Modalities Ch. 14 Flashcards
what is sound
form of vibrational or acoustic energy
sounds travel in waves
what sounds can we hear?
16,000 - 20,000 Hz
ultrasound
inaudible, acoustic vibrations
high frequency
may produce thermal and/or nonthermal physiologic effects
types of ultrasound
diagnostic -internal structure imaging -5MHz, 3.4 mW/cm2 surgical -tissue destruction owing to thermal and mechanical effects -0.10 MHz, 20-100 W/Cm therapeutic -thermal and subthermal effects -0.75 to 3 MHz,
therapeutic ultrasound
advantage over other nonacoustic heating modalities
tissues high in collagen (tendons, muscles, ligaments, joint capsules, meniscus, and cortical bone) can be heated to a therapeutic range
anatomy of an ultrasound machine
generator -where electrical current is generated applicator transducer -converts electrical energy to acoustic energy -houses the crystal crystal
how does ultrasound work
generator produces a high-frequency alternating current
current travels through the coaxial cable
crystal in the transducer converts electrical energy to sound energy
-reverse piezoelectric effect
reverse piezoelectric effect
mechanical energy being produced by electric energy
what happens to the crystal
crystal expands and contracts
- rarefaction - crystal expands
- neutral
- compression - crystal has a high molecular density
- neutral
- rarefaction
- etc.
attenuation
decrease in energy as ultrasound passes through various tissue layers
Law of Grotthus-Draper
-the more energy that is absorbed by superficial leaves less energy to be absorbed by deeper tissues
ultrasound effects on tissue
penetrates through tissues high in water content -fat absorbed in tissues high in protein -muscles -nerves refracted at joints reflects or bounces off bone -certain degree is absorbed in superficial bone
how is tissue heated
ultrasound is absorbed by tissue
causes molecules to rotate and bounce off one another
results in heat or nonthermal effects
Effective Radiating Area (ERA)
portion of the sound head that is producing the therapeutic effect
ERA determinants
size of sound head
size of crystal
quality of crystal
beam nonuniformity ration (BNR)
amount of variable intensity within the ultrasound beam
Ratio = variability:average output intensity
should be as close as possible to 1:1
most manufacturers accept <6:1
8.5 w/cm2 can damage tissue
PAMBNR
peak area of the maximum BNR
ultrasound parameters
duty factor frequency intensity treatment length treatment size application technique
duty factor
pulsed or continuous
frequency
1 and 3 MHz
intensity
power
treatment length
depends on treatment goals
treatment size
depends on area you are treating and sound head size
continuous ultrasound
sound waves are delivered continually at the determined frequency
pulsed ultrasound
sound waves are delivered in pulses
pulse period
length of entire pulse including the off time
pulse duration
length of the on time of the pulse
duty cycle ratio
% “on time” (pulse duration) in relation to “pulse period”
when do you use pulsed?
when you do not want the therapeutic effects
frequency
how many times does the crystal change shape
determines depth of treatment
-3 MHz: surface to 2.5 cm
-1 MHz: 2.5-5 cm
power
the total amount of ultrasound energy produced by the generator
measure of pulse width and frequency
measures in watts
intensity
the rate at which power is delivered to the tissue
determined by power and ERA
measured in W/cm2
greater intensity = greater rate of heating
what should the patient feel?
