Intro to U/S Flashcards
- Physiatrists have been involved in US for > ______ decades
- American Institute for Ultrasound in Medicine (AIUM), founded by physiatrists in ______
3 Although initially recognized for ______, MSK US now by used by many physiatrists for _____ and _____ procedures
4 High frequency, real-time MSK US was introduced in _____
- 5
- American Institute for Ultrasound in Medicine (AIUM), founded by physiatrists in 1951
(Multidisciplinary medical association dedicated to advancing the safe and effective use of ultrasound. Education, research, development of guidelines, and accreditation) - Although initially recognized for therapeutic potential, MSK US now by used by many physiatrists for diagnostic and interventional procedures
- High frequency, real-time MSK US was introduced in the 1980’s
improvement in computer technology has lead to a wide expansion of roles of MSK US in PM&R practice
____ is the use of high frequency sound waves to image soft tissues and bony surfaces
MSK US
MSK US can be used for
- Diagnostics: 5
- Interventional procedures: 4
- Diagnostics
- Tendons (tendinopathy, tears)
- Muscles (strains, contusions)
- Nerves (entrapment)
- Ligaments (sprains)
- Joints (effusion)
2 Interventional Procedures
- Injections
- Tenotomy
- Aspiration/lavage
- Biopsy
Advantages of MSK US (8)
1 Serves as an extension of the physical exam
2 Allows real-time dynamic imaging
3 Allows accurate needle placement for both diagnostic and therapeutic procedures
4 No need for bulky equipment/extra personnel
5 No radiation exposure for patient
6 No radiation exposure for the physician
7 Cost effective compared to other imaging modalities
8 Exquisite detail with hi-res of superficial structures compared to MRI
Disadvantages of MSK US (5)
1 Limited field of view 2 Incomplete evaluation of bones and joints 3 Limited penetration 4 Equipment cost and variable quality 5 Operator dependent
In US, electric voltage is generated by the base unit. Converted to sound wave by ______
reverse piezoelectric effect of crystals in the transducer element
Waves of compression and relaxation used to make image.
Ultrasound reads at ___ Hz
20
- US travels through various materials at different velocities. The majority of tissues in the body transmit sound at approx
2 The higher the _____, the faster the sound travels through the tissue
3 Air for example, is a combination of gases (having low density) and conducts sound at a speed that travels at _____.
- The speed of sound in bone, a highly dense structure, is ________
- The less dense soft tissues and bodily fluids transmit sound at an average speed of about ___________
- 1500 m/sec
- tissue density
- 331 meters per second
- 4,080 meters per second.
- 1540 m/sec.
Sound waves are reflected at the boundary between two structures.
Dependent on two factors:
1.
2.
- impedance of the media
- alike = less reflection
- different = more reflection - Angle of incidence (perpidicular vs oblique)
Perpendicular incidence:
- Sound waves travel:
- Some ____ and some ____
- perpendicular to the boundary of two media
2. reflec back, pass through
Oblique incidence:
- Travels by:
- Some reflected back, but how?
- Some passes through, but how?
What is a transmission angle?
Oblique incidence:
1 Sound wave not perpendicular to the boundary
2 Some reflected back, but at an angle equal to the incident angle
3 Some passes through, but is refracted ( his iscalled the transmission angle)
_____ is reflection of sound waves from a smooth surface
specular reflection
_____ is redirection of sound in many directions iwth some reflected back to the transducer, allowing visualization (eg rough edges or torn tissue, or heterogenous media such as an abscess)
scattering.
