ultrasound Flashcards
brief definition of ultrasound
Inaudible , acoustic vibrations of high frequency that produce either thermal or non-thermal physiologic effects
ultrasound relies on what
Relies on molecular collision for transmission
Collisions cause molecule displacement and a wave of vibration
what is a longitudinal wave
Displacement is in the direction of wave propagation
Travels in both liquids and solids (Soft tissue)
do longitudinal wave travel in liquid and in solid
yes
what is a transverse wave
Displacement is perpendicular to direction of propagation
do transverse wave travels in solid and in liquid
no only in solids (bone)
which frequency have greater depth of penetration
lower frequencies
which frequency have more superficial absorption
higher
vélocity of transmission related to
tissue density -> the higher the density the greater the velocity
attenuation is what and du to what
Decrease in energy intensity
Decrease is due to absorption, dispersion, or scattering resulting from reflection and refraction
absorption (increase/decrease) as frequency (increase/decrease)
increase, increase
which type of tissue decrease absorption
tissue high in water content
which type of tissue increase absorption
tissue high in protein
where in the body there is the highest absorption rate
in bone, nerve, muscle, fat
what determine the amount of reflected or transmitted of ultrasound
acoustint impedance (tissue density x speed of transmission )
the most energy will tramitted if the acoustic impedance is
the same
the larger the difference in acoustic impedance the (more/less) energy is reflected
more
what happen if the transducer is in contact with air
completly reflected
transducer through
transmitted
muscle/fat interface will do what
reflected and refracted
soft tissue/bone interface will
reflected, create standing wave or hot spot
step of an ultrasound generator
electrical output -> mechanical vibration -> acoustic sound wave-> absorbed in the tissue
role of the crystal in the transducer
Crystal converts electrical energy to sound energy through mechanical deformation
When an alternating current is passed through a crystal it will expand and compress
what is the direct effect of the cristal
Direct Effect - An electrical voltage is generated when the crystal expands and compresses
what is the indirect effect of the crystal
Indirect or Reverse Effect - As alternating current reverses polarity the crystal expands and contracts producing ultrasound
what is the effective radiating area (ERA)
That portion of the surface of the transducer that actually produces the sound wave
Should be only slightly smaller than transducer surface
what’s the frequency range of therapeutic ultrasound
0.75 to 3.0 MHz
depth of penetration is intensity depend or frequency depend
frequency
1 mHZ transmitted or absorpted
both, absorbed at 3-5 cm
3 MHz transmit or absorbed
absorbed superficialy at 1-2 cm
what is the ultrasound beam
concentrate energy in a limited area
larger head of ultrasound beam is more
collimated beam
smaller head of ultrasound beam is
more divergent beam
how is the distribution of energy near field of ultrasound beam
Distribution of energy is nonuniform due to the manner in which waves are generated and differences in acoustic pressure
how are the wave at point of maximum acoustic intensity
wave are indistinguishable and arrive simultaneously
how is the distribution of energy far field
Energy is more evenly distributed and the beam becomes more divergent
what is the beam non uniformity ration (BNR)
Indicates the amount of variability in intensity within the beam
what is the ratio of BNR and what is the ideal BNR and typical BNR
Highest intensity found in the beam relative to the average intensity of the transducer
ideal: 1:!
typical: 6:1
The (lower/greater) the BNR the more even the intensity
lower
better generator have (lower/greater) BNR and why
low because provide more even intensity through the field
if the intensity is 1.5 W/cm2 the peak intensity in the field would be
9 W/cm2
what is the PAMBNR
represent the size of the peak intensity
what does a small PAMBNR represent
small or any hot spot
large PAMBNR means what
large hot spot
pulsed ultrasound vs continuous ultrasound
continuous: intensity remains constant over time
pulsed: intensity is interrupted thys averege intensity of output over time is low
duty cycle may be set to _% or _ %
20 or 50
intensity means
rate at which energy is delivered per unit area
recommandation for intensity
lowest intensity at the highest frequency which transmits energy to a specific tissue to achieve a desired therapeutic effect
thermal vs non-thermal effects
thermal: tissue healing
non-thermal ; tissue repaire at the cellular level
when does thermal effect occurs
whenever the spatial average intensity is > 0.2 W/cm2
t/f Whenever there is a thermal effect there will always be a non-thermal effect
t
when do we want to use thermal effect
Increased collagen extensibility
Increased blood flow
Decreased pain
Reduction of muscle spasm
Decreased Joint stiffness
Reduction of chronic inflammation
what is mild, moderate, vigorous heating
mild: increase of 1º
moderate: increase of 2-3º
vigorous: increase of 3-4º
effect of mild heating
accelerate metabolic rate in tissue, reduce mild inflammation
effect of moderate heating
reduce muscle spams, pain, chronic inflammation, increase blood flo
effect of vigorous heating
decrease viscoelastic propreties of collagen, increase ROM and tissue extensibility
effect of non-thermal
Increased fibroblastic activity
Increased protein synthesis
Tissue regeneration
Reduction of edema
Bone healing
Pain modulation
all of non-thermal physiologic effect occurs through what
acoustic micro streaming and/or cavitation
what is micro streaming
Unidirectional flow of fluid and tissue components along the cell membrane interface resulting in mechanical pressure waves in an ultrasonic field
what miscrostreaming do the cell membrane
alter permeability to sodium and calcium
what is cavitation
Formation of gas filled bubbles that expand and compress due to pressure changes in fluid
stable cavitation result in
in an increased fluid flow around these bubbles
what is unstable cavitation
results in violent large excursions in bubble volume with collapse creating increased pressure and temperatures that can cause tissue damage
therapeutic benefits are derived only from stable or unstable cavitation ?
