Week 3: Therapeutic Ultrasound Flashcards
What is ultrasound?
- high freq sound waves (>20,000Hz)
- causes vibration of the material it passes through
Attenuation
as an ultrasound travels through material it decreases in intensity as it travels through a tissue
high density human tissue
connective tissue, ligaments, fascia, bone, tendons
- faster absorption than low density
T or F: US is transmitted poorly through air because it is low density. That is why we use aqueous gel or water to transmit waves to body tissues
true
Absorption and when is it higher ?
- conversion of US energy into thermal energy
- depends on type of tissue and freq
- its higher in tissues with high collagen and when a high freq is used
refracted
- waves passing through denser material are bent and no longer follow original path
Reflection
- depends on angle of interface between tissues of differing density
- standing wave may create a “hot spot”
Bone absorbs how much
96%
Low density of human tissues
blood, fat, muscle
How are sound waves produced
- piezoelectric crystals expands (and compresses the material in front of it) and contracts (rarefies material in front)
- only contracts and expands in the center
Compression
vs
Rarefaction
Compression: areas of increased density of molecules
Rarefaction: areas of decreased density of molecules
Beam Non-uniformity Ratio (BNR)
- range of intensity
- expresses variance in acoustic energy across the beam
- spatial peak intensity/spatial average intensity
best = 1-2, avg =5
Frequency
determines how deep the US will penetrate the tissue
- 1MHz - 6cm depth
- 3-3.3 MHz - 2.5 cm depth
T or F: Frequency and depth are directly proportional
False, they’re inversely related
Intensity
power of us energy is product of wave phase duration and wave amp
- spacial avg intensity
- power measured in watts
Mode: US Pulsed
- bouts of energy on and off
- pulse on / (pulse on + off)
Common: 20% and 50% pulsed
treatment area for US
- 2x ERA (maximum 4x ERA)
Treatment Duration & Number
2-3x / week for 10-15 treatments
do you want US parallel or perpendicular to the skin surface?
perpendicular with soundhead in contact with the skin to minimize reflection
Patterns for Moving sound head
- parallel overlapping strokes
- overlapping circles
Thermal effects of US & how to make it occur more rapidly
- creating a deeper heat
- increase power/intensity, increase duration, higher freq, smaller tx area
Non-thermal effects of US
- used to alter membrane permeability and accelerate tissue healing
- during high degree with low intensity US (pulsed)
Cavitation
cycles of compression and rarefaction create gas bubbles
Microstreaming
cavitation produces currents and may change cell permeability and activity
acoustic streaming
forward movement of fluid by US waves
effects and usage of Low intensity pulsed US
- increases bone angiogenesis
- stimulates osteogenesis
- enhances production of calcifies bone matrix
- to facilitate healing of fractures/repair tendon-bone junctions
Can you use US to deliver a topical drug?
Yes!! Its called phonophoresis
- antiinflammatory
- nsaids
- analgesics
Contraindications to THERMAL US
- PREGNANCY (over low back/abdomen)
- over malignancy
- over active epiphyseal bone growth
- TB infection
- Hemorrhagic conditions
- Impaired circulation
Contraindications to PULSED US
- PREGNANCY (over low back/abdomen)
- over malignancy
- hemorrhagic conditions
What to look at to assess if US is effective?
- look at pain, TTP, resisted motion tenderness, ROM,
- Documentation
US is good for what types of pain?
- Myofascial pain!!
- back pain has conflicting evidence
and shoulder pain has no evidence
US is good for what type of inflammatory condition?
- carpal tunnel syndrome & calcified tendonitis
- little evidence for lateral epicondylitis
