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MSK Ultrasound

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greg condie

on 9 April 2015

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Transcript of MSK Ultrasound

MSK Ultrasound
Introduction to Musculoskeletal Ultrasound (MSKUS)
Practice safe physics
The physics of Ultrasound
Image is everything!
MSKUS characteristics
KNOBOLOGY
The beam of ultrasound comes from a
small device called a transducer
MSKUS of the Wrist and Shoulder
Wrist
Transducers: more than meets the eye
Ultrasound Characteristics
The Wave of the Future
l

Course objectives
Discuss basic
ultrasound physics
including propagation speed, impedance, and focusing.
 
Discuss transducer
frequency
and its relationship with image quality.
  
Explain how to properly hold the transducer when performing ultrasound.
 
Explain transducer movements and how they affect image characteristics.
 
Discuss ultrasonographic appearance of normal musculoskeletal structures including:
muscle, tendon, ligament, peripheral nerve, cyst, and subcutaneous tissue
.
 
Discuss the types of
artifacts
that can occur when performing musculoskeletal ultrasound.
 
Discuss key
wrist and shoulder anatomical structures
when performing diagnostic musculoskeletal ultrasound.

MSUS is a safe, inexpensive,
noninvasive, easily accessible imaging modality that provides real-time imaging
during dynamic maneuvers
Ultrasound can be used to evaluate nerve, tendon,
muscle, ligament, and joint disorders and to guide therapeutic procedures
MRI VS. Ultrasound
Whats an Ultrasound?
Its a soundwave or mechanical longitudinal wave described as displacement of pressure
Propagation
An ultrasound image is formed from numerous pulses that reflect/echo back to the transducer
The
production and detection
of echoes
form the basis of the technique that is used
in all diagnostic instruments. A
reflection
occurs at the boundary between two materials
provided that a certain
property
of the
materials is different.
Ultrasound tranducers are based on the pizza-electric effect
"Plug and play"
High-frequency transducers provide resolution equivalent or superior to currently available magnetic resonance imaging (MRI) scanners.
Unlike MRI or computed tomography, MSK US also offers the capability of performing dynamic imaging. Clinicians can palpate under the transducer (ie, sonopalpation) to visualize the structures localizing to a patient's complaints
Ultrasound has similar sensitivity and specificity for diagnosis of rotator cuff pathology when compared with MRI
Name this transformer?
Ok this is a Sound wave
Frequency
number of cycles or pressure changes
(oscillations)
that occur in 1 second
Hertz: cycles per second
In MSKUS, we commonly use frequencies from
2-10
MHz (10^6)

Can you hear me now?
15 kHz to 90 kHz
BATS
40 Hz to 60,000 Hz
DOGS
Dolphins
20Khz to 150 Khz
Propagation speed

is the speed at which sound can travel through a medium
Electromagnetic waves can travel across a vacuum like X rays, but
sound waves require a medium for propagation.

The speed of sound is
fixed for any given medium
. Dense, rigid materials (e.g. bone:c z 3000 m/s) transmit sound faster than light, compressible materials (e.g. air: c z 330 m/s).

The speed of sound in the soft
tissues of the body ranges from 1400 m/s (fat) to 1750 m/s(tendon), with an average speed of
1540 m/s.
speed =wavelength x frequency
Is there an Echo in here?
To achieve the
depth of resolution required for clinical
uses, pulsed beams are used. Typically, the
pulses are a millisecond or so long and
several thousand are emitted per second
Transducers transmit 1% of the
time and ‘listens’ for the reflected echoes 99% of the time
"UNlike men who talk 99% of the time and listen for 1 %"
not a real quote
Impedence: why do we care?
If two materials have the same acoustic impedance, their boundary will not produce an echo; where a small impedance causes a weak echo
More impedence
If the difference in acoustic impedance
is large
( Mismatch )
, a strong echo
will be produced. If the difference in acoustic
impedance is very large, all the ultrasound
will be totally reflected.
They can bounce
(reflection)
,
bend
(refraction)
, scatter
(diffraction)
, and convert their kinetic
energy into heat energy
(absorption)
This
property
is known as the (z)
acoustic impedance
and is the product of the density and propagation speed