4 steps of creating an image on US
- returning sound waves detected by transducer
- sound waves converted to volts via piezoelectric effect
- volts assigned gray scale shade
- image produced on screen
sounds waves are converted to volts via:
piezoelectric effect
____ is the ability to distinguish two objects when they are directly over each other.
Mainly determined by:
axial resolution
frequency of the transducer - higher the frequency, greater the axial resolution
____ is the ability to distiguish two objects as separate when they are located side by side and of equal distance from the transducer
horizontal resolution
The determinants of beam width are: 3
- Transducer frequency (beam width increases with lower frequency transducers)
2 Focusing of the beam
3 Gain (increased gain will increase the beam width and reduce resolution
How does an US wave focus?
narrows to 1/2 its initial width, then widens - narrow region has the most concentrated sound waves = best resolution.
Which probe?
End is flat
Waves exit perpendicular to transducer surface
Limted field of view
Good for superficial structures
linear array
which probe
End is curved Waves exit in a fan shape Large field of view Increase risk of anisotropy Good for deep structures
curvilinear array
High frequency vs low frequency probes:
- resolution
- penetration
- deep vs superficial
which is better?
described in:
Frequency
Described in megahertz (ie. 12-15 mHZ)
- High frequency
Greater resolution
Lower penetration
Superficial structures
2 Low frequency
Lower resolution
Greater penetration
Deeper structures
Probe handling is a ____
contact sport
Types of probe movements:
- Translation
- Tilt (wag)
- Heel-toe
- rotation
- pressure
Four steps to image optimization
- depth - area of interest in center of screen
- focal zone - adjust to level of object being imaged
- gain - adjust so overall brightness optimizes detail
- time gain compensation - allows segmental changes in gain. Used to improve detail of object at different depths
Time gain compensation:
- Allows for:
- Used to:
Allows segmental changes in gain
Used to improve detail of object at different depths
Power Doppler:
- Single ___
- Detects:
- Not ____ dependent
- More ___, Less ___
- Good for: 3
Power Doppler: 1. Single color 2 Detects ANY movement 3 Not angle dependent 4 More sensitive, less specific 5 Good for: - Slow flow - Deep vessels - Small vessels (Neovascularization in tendinopathy!!!)
Linear transducer waves can be steered at an angle which is called:
Can create ______
trapezoidal imaging and beam steering.
Can create a trapezoidal image similar to a curvilinear to increase field of view
Can “steer” your beam toward your needle
Whats this?
Probe glided along surface
New echoes stitched together
Creates picture wider than transducer face (normal field of view)
Extended field/panoramic
good for looking at tendon length
Images and properties used during terminology will change depending on
what structures surround the image
- No reflection: (black)
- Low reflection: (darker)
- Same reflection: (same)
- High reflection (Lighter)
- anechoic
- Hypoechoic
- Isoechoic
- Hyperechoic
Long plane, in-plane:
Short plane, Out-of-plane:
Longitudinal
transferse (axial)
Soft tissues appear different when the angle of the transducer is changed
This is what parallel and oblique incidence does to your image
anisotropy — artifact!
example of anisotropy
tendons appear hyperechoic (bright) when the probe is parallel to the tendon fiber surface, but hypoechoic (dark) when the transducer is angled obliquely.
This can help or hurt your interpretation
Use wag or heel-toe to chage anisotropy
____ occurs behind a tissue (media) that does not allow sound waves to penetrate
Posterior acoustic shadowing
____ Occurs behind a tissue (media) that easily allows sound waves to pass (like fluid)
Posterior acoustic enhancement
How do these structures look on US?
- Bone
- Hyaline cartilage
- Subcutaneous tissue
- Muscle
- Tendon
- Ligament
- Nerve
- Hyperechoic surface with posterior acoustic shadow
- Hypoechoic, very uniform
- Loose homogenous pattern
- Tight homogenous pattern
- Fibrillar pattern
- Striated pattern
- Fascicular (hyperechoic to muscle, hypoechoic to tendon)
absorption of a sound wave is enhanced by
increased frequency of the transducer and greater tissue viscosity
Four things that can cause anechoic shadowing
bone
calcification
foreign bodies
gas
With regard to shadowing, an object (such as bone/calcification) with a small radius of curvature or rough surface with display as _____ whereas an object with a large radius of curvature and a smooth surface will display as _____
- clean shadow
2. dirty shadow (resulting from superimposed reverberation echoes)
refractile shadowing can occur when?
