06-14: Ultrasound Flashcards
Piezoelectric Effect
Piezoelectric transducer (head) converts electrical energy into sound
Definition of ultrasound
- Deep heat transferred through conversion
- Uses vibration to produce thermal and no thermal effects
- Acoustic effects = friction = effects
Depth of US
- Tissue temp increases up to depths of 5cm
- Requires coupling agent (gel)
Reverse Piezoelectric Effect
- Electricity applied to crystal through AC at a specific frequency will produce movement in the crystal that creates US waves at that same frequency
- Therapeutic US uses those waves to create vibrations in the tissue that has thermal effects if continuous US and/or non-thermal effects for continuous or pulsed US
Size of Transducer head
- Selected for body part treated
Penetration
- US penetrates through tissue with high water content
- Ex: Fat
Attenuation
- Loss of heat during transmission through the tissues
- Occurs when US absorbed into dense tissue with high protein (muscle, nerve, bone)
- Greatest heating occurs where absorption is greatest
- Penetration and absorption are inversely related
Reflection
- US is reflected when It travels through air or through interface between two different types of tissue
- Causes hotspots (tissue in front of bony areas will get reflections that can burn - deep burn)
- Can burn tissue
- Reason for cooling gel - allows penetration into tissue
Refraction
Waves change somewhat as they pass through tissue
More reflection
- Holding transducer in air causes reflection and build up of heat that can damage crystal or burn patient when you make contact.
- Coupling medium must be used to transmit sound waves between sound head and pt without allowing air between
- US transmitted through fat and reflected and refracted at muscle interface.
- At bone-soft tissue interface, almost all vibration reflected. Reflected energy runs into new energy, can create hotspot and damage tissue
- Moving transducer using pulsed US. can he’ll avoid hotspots
Depth of penetration
- Derermined by US frequency, not intensity (W/cm2)
- Higher frequency sounds absorbed by more superficial tissues
- Lower frequency sound waves have greater depth of perception
Frequency
- 0.75-3MHz
- 1 MHz: Heating deeper tissue, up to 5cm DOP
- 3 MHz: higher temp, absorbed in more superficial tissues, heard faster, less than 2cm DOP
Continuous mode
Thermal or non- thermal effects, elevates tissue temp
Pulsed mode
Non-thermal effects
Duty Cycle
- Amount of total treatment time during which ultrasound is generated
- Continuous: 100% duty cycle
- US waves continuously generated 100%
- Higher intensity of thermal effect; also has non-thermal
- Pulsed: 20% duty cycle
- US generated 20% of time
- Non-thermal
Intensity
- Measure of the rate energy is being delivered per unit area
- W/cm2
- Range from .25-3.0 w/cm2
- Deteines rate heating occurs, but not DOP
Thermal effects
- increased collagen extensibility
- decrease joint stiffness
- pain relief
- increased blood flow
- decrease muscle spasm
- May have mild inflammatory response to help chronic inflammation
Non-thermal effects
- stimulation of tissue regeneration
- increase macrophage responsiveness
- pain relief
- soft tissue repair
- increase blood flow
- increase skin and cell membrane permeability
Cavitation
- acoustic energy causes micro bubbles in tissue fluids to wxpand and contract
Stable cavitation
Bubbles expand and contract in response to repeated pressure changed but do not burst
- small flow of fluid around bubbles (microstreaming)
- flies in a unidirectional movement along boundary of cell mnrancdz; can alter structure and function
Transient cavitation
Micro bubbles burst and cause increase in temp and pressure - not a good thing
Acoustic
Microstreaming
Consistent and unidirectional flow of cellular fluids that results from US
Indications
Soft tissue repair Decrease inflammatory response Decrease pain Contracture Bone fracture Trigger point Dermal ulcer Scar tissue Muscle spas plantar wary
Contraindications
Over eyes Over pregnant uterus Over cemented prosthetic joint Impaired circulation Thronbohlebotis Impaired pain or temp sensory deficits Over heart Over tested Over epiphyte all areas in childr Infection Malignancy
Coupling agents
Get rid of air between transducer and pt so US can be transmitted
Us gel room temp or warmed
Gel packs, pads, hydrogel sheets - over wounds
Immersion for irregular body part
Water filled bladder
analgesic cremes
MedicTikns
Treatment parameters
Coupling agent Thermal or nonthermal Duration: 5-10 min, 2-3x size of transducer requires 5 min Frequency 1 or 3 MHz Duty cycle applies to pulsed Intensity - continuous: ,5-2 w/cm2 Pulsed .5 - ,75w/cm
