Ultrasound Flashcards
Can we as humans hear the sounds that ultrasound gives off?
no
what does ultrasound do?
it has a deep heating modality that penetrates skin and subcutaneous fat
it is used to heat muscles, tendons, ligaments, joints capsules and scar tissues
it also has non thermal mechanical effects
can ultrasound heal bone fractures?
slowly, in low intensities
can ultrasound help heal wounds?
yes, when it is non-contact, low frequencies
what is the most common use for ultrasound among chiropractors?
deep heating modality
what is the second most common heating modality in the US?
ultrasound
How does ultrasound work?
an electrical current is passed through a crystal causing it to vibrate
this causes soundwaves to be generated
crystal is usually what kind of material?
quartz, lead zirconate, lead titanate, barium titanate, nickel colbalt ferrite about 2-3mm in thickness
what is the duty cycle of ultrasound?
divide time sound is delivered by total treatment time
continuous vs pulsed?
continuous- 100%
pulsed- 20-50%
piezoelectric effect
mechanical deformation of a crystal causes an electrical current to form
reverse piezoelectric effect
alternating current is passed through a crystal
results in very fast contraction and expansion of the crystal
vibration produces high frequency sound waves
why must ultrasound have well insulated cables?
because it requires a high voltage
another name for near field? What is the near field?
fresnel zone
treatment area
another name for farfield?
Fraunhofer zone
what are the coupling agents used with ultrasound?
gel
gel pad
tap water
spatial peak intensity
maximum intensity delivered during continuous ultrasound energy
spatial average intensity
average intensity delivered during pulsed delivery of ultraound energy
ERA
effective radiating area
area of the sound head that produces sound energy
always smaller than the size of the ultrasound heat
BNR
beam nonuniformity ratio
amount of variability of the beam
ratio between the peak intensity of the ultrasound beam divided by the average intensity of the ultrasound beam
used to compare quality of different machines
what is the acceptable range of BNR?
1:1, but within the range of 2:1 and 8:1 is acceptable
why does the BNR ratio need to be so low?
allows for more uniform intensity of the sound wave
eliminates hot spots
allows for higher dosage without discomfort
allows for greatest comfor and safety
PAMBNR
peak area of the maximum beam nonuniformity ratio
large= peak intensity covers a larger area of the sound head
small= peak intensity covers a small area
larger= less uniform heating
when using ultrasound, where must the head be on the skin?
flat against skin
describe underwater ultrasound
indirect
used in plastic (not metal) bucket
sound head needs to be parallel to the part
True or false: more watts in ultrasound do NOT mean greater penetration
true
frequency of ultrasound
typically 1-3 MHz
frequency dictates depth of heating
high frequency (3mHz)
absorbed more rapidly therefore affects superficial tissues
low frequency (1MHz)
absorbed at a slower rate therefore affects deeper tissues
which kind of ultrasound is best for getting to the bone, tendon, cartilage, ligaments, and joint capsules?
continuous
reflection
the reversal of the direction of propagation of the ultrasound wave
acoustic impedance of muscle, fat and water is low, therefore the tissue closest to bone gets increased heating
refraction
change of ultrasound wave from a straight path when pasing obliquely from one medium to another
can lead to concentrations of ultrasound at the point of refraction (where tendon joins bone)
What are the effects of ustrasound?
causes increase in metabolic actiivty which increases oxygen demand, which leads to increased blood flow
what are the therapeutic effects of ultrasound
increase extensibility of collagen fibers of tendons and joint capsules
increase blood flow
increase cell metabolism
increase collegen synthesis
decreased joint stiffness
decreased muscle spasm
enhanced tendon, ligament and muscle healing
which tissues heal more rapidly after an ultrasound treatment?
superficial layers
what should you do immediately after the ultrasound treatment?
manipulation or stretching
what are the effects of non thermal tissues?
affects tissue healing and alters cellular activity
stimulation of fibroblast activity
increased blood flow
increased proteins associated with injury repair
how does non thermal ultrasound work?
through acoustical streaming and stable cavitation
acoustical streaming
movement of fluids along cell membranes due to mechanical pressure exerted by the sound waves
microstreaming
movement that occurs in direction of the sound waves
facilitates fluid movement and inceases cell membrane permeability
cavitation
formation of gas filled bubles from pressure changes in tissue fluids
bubbles expand and contract with ultrasound waves
stable cavitation
rhythmic expansion and contraciton of bubbles during repeated pressure changes over many acoustic cycles
facilitates fluid movment and membrane transport
unstable cavitation
collapse of gas bubbles which may cause tissue damage
associated with low frequency, high intensity ultrasound (not therapeutic)
what are the contraindications of ultrasound?
malignancy hemorrhage ischemia thrombus infection gonads eye pelvic, abdominal and lumbar areas of pregnant women spinal cord after laminectomy plastic and cemented implants (metal is okay) near or over electronic implants unknown etiology
what are the risks for ultrasound?
bony prominences (avoid, use indirect technique, smaller sound head) epiphyseal plate (may alter bone growth)
what is the treatment size usually?
5-8 minutes
what are the stipulations for treatment time?
depends on size of treatment area
never treat for more than a total of 15 minutes
break large treatment areas into 2 or 3 smaller areas and treat for 5 minutes per region
what is phonophoresis
AKA sonophoresis
similar to iontophoresis
uses sound energy to drive medication into the tissue
medication does not need to have a charge
what are the “uses” for ultrasound and electrical stimulation?
trigger points
epicondylitis
superficial pain areas
decrease adhesions
ultrasound head becomes what when using both ultrasound and electrical stimulation?
treating electrode
what is low intensity pulsed ultrasound used for?
fracture healing
home units for patients to apply 1 time a day for 20 minutes
what is non contact low frequency ultrasound used for?
wound cleaning and debridement
propels sterile saline across wound
stimulates healing
