Therapeutic Ultrasound Flashcards
(28 cards)
What does electro therapy do?
Delivers energy to cell membrane which
- forces membrane to change behaviour
- produce membrane and cellular excitement
How does therapeutic ultrasound work?
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
What is therapeutic ultrasound?
- 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.
What are the two types of waves?
- Transverse
- Longitudinal - compression (frequent) and rarefraction (not as frequent)
What are the properties of waves?
Frequency
Wavelength
Velocity
What is frequency?
Number of times a particle experiences a complete compression cycle in a second
What is wavelength?
Distance between two equivalent points (same amplitude) on the wavelength
What is velocity?
Speed at which a wave travels through a medium
How do you calculate velocity?
Velocity = frequency x wavelength
What characteristics does the beam have?
- It’s not uniform
- It changes in its nature with distance from transducer
What is the near field?
Beam nearest the treatment head
10 cm long
Has different frequency of waves
What is the far field?
Beyond near field.
More uniform frequency of waves
What do all tissues have?
Have a resistance or impedance to passage of sound waves
What is impedance determined by?
Density and elasticity
Greater impedance = greater reflection
Why is a medium used?
Decrease impedance as applied to steel head and impedance is greatest between air and steel
Should strike at 90 degrees
What are the types of medium used?
Gel
H20
Lotion
Where is most energy absorbed?
- 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
When would you use:
Ultrasound
Laser
Pulsed shortwave
Ultrasound - dense collagen tissues
Laser - superficial vascular tissues
Pulsed shortwave - low impedance and wet tissues eg muscle and oedema
What are the thermal therapeutic effects of US?
Particles oscillate
Vibration produces heat
What are the mechanical therapeutic effects?
Cavitation -stable:
Formation of gas bubbles that gently build up and creates more waves
Acoustic streaming:
Change in membrane excitability
Micro-massage - little evidence
What are the different settings for ultrasound?
Frequency MHZ
Pulse ratio
Intensity - watts per cm2
Time - mins
What is pulse US and pulse ratio?
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
How do you change frequency?
Depends on depth of target tissue
Superficial = 3 MHz Deep = 1mhz
How do you alter intensity?
Amount of energy supplied by machine
Acute: 0.1-0.3
Subacute: 0.2-0.5
Chronic: 0.3-0.8
