Ultrasound Imaging

Question 1

describe how USI works

Answer 1

1. A current is applied to a crystal which causes oscillations at the base frequency which creates an ultrasound beam
2. Beam applied through soft tissues
3. Reflected beams received by crystals, causing charge
4. from this data, image is contructed

Question 2

where is the intensity greatest in an ultrasound beam?

Answer 2

center of beam

Question 3

what is the focal zone?

Answer 3

narrowest zone along long axis of beam

Question 4

list and describe the 2 scanning planes in USI

Answer 4

1. longitudinal sonogram → long axis of transducer aligned to long axis of structure
2. transverse sonogram → transducer applied across structure

Question 5

the field of view in USI is the same as ______

Answer 5

long axis of transducer

Question 6

define hyperechoic

Answer 6

“lots of echoes”

appear as light gray

hyperechoic masses are not as dense as hypoechoic ones are. They may contain air, fat, or fluid

Question 7

define hypoechoic

Answer 7

“not many echoes”

appear as dark gray

hypoechoic masses are more dense or solid than usual

Question 8

list tissue types that are normally hyperechoic (3)

Answer 8

1. cortical bone
2. tendons and ligaments
3. nerves

Question 9

list tissue types that are normally hypoechoic

Answer 9

1. muscle
2. bursa
3. hyaline cartilage

Question 10

how would a tendon or ligament injury appear on USI

(strain versus rupture)

Answer 10

1. strains → thickening, of mixed echogenicity, disrupted fiber pattern
   
   1. hypoechoic if inflammation or hematoma
2. ruptures → disruption of fibrous bands; initially filled with hypoechoic hematoma, and separation of ends

Question 11

describe how a muscle strain vs rupture my appear on USI

Answer 11

1. strain → disruption of fibrous bands, hypoechoic hematoma in early stages
2. rupture → retraction of muscle

Question 12

describe how an abnormal bursa would look with USI

Answer 12

increased width of bursa

in later stages, hyperechoic thickening of bursa walls

Question 13

describe how abnormal hyaline cartilage may look with USI

Answer 13

early changes display inhomogenous thickening

later irregularity and disruption

Question 14

describe how a nerve compression may look with USI

Answer 14

flattening, swelling proximal to compression

Question 15

describe how a cyst may look with USI

Answer 15

normally anechoic

abnormally → increased volume, thickened walls, separations, debris

Question 16

how is blood velocity measured with Doppler US?

Answer 16

measured on the difference of:

• when moving toward the transducer, sound waves reflected off of blood cells arrive back at transducer faster
• when moving away from transducer, sound waves reflected off of blood cells arrive at transducer slower

Question 17

what does doppler US provide information on? (3)

Answer 17

1. presence of blood flow
2. direction of blood flow
3. gross circulation abnormalities

Question 18

how is blood flow through a narrowing foramen (stenosis) characterized with doppler US?

Answer 18

increased speed and turbulence

Question 19

list several clinical indications and benefits of USI (5)

Answer 19

1. ID/Differentiation of MSK lesion
2. Real-time assessment
   
   1. allows for dynamic testing (shoulder, subluxing ankle evertors, etc.)
3. Biofeedback → RUSI
4. Continuous monitoring of health conditions
5. Doppler US

Question 20

what is RUSI?

Answer 20

real-time ultrasound imaging

rehabilitative ultrasound imaging

Ex → LBP → RUSI can help you see activation of TrA or Multifidus

Question 21

list several advantages of musculoskeletal ultrasound (11)

Answer 21

1. high-resolution soft tissue imaging
2. ability to image in real-time
3. facilitates dynamic examination of anatomic structures
4. can interact with the pt while imaging
5. minimally affected by metal artifact (ie, implants and hardware)
6. ability to guide procedures (eg, aspirations, injections)
7. enables rapid contralateral limb examination for comparison
8. portable
9. relatively inexpensive
10. lacks radiation
11. no known contraindications

Question 22

list general advantages of ultrasound imaging relative to MRI

Answer 22

1. low cost and portability
2. no contraindications, orthopedic hardware not a problem
3. ability to visualize structures not limited by orthogonal planes
4. continuous modification of imaging based on findings
5. palpation, stress, testing, and application of resistance while imaging

Question 23

list advantages of USI over MRI

Answer 23

1. Muscles → architecture, imaging while testing with resistance
2. Tendons → fiber structure, degenerative changes, longitudinal tears
3. Ligaments → fiber structure, ability to stress test while imaging
4. Cysts and bursae → separation, debris not seen on MRI

Question 24

list disadvantages of USI relative to MRI

Answer 24

1. Joints; Intra-articular structures → limited ability to show joint surfaces and intra-articular surfaces
2. Bones → can only show cortical outline of bone
3. Scanning across lung fields → US does not cross air/tissue interfaces

Question 25

list technical disadvantages of musculoskeletal US

Answer 25

1. limited field of view
2. incomplete evaluation of bones and joints
3. limited penetration

Question 26

list several examples of common clinical application of MSK USI

Answer 26

1. Tendinopathies
2. Muscle strains
3. Front-line diagnostics for pt’s with shoulder pain
4. assessment of superficial areas of joint (e.g posterior GH joint pathology)
5. Post-op assessment
6. joint stability w/dynamic stress testing
7. peripheral nerve compression
8. superficial disruption of bone cortices (eg rib frx)
9. inflammatory arthropathies (eg. RA)

Question 27

list several shoulder pathologies that USI can help diagnose

Answer 27

1. rotator cuff and biceps tendon lesions
2. swelling in bursae
3. subacromial impingement (dynamic assessment)