Therapeutic US Flashcards
What frequency is US?
> 20,000 Hz
What frequency is therapeutic US?
1.0-3.0MHz
What type of tissue can be treated with therapeutic US?
soft tissue 1-5cm deep
the transducer contains what type of crystal? how is it deformed? what is condensation? what is rarefraction? what’s an US wave?
- piezoelectric
- voltage used to deform crystal
- condensation is when crystal expands and compresses material in front of it
- rarefraction is when crystal retracts, dispersing material in front of it
- US wave= repeated cycles of compression/expansion of the crysal
What is intensity? And how is it measured?
strength of US (W/cm^2)
What is frequency and what does it effect?
- number of times a molecule oscillates within 1 second
- affects the depth of penetration of the US
What’s depth:frequency rule?
- higher frequencies penetrate deeper areas
- 3MHz for superficial regions <2.5 cm deep.
- 1MHz for deep regions 2.5-5cm deep
What are the modes of US and when do you use each?
Continuous- thermal affects
Pulsed- non-thermal effects
What is duty cycle and what mode is it related to?
- related to pulsed mode
- percent of time during one pulse that the beam is present
What is the effective radiating area?
-a little smaller than the sound head because there is cement around the crystal
spatial peak intensity
place on transducer with highest intensity
spatial average intensity
average intensity about the tranducer
non-uniformity beam ratio
- ratio of spatial peak intensity to spatial average intensity
- smaller ratio = more uniform beam
- acceptable for clinical use is <6:1 ratio
Contraindications for therapeutic US
- in region of cardiac pacemaker
- during pregnancy, over pelvic, abdominal, or lumbar regions
- to eyes
- over male/female reproductive organs
- in region of active bleeding or infection
- in region of tumor/malignancy
- in region of DVT/ thrombophlebites
- over heat, stellate, or cervical ganglia
- over epiphyseal plates of growing bones
Precautions for US
- over areas of sensory deficits
- on patients who are unable to clearly communicate
- over cemented prosthesis/ areas where plastic components are used
- fractures
- breast implants
What are the effects of US in biological tissues? What are effects influenced by?
- thermal effects- chronic sprains and strains, pain relief and decreased ROM
- non thermal effects- tissue regeneration, protein synthesis in fibroblasts, tendon repair
- influenced by properties of materials and the angle from which the energy strikes them
physiological effects of US
Thermal: increasing tissue temperature of superficial and deep tissue
- increase local blood flow
- increase collagen extensibility
- reduce pain
- reduce muscle spasm
- increased enzyme activity
- produce mild inflammatory response
Non thermal:
- promote soft tissue and bony tissue repair
- increased cell and tissue membrane permeability
What is acoustic impedence?
- ability of a material to transmit sound
- low impedence= high transmission and little sound absorbed
- high impedence = low transmission and lots of energy absorbtion
- i.e. blood = low impedence, bone = high
what are standing waves?
combined energies of 2 waves with an area of increased intensity
–> keep transducer moving!!!
what is attenuation?
- a measure of the decrease in sound energy as the sound travels, either by absorption, reflection, or refraction
- denser tissues w/ high protein (ie collagen) absorb US energy most effectively
blood< skin< tendon< cartilage<bone
what tissues experience high thermal effects? which experience low?
high absorption coefficients –> high collagen content –> greater thermal effects
low absorption coefficient –> low collagen content–> lesser thermal effects
how thermal effects are usefull
improve blood flow, nerve conduction, tissue extensibility
- accelerate metabolic rate
- decreased muscle guarding
- decreased pain perception
- increased soft tissue extensibility
- increased blood flow
how much temperature increase do you need for:
- increased metabolic rate
- reduce muscle spasm and pain, and increase blood flow
- increase tissue extensibility and inhibit sympathetic activity?
- 1 deg C
- 2-3 deg C
- 4 deg C
applying hot pack affects tissues how deep?
superficial 1-2mm of skin
heat or ice before US?
