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Ultrasound
Notes from Ultrasound PPT and handout and study guide
184
Anatomy
Graduate
03/27/2012

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Term
what is ultrasound?
Definition
a high frequency sound wave generated by applying an electrical current to a crystal designed to resonate with the frequency of the applied electrical field
Term
what type of energy is ultrasound
Definition
conversion energy
Term
what is conversion energy
Definition
taking one form of energy and turning it into another
Term
what happens when we apply electrical energy to a crystal?
Definition
it vibrates, putting out sound energy
Term
what was the original inspiration for US?
Definition
WWII and sonar: putting sound energy into the water to look for submarines
Term
what is the differene between sonar and ultrasound
Definition
in sonar, you listen for the return of the sound that bounces off a submarine. In PT/therapeutic ultrasound, you only dispense sound and don't listen for the return
Term
what is the frequency range of human hearing
Definition
20-20,000 Hz
Term
what is the frequency of middle C
Definition
256 Hz
Term
what is the frequency range of US
Definition
1 million to 3 million Hz
Term
what is required for the generation of sound waves
Definition
a medium for them to travel through
Term
what is a transducer
Definition
a crystal that converts electricity into sound waves
Term
what is the Piezo-Electric effect
Definition
If I deform a crystal, it will produce electrical energy
Term
what is the Reverse Piezo Electric Effect
Definition
applying electrical energy causes a crystal to change shape
Term
describe how an US head works
Definition
Run electricity through coaxial cable into US head. Piece (resonating coil) in the head gets electrified. Piece presses against crystal. Electrical energy causes crystal to vibrate/change shape. Crystal expands/contracts based on frequency we apply to it. US passes through front plate of US head.
Term
describe what makes up the frequency of the crystal
Definition
compression/rarefaction cycles/second
Term
define power
Definition
amount of energy being delivered by the unit = amount of energy/time
Term
what is the unit of power
Definition
Watts
Term
define intensity
Definition
power/surface area of the device
Term
what is the unit of intensity
Definition
watts/cm^2
Term
what is the WHO limit of intensity for US
Definition
3W/cm^2
Term
what are crystals in older units made of
Definition
quartz
Term
what are crystals in newer units made of
Definition
synthetics: Plumbium Zirconium Titinate (PZT) or Barium Titinate
Term
what can happen if you don't have gel/a medium on the US head
Definition
you can get a standing wave that oscillates and fractures the crystal
Term
what is the longest amount of time that you can hold the US up off the person
Definition
20-30s
Term
what does ERA stand for
Definition
effective radiating area
Term
what is effective radiating area
Definition
area of transducer from which US is generated = size of the ultrasound head
Term
do crystals produce an even vibration?
Definition
no
Term
what is spatial peak intensity
Definition
highest point of beam on the sound head
Term
what is the spatial average intensity
Definition
US beam or output averaged over the surface area of the US head
Term
are spatial peak intensities and spatial average intensities used for continuous or pulsed US
Definition
continuous
Term
for continuous US, does the power meter read spatial peak intensity or spatial average intensity?
Definition
spatial average intensity
Term
what are the units of spatial average intensity
Definition
W/cm^2
Term
what is beam non-uniformity ratio
Definition
ratio of spatial peak intensity to spatial average intensity
Term
what does beam non-uniformity ratio indicate
Definition
how smooth or evenly distributed the beam is
Term
what is the FDA limit of the beam non-uniformity ratio
Definition
6 to 1
Term
what is a very good beam non-uniformity ratio
Definition
2 to 1
Term
what is a benefit of having a 2:1 beam non-uniformity ratio?
Definition
very good crystals make a very smooth beam. Can slow down movement of the head without worrying about safety
Term
what is a disadvantage of having a 2:1 beam non-uniformity ratio
Definition
these devices are rare and very expensive
Term
if you're using WHO's upper limit of intensity and FDA's upper limit for beam non-uniformity ratio, what's the highest power you can have?
Definition
3W/cm^2 x 6 =18W/cm^2
Term
how do you calculate the spatial peak intensity
Definition
SAI x beam non-uniformity ratio
Term
what is the duty cycle
Definition
the proportion of time the US is on to the total time
Term
why might you want to know what the SPI is?
Definition
to know what the hottest point of the beam is
Term
if the duty cycle is on 1:5, how much of the time in percentage is the US on
Definition
20.00000%
Term
what is the usual duty cycle
Definition
2ms on and 8ms off
Term
what does the duty cycle help with
Definition
helps prevent getting too much energy applied
Term
are spatial average temporal averages and spatial average temporal pulses used with continuous or pulsed machines
Definition
pulsed
Term
what is the spatial average temporal peak?
