Basics of Ultrasound Imaging

Question 1

Describe ultrasound

Answer 1

• Portable, non-zoning, low cost = widely available
• Point of care/bedside
• 2-Dimensional slices of internal structures: transverse, sagittal, coronal, oblique
• Real time image capture

Question 2

Describe the production of an ultrasound image

Answer 2

• Transducer in US probe emits high-frequency sound pulses
• Pulses travel across body surface into patient’s body
• Encounter tissues with varying acoustic properties
• Some sound energy reflects back to the transducer (echo)
• Some energy continues to penetrate deeper tissues (through transmission)
• Echo signals processed & combined
• Generates an image of the scanned slice

Question 3

What are the different transducer types

Answer 3

• Abdominal (Convex or Curved Array) Probes
• Cardiac (Sector Array) Probes
• Linear (Linear Array) Probes

Question 4

Describe an abdominal probe

Answer 4

• Frequency: 2-5 MHz
• Used for general abdominal imaging, trans abdominal pelvic imaging, obstetrical imaging, & some musculoskeletal imaging
• Allows imaging up to depths of 20 cm
• Wide angle field of view for large deeper structures

Question 5

Describe a cardiac probe

Answer 5

• Frequency: 1.5-4.5 MHz
• Produce a triangular sector image
• Suited for imaging large, non-superficial structures through narrow sonographic windows
• Not ideal for imaging superficial structures

Question 6

Describe a linear probe

Answer 6

• Frequency: 8-15 MHz
• Offer the best image detail but limited depth penetration (5-6 cm max from skin surface)
• Used foe musculoskeletal, peripheral nerves, thyroid gland, breast, & superficial vascular imaging
• Produce rectangular shaped imaging with constant width from probe face to deepest part

Question 7

Describe how to control and manipulating the probe

Answer 7

• “Drop an anchor”
• Manipulate pressure, stabilization, adjust angle, rotation, tilt (think of the US beam as a flashlight
• All probes have an orientation marker that corresponds to the display: scans along longitudinal axis the marker is oriented cranially; scans along the transverse axis the marker is oriented to the patients right; & structures near the top of the image are superficial

Question 8

Define echogenicity

Answer 8

• Reflectivity of tissue in relation to surroundings
• Visible contrast in brightness at tissue interfaces

Question 9

Describe the appearance of tissues on US image

Answer 9

• Hyperechoic (White): high reflectivity (ex. bone)
• Hypoechoic (Gray): moderate reflectivity (ex. muscle)
• Anechoic (Black): little to non reflectivity (ex. fat)

Question 10

What do nerves look like on ultrasound

Answer 10

• Transverse view: hyperechoic surface with hypoechoic nerve fascicles (honeycomb appearance)
• Longitudinal view: hypoechoic stripes parallel to eve’s long axis (bundle of straws appearance)

Question 11

What do blood vessels look like on ultrasound

Answer 11

• Blood is anechoic, vessel walls are hyperechoic
• Arteries have circular profile in transverse view, thicker walls than veins
• Veins are readily compressible, arteries require substantial pressure

Question 12

What does skin look like on ultrasound

Answer 12

• smooth & bright (hyperechoic)
• epidermis & dermis differentiation requires specialized high-resolution ultrasound
• subcutaneous layer appears generally hypo echoic with fat & connective tissue septae

Question 13

What does skeletal muscle look like on ultrasound

Answer 13

• Transverse view: anechoic/hypoechoic with hyperechoic lines (starry sky appearance)
• Longitudinal view: anechoic/hypoechoic with elongated hyperechoic lines revealing fascicular architecture

Question 14

What do tendons look like on ultrasound

Answer 14

• Longitudinal view: fibrillar appearance with hyperechoic border
• Transverse view: Bristle-brush appearance with distinct hyperechoic surface

Question 15

What does bone look like on ultrasound

Answer 15

• hyperechoic surfaces with acoustic shadowing deep to the bone surface

Question 16

What does fluid look like on ultrasound

Answer 16

• anechoic (ex. blood, bile, urine)
• increased echogeniicity in tissues deep to fluid collections

Question 17

Describe depth of the ultrasound image

Answer 17

• R side of image
• Start deep
• Adjust depth so region of interest is center

Question 18

Describe focal point on ultrasound

Answer 18

• allows for best image detail for structures at ac certain depth

Question 19

Describe gain on ultrasound

Answer 19

• adjusts the brightness/darkness of image