US Flashcards
Ultrasound
Use of inaudible acoustic vibrations at high frequency to cause a physiological effect
ERA
Effective radiating area
- area of transducer from which US energy radiates
- 2x size of the sound head, takes 5-10 minutes
- area should be 1.5 - 4x ERA
BNR
Beam non-uniformity ratio
- rate of peak intensity to the average intensity (or output)
- usually 2:1 to 6:1
- the amount of energy produced by the sound head is not equal throughout the surface area so there are areas where US is applied that are receiving 5-6x the amount of energy so beacuas eof this, CONSTANT motion is required to prevent “hot spots”
Sound head
Transducer
- a crystal inside the sound head converts electrical energy into sound by alternately contracting and expanding
- creates a mechanical vibration
- generates US
- requires a transmission medium
Physiological effects: thermal
- phases of healing: subacute and chronic conditions, later part of proliferation and maturation phases Increases: 1. Tissue temp 2. Collagen extensibility 3. Circulation and nerve conduction 4. Cellular metabolism and enzymatic activity 5. Tissue perfusion 6. Pain threshold
Physiological effects: non-thermal
- phases of healing: acute and early subacute conditions; inflammation and early proliferation phases
1. No measurable increase in tissue temperature
2. Increases cell permeability and promotes normal cellular funciton
3. Decreases inflammation
Thermal US
Heats tissues with high collagen content
- ideal target tissues: tendons, ligaments, joint capsules, mm
- soft tissue shortening
- scar tissue
- pain control
- mm spasms and trigger points
- must be performed in conjunction with stretch/ROM program to be effective
Non-thermal US
- acute and/or post-acute conditions
- inflammation
- delayed soft tissue healing
- dermal ulcers/wound care
- tissue regeneration
Contras
- Cancer or over irradiated areas
- Pacemaker
- Blood clots
- Preganancy donut
- Active bleeding
- Decreased sensation
- Decreased circulation or vascular insufficiency
- Infection
- Fracture
- Metal
- Never over:
- epiphyseal plate in children
- implants (breast, booty, birth control)
- carotid sinus
- CNS tissue
- reproductive organs, eyes, or heart
Questions to ask yourself
- tx goals?
- where is pt in healing process?
- specifici tissue issue identified?
- size of area?
- depth of area?
- contras?
Frequency
Number of complete wave cycles per unit of time
- 1MHz absorption 3-5 cm
- 3MHz absorption 1-2 cm
Duty cycle
Proportion of the total treatment time the US is on
- continuous: 100% (thermal)
- pulsed: 20% - 50% (non-thermal)
Intensity
Power per unit area of the sound head; magnitude of force in a sound wave; quantity of energy delivered
- W/cm^2
- therapeutic treatment intensity = 0.5 - 2.5 W/cm^2
Thermal intensity
- 1 MHz = 1.5 - 2.5 W/cm^2
- 3 MHz = 0.5 - 1.5 W/cm^2
Non-thermal intensity
- 1 MHz = 0.5 - 1.0 W/cm^2
- 3 MHz = 0.5 - 1.0 W/cm^2
Duration
5 - 10 min treatment time
Methods of US application
Movement of sound head in smooth, rhythmical patterns, medium speed
- maintain direct contact with the skin/tissue at ALL times, using a conduction medium
Water
US applied in water is good for open wounds or for highly contoured areas where good contact with the skin is difficult to maintain
Assessment of US effectiveness
- a positive response should be evident within 3 treatment sessions
- change in S or O findings include: decreased pain, increased ROM and increased function
Potential adverse effects
- Periosteum burns!
- frequency is too high
- intensity is too high
- no continually moving US head - Infection through contamination
- always clean the US head with towel to remove gel then with alcohol wipe between pts
Documentation
- area of body treated
- frequency
- duty cycle
- intensity
- treatment time