- hot pack doesn’t do much
- fastest rate of heating came with warming the conduction medium
- don’t ice because could numb area and decrease sensation
non thermal effects of therapeutic US
microstreaming = small-magnitude movements that occur in the ions surrounding cells and within intracellular and extracellular fluids which is created with changing cell membrane permeability
cavitation = pulsation of small gas bubbles present in body fluids from compression and rarefraction, which is responsible for diffusion and cellular function changes
- increase intracellular calcium levles
- increase mast cell degranulation
- promotes macrophage responsiveness
- increases rate of protein synthesis by fibroblasts and tendon cells
- stimulates proteoglycan synthesis
Why use a coupling medium?
- US waves don’t travel effectively through air
- space between transducer and body can cause energy to reflect back to transducer and overheat and damage it
settings to increase temperature in superficial tissues?
Continuous (100% duty cycle)
freq= 3MHz
duration= 5-10 min.
intensity= 0.5-1.0 W/cm^2
Settings to increase temperature in deep tissues?
Continuous (100% duty cycle)
freq= 1MHz
duration = 5-10 min
intensity= 1.5-2.0 W/cm^2
settings for non thermal effects in superficial tissues?
Pulsed (20% duty cycle)
freq= 3MHz
duration = 5-10 min
Intensity = 0.5- 1.0 W/cm^2
settings for non thermal effects in deep tissues?
pulsed (20% duty cycle)
freq= 1MHz
duration = 5-10 min
Intensity= 0.5 - 1.0 W/cm^2
Settings to increase soft tissue extensibility
duration = 5-10 min deep tissue: freq=1MHz intensity = 1.5-2.0 W/cm^2 superficial tissue: freq = 3MHz intensity = 0.5-1.0 W/cm^2
apply stretch during heating and maintain after US application (for at least 4 min) while tissue is cooling
settings pain control
duration = 3-10 min deep: freq= 1MHz intensity= 1.5-2.0 W/cm^2 superficial freq = 3MHz intensity = 0.5-1.0 MHz
US for wound healing?
maybe pulsed? currently not enough evidence to support it.
20% duty cycle
3MHz freq
0.8-1.0 W/cm^2 intensity
duration = 5-10 min
- use gel and apply US around wound OR use US coupling sheet OR place transducer under water
US for healing surgical skin incision
believed to accelerate evolution of angiogenesis by altering cell membrane permeability (calcium ions) and stimulation angiogenic factor synthesis and release by macrophages
PULSED 20% duty cycle freq = 3MHz intensity = 0.5-0.8W/cm^2 duration = 3-5 minutes, 3-5 times a week
US for tendon and ligament injuries?
mixed findings, but research supports early use of US for facilitation of tendon healing after rupture with surgical repair
PULSED, low intensity (0.5-1.0W/cm^2) during acute phase.
20% duty cycle
freq= 1 or 3 MHz
Intensity = 0.5-1.0 W/cm^2
duration 2-5 min
later, CONTINUOUS and high intensity with stretching if chronic tendonitis accompanied by tissue shortening due to scarring
100% duty cycle
intensity = 1.0-2.5 W/cm^2
duration = 3-5 min.
US for bone healing
20% duty cycle
freq = 1.5 MHz
intensity = 30 mW/cm^2
20 min daily
US for musculoskeletal conditions of lower limb
currently no high quality evidence available to suggest ther. US is effective
What is phonophoresis and what are its advantages?
- thermal drug delivery
Advantages: - higher initial drug concentration at delivery site
- avoid gastric irritation
- avoid first pass metabolism by liver
- avoid pain/trauma/infection risk associated with injection
- allows delivery to larger area than is readily achieved by injection
US for heel pain?
no strong evidence to support
US for achilles tendon pain?
US as effective as the eccentric loading exercises. more studies needed
US and ankle ligaments?
ice and US improved pain, swelling, and function compared to immobalization
US and knee injuries?
US and ice more effective than ice alone, phonophoresis or iontophoresis for pain associated with extensor mechanism.
more research needed!
US and lateral epicondylitis?
one study supports
US and calcific tendonopathy of supraspinatus?
one study supports
SR of treating people with pain, musculoskeletal injuries and soft tissue lesions
only 2/10 suggest US is more effective
8/10 did not!
