Uses safe sound waves and no radiation to allow visualization of the inside of the body
Ultrasound
Emitting sounds and listening to the returning echos to locate objects or navigate
Echolcation
A computer programmed to transform sound echos into images
Ultrasound machine
Ultrasound machine has piezoelectric crystal that vibrates to create sound waves and works in the
1-20 MHz range
Consists of a head with footprint, connector to make sound waves, and a wire
Ultrasound transducer
Must be in contact with the body mucus membrane
Transducer probe
Assists sound waves to travel through the body cleanly
Gel
Different transducers emit sound at different frequencies allowing varying degrees of
Sound penetration
Increases resolution at the expense of penetration
Increasing frequency
Have a higher frequency (10-18 MHz) and are used for musculoskeletal, soft tissue, and superficial analysis
Linear transducer
A linear transducer works well up to about
6 cm penetration
Lower frequency transducers used on the abdomen and for deeper structures
Curvilinear or convex transducer
Has better penetration than a linear transducer, but worse resolution
Curvilinear transducer
What has a wider field of view, linear or curvilinear transducers?
Curvilinear
Has a wide beam and a lower frequency. Helps to guide beams through windows such as the ribs
Sector (phased array) transducer
Sector transducers are used for
Cardiac stuff
Give a rectangular image
Linear transducers
What are the characteristics of B mode ultrasound?
2d spectra of shades of grey
Bright echos = more reflective tissues
No echos = not reflective (i.e. fluids)
Can be used to detect real time motion
B mode Ultrasound
Weak or low echo
Hypoechoic
Bright echo
Hyperechoic
No echo or blackness
Anechoic
Equal echogenicity between 2 structures
Isoechoic
Ultrasound mode where red color indicates TOWARDS transducer and blue indicates AWAY from transducer
Doppler ultrasound
Doppler ultrasound is helpful in evaluating
Cardiovascular structures
5x more sensitive than doppler and is used to evaluate tumors or tendons
Power doppler
Used for low flow, and is one directional
Power doppler
What four things can happen to sound waves emitted from transducer?
- ) reflection back to transducer
- ) refraction
- ) scatter
- ) Attenuation
Travel further and are LESS attenuated
Lower frequency waves
Used for deeper structures. Less resolution
Lower frequency waves
Used for superficial structures. Better resolution
Higher frequency waves
Artifacts occur because of normal physics of sound waves. One example of an artifact in ultrasound is
Anisotrophy
Change in echogenicity of a structure dependent on angle of beam relative to that structure
Anisotrophy
A 3-7 degree change in the probe position may drastically change the
Echo
The order of anisotrophic structures is
Tendon > ligament > nerve
Current resolution for ultrasound is 200-450 um. It can detect foreign bodies as small as
0.5 mm
Ultrasound can even be used to detect
Non-radiopaque structures
On an ultrasound machine, the gain button controls
Brightness
Each musculoskeletal component (i.e. muscle, tendon, bone, cartilage, etc) has its own unique
Echosignature
In the sagital plane of muscle ultrasound, hypoechoic bundles are
Fibers/fasicles
In the sagital plane of muscle ultrasound, hyperechoic septae are
Fibroadipose and perimysium
Gives a multipennate pattern, like leaves on a leaf
Sagital muscle ultrasound
Gives an ultrasound that looks somewhat like starry night
Transverse muscle ultrasound
Non-compressible, non-vascular structures that connect muscle to bone
Tendons
Tightly packed and hyperechoic. Best viewed using sagital ultrasound
Tendon
In a transverse ultrasound of a tendon, what type of pattern do we see?
Bristle pattern, like the end of a broom
Compact packed fibrillar structure that often covers a capsule/joint to connect bone to bone
Ligament
Ligaments are usually imaged in what plane?
Sagital
Are ligaments vascular?
No
Ligaments can be hyper- or hypoechoic depending on
Surrounding structures
Gives a hyperechoic pattern with posterior shadows
Bone
Hypo-anechoic structures typically located at synovial joints
-pressure sensitive
Bursae and Synovia
What type of echo does hyaline cartilage give off?
Hypoechoic with uniform thickness
Lines bones and is non compressible with uniform thickness
Hyaline cartilage
What type of echo does fibrocartilage give?
Hyper/hypo echoic. Like salt and pepper
In the sagital plane, which part of nerves show up as
- ) hypoechoic
- ) hyperechoic
- ) Fasicles
2. ) Epineurium
In the short/transverse plane, nerves give what type of ultrasound?
A follicular pattern like a honeycomb
Are round and anechoic in the transverse plane
Vessels
In the longitudinal section, vessels appear as
Anechoic tubes
What method of ultrasound is great for vessels?
Doppler
Allows us to see the body in motion so we can correlate movements with pain and pathology of a structure
Dynamic Imaging
A valuable tool for many procedures such as a central line or joint aspirations because it allows for great accuracy while decreasing much of the risk
Needle Visualization
Describes how the beam loses energy as tissues absorb sound
Attenuation