Z= density x propagation speed
Percentage reflection of Ultrasound at boundaries

Boundary % Reflected
Fat/muscle 1.08
Fat/kidney 0.6
Soft tissue/water 0.2
Bone/fat 49
Soft tissue/air 99
Steel
Muscle
Audible sound is in the frequency range:
20 to 20,000 Hz (20 kHz) (10^3)
Ultrasound is defined as frequencies:

> 20 kHz

Hyperechoic
Hypoechoic
Impedance determines how much of a sound wave is reflected back through the first medium and how much is transmitted into the second medium
"One ping only"
Shoulder
The
biceps
tendon should be examined with
the forearm in supination and resting on the
thigh or with the arm in slight external rotation.
The tendon is examined in a transverse
plane (short axis), where it emerges from
under the
acromion,
to the musculotendinous
junction distally.
Rotate the arm externally fixing the elbow on the iliac crest to show the
subscapularis
tendon
and its insertion on the
lesser tuberosity
(slight supination of the hand may be helpful
to neutralize the tendency to lift and abduct the elbow from the lateral chest wall
Subscapularis
To examine the
supraspinatus
tendon, the arm can be extended posteriorly, and the
palmar aspect of the hand can be placed
against the superior aspect of the
iliac
wing
with the elbow flexed and directed toward
midline (instruct patient to place the hand in
the back pocket). Other positioning techniques
also may be helpful.
Supraspinatus
Impingement
Infraspinatus and Teres Minor
Shoulder

-
Biceps tendon and muscle
-
Subscapularis muscle and tendon
-Dynamic examination for biceps subluxation (as indicated)
-
Acromioclavicular joint
-
Infraspinatus tendon and muscle
-
Teres minor tendon and muscle
-Posterior glenohumeral joint
-Spinoglenoid notch (region of suprascapular nerve)
-
Supraspinatus tendon and muscle, with subacromial-subdeltoid bursa
-Dynamic rotator cuff evaluation and impingement testing
-Suprascapular notch (as indicated)(suprascapular nerve)
- Extended field of view – supraspinatus & infraspinatus muscle bellies(as indicated)


Specifications of the Shoulder
Examination:
Patients should be examined in the sitting
position, preferably on a rotating seat.
Examination of the shoulder should be
tailored to the patient’s clinical circumstances
and range of motion.
GT
LT
SubSc
Corocoid
SubSc
LT
Delt
Biceps muscle and tendon
Pos 1
Pos 2
Del
Del
Acr
SupraS
SupraS
Hum
Dynamic assessment of
subacromial
(antero-superior) impingement can be attempted by
placing the probe in the coronal plane with its medial margin at the lateral margin of the
acromion. The patient abducts his arm while in internal rotation. With this maneuver, the
supraspinatus and the bursa can be seen passing deep to the coracoacromial arch
Dynamic Pos 2
Dynamic pos 1
Acr
SupraS
GT
GT
Acr
SupraS
The
infraspinatus
and
teres minor
tendons
should be examined by placing the transducer
at the level of the
glenohumeral
joint
below the scapular spine while the forearm
rests on the thigh with the hand supinated
Infra
TM
Del
With the transducer in the coronal plane
over the shoulder you may examine the
acromioclavicular joint.
AC
Cl
joint space
The indications for ultrasound of the
wrist and hand include but are not
limited to soft tissue injury, tendon
pathology (tendinopathy, tenosynovitis,
and tears), arthritis, soft tissue masses or
swelling (including ganglion cysts), nerve
entrapment, effusion, foreign bodies, and
bone injury. This examination is usually
tailored to the clinical presentation
The patient sits with hands resting on
a table placed anteriorly.
The volar examination requires the wrists to be placed flat or in mild dorsiflexion with
palm up
The dorsal scan requires the
wrist to be placed palm down with mild
volar flexion.
The
extensor retinaculum divides the
dorsal aspect of the wrist into 6
compartments, which accommodate
9 tendons
Protocol
Wrist and Hand

