Ultrasound & Diathermy Flashcards
What is ultrasound used for?
diagnostic imaging-3.5MHz to 10MHz
loosening jt replacements in need of revision
therapeutic effects
Therapeutic ultrasound ranges in what Hz?
750,000 to 3,000,000Hz
Most frequently used are 1 MHz & 3MHz
What kind of sound is ultrasound?
Acoustic sound
Therapeutic Ultrasound
Considered a deep heating agent
Thermal and non-thermal effects
converts electrical energy to acoustical energy
What is a transducer?
converts one form of energy to another
Piezoelectric crystal
a crystal capable of contracting and expanding. Creates the “piezoelectric effect”
What is the reverse piezoelectric effect?
as the AC reverses polarity, the crystal expands and contracts producing US energy
travels through tissues and is absorbed.
Effective Radiating Area (ERA)
area of sound head that produces ultrasonic waves; expressed in cm2
- portion of the heads surface area that produces US wave (always lesser than actual size of sound head)
- energy output greatest at center of ERA (temp too)
Describe energy from US?
multiple waves come from head
energy diverges as it moves away from the source
becomes less consistent farther away from the head
Not uniformed-most energy emitted toward center of sound head
Beam nonuniformity ratio (BNR)
the consistency of the US output; ratio b/w highest intensity in an US beam and the output reported on the meter
lower the ratio the more uniform the beam is
8:1 is unsafe
Whats good about a lower BNR
makes the treatment more comfortable by reducing hot spots and reducing risk of periosteal pain
What are hot spots?
because of the existence of high-intensity areas in the beam—-gotta keep it moving
What is required to be on FDA label?
output frequency ERA BNR Beam profile Calibration and date of last service
What tissues are capable of greater absorption?
higher protein density tissues have higher rate of absorption
-tendon, ligaments, muscle tissues
What tissues absorb less US energy?
higher water content and low protein content like blood and fat
Why do cartilage and bone reflect US energy?
Because they are SO highly dense with protein the energy strikes the surface and is likely to be reflected.
What is frequency for US?
defined as the # of waves per second
Hz or PPS
Hz: cycles per second
MHz=1,000,000 cycles per second
What frequency do 1 and 3 have?
1 MHz= low frequency, more deep (4cm)
3 MHz= high frequency, more superficial (2cm)
Characteristics of 3MHz
3 MHz heats tissue at least 3x faster than 1 MHz so absorption occurs much faster
absorbed superficially
heating effects do not last as long as 1 MHz
Dosage (intensity)
Watts/surface area (W/cm2)
Higher the dose means higher amount of sound energy delivered to tissues in less time.
Longer treatment time needed for lower intensities
Common=1.5
Doses greater than 2.5-3.0 may cause tissue damage
What are some common intensities?
.5-.75= knee, elbow, iliac crest, wrist, AC joint, ankle (BONY)
.75-1.0=forearm, shldr, anterior lower leg (bone closer to surface)
1.0-1.5=calf, upper arm, lateral leg (more muscle)
1.5-2.0= thigh, buttocks (more fat)
2.0-2.5=thigh, buttocks on larger bodies
Treatment time and thermal effects
3Mhz is most effective the higher the intensity the faster the temperature increases
Treatment Area parameters
No greater than 2-3x the ERA
Move sound head in slow manner to prevent hot spots
Maintain contact with skin
Larger areas= decreased acoustic energy reaching tissues and less temp increases—so perform separate tx
What are the 3 coupling methods for US
Direct Coupling
Pad (bladder) method
Immersion method
Direct Coupling
Transducer with gel in direct contact with skin
decreases in irregular shaped areas and areas with a lot of hair—move sound head slowly
Movements of transducer
moving too rapidly decreases the total amount of energy absorbed per unit area
pt complains of pain or excessive heat–decrease intensity but increase time
keep constant pressure
Pad (bladder) method
Pads are formed from US gel and packed tightly in order to hold shape
Advantages of Pad method
conforms to irregular shaped area and limits the size of treatment area allowing more energy to be transmitted
Immersion Method
treat irregular shaped areas
sound head ~1” away from area
sound head should be facing target tissue and remain at 90 degree angle
Continuous vs pulsed US
determines thermal vs non-thermal effects