Definition
the spatial average intensity when the machine is pulsed "on."
Term
what is spatial average temporal average
Definition
the spatial average temporal pulse averaged over the entire pulse.
Term
how can you calculate spatial average temporal average?
Definition
SATA = SATP x duty cycle
Term
for pulsed US, what does the meter reading show?
Definition
Spatial Average Temporal Peak
Term
what measure shows the actual energy delivered to the tissue over time?
Definition
spatial average temporal average
Term
what is the duty cycle for a machine that pulses on for 2ms and then off for 8ms?
Definition
20% duty cycle
Term
if the machine says that the SATP is 1W/cm^2, and we are using a 20% duty cycle, what is the SATA or the energy that is actually being delivered to the tissue?
Definition
0.2W/cm^2
Term
what does the sound field look like?
Definition
hour glass on its side
Term
what is the near field?
Definition
first half of the hour glass of the sound field near the transducer
Term
what is the far field?
Definition
2nd half of the hour glass shape of the sound field away from the transducer
Term
does US work in near field or far field
Definition
near field
Term
define absorption
Definition
conversion of mechanical energy into heat
Term
do all tissues absorb sonic energy in the same way
Definition
no
Term
how does high collagen content relate to absorption
Definition
high collagen content leads to high absorption
Term
what determins absorption
Definition
tissue, frequency
Term
define reflection
Definition
redirection of an incident beam
Term
what is acoustical impedance
Definition
a tissue's opposition to the passage of soundwaves
Term
where is reflection highest
Definition
between tissues with greatest acoustical impedance differences
Term
what can you do to avoid reflection
Definition
be sure that the head of the US is aimed at the tissue you want to treat
Term
how much reflection occurs between air-skin
Definition
100.00000%
Term
how much reflection occurs between soft tissue-bone?
Definition
35.00000%
Term
how much reflection occurs between transducer-medium
Definition
0.10000%
Term
how can you eliminate acoustical impedance from air-skin?
Definition
gel
Term
if someone complains of deep ache with US, what is happening
Definition
energy is reflecting off bone
Term
define refraction
Definition
re-direction of a wave at an interface
Term
what is the difference between refraction and reflection
Definition
reflection stays in the first medium; refraction goes into the 2nd medium, just not at the angle you want
Term
why do we want to try to reduce reflection and refraction?
Definition
so that we get the greatest absorption that we can
Term
define attenuation
Definition
decrease of US intensity as it goes through the tissue
Term
what 3 things cause attenuation
Definition
reflection, refraction, absorption
Term
how much of the energy that goes into the tissue is absorbed
Definition
half
Term
what happens to the energy that goes into tissue that is not absorbed?
Definition
reflected/refracted
Term
how does high collagen content relate to attenuation?
Definition
high collagen = high attenuation
Term
how does frequency affect absorption
Definition
high frequency increases absorption
Term
how does frequency affect attenuation?
Definition
high frequency increases attenuation
Term
if you get the US past the tissue interface, does bone absorb US well?
Definition
yes
Term
where does most absorption occur?
Definition
tendon/cartilage
Term
why is there not a lot of absorption of US in bone?
Definition
reflection
Term
what determines the depth that US energy will go
Definition
frequency
Term
does increasing amplitude make the US go deeper
Definition
no
Term
what does increasing amplitude do
Definition
gives you more power/energy within the depth you choose to work at
Term
what frequency is required to have most energy absorbed in 5cm
Definition
1MHz
Term
what frequency is required to have most energy absorbed in 2.5cm
Definition
3MHz
Term
define cavitation
Definition
formation or growth of gas-filled bubbles generated by the US vibration
Term
what is stable cavitation
Definition
oscillation of bubbles without bursting
Term
what is stable cavitation used for
Definition
non-thermal effects
Term
what does stable cavitation vibration do
Definition
affects the cell membrane
Term
when are you at risk for unstable cavitation
Definition
when you go over 3W/cm^2
Term
what happens in unstable cavitation
Definition
bubbles increase in size and burst
Term
what are the results of unstable cavitation
Definition
increased pressure, temperature; tissue destruction; free radical production (goldfish story)
Term
what is microstreaming
Definition
eddying produced around a vibrating object
Term
what is acoustic streaming
Definition
circular flow of fluids, like a latte steamer. Mixes up the fluid in the tissue.
