoes
•  Gain can be adjusted
either in the near field, far
field, or overall image
•  Gain is adjusted so that
the image is uniform
Too deep
GAIN
COLOR-FLOW DOPPLER
•  Color-flow allows you to
confirm the presence or
absence of vascular
structures
•  Doppler is super-imposed
over the B-mode image
COLOR-FLOW DOPPLER
COLOR-FLOW DOPPLER
MOVEMENTS
SLIDING
•  In 1999, the American Institute for Ultrasound
Medicine (AIUM) established terminology to
describe transducer movements.
•  These terms do not include specification of
direction (i.e. proximal, distal, clockwise)
•  In general, a transducer can be manipulated in
five ways: sliding, tilting, rocking, rotating and
compressing.
ROCKING
•  Rocking can be used to
correct air artifact and
increase contact of the
transducer
•  Sliding allows the provider
to find the appropriate level
to perform the block
TILTING
•  Tilting improves nerve
image by accounting the
effect of anistropy
ANISTROPY
Transducer Tilted
ROTATING
Transducer perpendicular
•  Rotating allows the
provider to optimize all
structures in the image on
the same plane
COMPRESSING
ORIENTATION
•  Proper placement of the transducer in relation to
•  Compressing can be used
to decrease space from
the skin to the desired
structure
the patient is key to obtaining a correct image
•  The transducer should be oriented to the
anesthetist’s left in cross-section or toward the
patient’s head in longitudinal view
•  When the transducer is not properly oriented, a
“mirror-image” will result
ORIENTATION
PROPER ORIENTATION
IMPROPER ORIENTATION
ERGONOMICS
•  Appropriate bed height
•  Ultrasound in line with the
provider and patient
•  Scanning arm supported
•  Assistant (if available)
•  Proper transducer handling
ERGONOMICS
Poor Ergonomics
WHAT NOW?
Good Ergonomics
OPTIMIZE THE IMAGE
•  Use PLENTY of gel. Gel acts as a coupler
between the transducer and the skin, and
improves the image quality
•  Ensure your transducer is initially perpendicular
and flat against the skin
•  Optimize your depth so the structures you wish to
image are in the center of the screen
•  Adjust your gain to make picture look uniform
•  You have the right patient, discussed the
proposed anesthetic technique, obtained consent,
verified the site, and gathered your supplies
•  Select the appropriate frequency transducer
•  Imagine how the image should appear on the
monitor
•  Use good ergonomics
•  Apply sufficient gel to the transducer
•  Jump in!
NEEDLE VISUALIZATION
In-Plane
NEEDLE VISUALIZATION
Out-of-Plane
SAFETY STRATEGIES
•  Ultrasound itself is non-invasive
•  Ultrasound-guided procedures introduce a needle
and/or local anesthetic into the patient increasing
the potential for complications
•  Needle insertion should first be practiced using a
phantom numerous times, with emphasis placed
viewing the entire needle as it passes through the
tissue
•  Strategies such as wiggling, or hydro-location can
be used to verify the location of the needle tip
ANATOMY
•  Know it. Most nerves blocked using regional
anesthesia are in close proximity to arteries,
veins, or other vital organs (i.e. the lungs)
•  Anticipate what you will be seeing before you
start scanning.
•  Proper orientation of the picture make your
picture appear correctly
QUESTIONS?
REFERENCES
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