Ultrasound

Question 1

What range of US is used for diagnostics?

Answer 1

2 to 20 MHz

Question 2

What is an US Wave?

Answer 2

Extremely high frequency sound pressure

Question 3

Wave Reflection

Answer 3

• Waves reflect of interfaces (spot of change in density) between tissues
• Based on density
• Tissues absorb some of the tissue.

Question 4

Scattering

Answer 4

• 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

Question 5

How do probes on an US work?

Answer 5

• 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)

Question 6

Array styles on probes

Answer 6

• 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

Question 7

How do you determine what probe type to use?

Answer 7

• 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

Question 8

US Operating Modes

Answer 8

• 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

Question 9

Doppler

Answer 9

• 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.

Question 10

What operator mode is most often used for an Echocariography?

Answer 10

M-mode; Allows to go back and look at displacement of valves

Question 11

Artifact definition

Answer 11

Features that show up in the right conditions and can help with identifying things.

Question 12

Artifact - Enhancement

Answer 12

• 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.

Question 13

Artifact - Acoustic Shadow

Answer 13

• 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

Question 14

What does attenuate mean?

Answer 14

Too reduce a signal

Question 15

Artifact - Edge Shadow

Answer 15

• Large fluid structures refract sound waves (cast shadows)

Question 16

How do you obtain an image on an US?

Answer 16

• 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)

Question 17

How can US imaging be applied to Rehab?

Answer 17

• Articular Cartilage Thickness (Femoral)
• Ligament Tissue properties and tear (UCL)
• Tendon cross sectional area and ruptures (Patellar and calcaneal)
• Biofeedback (Transverse Abdominus)

Question 18

If someone torn there UCL, what would you expect to see?

Answer 18

• 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

Question 19

When performing biofeedback for the Transverse Abdominus, what do you want to see?

Answer 19

• See a widening of TrAb when contracted and Obliques to remain the same size.
• Analyze with M-mode

Question 20

How to take a measurement for US

Answer 20

• Apply acoustic gel
• Standardize!!
  – Probe location
  – Orientation
  – Angle
• Freeze target images
• Save to flash drives
  – Check with HIPAA compliance!

Question 21

How to analyze US images

Answer 21

• Include scaling object (reference line)
• Use software (Ex: ImageJ, Kinovea) to count pixels in 2D plane
  – Length
  – Area
  – Angle

Question 22

Practical Considerations - US Equipment

Answer 22

• 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

Question 23

Portable Units - Brands

Answer 23

Clarius Mobile Health (left)
~ $4,000-5,000

Butterfly iQ (right)
~ $1,999

https://clarius.com/classroom/?filter_specialities=sports-medicine
Good Dx Videos

Question 24

Diagnostic Implications

Answer 24

• 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