Ultrasound Flashcards
What range of US is used for diagnostics?
2 to 20 MHz
What is an US Wave?
Extremely high frequency sound pressure
Wave Reflection
- Waves reflect of interfaces (spot of change in density) between tissues
- Based on density
- Tissues absorb some of the tissue.
Scattering
- Irregular surface leads to particles scatter sound waves (not reflected directly back)
- Hypoechoic (Dark, does not return much echo)
- Hyperechoic (Light, returns signal back well) Ex: Bone
How do probes on an US work?
- They are a transducer (piezoelectric crystals) array that vibrate at high frequencies
- Emit waves and recieve reflections (electrical to sound energy, sound energy to electrical energy)
Array styles on probes
- Linear: Signal sent in directly parallel waves
- Curvilinear: Spread out as you get deeper into tissue. Ex: Fish sonar or image of a baby
- Phased: Hybrid of linear and curvilinear
How do you determine what probe type to use?
- Depends on the specific thing you are trying to look at; each have specialized frequencies
- ML6-15 is great at analyzing muscle
- Linear: Superficial structures (7 cm); Excellent images, Square references, Quantitative
- Curvilinear: Deeper structures (15-20 cm), spreads out so worse resolution, hard to measure things, more qualitative
US Operating Modes
- B-Mode
– 2D images of reflecions
– Measures depth of tissue interface along enitre length of transducer array
– Hyper/Hypoechoic structures, high quality image - Cine Mode
– Record continuous movie of B-mode image frames - M-mode (motion)
– Shoes time-scan of depth at one scline through the image. Often seen with a reference line. Can be used for biofeedback
Doppler
- Velocity of fluid
- Measured via blood cells (RBC) as particles
- Fluid without particles does not show flow (Dark); Ex: Urine
Particle must be big enough to scatter the US wave sent to know there is flow.
What operator mode is most often used for an Echocariography?
M-mode; Allows to go back and look at displacement of valves
Artifact definition
Features that show up in the right conditions and can help with identifying things.
Artifact - Enhancement
- Greater signal power passes through empty fluids. Therefore can see deeper. Ex: Bladder
- Hyperechoic as it is able to get through the fluid and be seen well.
Artifact - Acoustic Shadow
- Hyperechoic structure (Ex: Bone) blocks durther signals from returning
- Can’t see anything past bone as it is so dense it blocks all particles.
- The bone attenuates the signal
What does attenuate mean?
Too reduce a signal
Artifact - Edge Shadow
- Large fluid structures refract sound waves (cast shadows)
How do you obtain an image on an US?
- Select 2D plane to be your slice through the body
– Perspective error occurs when not fully aligned to an anatomical axis - Adjust focus depth (tuning for better image quality)
– Deep vs. superficial structures? - Adjust brightness contrast
– Imaging vessels, adipose tissue, or muscles? Depending on purpose determines brightness - Obtain reference landmarks
– How do you know where the probe is located on the body?
– Do you need to palpate structures, make marks, measure distances? - Stabilize your probe to avoid unwanted sliding (Two hands: one with probe, second cupping area US head is in)
How can US imaging be applied to Rehab?
- Articular Cartilage Thickness (Femoral)
- Ligament Tissue properties and tear (UCL)
- Tendon cross sectional area and ruptures (Patellar and calcaneal)
- Biofeedback (Transverse Abdominus)
If someone torn there UCL, what would you expect to see?
- The area that was torn will be black (hypoechoic) instead of white as it is likely filled with fluid from injury.
A: Not torn B: Torn
When performing biofeedback for the Transverse Abdominus, what do you want to see?
- See a widening of TrAb when contracted and Obliques to remain the same size.
- Analyze with M-mode
How to take a measurement for US
- Apply acoustic gel
- Standardize!!
– Probe location
– Orientation
– Angle - Freeze target images
- Save to flash drives
– Check with HIPAA compliance!
How to analyze US images
- Include scaling object (reference line)
- Use software (Ex: ImageJ, Kinovea) to count pixels in 2D plane
– Length
– Area
– Angle
Practical Considerations - US Equipment
- Line of sight
- Resolution
– How many millimeters per pixel on the image?
– Linear (7 cm) vs Curvilinear (15-20 cm) - Sampling frequency
– Are you observing fast movements? At very high speed, get a grainy image
– Biofeedback
– Alternative to EMG? - Frequency modes
– Adjustable driving frequencies to obtain better images with different target tissues? - Size and portability
Portable Units - Brands
Clarius Mobile Health (left)
~ $4,000-5,000
Butterfly iQ (right)
~ $1,999
https://clarius.com/classroom/?filter_specialities=sports-medicine
Good Dx Videos
Diagnostic Implications
- Assess injury risks
- Quick checks to rule out tears and ruptures
- Inflammation and swelling following acute injury can be observed
- Cost is much less than traditional radiographic methods (MRI, CT)
- PTs can order for an US image from a sonography in Wisconsin
