RTUS Flashcards
MSK ultrasound characteristics
- MSK US high-frequency sound waves (1-17 MHz)
- Amplitude < 0.1 W/cm2
- Image soft tissues and bone * Identify pathology
- Guide real-time procedures
what can MSK ultrasound identify
- Tendons * Nerves * Ligaments * Joint capsules * Muscles * Bone
Common uses for MSK ultrasound by PT’s
- To help guide clinical decision making
- Documenting changes in clinical conditions
- Dynamic tissue differentiation
- Identification of when to progress exercises or
activity - Localization of specific targets for manual
interventions or physical agents - To guide needle placement
- Blood flow or inflammatory changes
Point of care ultrasound imaging by PTs can identify pathology and/or be procedural:
- Neuromuscular reeducation
- Obtaining real-time information about the activation of specific muscles
- Patient biofeedback
- Monitoring real-time changes in morphology and movement
can you bill for imagining?
- not as imaging CPT code
- can use biofeedback code
benefits of MSK US
- Ability to image in real-time = hands-on, dynamic,
fast - Interactive – allows feedback from patient
- Generally unaffected by metal artifacts
- No radiation to patient or provider
- Exam of contralateral limb for comparison
- High resolution
- Real-time guidance for interventional procedures
- Sono palpation
- Portable
- (Relatively) inexpensive
echo
an ultrasound beam returning to its source
what produces the sound wave
Traditional diagnostic ultrasound beam generated within the US probe by the piezoelectric effect:
* the production of a pressure wave when an
applied voltage deforms
a crystal element
array
refers to the alignment of the crystals
(linear vs curvilinear)
what transducer shows deeper images?
curvilinear
How do you get an image from a newer portable US
- they are digitally produced by a silicon chip containing a 2S array of capacitive micro machined US transducers
reflection at an interface …..
increases when the density difference between two tissues at an interface increases
echogenicity
Echogenicity of the tissue refers to the ability to reflect or transmit US waves in the context of surrounding tissues and shows up as the
amplitude / brightness of the image
hyperechoic
more echoic than surrounding tissue (white)
anechoic
absence of echoes
black
hypoechoic
less echogenic than surrounding tissue
gray
homogenous tissues…
- have fewer interfaces and so less reflection occurs
- they will appear as hypoechoic structures on the screen
(bladder full of homogenous fluid)
bone
- appears black or anechoic on an ultrasound image with a bright hyperechoic rim
- It is black because the US beam cannot penetrate bone and casts an acoustic shadow
blood vessels
- appear black
- have a distinct appearance on color Doppler mode
(red/blue color indicates direction of flow not arterial/venous)
Ansiotrophy
irregularity you see because of the way you hold the transducer (artifact)
when is the reflected sound energy at its greatest as it is returned to the transducer
at an angle of isolation directly perpendicular to the tendon
optimal image when transducer is…
- 90 degrees from target
- Each degree from perpendicular will cause image to drop out
- Anisotropy appears black on screen
- Toggling and rocking transducer will fill in image
B Mode
- most commonly used to
visualize morphology and the position of structures and dynamic events through a snapshot in time
M Mode
movement, motion
doppler mode
- Velocity information is presented as a colored overlay on a B- mode image * Detects direction (blue is motion away from transducer, red towards)
- Velocity – high vs. low
orientation marker
- when the screen marker is on the left of the screen, the probe marker should be directed to the patients head or pt’s right side
2 different probe orientations
- short axis/transverse/cross sectional
- long axis/longitudinal/ same plane as target
tendons in long axis
have characteristic pattern of fine parallel lines, fibrillar appearance
- more hyper echoic and densely striated than muscle or ligaments
tendons in short axis
- appear round or flattened ovals with a punctate interior
- consider artifact
transverse view of muscle
starry night
ligaments in long axis
- fibrillar appearance
how can ligaments be differentiated from tendons