heat
warming
treatment length depends on
goals
size of area to be treated
intensity used
frequency (MHz)
rate of heating (per minute)
0.5 intensity (W/cm2) - 0.04 C at 1 MHz and 0.3 C at 3 MHz
dose according to goals
subacute inflammation
-
thermal effects
increased -extensibility of collagen fibers -metabolism -blood flow decreased -muscle stiffness -pain perception -muscle spasm altered nerve conduction velocity
thermal effects
-duration determined by
desired tissue temp. increase
frequency
intensity (patient comfort)
duty cycle of ultrasound: continuous
nonthermal/mechanical effects
calcium ion influx cell membrane alteration attraction of immune cells to the injured area vascular regeneration tissue regeneration wound healing increased -histamine release -phagocytic activity of macrophages -protein synthesis -capillary density of ischemic tissue -fibroblasts
mechanical effects
another name for thermal effects
mechanical vibrations occurring at the cellular level owing to
-stable cavitation
-acoustic streaming
cavitation
result of the physical forces of the soundwaves on microenvironmental gases within a fluid
compression and rerefaction cause these bubbles to expand and contract
good: stable cavitation (no tissue damage)
bad: unstable or transient cavitation (tissue damage from implosion or collapse of bubbles)
stable cavitation
compression and expansion of small gas bubbles in the blood and tissue
- cellular effects
- -increase in cell membrane diffusion
- -increased cellular activity
unstable cavitation
-occurs when
intensity is too high
when the soundhead is not moved
from a high BNR
acoustic microstreaming
mechanical pressure applied to the sound wave produces unidirectional movement of fluid along and/or around the cell membrane
can alter the cell membrane’s structure and function
acoustic microstreaming cellular effects
stimulates protein synthesis increases capillary density increases ion flux stimulates serotonin release pain control
thermal effects
increased -extensibility of collagen fibers -metabolism -blood flow decreased -muscle stiffness -pain perception -muscle spasm altered nerve conduction velocity
thermal effects
-duration determined by
desired tissue temp. increase
frequency
intensity (patient comfort)
duty cycle of ultrasound: continuous
nonthermal/mechanical effects
calcium ion influx cell membrane alteration attraction of immune cells to the injured area vascular regeneration tissue regeneration wound healing increased -histamine release -phagocytic activity of macrophages -protein synthesis -capillary density of ischemic tissue -fibroblasts
mechanical effects
another name for thermal effects
mechanical vibrations occurring at the cellular level owing to
-stable cavitation
-acoustic streaming
cavitation
result of the physical forces of the soundwaves on microenvironmental gases within a fluid
compression and rerefaction cause these bubbles to expand and contract
good: stable cavitation (no tissue damage)
bad: unstable or transient cavitation (tissue damage from implosion or collapse of bubbles)
stable cavitation
compression and expansion of small gas bubbles in the blood and tissue
- cellular effects
- -increase in cell membrane diffusion
- -increased cellular activity
unstable cavitation
-occurs when
intensity is too high
when the soundhead is not moved
from a high BNR
acoustic microstreaming
mechanical pressure applied to the sound wave produces unidirectional movement of fluid along and/or around the cell membrane
can alter the cell membrane’s structure and function
acoustic microstreaming cellular effects
stimulates protein synthesis increases capillary density increases ion flux stimulates serotonin release pain control
US indications
soft tissue healing and repair resolving pitting edema scar tissue and joint contracture heat and stretch routine chronic inflammation bone healing assessing stress fractures pain effects of deep heat
low intensity US for bone
unadjustable preset low intensity pulsed US parameters -1.5 MHz frequently -20% duty cycle -0.15 W/cm2 20-30 minutes daily may or may not work
US contraindications
heart disease and pacemakers
pregnant uterus
testes
directly over the heart, eyes, spinal cord, carotid sinus, cervical stellate ganglion, or vagus nerve
directly over areas of absent or diminished sensation
more contraindications
malignant tumors or cancerous lesions
over areas of circulatory insufficiency
acute or severe sepsis or local infection
over epiphysis in growing bones (calcium influx)
-females 15.5 years old
-males 17.5 years old
danger of hemorrhage immediately after injury
size of the treatment area
should be limited to an area no more than twice the size of the soundhead
transducer movement
use slow strokes covering about 4 cm/sec.
- can use back and forth or circular strokes
- keep the faceplate flat on the surface being treated
application technique - coupling medium
ultrasound requires a medium or couplant to be placed between the soundhead and the skin so that air does not interfere with transmission of ultrasound
gel: most common
water: water immersion technique over bony prominences
gel pads: over bony prominences
immersion technique
used to treat small areas when soundhead cannot lie flat on the tissue surface (bony prominences)
soundhead does not touch tissue, but is held 0.5 cm away from and perpendicular to the target tissues
may need to increase intensity by as much as 50%
ultrasound gel pads
small areas
bony prominences
use gel between both soundhead and pad and pad and skin
other uses of US
phonophoresis
- ultrasound to increase cell membrane permeability
- facilitates the delivery of medication molecules to precise locations in the body
common medications used in phonophoresis
anti-inflammatories -cortisol -salicylates -dexamethasone analgesics -lidocaine
heat and stretch
heat the area before
- or during stretching
- joint mobilizations
- friction massage
stretching window
time period (window of opportunity) of vigorous heating when stressed tissues undergo their greatest extensibility and elongation tissue heated to 40C will drop to 38C within 5-10 minutes after an ultrasound treatment has terminated
guidelines for use
obtain history determine goal position patient comfortably inspect treatment area obtain appropriate size of the soundhead determine frequency set duty cycle apply couplant set treatment time maintain contact adjust intensity to perception of heat terminate treatment assess efficacy record treatment response and parameters