Volar:
- Carpal tunnel contents
- Flexor retinaculum
- Median nerve
- Flexor pollicis longus tendon
- Flexor digitorum profundus and superficialis tendons
- Dynamic examination with flexion & extension – tendon & nerve motion
-Palmaris longus tendon
- Flexor carpi radialis longus tendon and radial artery (occult ganglion cyst)
- Ulnar nerve and ulnar artery within Guyon’s canal
- Flexor carpi ulnaris tendon
- Trace all tendons followed to their sites of insertion if clinically indicated
- Joints as clinically indicated (e.g. volar radiocarpal joint)

Ulnar/Medial:
- Extensor carpi ulnaris tendon and muscle
- Dynamic examination for extensor carpi ulnaris subluxation (as indicated)
- Triangular fibrocartilage complex and meniscus homologue
- Ulnocarpal joint


Keeping the patient’s wrist halfway between pronation and supination, place the probe
over the lateral aspect of the radial styloid to examine the first compartment of the
extensor tendons -
abductor pollicis longus
(ventral) and
extensor pollicis brevis
(dorsal
APL
EPB
Radial
Styloid
A
nimal
PL
antet &
E
at
P
eanut
B
utter
A
V
RN
Second Compartment
With the palm facing the examination table, shift the probe medially on
transverse planes to depict the second compartment -
extensor carpi radialis longus and extensor carpi radialis brevis tendons
ECRL
ECRB
Radius
R U
Find the Lister tubercle over the dorsal
radius as the bone landmark to separate the
second compartment (lateral) from the third
compartment (medial).
EPL
is present
Third compartment
ECRB
EPL
Lt
R U
Fourth and Fifth Compartment
Place the transducer on the transverse plane over the mid dorsal wrist to examine the
fourth –
extensor digitorum communis and extensor indicis proprius
– and fifth –
extensor
digiti minimi
– compartments
Lt
ECRB
ECRL
EPL
EDC
EI
EDM
Radius
Ulna
Sixth Compartment
Place the wrist in slight radial deviation to examine the sixth compartment –
extensor
carpi ulnaris.
Ulna
ECU
Volar: The carpal tunnel
M
Sca
Pis
fpl
FCR
d
d
d
d
s
s
s
s
A
Check the flexor retinaculum and each of the nine long flexor tendons (four from
the
flexor digitorum superficialis,
four from the
flexor digitorum profundus
and the
flexor pollicis longus
radially) contained within the carpal tunnel.
Trap
Ham
M
hook
fpl
d
d
d
d
s
s
s
s
A
Identify the two bony landmarks of the distal carpal tunnel – the trapezium tubercle (radial
sided) and the hamate hook (ulnar sided).
First Compartment
Transducer or not?
WEll no actually the

Piezoelectric
effect

The conversion of electromagnetic energy (volts) to mechanical energy
-
How you get the sound waves

‘Reverse’ piezoelectric effect
The conversion of mechanical energy to electromagnetic energy (volts)
-
How you get your image

The transducer element of a simple
probe is usually a disk-shaped crystal
The size of the crystal determines the frequency
Think hammer and bell.
= vibration
= vibration
A electrical pulse is applied to the crystal
Lead zirconate titanate (PZT)
Doppler
The Doppler information
can be presented in two ways
In color
Doppler, the direction of blood flow or
movement is mainly shown,

with flow
away from the probe colored red
and
flow
toward the probe colored blue
Power
Doppler, on the other hand, shows magnitude
of flow
.
Power Doppler is often
more sensitive to movement.
-
blue shows the
greatest flow
and
red the least flow.
Neovascularization
is the development of small vessels within tissue. This commonly occurs in the synovium of patients with rheumatoid arthritis and in the attempted healing of degenerative tendons
Definition – a decrease in amplitude and intensity with distance as a wave travels through a medium
velocity = frequency x wavelength

Increasing frequency decreases penetration but improves resolution (detail) by shortening ultrasound pulses and tightening the focus: usually around 3-12 hz
Attenuation

