ultrasound Flashcards
definition
inaudible, acoustic vibrations of high frequency that may produce either thermal or non thermal physiologic effects
rationale
to introduce thermal and mechanical effects
to help with tissue repair and pain relief
to facilitate wound debridement
to promote and accelerate bone growth
how does ultrasound affect pain
decreases pain
–> via elevation of pain threshold by activating thermal receptors
–> reduces inflammation
–> reduces muscle spasm
contraindications
in conjunction w/ x-rays, radiation or radioactive isotopes
over the eyes, carotid sinus, testes, epiphyseal plates , cemented prosthetic, cervical ganglia, heart, pacemakers and bony prominence
pt w/ cancer, severe or acute cardiac dzs, thrombophlebitis
over pregnant uterus, over spinal cord after a laminectomy, over an infection
precautions
unhealed fx sites
joint cement
primary repair of tendon or ligament
reproductive organs
impaired circulation
acute inflammation
osteoporosis
plastic or metal implants
thermal ultrasound effects
increases extensibility of collagen and blood flow
decreases joint stiffness and muscle spasm
helps to relieve pain
thermal ultrasound benefits
increasing collagen extensibility
decrease in joint stiffness
decrease in muscle spasm
decrease in pain
increased blood flow
increased inflammatory response
thermal ultrasound disadvantages
can only heat a small area
no more than 2 times the head of the transducer
non-thermal ultrasound effects
increases macrophage responsiveness
increases blood flow and membrane permeability
aids in soft tissue repair
provides pain relief
nonthermal ultrasound key note
there is still some sort of heat occurring during any duration of this treatment
advantages of non thermal ultrasound
increases the healing process
–> stimulation of fibroblast activity
–> increased protein synthesis
–> increased blood flow
benefits during all 3 stages of healing
how does nonthermal ultrasound work
cavitation
acoustic micro steaming
cavitation
defined as the formation of gas filled bubbles that expand and compress b/w of ultrasonically induced pressure changes in tissue fluids
increase its flow in fluid around the vibrating bubble
increases cell membrane permeability which increases as intensity increases
acoustic micro steaming
the movement of fluids along the boundaries of cell membranes
results in change in cell wall permeability which allows healing to occur
transmission of acoustic energy
uses molecular collision
by using a coupling medium –> absorption is enhanced by causing vibration
through the medium there is a minimum amount of displacement to the surrounding tissues
eventually the wave of vibration is propagated through the entire medium
wave transmition
2 types of waves
longitudinal
transverse
longitudinal
molecules are displaced in a direction the wave travels
particles become compressed and decompressed
can travel through solids and liquids
transverse
molecules are displaced at right angles to the direction the wave travels
particles become compressed and decompressed
only travel in solids
frequency of wave transmission
frequency of wave transmission –> transverse waves
acoustic sound is transmitted between 16 kHz and 20 kHz
therapeutic ultrasound is b/w .75 and 3 MHz
the greater the frequency the more focused the beam
the lower the frequency the greater the dept of penetration
components
high frequency electrical generator and transducer
transducer
components –> transducer
known as the applicator or sound head
composed of piezoelectric crystal such as quartz or synthetic ceramic
crystal converts electrical energy to acoustic energy through mechanical deformation
reverse piezoelectric effect
occurs when AC electrical current runs through a crystal
will cause the crystal to expand and contract which causes production of ultrasound
attenuation
transmission through various tissues reduces the intensity of ultrasound energy
decreased intensity is due to absorption of that energy as it passes through tissues
acoustic impedance
defined as the reflection or refraction of a sound wave
occurs when it encounters a boundary or an interference b/w 2 tissues
reflection
refraction
reflection
occurs when ultrasound waves bounce back from obstacles and boundaries to the ultrasound wave
known as the standing wave
clinical significance
clinical significance of reflection
99% reflection from metal to air is why a gel must be used
also why you must never turn on the machine which transducer in the air
hot spot
hot spot –> reflection –> clinical significance
repetition of a continuous wave when the path of new and reflected waves coincide results in the sum of both waves
can result in a severe internal burn
to prevent must move head continuously
refraction –> acoustic impedance
ultrasound wave bounces at angle away from the ultrasound
production of heat
