Therapeutic Ultrasound

Question 1

What does electro therapy do?

Answer 1

Delivers energy to cell membrane which

• forces membrane to change behaviour
• produce membrane and cellular excitement

Question 2

How does therapeutic ultrasound work?

Answer 2

High frequency sound waves absorbed in the body are pulsed for an average low intensity

Average low intensity tickles cells - increases cellular activity which promotes natural body resources

Has pro inflammatory response - increases proliferation and remodelling - not normally used on acute stages

Question 3

What is therapeutic ultrasound?

Answer 3

• Mechanical energy
• Mechanical vibration creates sound energy
• The normal human sound range is from 20Hz to 15/20,000Hz
• Below 20Hz these vibrations are not recognisable as sound.

Question 4

What are the two types of waves?

Answer 4

• Transverse

- Longitudinal - compression (frequent) and rarefraction (not as frequent)

Question 5

What are the properties of waves?

Answer 5

Frequency
Wavelength
Velocity

Question 6

What is frequency?

Answer 6

Number of times a particle experiences a complete compression cycle in a second

Question 7

What is wavelength?

Answer 7

Distance between two equivalent points (same amplitude) on the wavelength

Question 8

What is velocity?

Answer 8

Speed at which a wave travels through a medium

Question 9

How do you calculate velocity?

Answer 9

Velocity = frequency x wavelength

Question 10

What characteristics does the beam have?

Answer 10

• It’s not uniform

- It changes in its nature with distance from transducer

Question 11

What is the near field?

Answer 11

Beam nearest the treatment head
10 cm long
Has different frequency of waves

Question 12

What is the far field?

Answer 12

Beyond near field.

More uniform frequency of waves

Question 13

What do all tissues have?

Answer 13

Have a resistance or impedance to passage of sound waves

Question 14

What is impedance determined by?

Answer 14

Density and elasticity

Greater impedance = greater reflection

Question 15

Why is a medium used?

Answer 15

Decrease impedance as applied to steel head and impedance is greatest between air and steel
Should strike at 90 degrees

Question 16

What are the types of medium used?

Answer 16

Gel
H20
Lotion

Question 17

Where is most energy absorbed?

Answer 17

• In superficial tissues rather than deep = exponential pattern
• Blood and fat absorb least energy
• Tendon ligaments fascia and scar tissue absorb most energy due to protein

Question 18

When would you use:

Ultrasound
Laser
Pulsed shortwave

Answer 18

Ultrasound - dense collagen tissues

Laser - superficial vascular tissues

Pulsed shortwave - low impedance and wet tissues eg muscle and oedema

Question 19

What are the thermal therapeutic effects of US?

Answer 19

Particles oscillate

Vibration produces heat

Question 20

What are the mechanical therapeutic effects?

Answer 20

Cavitation -stable:

Formation of gas bubbles that gently build up and creates more waves

Acoustic streaming:

Change in membrane excitability

Micro-massage - little evidence

Question 21

What are the different settings for ultrasound?

Answer 21

Frequency MHZ
Pulse ratio
Intensity - watts per cm2
Time - mins

Question 22

What is pulse US and pulse ratio?

Answer 22

Waves delivered in bursts e.g 1 burst on, one burst off 1:1

For acute damage - use lower pulse ratio 1:4
For chronic - use 1:1
Subacute: 1:2

Question 23

How do you change frequency?

Answer 23

Depends on depth of target tissue

Superficial = 3 MHz
Deep = 1mhz

Question 24

How do you alter intensity?

Answer 24

Amount of energy supplied by machine

Acute: 0.1-0.3
Subacute: 0.2-0.5
Chronic: 0.3-0.8

Question 25

How to calculate dosage:

Answer 25

Frequency : superficial or deep?
Pulse factor – (add both parts of ratios); severity?
Intensity: severity?  
Area size - (number of times
the treatment head
fits over the lesion)

Time = pulse factor x assessment head

Question 26

What are the contraindications of US?

Answer 26

Patient cannot cooperate
Not over uterus in pregnancy
Active tumour
Recent bleeding
Vascular problems
Over sensitive organs

Question 27

What are the precautions of US?

Answer 27

Over ant neck
Significant loss of sensation
Devitalised tissue
Local acute skin conditions

Question 28

What are the mandatory warnings?

Answer 28

Lowest intensity possible to give therapeutic response
Keep treatment head moving - else destroy crystal
Test for hot and cold
Caution over pacemakers