Term
how does acoustic streaming compare to microstreaming
Definition
acoustic streaming is larger in scale than microstreaming
Term
what does acoustic streaming do
Definition
alters cellular activity by moving fluid around. Helps get nutrition to cells
Term
what are some non-thermal effects of US
Definition
increased cell membrane permeability, increased intracellular calcium, histamine release, increased macrophage response
Term
why is it good to have increased cell membrane permeability
Definition
can move things into/out of cell more easily
Term
why is it good to have increased intracellular calcium
Definition
helps you get a better muscle contraction
Term
why is it good to have histamine release
Definition
changes chemical composition in the area; causes mast cells to send out chemical signals to start inflammatory/healing
Term
why is it good to have an increased macrophage response
Definition
macrophages help clean up the area
Term
when do non-thermal US effects occur?
Definition
always, whenever you use US
Term
does low energy US have more non-thermal or thermal effects
Definition
non-thermal effects
Term
does high energy US have more thermal or non-thermal effects
Definition
more thermal effects, but non-thermal effects are still occurring
Term
is it possible to get only non-thermal effects
Definition
yes, by using low energy
Term
is it possible to get only thermal effects
Definition
no
Term
what are the thermal effects of US
Definition
same as superficial heating, denatures collagen bonds, improved blood flow, periosteal pain
Term
how US heating different from superficial heating
Definition
smaller specific, deeper areas
Term
why is it good to denature collagen bonds
Definition
allows us to reform collagen into the direction we want it to go
Term
what 3 factors affect heating
Definition
collagen content, frequency, intensity
Term
what are some tissues with high collagen content
Definition
tendon, ligament, capsule, fascia
Term
what is an absorption coefficient
Definition
the amount of absorption by a tissue
Term
how does the rate of temperature increase relate to absorption coefficient
Definition
proportional
Term
how does collagen content relate to temperature increase
Definition
the higher the collagen, the greater the temperature increase because it absorbs more
Term
how does frequency relate to rate of heating
Definition
higher frequency = higher rate of heating
Term
do high or low frequencies travel farther
Definition
low frequencies travel farther (think of subwoofer in a car)
Term
to have the same heating results, what will you need to change and now if you want to increase frequency?
Definition
If you are going to increase frequency, you need to decrease intensity and/or duration.
Term
do non-thermal effects occur at low or high temperature changes?
Definition
low
Term
if we increase temperature by 1C, is that a thermal or a non-thermal effect
Definition
non-thermal effects
Term
what are the effects of increasint temp by 1C
Definition
increased metabolism and healing
Term
what are the effects of increasing temp by 2-3C
Definition
decrease pain and spasm
Term
if we increase temp by 4C, is that a thermal or non-thermal effect?
Definition
thermal
Term
what is the effect of increasing temp by 4C?
Definition
collagen extensibility
Term
at what temperature are we getting thermal effects
Definition
40C and above
Term
how long do you have after using US to stretch someone and take advantage of the thermal range
Definition
3-5 minutes
Term
why is it good to stretch someone during US
Definition
that way, you're sure to be stretching them as soon as they're in the thermal range
Term
do you get a faster rise into the thermal range using 3MHz or 1MHz?
Definition
3MHz
Term
what are indications for US/conditions for which you would treat with US?
Definition
soft tissue shortening, tendon injuries, tendon calcification, pain, plantar warts, dermal ulcers
Term
how does US help with soft tissue shortening
Definition
helps to try to lengthen tissue
Term
how does US help with tendon injuries
Definition
lengthen tissues, promote healing
Term
how does US help with tendon calcification
Definition
helps with calcium deposit resorption
Term
how does US help with pain
Definition
used to address the cause of pain
Term
what are draper's indications for US
Definition
acute/post acute, soft tissue healing/repair, scar, joint contracture, chronic inflammation, increase collagen extensibility, reduce muscle spasm, pain modulation, increase protein synthesis, tissue regeneration, bone healing, non-union fractures, inflammation with myositis ossificans (resorb extra bone growth), plantar warts, trigger points
Term
what are the basic indications for US
Definition
healing, pain, muscle spasm, connective tissue changes, blood flow changes
Term
what are the purposes of phonophoresis
Definition
facilitates transdermal delivery; increases pores in stratum corneum so that molecule can move through the tissue
Term
what is phonophoresis
Definition
sound energy that changes the epidermis to the point that medicinal molecules can get through
Term
what medicine is typically used with phonophoresis
Definition
cortisone
Term
does phonophoresis work, according to research?
