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Transcript of MSK Ultrasound
Introduction to Musculoskeletal Ultrasound (MSKUS)
Practice safe physics
The physics of Ultrasound
Image is everything!
The beam of ultrasound comes from a
small device called a transducer
MSKUS of the Wrist and Shoulder
Transducers: more than meets the eye
The Wave of the Future
including propagation speed, impedance, and focusing.
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
that can occur when performing musculoskeletal ultrasound.
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
An ultrasound image is formed from numerous pulses that reflect/echo back to the transducer
production and detection
form the basis of the technique that is used
in all diagnostic instruments. A
occurs at the boundary between two materials
provided that a certain
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
number of cycles or pressure changes
that occur in 1 second
Hertz: cycles per second
In MSKUS, we commonly use frequencies from
Can you hear me now?
15 kHz to 90 kHz
40 Hz to 60,000 Hz
20Khz to 150 Khz
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
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
If the difference in acoustic impedance
( 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
, and convert their kinetic
energy into heat energy
is known as the (z)
and is the product of the density and propagation speed
Z= density x propagation speed
Percentage reflection of Ultrasound at boundaries
Boundary % Reflected
Soft tissue/water 0.2
Soft tissue/air 99
Audible sound is in the frequency range:
20 to 20,000 Hz (20 kHz) (10^3)
Ultrasound is defined as frequencies:
> 20 kHz
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"
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
to the musculotendinous
Rotate the arm externally fixing the elbow on the iliac crest to show the
and its insertion on the
(slight supination of the hand may be helpful
to neutralize the tendency to lift and abduct the elbow from the lateral chest wall
To examine the
tendon, the arm can be extended posteriorly, and the
palmar aspect of the hand can be placed
against the superior aspect of the
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.
Infraspinatus and Teres Minor
Biceps tendon and muscle
Subscapularis muscle and tendon
-Dynamic examination for biceps subluxation (as indicated)
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
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.
Biceps muscle and tendon
Dynamic assessment of
(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
should be examined by placing the transducer
at the level of the
below the scapular spine while the forearm
rests on the thigh with the hand supinated
With the transducer in the coronal plane
over the shoulder you may examine the
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
The dorsal scan requires the
wrist to be placed palm down with mild
extensor retinaculum divides the
dorsal aspect of the wrist into 6
compartments, which accommodate
Wrist and Hand
- 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)
- 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
extensor pollicis brevis
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
Find the Lister tubercle over the dorsal
radius as the bone landmark to separate the
second compartment (lateral) from the third
Fourth and Fifth Compartment
Place the transducer on the transverse plane over the mid dorsal wrist to examine the
extensor digitorum communis and extensor indicis proprius
– and fifth –
Place the wrist in slight radial deviation to examine the sixth compartment –
Volar: The carpal tunnel
Check the flexor retinaculum and each of the nine long flexor tendons (four from
flexor digitorum superficialis,
four from the
flexor digitorum profundus
flexor pollicis longus
radially) contained within the carpal tunnel.
Identify the two bony landmarks of the distal carpal tunnel – the trapezium tubercle (radial
sided) and the hamate hook (ulnar sided).
Transducer or not?
WEll no actually the
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.
A electrical pulse is applied to the crystal
Lead zirconate titanate (PZT)
The Doppler information
can be presented in two ways
Doppler, the direction of blood flow or
movement is mainly shown,
away from the probe colored red
toward the probe colored blue
Doppler, on the other hand, shows magnitude
Power Doppler is often
more sensitive to movement.
blue shows the
red the least flow.
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
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
brachialis and biceps brachii muscles in long axis
Normal patellar tendon
Tibial collateral ligament
distal anterior femur- hyaline cartilage
Cross sectional view
Maintaining correct hand contact and body positioning is vital for accurate imaging
Position is key
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
Definition: The property of being directly dependent
(echogenicity of the image) is
on the transducer angle:
Perpendicular vs. oblique
anisotropic as it curves
Achilles tendon in long axis shows hyperechoic ossification
with posterior acoustic shadowing
Finger flexor tendon
velocity = frequency x wavelength
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
initial reflection is received by the transducer,
the system thinks the emitted
sound is coming from structures deeper
in the body.
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
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
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
flexor carpi radialis tendon
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
Get excited ....................
by Gregory Condie DO
Which is why we use ultrasound gel
Which takes away the impedence of air!!!
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
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!