- Ligaments can be differentiated from tendons by noting their more compact fibrillar pattern;
- they are less regularly hyperechoic than tendons due to higher collagen density in tendons
- Bone to bone
Nerves
- Nerves are visible running
along fascial planes, paired with blood vessels, and sometimes within muscles - Longitudinally, they appear as hyperechoic fibrillar cords, they may look similar to tendons but are more hyperechoic with loosely packed fibers
- In transverse view, the nerve fascicles give a “honeycomb” appearance and are less densely fibrillar than tendons
Hyperechoic Characteristics
- High tissue density
- high amount of reflective echoes
- bright
- surface of bone, normal tendon, calcific deposits
Hypoechoic Characteristics
- Moderate tissue density
- Moderate amount of reflective echoes
- gray
- normal muscle, disease tendons, normal fat pad, normal synovium, normal ligs, certain soft tissue masses, complex fluid collections
Anechoic Characteristic
- minimal tissue density
- min amount of reflective echoes
- black
- hyaline cartilage, fluid collections, cysts, normal burial spaces, tendon tear
gain
controls overall amplification of returning signal (think volume knob)
time gain compensation
to control for signal attenuation
depth (field of view)
goal is to target all pertinent anatomy; make
image as big as possible but still see bone
learn about all sorts of imaging on slide 63
p 29 and slide 64 too
advantages of MSK US
- hands on dynamic examination
- together with information gained from the hx, PE, and available dx testing, can help to define the clinical question
- US generally unaffected by metallic artifacts
- comparative exams of the contralateral extremity
Disadvantages of MSK US
- limited field of view
- incomplete evaluation of bones and joints
- limited penetration
- operator dependent
- lack of formal education
- cost and availability to PTs
- variable image quality
considerations as you begin to scan
- Set up the exam beforehand so as to be comfortable for both patient
and PT - Perform the exam based on the focal complaint
- Compare to normal contralateral anatomy
- Obverse structures throughout their dynamic range when possible
- Always account for anisotropy in the study of tendons and nerves
- Develop good recognition of normal structures
- Use copious gel, water or stand-off pad over painful or
topographically convoluted surfaces - Scan all structures in two planes, i.e. longitudinal and transverse
- Always know one’s limits and that of the tools being used
Steps for RTUS success
- Know your anatomy
- Capture a good image
- Recognize structures
- Analyze the image
- Compare to opposite side
- Correlate to clinical findings
- ?add dynamic component to imaging
Multifidus Dysfunction
- Decreased lumbar multifidus cross-sectional area in LBP
- Evidence of asymmetrical atrophy of lumbar multifidus in acute unilateral
LBP, ipsilateral to side of symptoms and present with chronic LBP - Presence of fatty infiltrate in lumbar multifidus in those with LBP and with
aging
Multifidus Cues
- Prone over pillow
- “Swell” or “contract” without moving spine
- Utilize manual cues or RTUS biofeedback
- Contralateral Arm Lifting Task (CALT)
- Isometric training has suggested
- Slow sustained contraction, 10x10sec.
- Several studies include visual aids (models, anatomy, etc)
General considerations for smaller areas
- Use smaller transducer, if possible, with generous use of gel or gel pad
- Consider transducer pressure
Achilles Tendon Exam
- Paratenon, not a synovial sheath
- Elliptical shape on transverse images
- Normal AP thickness ~5mm
- Tears of the Achilles tendon most commonly
occur ~2–6 cm proximal to the calcaneal insertion site
MSK RTUS and Elastography
- Elastography maps the elastic properties and stiffness of soft tissue.
- “Sonoelastography” has been used to examine tendon stiffness or changes
within muscle
Marathon runners and elastography
- Marathon runners demonstrate a higher prevalence of morphological
alterations mid-Achilles compared to non-runners (AP thickness, hypoechogenicity, & neovascularization) - Reduced tendon stiffness at baseline associated with post-marathon Achilles tendon pain
Plantar fascia thickness and plantar fasciitis
> 4 mm consistent with plantar fasciitis