Definition
no
Term
what medicines are transferred well with phonophoresis
Definition
lidex gel, theragesic cream, mineral oil
Term
when doing phonophoresis, what should you do first?
Definition
regular US, so that the medicine doesn't block the US
Term
what are contraindications for US
Definition
tumors, pregnancy, CNS, joint cement/plastic, pacemakers, thrombophlebitis, eyes, reproductive organs
Term
why no US over tumors
Definition
increasing blood flow increases tumor growth
Term
why no US over pregnancy
Definition
could affect pregnancy
Term
when not to use US over spinal cord
Definition
if person has had a laminectomy or other exposure of CNS
Term
why no US over joint cement/plastic
Definition
US can break up cement. Plastic absorbs US and will heat up
Term
why no US for pacemakers
Definition
plastic casing, metal parts
Term
where can you not use US for someone with pacemaker
Definition
L chest, shoulder
Term
what are precautions for US
Definition
acute inflammation, epiphyseal plates, fractures, breast implants
Term
why is acute inflammation only a precaution for US
Definition
you can still use non-thermal US
Term
why are fractures only precautions for US
Definition
US can create pain, but can also be used to help heal fractures
Term
what are adverse effects of US
Definition
burns, blood cell stasis
Term
what is blood cell stasis
Definition
red blood cells form into bands, capillary circulation stops.
Term
is blood cell stasis common
Definition
no, it is rare
Term
when does blood cell stasis happen
Definition
if you use high energy for a long time
Term
what are US treatment choices you can make
Definition
frequency, duty cycle, intensity, duration
Term
how to determine duty cycle
Definition
choose based on the effect that you want. Can be continuous or pulsed.
Term
what does intensity determine?
Definition
effects of US
Term
what is dose level?
Definition
temperature change
Term
what 3 things combine to get dose level
Definition
frequency, intensity, duration
Term
what are techniques for application of US
Definition
direct contact: moving, stationary; underwater; balloon (plastic glove filled with water)
Term
is it possible to get a thermal change using pulsed US?
Definition
yes, but you have to do it for a long duration at a high intensity
Term
is it possible to get nonthermal changes using continuous US?
Definition
yes, if you do it for a short duration at a low intensity
Term
when would you use direct contact, stationary as an US technique?
Definition
trigger points
Term
what tissue has the highest absorption coefficient?
Definition
bone
Term
after bone, what tissue has the highest absorption coefficient?
Definition
cartilage
Term
close to cartilage, what tissue has the 3rd highest absorption coefficient?
Definition
tendon
Term
which tissue has the lowest absorption coefficient?
Definition
blood
Term
why to use continuous vs. pulsed US
Definition
use continuous for more thermal effects, use pulsed for more nonthermal effects (though both effects can be acquired using both applications)
Term
how to determine size of US head
Definition
choose based on the size of area to be treated.
Term
how does the ERA relate to the size of the US head
Definition
the ERA (actual surface of the crystal that delivers the energy) is always smaller than the area of the US head.
Term
how big should your treatment area be in relation to ERA?
Definition
all treatments should be contained within an area only 2x size of the ERA
Term
what frequency to use if target is deeper than 1 inch?
Definition
1MHz
Term
what frequency to use if target is less than 1 inch deep?
Definition
3MHz
Term
what to do if your US head is smaller than the area you want to treat
Definition
either increase intensity, increase duration, or do more than 1 consecutive treatment (which will still take more time)
Term
if using water as US medium, what must you do?
Definition
clear off bubbles
Term
how to achieve thermal effects using 1MHz continuous?
Definition
5-10 minutes at 1-2W/cm^2
Term
how to achieve thermal effects using 3MHz continuous?
Definition
3-5 minutes at 1-1.5W/cm^2
Term
how to achieve nonthermal effects at 1MHz continuous
Definition
5-10 minutes at .25-.7W/cm^2
Term
how to achieve nonthermal effects at 3MHz continuous
Definition
5 minutes at .25-.7W/cm^2
Term
how to achieve nonthermal effects at 1MHz 20% pulsed
Definition
5-10 minutes at 1-2W/cm^2, SATA =.2-.4W/cm^2
Term
how to achieve nonthermal effects using 3MHz pulsed
Definition
3-5 minutes at 1-1.5W/cm^2, SATA = .2-.3W/cm^2
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