heat is produced by the absorption of ultrasound waves
structures with high absorption will get heated much easier
order of low to high absorption
water
blood
fat
muscles
tendons
cartilage
peripheral nerve
bone
advantages as a heating modality
ability to heat deep structures w/o heating superficial structures
skin and fat can be bypassed
types of ultrasound
continuous
pulsed
continuous
sound intensity is constant throughout the treatment
ultrasound is absorbed 100% of the time
produces much more heat than pulsed
pulsed
interrupted intensity
there’s an on off time
no energy is produced during off period
duty cycle refers to the on time
utilized early on during the healing b/c there is little heat produced
effective radiating area
defined as the surface of the transducer producing the sound wave
dependent on the surface area of the crystal
usually the perimeter of the transducer has no therapeutic effect
beam non-uniformity ratio
define as the variability of ultrasound beam intensity
the lower the BNR the more uniform the output of the machine
FDA is acceptable b/w 2 and 6
optimally want 1:1 ration but acceptable up to 6:1 ration
clinical significance
clinical significance –> BNR
the higher the BNR the greater the likelihood of tissue damage
the lower the BNR the less chance of hotspots
the higher the BNR the faster one must move the transducer to safely treat the pt
ultrasound parameters
frequency
duty cycle
measuring energy
frequency
defined as a number of wave cycles completed during each cycle
ultrasound frequency is either 1 MHz or 3 MHz
1 MHz
less energy is absorbed in the superficial tissue and there is greater penetration
tissue healing occurs slower
3 MHz
there is much more superficial heating
tissue heating occurs slower
duty cycle
defined as the percentage of time that the ultrasound is actually on
equated by duration of pulse (on time) divided by pulse period (on + off)
measuring energy
power
intensity
measuring energy –> power
measured in watts
defined as the electrical energy delivered to the crystal
intensity
measured in watts/cm2
refers to the avg power delivered over the ERA
therapeutic use –> intensity
b/w .25 watts/cm2 - 3 W/cm2
usually b/w .5 and 2
depends on goal of the treatment
too much will cause damage
too little will have no effect
acute
.1-.5 W/cm2
no heat for pt
subacute
.5-1.0 W/cm2
no to minimal heat felt by pt
chronic
1.0-2.0 W/cm2
heating/warmth felt by pt
non-thermal
no temp increase
used for acute injury, edema, healing
mild thermal
1 degree C temp increase
subacute injury or hematoma
moderate thermal
2 degrees C increase
used for chronic inflammation, pain, trigger points
vigorous
4 degrees C increase
used for stretch collagen
acute condition (specifics)
tissue repair
low intensity
pulsed (0.5 W/cm2) for non thermal effect
chronic condition
muscle spasm or stiffness
high intensity
continuous (1-3 w/cm2) for thermal effect
ultrasound delivery techniques
direct contact
immersion
bladder
direct contact –> delivery
occurs when direct contact is made b/w the ultrasound transducer and pt with a medium in b/w
surface must be larger than the transducer
be certain to utilize enough medium
how much gel should be applied to the transducer
1-2 millimeters
too little –> burn the pt
too much –> cause air pockets
what should we try to exclude
air so that most of the sound energy has ability to penetrate tissue
immersion technique
used when the treatment area is smaller than the transducer head
used when treatment area is irregular
used when a bony prominence makes direct contact difficult
underwater coupling
32% less energy is absorbed
40-60% less effective than direct contact for thermal purposes
to compensate increase intensity
underwater coupling
immerse body part in basin filled with water
establish treatment duration depending on size of area to be treated
maintain sound head parallel to treatment surface at a distance of .5 to 3 cm
move sound headed circular or linear overlapping strokes at rate of 2-4 inches per second
bladder technique
balloon or surgical glove filled with water
only 50% of energy enters the tissues
technique is not usually recommended
phonophoresis
delivery of meds into the body via ultrasound
transdermal drug delivery as sound waves push meds deep into the body
treatment parameters –> phonophoresis
frequency = 3 MHz
duty cycle = 20%
duration = 5-10 min for an area 2-3 times the size of the ERA
advantages –> phonophoresis
medication is spread over the local area
increase concentration at delivery site
non invasive
medication bypasses the liver
avoid pain, trauma, infection via injection
prevents gastric irritation
indications –> phonophoresis
muscle soreness
tissue inflammation
tendonitis
bursitis
strains/sprains
epicondylitis
common medications used –> phonophoresis
hydrocortisone
lidocaine
iodine
salicylate
zinc
documentation
record specific parameters