stable
how can we maximized non-thermal effect
while minimizing thermal effect : using spatial average intensity of 0.1-0.2 W/cm2 with continuous ultrasound, set duty cycle at 20% at 1 W/cm2 or set duty cycle at 50% at 04 W/cm2
which conditions btw acute or chronic require more treatment over a short period of time
acute 2x/day for 6-8 days
which condition btw acute and chronic require less treatment over a longer period
chronic alternating day for 10-12 treatments
what is the limit treatment for ultrasound
14
consideration for determining treatment duration
size of the area to be treated
what we want to do btw thermal or non-thermal effect
intensity of treatment
size of treatment area should be 2-3 time (larger/smaller) Thant the _ of the crystal transducer
larger, ERA
what needed to be done if the area to be treated is larger
use shortwave diathermy, superficial hot pack or hot whirlpool
increase intramuscular temperature at 3cm after 10 min with hydrocollator pack and 1 MHz ultrasound
hydro: 0.8 º
mhz: 4.0º
increase temperature at 1cm below fat layer after 4min with hot whirlpool and 3 MHz ultrasound
hot: 1.1
mhz: 4.0
ultrasound intensity should be adjusted considerate what
patient tolerance,Increase to the point where there is warmth and then back down until there is general heating
what to do if you decrease intensity during treatment
increase treatment duration
ultrasound should be ( temperature/ time) dependant not (temperature/time) dependant
temperature, time
purpose of coupling method
minimize air and maximize contact with the tissue
name some coupling method and the best one
Include gel, water, mineral oil, distilled water, glycerin, analgesic creams
Gel seems to be the best coupling medium
name some coupling method and the best one
Include gel, water, mineral oil, distilled water, glycerin, analgesic creams
Gel seems to be the best coupling medium
benefit of heating gel
patient confort but don’t increase efficiency of treatment
benefit of immersion technique
good for treating irregular surface
what should be use for the immersion technique
A plastic, ceramic, or rubber basin should be used
Tap water is useful as a coupling medium
transducer should move how with the surface at _ cm
parallel at 0.3-0.5 cm
bladder technique is good for
treating irregular surface
what is use with bladder technique
balloon filled with water, both side of balloon should be liberally coated with gel
applicator should be moved at about
4 cm/sec
is stationary technique recommend
no
low bnr allow for slower or rapid movement
slower
what can arrive with high bar
cavitation and periosteal irritation
do cooling the tissue does facilitate an increase in temperature
no
analgesic effect of ice can interfere with what
perception of heating
what can be use to treat myofascial trigger point
ultrasound and EMS when used in combination with stretching
ultrasound is recognized as a effective modality to treat what
soft tissu and boney lession
what happen physiologically when using ultrasound soft tissue healing and repair
During inflammatory stage cavitation and streaming increases transport of calcium across cell membrane releasing histamine
Histamine stimulate leukocytes to “clean up”
Stimulates fibroblasts to produce collagen
how does ultrasound help with scar tissu and joint contracture
Increased temperature causes an increase in elasticity and a decrease in viscocity of collagen fibers
Increases mobility in mature scar
ultrasound is seams effective with chronic inflammation because
Ultrasound does seem to be effective for increasing blood flow for healing and reduction of pain
benefit of ultrasound with bone healing
Ultrasound accelerates fracture repair
Ultrasound given to an unstable fracture during cartilage formation may cause cartilage proliferation and delay union (Dyson, 1989)
Ultrasound has no effect on myositis ossificans but may help reduce surrounding inflammation
Ultrasound not effective in detecting stress fractures
do ultrasound help decrease pain
no but may increase threshold for activation of free nerve ending, superficial activation of free nerve ending and may affect gating
t/f ultrasound help drive topical application into tissue
t
why using ultrasound help to drive topical application
non-thermal effect increase tissue permeability and acoustic pressure drive molecule into tissue
reasons for hot spot
not moving enough
ERA/BNR
close to bone