The Doppler effect (C. J. Doppler, 1842) is the apparent change
in frequency of a wave due to relative motion (velocities) of the
wave source (vs) and observer (vo); or in the case of a reflected
wave, motion of the reflector. Think ambulence siren and observor
Honey comb or speckled appearance

Nerve
Tendon
Fibrillar echotexture
Muscle
Relatively hypo-echoic

brachialis and biceps brachii muscles in long axis
Normal patellar tendon
Tibial collateral ligament
Ligament
Fibrillar texture
Bone
Hyperechoic
Cartilage
Hypo-echoic
distal anterior femur- hyaline cartilage
Cross sectional view
"short axis"
Longitudinal view
"long axis"
Maintaining correct hand contact and body positioning is vital for accurate imaging
Position is key
Transducer Maneuvers
Heel-toe
Toggle
Tibialis posterior (P) and flexor digitorum longus (F) tendons in short axis at the ankle show normal tendon hyperechogenicity (A) and hypoechoic anisotropy
Long head of the biceps tendon at the lesser tuberosity in long axis
They allow you to optimize the structure being imaged and allow for accurate identification of structures
Toggle
Heel-toe
Anisotropy
Definition: The property of being directly dependent

The
property
(echogenicity of the image) is
dependent
on the transducer angle:
Perpendicular vs. oblique
Oblique
Perpendicular
becomes
anisotropic as it curves

Acoustic Shadow
Achilles tendon in long axis shows hyperechoic ossification
(red arrow)
with posterior acoustic shadowing
(yellow arrows)
Wavelength
Amplitude
Distance
Velocity
Frequency
Period
Finger flexor tendon
velocity = frequency x wavelength
= 1/T
Reverberation
Ring down effect
Ring-down artifacts are
produced when small crystals such as
cholesterol or air bubbles
resonate at the
ultrasound frequency and emit sound.
Because the sound is emitted
after
the
initial reflection is received by the transducer,
the system thinks the emitted
sound is coming from structures deeper
in the body.
Reverberation artifacts
appear as multiple equally spaced lines
along a ray line.
This is caused by the sound bouncing back and forth
between tissue boundaries and then returning
to the receiver
Air bubbles
Enhancement
Enhancement is seen as
an abnormally high brightness.
This occurs when sound travels through a medium with an attenuation rate lower than surrounding tissue.
Enhancement of tissues deeper than
cysts or ducts
is common.
Gain
When optimizing a MSKUS image, the gain is adjusted to improve differentiation between black/white lines.

You are altering the image recorded by the crystals in the transducer

The optimum gain setting
is determined by the
ambient light of the
room.

power doppler
Median
nerve
flexor carpi radialis tendon
long
Short
Anisotropy

1) David Williams. The physics of ultrasound. . ANAESTHESIA AND INTENSIVE CARE MEDICINE 13:6 264

2)Jon Finnoff. PASSOR Legacy Award Lecture 2009: The Past, Present, and Future of Musculoskeletal Ultrasound in Physiatry. American Academy of Physical Medicine and Rehabilitation Vol. 2, 6-13, January 2010

3)Jon F, et al. A Musculoskeletal Ultrasound Course for Physical Medicine and Rehabilitation Residents. . Am. J. Phys. Med. Rehabil. Vol. 89, No. 1, January 2010

4)John A. Basic physics of ultrasound imaging. Crit Care Med 2007 Vol. 35, No. 5

5) Kremkau, FW. Sonography Principles and Instruments, Ed 7. Elsevier. St. Louis, MO. 2006

6) Jacobson JA. Fundamentals of Musculoskeletal Ultrasound, Ed 2. Elsevier. Philadelphia, PA. 2012





References:
Get excited ....................
by Gregory Condie DO
VCU PM&R

Acoustic Impedence
Echogenicity
Which is why we use ultrasound gel
Which takes away the impedence of air!!!
Anisotropy
The attenuation of the sound through the fluid in these tissues is less than that of the surrounding tissues and results in this abnormal brightness
A
P
SOUNDWAVE
Characteristics of a soundwave
the transducer is about the size of a deck of cards, but the beam is about the size of a single card!
vs.
Full transcript