Continuous=thermal 100%
pulsed=non-thermal at cellular level % of 100% dependent upon treatment goal
Thermal mode
effective in heating the dense collagenous tissues
requires high intensity
continuous
Thermal effects: mild heating
mild heating of 1 C= increase metabolic activity, initiation of inflammatory process
Moderate heating
2-3 C= increased blood flow, decreased pain, decreased muscle spasm, decreased chronic inflammation
Vigorous heating
3-4 C= results in improved viscoelastic properties of collagen
Non-thermal effects
primarily occurs with pulsed US
little heat is produced due to dissipation occuring during off times
Cavitation
formation of gas filled bubbles that expand and compress, causing pressure changes in tissue fields
Stable and Unstable
Stable Cavitation
rhythmic contraction and expansion of gas bubbles; facilitates fluid mvmt and membrane transport=Good
Unstable Cavitation
formation of bubbles at the low pressure part of the US cycle; results in bubble collapse and tissue damage–> bad
Acoustical Micro-streaming
unidirectional mvmt of fluids along the boundaries of cell membranes
US causes interstitial fluids to flow
Fluids strike cell membranes—altering their permeability to Na and Ca ions (important to healing process)
Cells response to acoustical streaming
increases cell membrane permeability alters cell membrane diffusion rate increased histamine release mast cell degranulation increased rate of protein synthesis
Indications of US
prior to stretching and manual therapy when pt has restricted ROM
Scar tissue and jt contracture
identifying stress fxs
Precautions of US
always use lowest intensity which produces a therapeutic response
educate pt on what they will feel
do not use over metal implants or pt with pacemakers
Contraindications
Acute conditions ischemic areas impaired circulation DVT over active infections around heart, eyes, skull, and genitalia pregnancy over fx sites (unless used to identify) cancer
Combo US/Electrical Stimulation
used to treat:
trigger points
muscle spasms
output parameters:
thermal US
motor level electrical stim
Phonophoresis
US used to deliver medication
opens pathways to drive molecules into tissues
not likely to damage or burn skin like iontophoresis could
Common medications for phonophoresis
dexamehtasone (analgesic)
hydrocortisone (anti-inflammatory)
Short wave Diathermy
local heating by high frequency electromagnetic waves
increase in local blood flow from tissue heating is primary benefit (thought to be)
Continuous diathermy
used mainly with chronic injuries
increases tissues temperature
increased risk of burns
Pulsed diathermy
may or may not increase temp
pulses allow for increased tx intensity and duration
Advantages of diathermy
thermal effects similar to US but effect deeper tissue
heats larger area of tissue
doesn’t reflect from bone so less likely to create hot spots
pulsed can create thermal effects as well, heat retained 3x longer
Disadvantages of diathermy
expensive
can only treat one pt at a time
potential for burns
Pulsed SWD
used to heat deep tissues
-higher the pulse frequency, the greater the tissue heating
Heats tissues at depths of 3-5 cm
Tissue temp controlled by length of application
-max increases 4-6 C
2 types of shortwave diathermy
induction field generators
capacitive field generators
Induction field generators
places the pt in the electromagnetic field
produce greatest heat w/in muscle directly beneath the coil
induction cable or drum—drum is most commonly used
Greatest heating occurs in tissues with what?
good electrical conductance=muscles, blood vessels, and nerves
Capacitive Field Generators
body is actually placed in electric field and is a part of the circuit—placed b/w 2 electrodes of opposite charge
-tissues with greatest resistance create most heat as current flows through path of least resistance—not recommended for fat people
When should you use diathermy?
if skin or underlying soft tissue is tender
areas where subcutaneous fat is thick and deep heating required—induction method
when needing to increase tissue temp over a large area
Effects of Diathermy
alters collagen properties, allowing it to elongate
requires stretching during and/or immediately after tx
Contraindications of Diathermy
metal implants or metal jewelry cardiac pacemakers ischemic areas PVD tendency to hemorrhage pregnant sensory loss cancer
