Ultrasound

Question 1

What is sound?

Answer 1

Waves that transmit energy

Question 2

Why is “ultra” used in ultrasound?

Answer 2

Frequency greater than 20,000 cycles per second is ultra

Question 3

How is sound transmitted

Answer 3

Waves transmitted by energy alternately compress and rarefy material. You need a medium, otherwise they disperse

Question 4

Frequency in sound waves is:

Answer 4

of compression/rarefraction cycles per unit of time expressed in cycles/sec or hertz

Question 5

What measurement is used to describe frequency in ultrasound?

Answer 5

Hertz

Question 6

At what frequency is therapeutic US used?

Answer 6

> 20,000 cycles/sec.

Question 7

What determines which frequency is used w US?

Answer 7

How deep Tx needs to go.

Question 8

What’s the diff between continuous and pulsed US?

Answer 8

Continuous is thermal. Pulsed is nonthermal effects

Question 9

What is duty cycle?

Answer 9

On off time

Question 10

Duty cycle for continuous US?

Answer 10

100%

Question 11

Most common duty cycle for pulsed US

Answer 11

20-80% or 1:5 ratio

Question 12

In what measurement is the intensity if US registered on the US unit?

Answer 12

Watts/ cm2

Question 13

What is cavitation?

Answer 13

Formation, growth, and pulsation of gas filled bubbles caused by US

Question 14

Stable vs unstable cavitation

Answer 14

Stable: bubbles oscillate in size throughout cycles but don’t burst.
Unstable: bubbles grow over # of cycles and then implode

Question 15

When is unstable cavitation more likely to occur?

Answer 15

Increased temp & increased pressure

Question 16

What is ERA?

Answer 16

Effective radiating area aka size of a sound head

Question 17

Contraindications for US

Answer 17

Malignant tumor
Pregnancy
CNS tissue
Joint cement
Plastic components
Pacemaker
Thrombophlebitis
Eyes
Reproductive organs
Shallow or weak bone

Question 18

Purpose of thermal US

Answer 18

Increase metabolic rate
Decrease pain and mm spasm
Increase circulation
Increase soft tissue extensibility

Question 19

What should occur immediately after US?

Answer 19

Massage
Stretch
Exercise

Question 20

Recommended duration for US?

Answer 20

5-10 min for each Tx area that’s twice the size of ERA or transducer head

Question 21

Pulsed

Answer 21

Nonthermal

20% frequency

Question 22

Continuous

Answer 22

Thermal

100% frequency

Question 23

To avoid pain with US

Answer 23

More gel (medium)
Avoid over bone
Flatten transducer head and don't scoop gel

Question 24

Rate of transducer head

Answer 24

Slow

4cm/sec

Question 25

How electrical energy is converted to mechanical in US

Answer 25

Transducer has crystal inside made of piezoelectric properties, causing it to respond to AC by expanding/contracting @ same frequency that current changes polarity.
Crystal expands=compress the material in front of it.
Crystal contracts=thins area in front of it

Question 26

To penetrate deeper tissues using ultrasound u should:

Answer 26

Use a lower frequency

Question 27

Desired effects of ultrasound

Answer 27

Increase cell permeability
Mast cell degranulation
Increased collagen synthesis

Question 28

How are tissues heated using ultrasound

Answer 28

Heat accumulates in tissues by conversion of kinetic energy

Question 29

Does pulsed ultrasound minimize temp increase?

Answer 29

Yep

Question 30

The ERA is what size?

Answer 30

Smaller than size of soundhead

Question 31

Ideal parameters for using ultrasound before stretching shortened soft tissue?

Answer 31

1-2w/cm continuous

Question 32

Ideal parameters for modulating inflammation during ultrasound

Answer 32

1-3mhz, .5-1w/cm2

Pulsed 20%