Ultrasound Imaging and Muscle Function (WEEK 13) Flashcards
What is U/S imaging used for?
- diagnosis of structural pathology - contusion, stress fracture
- muscle function (morphology/behaviour):
Rehabilitative U/S Imaging (RUSI) function
scope of practice used for:
- Biofeedback to restore NM function
- Perform research aimed at clinical practice
- Evaluate morphology and function of muscle during physical task
Real-time U/S (RTUS) How do we identify if a ligament is torn?
- RUSI the MCL while applying a values force
allows us to see the muscle change in real time
Ultrasound soundwaves
2.5-15.0 MHz
electrical sound wave –> sound wave via transducer
USI Image generation: Propogation/Reflection capacity
- US wave characteristics
2. Tissue characteristics (acoustic impedance)
Effect of acoustic impedance
Breaks up and dissipation as a results of: absorption, scatter, reflection due to different acoustic impedance
- adipose, fascia, muscle, bone
How is image created?
Reflection: the transducer can determine where along the head it came back, the length of time it took to reflect back, amplitude of echo
superficial - pixel at top of image
deep - pixel at Botton of image
Color pixel
intensity of echo
fluid - why is it referred to as hypo or anechoic?
Fluid = poor reflection –> black
Bone cortex - hyperechoic?
dense collagen are good at reflecting sounds –> white
muscle vs. tendon - hyper or hypo?
muscle = collagen (unorganized) and blood = hypo (black)
tendon = more organized, dense = hyper (white)
Define hyperechoic
medium that is more echogenic that surrounding tissue.
- appears whiter and brighter e.g. bone cortex, bone, dense fascia
Define hypoechoic
medium that is less echogenic than surrounding tissue
- appears darker e.g. fluid
Define echogenity
collagen vs. fluid
reflective property of tissue provides insight about composition
- collagen = > echogenicity (WHITE)
- fluid content =
Architectural Characteristics
RUSI - compares differences/changes in parameters (shape, size, and other structural characteristics/pennation pattern
Echogenicity: Low Back Pain findings
Conventional USI detect altered lumbar CT in persons with LBP
- 25%>perimuscular thickness & echogenicity (WHITE)
- factors? genetics, abnormal movement patterns, chronic inflammatino
Architectural Characteristics: IAK injury
refers to size and shape
- conventional USI measures the CSA of vastis medals 3-10 years post intra-articular knee injury. 3.8x more likely to have difference in VM CSA > 15%
Validity: USI and muscle
- good agreement (0.7-0.9) measurement of muscle size
USI function:
tells us about muscle size but cannot tell us anything about why it is this way
USI & EMG inconsistency
inconsistent correlation (e.g. RA, EO, IO, TA)
Shape of muscle: Muscle activity
contract (shorten)
relax (lengthen)
Shape of muscle: Resting state
increased/decreased resting length will affect the thickness and extensibility
Shape of muscle: Resting activity
competing forces increase thickness of muscle(?)
e. g. Oblique tone & Intra-Abdmonial Pressure
(e. g. TA thicker in erect sitting that slouched)
Shape of muscle: Out of plane changes
Depending on plane will affect the thickness of muscle
Shape of muscle: type of muscle contraction
eccentric - thin
concentric - thick
Factors that influence change in muscle shape
- muscle activity
- resting state (length and activity)
- extensibility/structure of myofascial unit (muscle, tendon, fascia, pennation, lamentation)
- Types of muscle contraction
- Competing forces (e.g. abdmoninal muscles)
- imagining technique (out of plane, body motion)
Correctly Interpre4ng Dynamic USI Studies
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