at the edge of foreign bodies or the end of a torn achilles or patellar tendon
___ can occur during imaging of fluid and soft tissue tumors, such as peripheral nerve sheath tumors and giant cell tumors of tendon sheath.
posterior acoustic enhancement or increased through-transmission
sound beam is relatively less attenuated compared with adjacent tissues; therefore, the deeper soft tissues will appear relatively hyperechoic compared with the adjacent soft tissues.
Another artifact with musculoskeletal implications is _____. This occurs when the surface of an object is smooth and flat, such as a metal object or the surface of bone. In this situation, the sound beam reflects back and forth between the smooth surface and the transducer and produces a series of linear reflective echoes that extend deep to the structure
If the series of reflective echoes is more continuous deep to the structure, the term ____ is used, as may be seen with metal surfaces
posterior reverberation
ring-down artifact
Related to posterior reverberation is the _______ such as that seen with soft tissue gas ( Fig. 1-20 ), which appears as a short segment of posterior bright echoes that narrows further from the source of the artifact
comet-tail artifact,
Comet-tail artifact.Ultrasound over an infected subacromial-subdeltoid bursa (arrows) shows hyperechoic foci of gas with comet-tail artifact \
sound beams with spatial compound sonography are produced at several different angles, with information combined to form a single ultrasound image. Known as?
spatial compound imaging
This improves tissue plane definition, but it has a smoothing effect, and motion blur is more likely because frames are compounded ( Fig. 1-21 ). One must be aware that the use of spatial compounding may reduce the artifact produced by a foreign body, which may decrease its conspicuity
_____ uses frequencies produced during ultrasound beam propagation through tissues are used to produce the image. This technique assists in evaluation of deep structures and also improves joint and tendon surface visibility. 11 The technique may more clearly delineate the edge of a soft tissue mass ( Fig. 1-22 ) or a fluid-filled tendon tear
tissue harmonic imaging
_____ is used to assess the elastic properties of tissue. With this technique, compression of tissue produces strain or displacement within the tissue. Displacement is less when tissue is hard; it is displayed as blue on the ultrasound image, whereas soft tissue is displayed as red ( Fig. 1-27 ). With regard to musculoskeletal applications, normal tendons appear as blue, whereas areas of tendinopathy, such as of the Achilles tendon or common extensor tendon of the elbow, appear as red.
ultrasound elastography ,
What is aliasing?
when the Doppler shift frequency of blood is greater than the detected frequency, which causes an error in frequency measurement
To correct for aliasing (when the Doppler shift frequency of blood is greater than the detected frequency, which causes an error in frequency measurement), one can increase the pulse repetition frequency, lower the ultrasound frequency, or increase the angle between the sound beam and the flow direction toward perpendicular.
Ultrasound uses the ______, in which the sound frequency of an object changes as the object travels toward or away from a point of reference, to obtain information about blood flow.
Color flow imaging shows colored blood flow superimposed on a gray-scale image, in which two colors such as red and blue represent flow____ and _____ the transducer, respectively
Doppler effect
toward, away from
____ is another method of color Doppler ultrasound that is more sensitive to blood flow (it shows small vessels and slow flow rates) compared with conventional color Doppler, and it assigns a color to blood flow regardless of direction ( Fig. 1-30 ).
Power Doppler
Power Doppler is extremely sensitive to movement of the transducer, which produces a flash artifact. It is important to adjust the color gain optimally for Doppler imaging to avoid artifact if the setting is too sensitive and for false-negative flow if sensitivity is too low. To optimize power Doppler imaging, set the color background (without the gray-scale displayed) so that the lowest level of color nearly uniformly is present, with only minimal presence of the next highest color level. 22
