15/16: Diagnostic Ultrasound - Mahoney

Question 1

basics of how ultrasound works

Answer 1

When the ultrasound encounters tissues, the wave hits the tissue and reflects part of the wave back to the probe

This causes a reflective pattern and this information is projected as an image

Question 2

“sonar”

Answer 2

A-mode ultrasound

Produced on an oscilloscope
It measures how far the echo has traveled and how loud the echo is when it gets back
Uses a single transducer
Cannot determine what object looks like

Question 3

“b-mode”

Answer 3

2-dimensional picture
Like A-mode, but adds direction, as well as, deciphers all types of echoes, both strong and weak

Can recognize size and shape of object

Uses a linear array of transducers
Most commonly used type of ultrasound

Question 4

m-mode

Answer 4

M-mode: Motion picture

Like B-mode, but can image fetal movements, heart pumping

Question 5

away from doppler

toward the doppler

Answer 5

Color doppler (“BART”)

Blue signals indicate blood flow away from the probe

Red signals indicate blood flow towards the probe

Question 6

Piezoelectricity

Answer 6

Transducer (probe) contains linear array of thin crystals (lead zirconate titanate) linked to the electrical system of the machine

Machine applies a rapidly alternating electrical current to the crystals > vibration > generate sinusoidal sound wave (mechanical energy)

Question 7

specifics for msk transducers

Answer 7

Musculoskeletal transducers located in the probe produce the sound at 7.5-12 Mhz (megahertz) which is then pulsed at 20 microsecond intervals

Question 8

notch placement

Answer 8

medial or proximal

Question 9

Higher frequency waves penetrate less than lower frequency, but _________ increases

Answer 9

resolution

Resolution is the ability of the ultrasound machine to distinguish two structures (reflectors or scatterers) that are close together as separate

Frequency and wavelength of the ultrasound beam are inversely related

Question 10

attenuation

Answer 10

Attenuation results in echoes from deep tissue being displayed less intensely than those from superficial structures

The deeper the signal travels into the tissue, the more it is absorbed, and the weaker the signal that is reflected back from the tissue. This is known as attenuation

Question 11

impedance

Answer 11

The amount of reflection is dependent upon the impedance of the tissue

Impedance is a property of a tissue defined as density of tissue and velocity of sound in that tissue. Air is low, bone is high

we use gel with impedance similar to human tissue

Question 12

Hyperechoic
Hypoechoic
Anechoic

Answer 12

Hyperechoic-white-reflect majority of wave
Hypoechoic-gray-reflect some of wave
Anechoic-black-reflect none of the wave

Question 13

near zone vs. far zone ***

Answer 13

Near zone (field): the region of a sound beam in which the beam diameter decreases as the distance from the transducer increases-area nearest to the transducer

Far zone (field): the region of a sound beam in which the beam diameter increases as the distance from the transducer increases-area furthest from transducer

Question 14

Anisotropy

Answer 14

Occurs when the beam is not directly perpendicular to fibrillar tissues (tendon, ligament, fascia) being examined

Instead of looking hyperechoic, the structure becomes more hypoechoic as the angle increases, and, therefore, looks inflammed when it is not

Less ultrasound reflected, so image is darker

Question 15

shadowing

Answer 15

Occurs when ultrasound beam is reflected, resorbed, or refracted from bone or calcified object

Acoustic shadowing -false anechoic area (dark shadow) below the reflective surface

Edge shadowing-dark shadow behind the edge of spherical structures when beam reflects off rounded surface

Question 16

posterior acoustic enhancement

Answer 16

Occurs during imaging of fluid

Deep to a fluid collection, the soft tissue will appear relatively hyperechoic compared with the adjacent soft tissues

Question 17

posterior reverberation

Answer 17

Occurs when surface of object is smooth and flat (metal foreign body or surface of bone)

Beam reflects back and forth between the surface and transducer producing a series of linear reflective echoes that extend deep to the structure

Question 18

Refraction

Answer 18

Depicts real structures in the wrong position

Duplicates structures

Caused by bending of ultrasound at interface of two materials

Minimize by keeping beam as close to 90° to structure

Question 19

Gain Knob

Time Gain Compensation (TGC)

Depth Knob

Focus Knob

Frequency Knob

Answer 19

Gain Knob: Controls overall brightness of the image
Time Gain Compensation (TGC): Allows adjustment of image brightness at selective depth
Depth Knob: Allows adjustment of the depth of field of view
Focus Knob: Allows focus of ultrasound beam to area of interest
Frequency Knob: Adjust Frequency to balance depth and resolution needs

Question 20

tarsal tunnel

Answer 20

tom
dick
very 
nervous 
harry

Question 21

good tom hates all dicks

Answer 21

great saphenous v. 
TA
EHL
artery
EDL 

anterior ankle structures

Question 22

sweep
slide
rock/tilt
fan
rotate

Answer 22

Sweep: Move entire probe perpendicular to the length of the probe (like a broom)
Slide: Move entire probe in line with the length of the probe
Rock/Tilting: With the probe kept on one spot, tilt the probe along its long axis (like the leg of a rocking chair)
Fan: With the probe kept on one spot, tilt the probe along its short axis (like a fan)
Rotate: Rotate position of probe to align with anatomy (Like hands on a clock)